| // Copyright 2020 The Tint Authors. | 
 | // | 
 | // Licensed under the Apache License, Version 2.0 (the "License"); | 
 | // you may not use this file except in compliance with the License. | 
 | // You may obtain a copy of the License at | 
 | // | 
 | //     http://www.apache.org/licenses/LICENSE-2.0 | 
 | // | 
 | // Unless required by applicable law or agreed to in writing, software | 
 | // distributed under the License is distributed on an "AS IS" BASIS, | 
 | // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. | 
 | // See the License for the specific language governing permissions and | 
 | // limitations under the License. | 
 |  | 
 | #include "src/tint/resolver/resolver.h" | 
 |  | 
 | #include <algorithm> | 
 | #include <cmath> | 
 | #include <iomanip> | 
 | #include <limits> | 
 | #include <utility> | 
 |  | 
 | #include "src/tint/ast/alias.h" | 
 | #include "src/tint/ast/array.h" | 
 | #include "src/tint/ast/assignment_statement.h" | 
 | #include "src/tint/ast/attribute.h" | 
 | #include "src/tint/ast/bitcast_expression.h" | 
 | #include "src/tint/ast/break_statement.h" | 
 | #include "src/tint/ast/call_statement.h" | 
 | #include "src/tint/ast/continue_statement.h" | 
 | #include "src/tint/ast/depth_texture.h" | 
 | #include "src/tint/ast/disable_validation_attribute.h" | 
 | #include "src/tint/ast/discard_statement.h" | 
 | #include "src/tint/ast/for_loop_statement.h" | 
 | #include "src/tint/ast/id_attribute.h" | 
 | #include "src/tint/ast/if_statement.h" | 
 | #include "src/tint/ast/internal_attribute.h" | 
 | #include "src/tint/ast/interpolate_attribute.h" | 
 | #include "src/tint/ast/loop_statement.h" | 
 | #include "src/tint/ast/matrix.h" | 
 | #include "src/tint/ast/pointer.h" | 
 | #include "src/tint/ast/return_statement.h" | 
 | #include "src/tint/ast/sampled_texture.h" | 
 | #include "src/tint/ast/sampler.h" | 
 | #include "src/tint/ast/storage_texture.h" | 
 | #include "src/tint/ast/switch_statement.h" | 
 | #include "src/tint/ast/traverse_expressions.h" | 
 | #include "src/tint/ast/type_name.h" | 
 | #include "src/tint/ast/unary_op_expression.h" | 
 | #include "src/tint/ast/variable_decl_statement.h" | 
 | #include "src/tint/ast/vector.h" | 
 | #include "src/tint/ast/while_statement.h" | 
 | #include "src/tint/ast/workgroup_attribute.h" | 
 | #include "src/tint/resolver/uniformity.h" | 
 | #include "src/tint/sem/break_if_statement.h" | 
 | #include "src/tint/sem/call.h" | 
 | #include "src/tint/sem/for_loop_statement.h" | 
 | #include "src/tint/sem/function.h" | 
 | #include "src/tint/sem/if_statement.h" | 
 | #include "src/tint/sem/index_accessor_expression.h" | 
 | #include "src/tint/sem/loop_statement.h" | 
 | #include "src/tint/sem/materialize.h" | 
 | #include "src/tint/sem/member_accessor_expression.h" | 
 | #include "src/tint/sem/module.h" | 
 | #include "src/tint/sem/statement.h" | 
 | #include "src/tint/sem/struct.h" | 
 | #include "src/tint/sem/switch_statement.h" | 
 | #include "src/tint/sem/type_conversion.h" | 
 | #include "src/tint/sem/type_initializer.h" | 
 | #include "src/tint/sem/variable.h" | 
 | #include "src/tint/sem/while_statement.h" | 
 | #include "src/tint/type/abstract_float.h" | 
 | #include "src/tint/type/abstract_int.h" | 
 | #include "src/tint/type/array.h" | 
 | #include "src/tint/type/atomic.h" | 
 | #include "src/tint/type/depth_multisampled_texture.h" | 
 | #include "src/tint/type/depth_texture.h" | 
 | #include "src/tint/type/multisampled_texture.h" | 
 | #include "src/tint/type/pointer.h" | 
 | #include "src/tint/type/reference.h" | 
 | #include "src/tint/type/sampled_texture.h" | 
 | #include "src/tint/type/sampler.h" | 
 | #include "src/tint/type/short_name.h" | 
 | #include "src/tint/type/storage_texture.h" | 
 | #include "src/tint/utils/defer.h" | 
 | #include "src/tint/utils/math.h" | 
 | #include "src/tint/utils/reverse.h" | 
 | #include "src/tint/utils/scoped_assignment.h" | 
 | #include "src/tint/utils/string.h" | 
 | #include "src/tint/utils/transform.h" | 
 | #include "src/tint/utils/vector.h" | 
 |  | 
 | namespace tint::resolver { | 
 | namespace { | 
 |  | 
 | constexpr int64_t kMaxArrayElementCount = 65536; | 
 | constexpr uint32_t kMaxStatementDepth = 127; | 
 |  | 
 | }  // namespace | 
 |  | 
 | Resolver::Resolver(ProgramBuilder* builder) | 
 |     : builder_(builder), | 
 |       diagnostics_(builder->Diagnostics()), | 
 |       const_eval_(*builder), | 
 |       intrinsic_table_(IntrinsicTable::Create(*builder)), | 
 |       sem_(builder, dependencies_), | 
 |       validator_(builder, | 
 |                  sem_, | 
 |                  enabled_extensions_, | 
 |                  atomic_composite_info_, | 
 |                  valid_type_storage_layouts_) {} | 
 |  | 
 | Resolver::~Resolver() = default; | 
 |  | 
 | bool Resolver::Resolve() { | 
 |     if (builder_->Diagnostics().contains_errors()) { | 
 |         return false; | 
 |     } | 
 |  | 
 |     builder_->Sem().Reserve(builder_->LastAllocatedNodeID()); | 
 |  | 
 |     // Pre-allocate the marked bitset with the total number of AST nodes. | 
 |     marked_.Resize(builder_->ASTNodes().Count()); | 
 |  | 
 |     if (!DependencyGraph::Build(builder_->AST(), builder_->Symbols(), builder_->Diagnostics(), | 
 |                                 dependencies_)) { | 
 |         return false; | 
 |     } | 
 |  | 
 |     bool result = ResolveInternal(); | 
 |  | 
 |     if (!result && !diagnostics_.contains_errors()) { | 
 |         TINT_ICE(Resolver, diagnostics_) << "resolving failed, but no error was raised"; | 
 |         return false; | 
 |     } | 
 |  | 
 |     // Create the semantic module | 
 |     builder_->Sem().SetModule(builder_->create<sem::Module>( | 
 |         std::move(dependencies_.ordered_globals), std::move(enabled_extensions_))); | 
 |  | 
 |     return result; | 
 | } | 
 |  | 
 | bool Resolver::ResolveInternal() { | 
 |     Mark(&builder_->AST()); | 
 |  | 
 |     // Process all module-scope declarations in dependency order. | 
 |     for (auto* decl : dependencies_.ordered_globals) { | 
 |         Mark(decl); | 
 |         if (!Switch<bool>( | 
 |                 decl,  // | 
 |                 [&](const ast::Enable* e) { return Enable(e); }, | 
 |                 [&](const ast::TypeDecl* td) { return TypeDecl(td); }, | 
 |                 [&](const ast::Function* func) { return Function(func); }, | 
 |                 [&](const ast::Variable* var) { return GlobalVariable(var); }, | 
 |                 [&](const ast::StaticAssert* sa) { return StaticAssert(sa); }, | 
 |                 [&](Default) { | 
 |                     TINT_UNREACHABLE(Resolver, diagnostics_) | 
 |                         << "unhandled global declaration: " << decl->TypeInfo().name; | 
 |                     return false; | 
 |                 })) { | 
 |             return false; | 
 |         } | 
 |     } | 
 |  | 
 |     if (!AllocateOverridableConstantIds()) { | 
 |         return false; | 
 |     } | 
 |  | 
 |     SetShadows(); | 
 |  | 
 |     if (!validator_.PipelineStages(entry_points_)) { | 
 |         return false; | 
 |     } | 
 |  | 
 |     if (!validator_.PushConstants(entry_points_)) { | 
 |         return false; | 
 |     } | 
 |  | 
 |     if (!enabled_extensions_.Contains(ast::Extension::kChromiumDisableUniformityAnalysis)) { | 
 |         if (!AnalyzeUniformity(builder_, dependencies_)) { | 
 |             if (kUniformityFailuresAsError) { | 
 |                 return false; | 
 |             } | 
 |         } | 
 |     } | 
 |  | 
 |     bool result = true; | 
 |     for (auto* node : builder_->ASTNodes().Objects()) { | 
 |         if (!marked_[node->node_id.value]) { | 
 |             TINT_ICE(Resolver, diagnostics_) | 
 |                 << "AST node '" << node->TypeInfo().name << "' was not reached by the resolver\n" | 
 |                 << "At: " << node->source << "\n" | 
 |                 << "Pointer: " << node; | 
 |             result = false; | 
 |         } | 
 |     } | 
 |  | 
 |     return result; | 
 | } | 
 |  | 
 | type::Type* Resolver::Type(const ast::Type* ty) { | 
 |     Mark(ty); | 
 |     auto* s = Switch( | 
 |         ty,  // | 
 |         [&](const ast::Void*) { return builder_->create<type::Void>(); }, | 
 |         [&](const ast::Bool*) { return builder_->create<type::Bool>(); }, | 
 |         [&](const ast::I32*) { return builder_->create<type::I32>(); }, | 
 |         [&](const ast::U32*) { return builder_->create<type::U32>(); }, | 
 |         [&](const ast::F16* t) -> type::F16* { | 
 |             return validator_.CheckF16Enabled(t->source) ? builder_->create<type::F16>() : nullptr; | 
 |         }, | 
 |         [&](const ast::F32*) { return builder_->create<type::F32>(); }, | 
 |         [&](const ast::Vector* t) -> type::Vector* { | 
 |             if (!t->type) { | 
 |                 AddError("missing vector element type", t->source.End()); | 
 |                 return nullptr; | 
 |             } | 
 |             if (auto* el = Type(t->type)) { | 
 |                 if (auto* vector = builder_->create<type::Vector>(el, t->width)) { | 
 |                     if (validator_.Vector(vector, t->source)) { | 
 |                         return vector; | 
 |                     } | 
 |                 } | 
 |             } | 
 |             return nullptr; | 
 |         }, | 
 |         [&](const ast::Matrix* t) -> type::Matrix* { | 
 |             if (!t->type) { | 
 |                 AddError("missing matrix element type", t->source.End()); | 
 |                 return nullptr; | 
 |             } | 
 |             if (auto* el = Type(t->type)) { | 
 |                 if (auto* column_type = builder_->create<type::Vector>(el, t->rows)) { | 
 |                     if (auto* matrix = builder_->create<type::Matrix>(column_type, t->columns)) { | 
 |                         if (validator_.Matrix(matrix, t->source)) { | 
 |                             return matrix; | 
 |                         } | 
 |                     } | 
 |                 } | 
 |             } | 
 |             return nullptr; | 
 |         }, | 
 |         [&](const ast::Array* t) { return Array(t); }, | 
 |         [&](const ast::Atomic* t) -> type::Atomic* { | 
 |             if (auto* el = Type(t->type)) { | 
 |                 auto* a = builder_->create<type::Atomic>(el); | 
 |                 if (!validator_.Atomic(t, a)) { | 
 |                     return nullptr; | 
 |                 } | 
 |                 return a; | 
 |             } | 
 |             return nullptr; | 
 |         }, | 
 |         [&](const ast::Pointer* t) -> type::Pointer* { | 
 |             if (auto* el = Type(t->type)) { | 
 |                 auto access = t->access; | 
 |                 if (access == ast::Access::kUndefined) { | 
 |                     access = DefaultAccessForAddressSpace(t->address_space); | 
 |                 } | 
 |                 auto ptr = builder_->create<type::Pointer>(el, t->address_space, access); | 
 |                 if (!ptr) { | 
 |                     return nullptr; | 
 |                 } | 
 |                 if (!validator_.Pointer(t, ptr)) { | 
 |                     return nullptr; | 
 |                 } | 
 |                 if (!ApplyAddressSpaceUsageToType(t->address_space, el, t->type->source)) { | 
 |                     AddNote("while instantiating " + builder_->FriendlyName(ptr), t->source); | 
 |                     return nullptr; | 
 |                 } | 
 |                 return ptr; | 
 |             } | 
 |             return nullptr; | 
 |         }, | 
 |         [&](const ast::Sampler* t) { return builder_->create<type::Sampler>(t->kind); }, | 
 |         [&](const ast::SampledTexture* t) -> type::SampledTexture* { | 
 |             if (auto* el = Type(t->type)) { | 
 |                 auto* sem = builder_->create<type::SampledTexture>(t->dim, el); | 
 |                 if (!validator_.SampledTexture(sem, t->source)) { | 
 |                     return nullptr; | 
 |                 } | 
 |                 return sem; | 
 |             } | 
 |             return nullptr; | 
 |         }, | 
 |         [&](const ast::MultisampledTexture* t) -> type::MultisampledTexture* { | 
 |             if (auto* el = Type(t->type)) { | 
 |                 auto* sem = builder_->create<type::MultisampledTexture>(t->dim, el); | 
 |                 if (!validator_.MultisampledTexture(sem, t->source)) { | 
 |                     return nullptr; | 
 |                 } | 
 |                 return sem; | 
 |             } | 
 |             return nullptr; | 
 |         }, | 
 |         [&](const ast::DepthTexture* t) { return builder_->create<type::DepthTexture>(t->dim); }, | 
 |         [&](const ast::DepthMultisampledTexture* t) { | 
 |             return builder_->create<type::DepthMultisampledTexture>(t->dim); | 
 |         }, | 
 |         [&](const ast::StorageTexture* t) -> type::StorageTexture* { | 
 |             if (auto* el = Type(t->type)) { | 
 |                 if (!validator_.StorageTexture(t)) { | 
 |                     return nullptr; | 
 |                 } | 
 |                 return builder_->create<type::StorageTexture>(t->dim, t->format, t->access, el); | 
 |             } | 
 |             return nullptr; | 
 |         }, | 
 |         [&](const ast::ExternalTexture*) { return builder_->create<type::ExternalTexture>(); }, | 
 |         [&](Default) { | 
 |             auto* resolved = sem_.ResolvedSymbol(ty); | 
 |             return Switch( | 
 |                 resolved,  // | 
 |                 [&](type::Type* type) { return type; }, | 
 |                 [&](sem::Variable* var) { | 
 |                     auto name = builder_->Symbols().NameFor(var->Declaration()->symbol); | 
 |                     AddError("cannot use variable '" + name + "' as type", ty->source); | 
 |                     AddNote("'" + name + "' declared here", var->Declaration()->source); | 
 |                     return nullptr; | 
 |                 }, | 
 |                 [&](sem::Function* func) { | 
 |                     auto name = builder_->Symbols().NameFor(func->Declaration()->symbol); | 
 |                     AddError("cannot use function '" + name + "' as type", ty->source); | 
 |                     AddNote("'" + name + "' declared here", func->Declaration()->source); | 
 |                     return nullptr; | 
 |                 }, | 
 |                 [&](Default) -> type::Type* { | 
 |                     if (auto* tn = ty->As<ast::TypeName>()) { | 
 |                         if (IsBuiltin(tn->name)) { | 
 |                             auto name = builder_->Symbols().NameFor(tn->name); | 
 |                             AddError("cannot use builtin '" + name + "' as type", ty->source); | 
 |                             return nullptr; | 
 |                         } | 
 |                         return ShortName(tn->name, tn->source); | 
 |                     } | 
 |                     TINT_UNREACHABLE(Resolver, diagnostics_) | 
 |                         << "Unhandled resolved type '" | 
 |                         << (resolved ? resolved->TypeInfo().name : "<null>") | 
 |                         << "' resolved from ast::Type '" << ty->TypeInfo().name << "'"; | 
 |                     return nullptr; | 
 |                 }); | 
 |         }); | 
 |  | 
 |     if (s) { | 
 |         builder_->Sem().Add(ty, s); | 
 |     } | 
 |     return s; | 
 | } | 
 |  | 
 | sem::Variable* Resolver::Variable(const ast::Variable* v, bool is_global) { | 
 |     return Switch( | 
 |         v,  // | 
 |         [&](const ast::Var* var) { return Var(var, is_global); }, | 
 |         [&](const ast::Let* let) { return Let(let, is_global); }, | 
 |         [&](const ast::Override* override) { return Override(override); }, | 
 |         [&](const ast::Const* const_) { return Const(const_, is_global); }, | 
 |         [&](Default) { | 
 |             TINT_ICE(Resolver, diagnostics_) | 
 |                 << "Resolver::GlobalVariable() called with a unknown variable type: " | 
 |                 << v->TypeInfo().name; | 
 |             return nullptr; | 
 |         }); | 
 | } | 
 |  | 
 | sem::Variable* Resolver::Let(const ast::Let* v, bool is_global) { | 
 |     const type::Type* ty = nullptr; | 
 |  | 
 |     // If the variable has a declared type, resolve it. | 
 |     if (v->type) { | 
 |         ty = Type(v->type); | 
 |         if (!ty) { | 
 |             return nullptr; | 
 |         } | 
 |     } | 
 |  | 
 |     if (!v->initializer) { | 
 |         AddError("'let' declaration must have an initializer", v->source); | 
 |         return nullptr; | 
 |     } | 
 |  | 
 |     auto* rhs = Materialize(Expression(v->initializer), ty); | 
 |     if (!rhs) { | 
 |         return nullptr; | 
 |     } | 
 |  | 
 |     RegisterLoadIfNeeded(rhs); | 
 |  | 
 |     // If the variable has no declared type, infer it from the RHS | 
 |     if (!ty) { | 
 |         ty = rhs->Type()->UnwrapRef();  // Implicit load of RHS | 
 |     } | 
 |  | 
 |     if (rhs && !validator_.VariableInitializer(v, ast::AddressSpace::kNone, ty, rhs)) { | 
 |         return nullptr; | 
 |     } | 
 |  | 
 |     if (!ApplyAddressSpaceUsageToType(ast::AddressSpace::kNone, const_cast<type::Type*>(ty), | 
 |                                       v->source)) { | 
 |         AddNote("while instantiating 'let' " + builder_->Symbols().NameFor(v->symbol), v->source); | 
 |         return nullptr; | 
 |     } | 
 |  | 
 |     sem::Variable* sem = nullptr; | 
 |     if (is_global) { | 
 |         sem = builder_->create<sem::GlobalVariable>( | 
 |             v, ty, sem::EvaluationStage::kRuntime, ast::AddressSpace::kNone, | 
 |             ast::Access::kUndefined, | 
 |             /* constant_value */ nullptr, sem::BindingPoint{}, std::nullopt); | 
 |     } else { | 
 |         sem = builder_->create<sem::LocalVariable>(v, ty, sem::EvaluationStage::kRuntime, | 
 |                                                    ast::AddressSpace::kNone, | 
 |                                                    ast::Access::kUndefined, current_statement_, | 
 |                                                    /* constant_value */ nullptr); | 
 |     } | 
 |  | 
 |     sem->SetInitializer(rhs); | 
 |     builder_->Sem().Add(v, sem); | 
 |     return sem; | 
 | } | 
 |  | 
 | sem::Variable* Resolver::Override(const ast::Override* v) { | 
 |     const type::Type* ty = nullptr; | 
 |  | 
 |     // If the variable has a declared type, resolve it. | 
 |     if (v->type) { | 
 |         ty = Type(v->type); | 
 |         if (!ty) { | 
 |             return nullptr; | 
 |         } | 
 |     } | 
 |  | 
 |     const sem::Expression* rhs = nullptr; | 
 |  | 
 |     // Does the variable have a initializer? | 
 |     if (v->initializer) { | 
 |         ExprEvalStageConstraint constraint{sem::EvaluationStage::kOverride, "override initializer"}; | 
 |         TINT_SCOPED_ASSIGNMENT(expr_eval_stage_constraint_, constraint); | 
 |         rhs = Materialize(Expression(v->initializer), ty); | 
 |         if (!rhs) { | 
 |             return nullptr; | 
 |         } | 
 |  | 
 |         // If the variable has no declared type, infer it from the RHS | 
 |         if (!ty) { | 
 |             ty = rhs->Type()->UnwrapRef();  // Implicit load of RHS | 
 |         } | 
 |     } else if (!ty) { | 
 |         AddError("override declaration requires a type or initializer", v->source); | 
 |         return nullptr; | 
 |     } | 
 |  | 
 |     if (rhs && !validator_.VariableInitializer(v, ast::AddressSpace::kNone, ty, rhs)) { | 
 |         return nullptr; | 
 |     } | 
 |  | 
 |     if (!ApplyAddressSpaceUsageToType(ast::AddressSpace::kNone, const_cast<type::Type*>(ty), | 
 |                                       v->source)) { | 
 |         AddNote("while instantiating 'override' " + builder_->Symbols().NameFor(v->symbol), | 
 |                 v->source); | 
 |         return nullptr; | 
 |     } | 
 |  | 
 |     auto* sem = builder_->create<sem::GlobalVariable>( | 
 |         v, ty, sem::EvaluationStage::kOverride, ast::AddressSpace::kNone, ast::Access::kUndefined, | 
 |         /* constant_value */ nullptr, sem::BindingPoint{}, std::nullopt); | 
 |     sem->SetInitializer(rhs); | 
 |  | 
 |     if (auto* id_attr = ast::GetAttribute<ast::IdAttribute>(v->attributes)) { | 
 |         ExprEvalStageConstraint constraint{sem::EvaluationStage::kConstant, "@id"}; | 
 |         TINT_SCOPED_ASSIGNMENT(expr_eval_stage_constraint_, constraint); | 
 |  | 
 |         auto* materialized = Materialize(Expression(id_attr->expr)); | 
 |         if (!materialized) { | 
 |             return nullptr; | 
 |         } | 
 |         if (!materialized->Type()->IsAnyOf<type::I32, type::U32>()) { | 
 |             AddError("@id must be an i32 or u32 value", id_attr->source); | 
 |             return nullptr; | 
 |         } | 
 |  | 
 |         auto const_value = materialized->ConstantValue(); | 
 |         auto value = const_value->ValueAs<AInt>(); | 
 |         if (value < 0) { | 
 |             AddError("@id value must be non-negative", id_attr->source); | 
 |             return nullptr; | 
 |         } | 
 |         if (value > std::numeric_limits<decltype(OverrideId::value)>::max()) { | 
 |             AddError("@id value must be between 0 and " + | 
 |                          std::to_string(std::numeric_limits<decltype(OverrideId::value)>::max()), | 
 |                      id_attr->source); | 
 |             return nullptr; | 
 |         } | 
 |  | 
 |         auto o = OverrideId{static_cast<decltype(OverrideId::value)>(value)}; | 
 |         sem->SetOverrideId(o); | 
 |  | 
 |         // Track the constant IDs that are specified in the shader. | 
 |         override_ids_.Add(o, sem); | 
 |     } | 
 |  | 
 |     builder_->Sem().Add(v, sem); | 
 |     return sem; | 
 | } | 
 |  | 
 | sem::Variable* Resolver::Const(const ast::Const* c, bool is_global) { | 
 |     const type::Type* ty = nullptr; | 
 |  | 
 |     // If the variable has a declared type, resolve it. | 
 |     if (c->type) { | 
 |         ty = Type(c->type); | 
 |         if (!ty) { | 
 |             return nullptr; | 
 |         } | 
 |     } | 
 |  | 
 |     if (!c->initializer) { | 
 |         AddError("'const' declaration must have an initializer", c->source); | 
 |         return nullptr; | 
 |     } | 
 |  | 
 |     const sem::Expression* rhs = nullptr; | 
 |     { | 
 |         ExprEvalStageConstraint constraint{sem::EvaluationStage::kConstant, "const initializer"}; | 
 |         TINT_SCOPED_ASSIGNMENT(expr_eval_stage_constraint_, constraint); | 
 |         rhs = Expression(c->initializer); | 
 |         if (!rhs) { | 
 |             return nullptr; | 
 |         } | 
 |     } | 
 |  | 
 |     if (ty) { | 
 |         // If an explicit type was specified, materialize to that type | 
 |         rhs = Materialize(rhs, ty); | 
 |         if (!rhs) { | 
 |             return nullptr; | 
 |         } | 
 |     } else { | 
 |         // If no type was specified, infer it from the RHS | 
 |         ty = rhs->Type(); | 
 |     } | 
 |  | 
 |     if (!validator_.VariableInitializer(c, ast::AddressSpace::kNone, ty, rhs)) { | 
 |         return nullptr; | 
 |     } | 
 |  | 
 |     if (!ApplyAddressSpaceUsageToType(ast::AddressSpace::kNone, const_cast<type::Type*>(ty), | 
 |                                       c->source)) { | 
 |         AddNote("while instantiating 'const' " + builder_->Symbols().NameFor(c->symbol), c->source); | 
 |         return nullptr; | 
 |     } | 
 |  | 
 |     const auto value = rhs->ConstantValue(); | 
 |     auto* sem = is_global ? static_cast<sem::Variable*>(builder_->create<sem::GlobalVariable>( | 
 |                                 c, ty, sem::EvaluationStage::kConstant, ast::AddressSpace::kNone, | 
 |                                 ast::Access::kUndefined, value, sem::BindingPoint{}, std::nullopt)) | 
 |                           : static_cast<sem::Variable*>(builder_->create<sem::LocalVariable>( | 
 |                                 c, ty, sem::EvaluationStage::kConstant, ast::AddressSpace::kNone, | 
 |                                 ast::Access::kUndefined, current_statement_, value)); | 
 |  | 
 |     sem->SetInitializer(rhs); | 
 |     builder_->Sem().Add(c, sem); | 
 |     return sem; | 
 | } | 
 |  | 
 | sem::Variable* Resolver::Var(const ast::Var* var, bool is_global) { | 
 |     const type::Type* storage_ty = nullptr; | 
 |  | 
 |     // If the variable has a declared type, resolve it. | 
 |     if (auto* ty = var->type) { | 
 |         storage_ty = Type(ty); | 
 |         if (!storage_ty) { | 
 |             return nullptr; | 
 |         } | 
 |     } | 
 |  | 
 |     const sem::Expression* rhs = nullptr; | 
 |  | 
 |     // Does the variable have a initializer? | 
 |     if (var->initializer) { | 
 |         ExprEvalStageConstraint constraint{ | 
 |             is_global ? sem::EvaluationStage::kOverride : sem::EvaluationStage::kRuntime, | 
 |             "var initializer", | 
 |         }; | 
 |         TINT_SCOPED_ASSIGNMENT(expr_eval_stage_constraint_, constraint); | 
 |  | 
 |         rhs = Materialize(Expression(var->initializer), storage_ty); | 
 |         if (!rhs) { | 
 |             return nullptr; | 
 |         } | 
 |         // If the variable has no declared type, infer it from the RHS | 
 |         if (!storage_ty) { | 
 |             storage_ty = rhs->Type()->UnwrapRef();  // Implicit load of RHS | 
 |         } | 
 |  | 
 |         RegisterLoadIfNeeded(rhs); | 
 |     } | 
 |  | 
 |     if (!storage_ty) { | 
 |         AddError("var declaration requires a type or initializer", var->source); | 
 |         return nullptr; | 
 |     } | 
 |  | 
 |     auto address_space = var->declared_address_space; | 
 |     if (address_space == ast::AddressSpace::kNone) { | 
 |         // No declared address space. Infer from usage / type. | 
 |         if (!is_global) { | 
 |             address_space = ast::AddressSpace::kFunction; | 
 |         } else if (storage_ty->UnwrapRef()->is_handle()) { | 
 |             // https://gpuweb.github.io/gpuweb/wgsl/#module-scope-variables | 
 |             // If the store type is a texture type or a sampler type, then the | 
 |             // variable declaration must not have a address space attribute. The | 
 |             // address space will always be handle. | 
 |             address_space = ast::AddressSpace::kHandle; | 
 |         } | 
 |     } | 
 |  | 
 |     if (!is_global && address_space != ast::AddressSpace::kFunction && | 
 |         validator_.IsValidationEnabled(var->attributes, | 
 |                                        ast::DisabledValidation::kIgnoreAddressSpace)) { | 
 |         AddError("function-scope 'var' declaration must use 'function' address space", var->source); | 
 |         return nullptr; | 
 |     } | 
 |  | 
 |     auto access = var->declared_access; | 
 |     if (access == ast::Access::kUndefined) { | 
 |         access = DefaultAccessForAddressSpace(address_space); | 
 |     } | 
 |  | 
 |     if (rhs && !validator_.VariableInitializer(var, address_space, storage_ty, rhs)) { | 
 |         return nullptr; | 
 |     } | 
 |  | 
 |     auto* var_ty = builder_->create<type::Reference>(storage_ty, address_space, access); | 
 |  | 
 |     if (!ApplyAddressSpaceUsageToType(address_space, var_ty, | 
 |                                       var->type ? var->type->source : var->source)) { | 
 |         AddNote("while instantiating 'var' " + builder_->Symbols().NameFor(var->symbol), | 
 |                 var->source); | 
 |         return nullptr; | 
 |     } | 
 |  | 
 |     sem::Variable* sem = nullptr; | 
 |     if (is_global) { | 
 |         sem::BindingPoint binding_point; | 
 |         if (var->HasBindingPoint()) { | 
 |             uint32_t binding = 0; | 
 |             { | 
 |                 ExprEvalStageConstraint constraint{sem::EvaluationStage::kConstant, "@binding"}; | 
 |                 TINT_SCOPED_ASSIGNMENT(expr_eval_stage_constraint_, constraint); | 
 |  | 
 |                 auto* attr = ast::GetAttribute<ast::BindingAttribute>(var->attributes); | 
 |                 auto* materialized = Materialize(Expression(attr->expr)); | 
 |                 if (!materialized) { | 
 |                     return nullptr; | 
 |                 } | 
 |                 if (!materialized->Type()->IsAnyOf<type::I32, type::U32>()) { | 
 |                     AddError("@binding must be an i32 or u32 value", attr->source); | 
 |                     return nullptr; | 
 |                 } | 
 |  | 
 |                 auto const_value = materialized->ConstantValue(); | 
 |                 auto value = const_value->ValueAs<AInt>(); | 
 |                 if (value < 0) { | 
 |                     AddError("@binding value must be non-negative", attr->source); | 
 |                     return nullptr; | 
 |                 } | 
 |                 binding = u32(value); | 
 |             } | 
 |  | 
 |             uint32_t group = 0; | 
 |             { | 
 |                 ExprEvalStageConstraint constraint{sem::EvaluationStage::kConstant, "@group"}; | 
 |                 TINT_SCOPED_ASSIGNMENT(expr_eval_stage_constraint_, constraint); | 
 |  | 
 |                 auto* attr = ast::GetAttribute<ast::GroupAttribute>(var->attributes); | 
 |                 auto* materialized = Materialize(Expression(attr->expr)); | 
 |                 if (!materialized) { | 
 |                     return nullptr; | 
 |                 } | 
 |                 if (!materialized->Type()->IsAnyOf<type::I32, type::U32>()) { | 
 |                     AddError("@group must be an i32 or u32 value", attr->source); | 
 |                     return nullptr; | 
 |                 } | 
 |  | 
 |                 auto const_value = materialized->ConstantValue(); | 
 |                 auto value = const_value->ValueAs<AInt>(); | 
 |                 if (value < 0) { | 
 |                     AddError("@group value must be non-negative", attr->source); | 
 |                     return nullptr; | 
 |                 } | 
 |                 group = u32(value); | 
 |             } | 
 |             binding_point = {group, binding}; | 
 |         } | 
 |  | 
 |         std::optional<uint32_t> location; | 
 |         if (auto* attr = ast::GetAttribute<ast::LocationAttribute>(var->attributes)) { | 
 |             auto value = LocationAttribute(attr); | 
 |             if (!value) { | 
 |                 return nullptr; | 
 |             } | 
 |             location = value.Get(); | 
 |         } | 
 |  | 
 |         sem = builder_->create<sem::GlobalVariable>( | 
 |             var, var_ty, sem::EvaluationStage::kRuntime, address_space, access, | 
 |             /* constant_value */ nullptr, binding_point, location); | 
 |  | 
 |     } else { | 
 |         sem = builder_->create<sem::LocalVariable>(var, var_ty, sem::EvaluationStage::kRuntime, | 
 |                                                    address_space, access, current_statement_, | 
 |                                                    /* constant_value */ nullptr); | 
 |     } | 
 |  | 
 |     sem->SetInitializer(rhs); | 
 |     builder_->Sem().Add(var, sem); | 
 |     return sem; | 
 | } | 
 |  | 
 | sem::Parameter* Resolver::Parameter(const ast::Parameter* param, uint32_t index) { | 
 |     auto add_note = [&] { | 
 |         AddNote("while instantiating parameter " + builder_->Symbols().NameFor(param->symbol), | 
 |                 param->source); | 
 |     }; | 
 |  | 
 |     for (auto* attr : param->attributes) { | 
 |         Mark(attr); | 
 |     } | 
 |     if (!validator_.NoDuplicateAttributes(param->attributes)) { | 
 |         return nullptr; | 
 |     } | 
 |  | 
 |     type::Type* ty = Type(param->type); | 
 |     if (!ty) { | 
 |         return nullptr; | 
 |     } | 
 |  | 
 |     if (!ApplyAddressSpaceUsageToType(ast::AddressSpace::kNone, ty, param->type->source)) { | 
 |         add_note(); | 
 |         return nullptr; | 
 |     } | 
 |  | 
 |     if (auto* ptr = ty->As<type::Pointer>()) { | 
 |         // For MSL, we push module-scope variables into the entry point as pointer | 
 |         // parameters, so we also need to handle their store type. | 
 |         if (!ApplyAddressSpaceUsageToType( | 
 |                 ptr->AddressSpace(), const_cast<type::Type*>(ptr->StoreType()), param->source)) { | 
 |             add_note(); | 
 |             return nullptr; | 
 |         } | 
 |     } | 
 |  | 
 |     sem::BindingPoint binding_point; | 
 |     if (param->HasBindingPoint()) { | 
 |         { | 
 |             ExprEvalStageConstraint constraint{sem::EvaluationStage::kConstant, "@binding value"}; | 
 |             TINT_SCOPED_ASSIGNMENT(expr_eval_stage_constraint_, constraint); | 
 |  | 
 |             auto* attr = ast::GetAttribute<ast::BindingAttribute>(param->attributes); | 
 |             auto* materialized = Materialize(Expression(attr->expr)); | 
 |             if (!materialized) { | 
 |                 return nullptr; | 
 |             } | 
 |             binding_point.binding = materialized->ConstantValue()->ValueAs<u32>(); | 
 |         } | 
 |         { | 
 |             ExprEvalStageConstraint constraint{sem::EvaluationStage::kConstant, "@group value"}; | 
 |             TINT_SCOPED_ASSIGNMENT(expr_eval_stage_constraint_, constraint); | 
 |  | 
 |             auto* attr = ast::GetAttribute<ast::GroupAttribute>(param->attributes); | 
 |             auto* materialized = Materialize(Expression(attr->expr)); | 
 |             if (!materialized) { | 
 |                 return nullptr; | 
 |             } | 
 |             binding_point.group = materialized->ConstantValue()->ValueAs<u32>(); | 
 |         } | 
 |     } | 
 |  | 
 |     std::optional<uint32_t> location; | 
 |     if (auto* attr = ast::GetAttribute<ast::LocationAttribute>(param->attributes)) { | 
 |         auto value = LocationAttribute(attr); | 
 |         if (!value) { | 
 |             return nullptr; | 
 |         } | 
 |         location = value.Get(); | 
 |     } | 
 |  | 
 |     auto* sem = builder_->create<sem::Parameter>( | 
 |         param, index, ty, ast::AddressSpace::kNone, ast::Access::kUndefined, | 
 |         sem::ParameterUsage::kNone, binding_point, location); | 
 |     builder_->Sem().Add(param, sem); | 
 |     return sem; | 
 | } | 
 |  | 
 | utils::Result<uint32_t> Resolver::LocationAttribute(const ast::LocationAttribute* attr) { | 
 |     ExprEvalStageConstraint constraint{sem::EvaluationStage::kConstant, "@location value"}; | 
 |     TINT_SCOPED_ASSIGNMENT(expr_eval_stage_constraint_, constraint); | 
 |  | 
 |     auto* materialized = Materialize(Expression(attr->expr)); | 
 |     if (!materialized) { | 
 |         return utils::Failure; | 
 |     } | 
 |  | 
 |     if (!materialized->Type()->IsAnyOf<type::I32, type::U32>()) { | 
 |         AddError("@location must be an i32 or u32 value", attr->source); | 
 |         return utils::Failure; | 
 |     } | 
 |  | 
 |     auto const_value = materialized->ConstantValue(); | 
 |     auto value = const_value->ValueAs<AInt>(); | 
 |     if (value < 0) { | 
 |         AddError("@location value must be non-negative", attr->source); | 
 |         return utils::Failure; | 
 |     } | 
 |  | 
 |     return static_cast<uint32_t>(value); | 
 | } | 
 |  | 
 | ast::Access Resolver::DefaultAccessForAddressSpace(ast::AddressSpace address_space) { | 
 |     // https://gpuweb.github.io/gpuweb/wgsl/#storage-class | 
 |     switch (address_space) { | 
 |         case ast::AddressSpace::kStorage: | 
 |         case ast::AddressSpace::kUniform: | 
 |         case ast::AddressSpace::kHandle: | 
 |             return ast::Access::kRead; | 
 |         default: | 
 |             break; | 
 |     } | 
 |     return ast::Access::kReadWrite; | 
 | } | 
 |  | 
 | bool Resolver::AllocateOverridableConstantIds() { | 
 |     constexpr size_t kLimit = std::numeric_limits<decltype(OverrideId::value)>::max(); | 
 |     // The next pipeline constant ID to try to allocate. | 
 |     OverrideId next_id; | 
 |     bool ids_exhausted = false; | 
 |  | 
 |     auto increment_next_id = [&] { | 
 |         if (next_id.value == kLimit) { | 
 |             ids_exhausted = true; | 
 |         } else { | 
 |             next_id.value = next_id.value + 1; | 
 |         } | 
 |     }; | 
 |  | 
 |     // Allocate constant IDs in global declaration order, so that they are | 
 |     // deterministic. | 
 |     // TODO(crbug.com/tint/1192): If a transform changes the order or removes an | 
 |     // unused constant, the allocation may change on the next Resolver pass. | 
 |     for (auto* decl : builder_->AST().GlobalDeclarations()) { | 
 |         auto* override = decl->As<ast::Override>(); | 
 |         if (!override) { | 
 |             continue; | 
 |         } | 
 |  | 
 |         OverrideId id; | 
 |         if (ast::HasAttribute<ast::IdAttribute>(override->attributes)) { | 
 |             id = builder_->Sem().Get<sem::GlobalVariable>(override)->OverrideId(); | 
 |         } else { | 
 |             // No ID was specified, so allocate the next available ID. | 
 |             while (!ids_exhausted && override_ids_.Contains(next_id)) { | 
 |                 increment_next_id(); | 
 |             } | 
 |             if (ids_exhausted) { | 
 |                 AddError( | 
 |                     "number of 'override' variables exceeded limit of " + std::to_string(kLimit), | 
 |                     decl->source); | 
 |                 return false; | 
 |             } | 
 |             id = next_id; | 
 |             increment_next_id(); | 
 |         } | 
 |  | 
 |         auto* sem = sem_.Get<sem::GlobalVariable>(override); | 
 |         const_cast<sem::GlobalVariable*>(sem)->SetOverrideId(id); | 
 |     } | 
 |     return true; | 
 | } | 
 |  | 
 | void Resolver::SetShadows() { | 
 |     for (auto it : dependencies_.shadows) { | 
 |         CastableBase* b = sem_.Get(it.value); | 
 |         if (!b) { | 
 |             TINT_ICE(Resolver, builder_->Diagnostics()) | 
 |                 << "AST node '" << it.value->TypeInfo().name << "' had no semantic info\n" | 
 |                 << "At: " << it.value->source << "\n" | 
 |                 << "Pointer: " << it.value; | 
 |         } | 
 |  | 
 |         Switch( | 
 |             sem_.Get(it.key),  // | 
 |             [&](sem::LocalVariable* local) { local->SetShadows(b); }, | 
 |             [&](sem::Parameter* param) { param->SetShadows(b); }); | 
 |     } | 
 | } | 
 |  | 
 | sem::GlobalVariable* Resolver::GlobalVariable(const ast::Variable* v) { | 
 |     utils::UniqueVector<const sem::GlobalVariable*, 4> transitively_referenced_overrides; | 
 |     TINT_SCOPED_ASSIGNMENT(resolved_overrides_, &transitively_referenced_overrides); | 
 |  | 
 |     auto* sem = As<sem::GlobalVariable>(Variable(v, /* is_global */ true)); | 
 |     if (!sem) { | 
 |         return nullptr; | 
 |     } | 
 |  | 
 |     for (auto* attr : v->attributes) { | 
 |         Mark(attr); | 
 |     } | 
 |  | 
 |     if (!validator_.NoDuplicateAttributes(v->attributes)) { | 
 |         return nullptr; | 
 |     } | 
 |  | 
 |     if (!validator_.GlobalVariable(sem, override_ids_)) { | 
 |         return nullptr; | 
 |     } | 
 |  | 
 |     // Track the pipeline-overridable constants that are transitively referenced by this variable. | 
 |     for (auto* var : transitively_referenced_overrides) { | 
 |         builder_->Sem().AddTransitivelyReferencedOverride(sem, var); | 
 |     } | 
 |     if (auto* arr = sem->Type()->UnwrapRef()->As<type::Array>()) { | 
 |         auto* refs = builder_->Sem().TransitivelyReferencedOverrides(arr); | 
 |         if (refs) { | 
 |             for (auto* var : *refs) { | 
 |                 builder_->Sem().AddTransitivelyReferencedOverride(sem, var); | 
 |             } | 
 |         } | 
 |     } | 
 |  | 
 |     return sem; | 
 | } | 
 |  | 
 | sem::Statement* Resolver::StaticAssert(const ast::StaticAssert* assertion) { | 
 |     ExprEvalStageConstraint constraint{sem::EvaluationStage::kConstant, "static assertion"}; | 
 |     TINT_SCOPED_ASSIGNMENT(expr_eval_stage_constraint_, constraint); | 
 |     auto* expr = Expression(assertion->condition); | 
 |     if (!expr) { | 
 |         return nullptr; | 
 |     } | 
 |     auto* cond = expr->ConstantValue(); | 
 |     if (auto* ty = cond->Type(); !ty->Is<type::Bool>()) { | 
 |         AddError( | 
 |             "static assertion condition must be a bool, got '" + builder_->FriendlyName(ty) + "'", | 
 |             assertion->condition->source); | 
 |         return nullptr; | 
 |     } | 
 |     if (!cond->ValueAs<bool>()) { | 
 |         AddError("static assertion failed", assertion->source); | 
 |         return nullptr; | 
 |     } | 
 |     auto* sem = | 
 |         builder_->create<sem::Statement>(assertion, current_compound_statement_, current_function_); | 
 |     builder_->Sem().Add(assertion, sem); | 
 |     return sem; | 
 | } | 
 |  | 
 | sem::Function* Resolver::Function(const ast::Function* decl) { | 
 |     uint32_t parameter_index = 0; | 
 |     utils::Hashmap<Symbol, Source, 8> parameter_names; | 
 |     utils::Vector<sem::Parameter*, 8> parameters; | 
 |  | 
 |     // Resolve all the parameters | 
 |     for (auto* param : decl->params) { | 
 |         Mark(param); | 
 |  | 
 |         {  // Check the parameter name is unique for the function | 
 |             if (auto added = parameter_names.Add(param->symbol, param->source); !added) { | 
 |                 auto name = builder_->Symbols().NameFor(param->symbol); | 
 |                 AddError("redefinition of parameter '" + name + "'", param->source); | 
 |                 AddNote("previous definition is here", *added.value); | 
 |                 return nullptr; | 
 |             } | 
 |         } | 
 |  | 
 |         auto* p = Parameter(param, parameter_index++); | 
 |         if (!p) { | 
 |             return nullptr; | 
 |         } | 
 |  | 
 |         if (!validator_.Parameter(decl, p)) { | 
 |             return nullptr; | 
 |         } | 
 |  | 
 |         parameters.Push(p); | 
 |  | 
 |         auto* p_ty = const_cast<type::Type*>(p->Type()); | 
 |         if (auto* str = p_ty->As<sem::Struct>()) { | 
 |             switch (decl->PipelineStage()) { | 
 |                 case ast::PipelineStage::kVertex: | 
 |                     str->AddUsage(type::PipelineStageUsage::kVertexInput); | 
 |                     break; | 
 |                 case ast::PipelineStage::kFragment: | 
 |                     str->AddUsage(type::PipelineStageUsage::kFragmentInput); | 
 |                     break; | 
 |                 case ast::PipelineStage::kCompute: | 
 |                     str->AddUsage(type::PipelineStageUsage::kComputeInput); | 
 |                     break; | 
 |                 case ast::PipelineStage::kNone: | 
 |                     break; | 
 |             } | 
 |         } | 
 |     } | 
 |  | 
 |     // Resolve the return type | 
 |     type::Type* return_type = nullptr; | 
 |     if (auto* ty = decl->return_type) { | 
 |         return_type = Type(ty); | 
 |         if (!return_type) { | 
 |             return nullptr; | 
 |         } | 
 |     } else { | 
 |         return_type = builder_->create<type::Void>(); | 
 |     } | 
 |  | 
 |     // Determine if the return type has a location | 
 |     std::optional<uint32_t> return_location; | 
 |     for (auto* attr : decl->return_type_attributes) { | 
 |         Mark(attr); | 
 |  | 
 |         if (auto* loc_attr = attr->As<ast::LocationAttribute>()) { | 
 |             auto value = LocationAttribute(loc_attr); | 
 |             if (!value) { | 
 |                 return nullptr; | 
 |             } | 
 |             return_location = value.Get(); | 
 |         } | 
 |     } | 
 |     if (!validator_.NoDuplicateAttributes(decl->attributes)) { | 
 |         return nullptr; | 
 |     } | 
 |  | 
 |     if (auto* str = return_type->As<sem::Struct>()) { | 
 |         if (!ApplyAddressSpaceUsageToType(ast::AddressSpace::kNone, str, decl->source)) { | 
 |             AddNote( | 
 |                 "while instantiating return type for " + builder_->Symbols().NameFor(decl->symbol), | 
 |                 decl->source); | 
 |             return nullptr; | 
 |         } | 
 |  | 
 |         switch (decl->PipelineStage()) { | 
 |             case ast::PipelineStage::kVertex: | 
 |                 str->AddUsage(type::PipelineStageUsage::kVertexOutput); | 
 |                 break; | 
 |             case ast::PipelineStage::kFragment: | 
 |                 str->AddUsage(type::PipelineStageUsage::kFragmentOutput); | 
 |                 break; | 
 |             case ast::PipelineStage::kCompute: | 
 |                 str->AddUsage(type::PipelineStageUsage::kComputeOutput); | 
 |                 break; | 
 |             case ast::PipelineStage::kNone: | 
 |                 break; | 
 |         } | 
 |     } | 
 |  | 
 |     auto* func = | 
 |         builder_->create<sem::Function>(decl, return_type, return_location, std::move(parameters)); | 
 |     builder_->Sem().Add(decl, func); | 
 |  | 
 |     TINT_SCOPED_ASSIGNMENT(current_function_, func); | 
 |  | 
 |     if (!WorkgroupSize(decl)) { | 
 |         return nullptr; | 
 |     } | 
 |  | 
 |     if (decl->IsEntryPoint()) { | 
 |         entry_points_.Push(func); | 
 |     } | 
 |  | 
 |     if (decl->body) { | 
 |         Mark(decl->body); | 
 |         if (current_compound_statement_) { | 
 |             TINT_ICE(Resolver, diagnostics_) | 
 |                 << "Resolver::Function() called with a current compound statement"; | 
 |             return nullptr; | 
 |         } | 
 |         auto* body = StatementScope(decl->body, builder_->create<sem::FunctionBlockStatement>(func), | 
 |                                     [&] { return Statements(decl->body->statements); }); | 
 |         if (!body) { | 
 |             return nullptr; | 
 |         } | 
 |         func->Behaviors() = body->Behaviors(); | 
 |         if (func->Behaviors().Contains(sem::Behavior::kReturn)) { | 
 |             // https://www.w3.org/TR/WGSL/#behaviors-rules | 
 |             // We assign a behavior to each function: it is its body’s behavior | 
 |             // (treating the body as a regular statement), with any "Return" replaced | 
 |             // by "Next". | 
 |             func->Behaviors().Remove(sem::Behavior::kReturn); | 
 |             func->Behaviors().Add(sem::Behavior::kNext); | 
 |         } | 
 |     } | 
 |  | 
 |     for (auto* attr : decl->attributes) { | 
 |         Mark(attr); | 
 |     } | 
 |  | 
 |     if (!validator_.NoDuplicateAttributes(decl->return_type_attributes)) { | 
 |         return nullptr; | 
 |     } | 
 |  | 
 |     auto stage = current_function_ ? current_function_->Declaration()->PipelineStage() | 
 |                                    : ast::PipelineStage::kNone; | 
 |     if (!validator_.Function(func, stage)) { | 
 |         return nullptr; | 
 |     } | 
 |  | 
 |     // If this is an entry point, mark all transitively called functions as being | 
 |     // used by this entry point. | 
 |     if (decl->IsEntryPoint()) { | 
 |         for (auto* f : func->TransitivelyCalledFunctions()) { | 
 |             const_cast<sem::Function*>(f)->AddAncestorEntryPoint(func); | 
 |         } | 
 |     } | 
 |  | 
 |     return func; | 
 | } | 
 |  | 
 | bool Resolver::WorkgroupSize(const ast::Function* func) { | 
 |     // Set work-group size defaults. | 
 |     sem::WorkgroupSize ws; | 
 |     for (size_t i = 0; i < 3; i++) { | 
 |         ws[i] = 1; | 
 |     } | 
 |  | 
 |     auto* attr = ast::GetAttribute<ast::WorkgroupAttribute>(func->attributes); | 
 |     if (!attr) { | 
 |         return true; | 
 |     } | 
 |  | 
 |     auto values = attr->Values(); | 
 |     utils::Vector<const sem::Expression*, 3> args; | 
 |     utils::Vector<const type::Type*, 3> arg_tys; | 
 |  | 
 |     constexpr const char* kErrBadExpr = | 
 |         "workgroup_size argument must be a constant or override-expression of type " | 
 |         "abstract-integer, i32 or u32"; | 
 |  | 
 |     for (size_t i = 0; i < 3; i++) { | 
 |         // Each argument to this attribute can either be a literal, an identifier for a module-scope | 
 |         // constants, a const-expression, or nullptr if not specified. | 
 |         auto* value = values[i]; | 
 |         if (!value) { | 
 |             break; | 
 |         } | 
 |         const auto* expr = Expression(value); | 
 |         if (!expr) { | 
 |             return false; | 
 |         } | 
 |         auto* ty = expr->Type(); | 
 |         if (!ty->IsAnyOf<type::I32, type::U32, type::AbstractInt>()) { | 
 |             AddError(kErrBadExpr, value->source); | 
 |             return false; | 
 |         } | 
 |  | 
 |         if (expr->Stage() != sem::EvaluationStage::kConstant && | 
 |             expr->Stage() != sem::EvaluationStage::kOverride) { | 
 |             AddError(kErrBadExpr, value->source); | 
 |             return false; | 
 |         } | 
 |  | 
 |         args.Push(expr); | 
 |         arg_tys.Push(ty); | 
 |     } | 
 |  | 
 |     auto* common_ty = type::Type::Common(arg_tys); | 
 |     if (!common_ty) { | 
 |         AddError("workgroup_size arguments must be of the same type, either i32 or u32", | 
 |                  attr->source); | 
 |         return false; | 
 |     } | 
 |  | 
 |     // If all arguments are abstract-integers, then materialize to i32. | 
 |     if (common_ty->Is<type::AbstractInt>()) { | 
 |         common_ty = builder_->create<type::I32>(); | 
 |     } | 
 |  | 
 |     for (size_t i = 0; i < args.Length(); i++) { | 
 |         auto* materialized = Materialize(args[i], common_ty); | 
 |         if (!materialized) { | 
 |             return false; | 
 |         } | 
 |         if (auto* value = materialized->ConstantValue()) { | 
 |             if (value->ValueAs<AInt>() < 1) { | 
 |                 AddError("workgroup_size argument must be at least 1", values[i]->source); | 
 |                 return false; | 
 |             } | 
 |             ws[i] = value->ValueAs<u32>(); | 
 |         } else { | 
 |             ws[i] = std::nullopt; | 
 |         } | 
 |     } | 
 |  | 
 |     uint64_t total_size = static_cast<uint64_t>(ws[0].value_or(1)); | 
 |     for (size_t i = 1; i < 3; i++) { | 
 |         total_size *= static_cast<uint64_t>(ws[i].value_or(1)); | 
 |         if (total_size > 0xffffffff) { | 
 |             AddError("total workgroup grid size cannot exceed 0xffffffff", values[i]->source); | 
 |             return false; | 
 |         } | 
 |     } | 
 |  | 
 |     current_function_->SetWorkgroupSize(std::move(ws)); | 
 |     return true; | 
 | } | 
 |  | 
 | bool Resolver::Statements(utils::VectorRef<const ast::Statement*> stmts) { | 
 |     sem::Behaviors behaviors{sem::Behavior::kNext}; | 
 |  | 
 |     bool reachable = true; | 
 |     for (auto* stmt : stmts) { | 
 |         Mark(stmt); | 
 |         auto* sem = Statement(stmt); | 
 |         if (!sem) { | 
 |             return false; | 
 |         } | 
 |         // s1 s2:(B1∖{Next}) ∪ B2 | 
 |         sem->SetIsReachable(reachable); | 
 |         if (reachable) { | 
 |             behaviors = (behaviors - sem::Behavior::kNext) + sem->Behaviors(); | 
 |         } | 
 |         reachable = reachable && sem->Behaviors().Contains(sem::Behavior::kNext); | 
 |     } | 
 |  | 
 |     current_statement_->Behaviors() = behaviors; | 
 |  | 
 |     if (!validator_.Statements(stmts)) { | 
 |         return false; | 
 |     } | 
 |  | 
 |     return true; | 
 | } | 
 |  | 
 | sem::Statement* Resolver::Statement(const ast::Statement* stmt) { | 
 |     return Switch( | 
 |         stmt, | 
 |         // Compound statements. These create their own sem::CompoundStatement | 
 |         // bindings. | 
 |         [&](const ast::BlockStatement* b) { return BlockStatement(b); }, | 
 |         [&](const ast::ForLoopStatement* l) { return ForLoopStatement(l); }, | 
 |         [&](const ast::LoopStatement* l) { return LoopStatement(l); }, | 
 |         [&](const ast::WhileStatement* w) { return WhileStatement(w); }, | 
 |         [&](const ast::IfStatement* i) { return IfStatement(i); }, | 
 |         [&](const ast::SwitchStatement* s) { return SwitchStatement(s); }, | 
 |  | 
 |         // Non-Compound statements | 
 |         [&](const ast::AssignmentStatement* a) { return AssignmentStatement(a); }, | 
 |         [&](const ast::BreakStatement* b) { return BreakStatement(b); }, | 
 |         [&](const ast::BreakIfStatement* b) { return BreakIfStatement(b); }, | 
 |         [&](const ast::CallStatement* c) { return CallStatement(c); }, | 
 |         [&](const ast::CompoundAssignmentStatement* c) { return CompoundAssignmentStatement(c); }, | 
 |         [&](const ast::ContinueStatement* c) { return ContinueStatement(c); }, | 
 |         [&](const ast::DiscardStatement* d) { return DiscardStatement(d); }, | 
 |         [&](const ast::IncrementDecrementStatement* i) { return IncrementDecrementStatement(i); }, | 
 |         [&](const ast::ReturnStatement* r) { return ReturnStatement(r); }, | 
 |         [&](const ast::VariableDeclStatement* v) { return VariableDeclStatement(v); }, | 
 |         [&](const ast::StaticAssert* sa) { return StaticAssert(sa); }, | 
 |  | 
 |         // Error cases | 
 |         [&](const ast::CaseStatement*) { | 
 |             AddError("case statement can only be used inside a switch statement", stmt->source); | 
 |             return nullptr; | 
 |         }, | 
 |         [&](Default) { | 
 |             AddError("unknown statement type: " + std::string(stmt->TypeInfo().name), stmt->source); | 
 |             return nullptr; | 
 |         }); | 
 | } | 
 |  | 
 | sem::CaseStatement* Resolver::CaseStatement(const ast::CaseStatement* stmt, const type::Type* ty) { | 
 |     auto* sem = | 
 |         builder_->create<sem::CaseStatement>(stmt, current_compound_statement_, current_function_); | 
 |     return StatementScope(stmt, sem, [&] { | 
 |         sem->Selectors().reserve(stmt->selectors.Length()); | 
 |         for (auto* sel : stmt->selectors) { | 
 |             Mark(sel); | 
 |  | 
 |             ExprEvalStageConstraint constraint{sem::EvaluationStage::kConstant, "case selector"}; | 
 |             TINT_SCOPED_ASSIGNMENT(expr_eval_stage_constraint_, constraint); | 
 |  | 
 |             const constant::Value* const_value = nullptr; | 
 |             if (!sel->IsDefault()) { | 
 |                 // The sem statement was created in the switch when attempting to determine the | 
 |                 // common type. | 
 |                 auto* materialized = Materialize(sem_.Get(sel->expr), ty); | 
 |                 if (!materialized) { | 
 |                     return false; | 
 |                 } | 
 |                 if (!materialized->Type()->IsAnyOf<type::I32, type::U32>()) { | 
 |                     AddError("case selector must be an i32 or u32 value", sel->source); | 
 |                     return false; | 
 |                 } | 
 |                 const_value = materialized->ConstantValue(); | 
 |                 if (!const_value) { | 
 |                     AddError("case selector must be a constant expression", sel->source); | 
 |                     return false; | 
 |                 } | 
 |             } | 
 |  | 
 |             sem->Selectors().emplace_back(builder_->create<sem::CaseSelector>(sel, const_value)); | 
 |         } | 
 |  | 
 |         Mark(stmt->body); | 
 |         auto* body = BlockStatement(stmt->body); | 
 |         if (!body) { | 
 |             return false; | 
 |         } | 
 |         sem->SetBlock(body); | 
 |         sem->Behaviors() = body->Behaviors(); | 
 |         return true; | 
 |     }); | 
 | } | 
 |  | 
 | sem::IfStatement* Resolver::IfStatement(const ast::IfStatement* stmt) { | 
 |     auto* sem = | 
 |         builder_->create<sem::IfStatement>(stmt, current_compound_statement_, current_function_); | 
 |     return StatementScope(stmt, sem, [&] { | 
 |         auto* cond = Expression(stmt->condition); | 
 |         if (!cond) { | 
 |             return false; | 
 |         } | 
 |         sem->SetCondition(cond); | 
 |         sem->Behaviors() = cond->Behaviors(); | 
 |         sem->Behaviors().Remove(sem::Behavior::kNext); | 
 |  | 
 |         RegisterLoadIfNeeded(cond); | 
 |  | 
 |         Mark(stmt->body); | 
 |         auto* body = builder_->create<sem::BlockStatement>(stmt->body, current_compound_statement_, | 
 |                                                            current_function_); | 
 |         if (!StatementScope(stmt->body, body, [&] { return Statements(stmt->body->statements); })) { | 
 |             return false; | 
 |         } | 
 |         sem->Behaviors().Add(body->Behaviors()); | 
 |  | 
 |         if (stmt->else_statement) { | 
 |             Mark(stmt->else_statement); | 
 |             auto* else_sem = Statement(stmt->else_statement); | 
 |             if (!else_sem) { | 
 |                 return false; | 
 |             } | 
 |             sem->Behaviors().Add(else_sem->Behaviors()); | 
 |         } else { | 
 |             // https://www.w3.org/TR/WGSL/#behaviors-rules | 
 |             // if statements without an else branch are treated as if they had an | 
 |             // empty else branch (which adds Next to their behavior) | 
 |             sem->Behaviors().Add(sem::Behavior::kNext); | 
 |         } | 
 |  | 
 |         return validator_.IfStatement(sem); | 
 |     }); | 
 | } | 
 |  | 
 | sem::BlockStatement* Resolver::BlockStatement(const ast::BlockStatement* stmt) { | 
 |     auto* sem = builder_->create<sem::BlockStatement>( | 
 |         stmt->As<ast::BlockStatement>(), current_compound_statement_, current_function_); | 
 |     return StatementScope(stmt, sem, [&] { return Statements(stmt->statements); }); | 
 | } | 
 |  | 
 | sem::LoopStatement* Resolver::LoopStatement(const ast::LoopStatement* stmt) { | 
 |     auto* sem = | 
 |         builder_->create<sem::LoopStatement>(stmt, current_compound_statement_, current_function_); | 
 |     return StatementScope(stmt, sem, [&] { | 
 |         Mark(stmt->body); | 
 |  | 
 |         auto* body = builder_->create<sem::LoopBlockStatement>( | 
 |             stmt->body, current_compound_statement_, current_function_); | 
 |         return StatementScope(stmt->body, body, [&] { | 
 |             if (!Statements(stmt->body->statements)) { | 
 |                 return false; | 
 |             } | 
 |             auto& behaviors = sem->Behaviors(); | 
 |             behaviors = body->Behaviors(); | 
 |  | 
 |             if (stmt->continuing) { | 
 |                 Mark(stmt->continuing); | 
 |                 auto* continuing = StatementScope( | 
 |                     stmt->continuing, | 
 |                     builder_->create<sem::LoopContinuingBlockStatement>( | 
 |                         stmt->continuing, current_compound_statement_, current_function_), | 
 |                     [&] { return Statements(stmt->continuing->statements); }); | 
 |                 if (!continuing) { | 
 |                     return false; | 
 |                 } | 
 |                 behaviors.Add(continuing->Behaviors()); | 
 |             } | 
 |  | 
 |             if (behaviors.Contains(sem::Behavior::kBreak)) {  // Does the loop exit? | 
 |                 behaviors.Add(sem::Behavior::kNext); | 
 |             } else { | 
 |                 behaviors.Remove(sem::Behavior::kNext); | 
 |             } | 
 |             behaviors.Remove(sem::Behavior::kBreak, sem::Behavior::kContinue); | 
 |  | 
 |             return validator_.LoopStatement(sem); | 
 |         }); | 
 |     }); | 
 | } | 
 |  | 
 | sem::ForLoopStatement* Resolver::ForLoopStatement(const ast::ForLoopStatement* stmt) { | 
 |     auto* sem = builder_->create<sem::ForLoopStatement>(stmt, current_compound_statement_, | 
 |                                                         current_function_); | 
 |     return StatementScope(stmt, sem, [&] { | 
 |         auto& behaviors = sem->Behaviors(); | 
 |         if (auto* initializer = stmt->initializer) { | 
 |             Mark(initializer); | 
 |             auto* init = Statement(initializer); | 
 |             if (!init) { | 
 |                 return false; | 
 |             } | 
 |             behaviors.Add(init->Behaviors()); | 
 |         } | 
 |  | 
 |         if (auto* cond_expr = stmt->condition) { | 
 |             auto* cond = Expression(cond_expr); | 
 |             if (!cond) { | 
 |                 return false; | 
 |             } | 
 |             sem->SetCondition(cond); | 
 |             behaviors.Add(cond->Behaviors()); | 
 |  | 
 |             RegisterLoadIfNeeded(cond); | 
 |         } | 
 |  | 
 |         if (auto* continuing = stmt->continuing) { | 
 |             Mark(continuing); | 
 |             auto* cont = Statement(continuing); | 
 |             if (!cont) { | 
 |                 return false; | 
 |             } | 
 |             behaviors.Add(cont->Behaviors()); | 
 |         } | 
 |  | 
 |         Mark(stmt->body); | 
 |  | 
 |         auto* body = builder_->create<sem::LoopBlockStatement>( | 
 |             stmt->body, current_compound_statement_, current_function_); | 
 |         if (!StatementScope(stmt->body, body, [&] { return Statements(stmt->body->statements); })) { | 
 |             return false; | 
 |         } | 
 |  | 
 |         behaviors.Add(body->Behaviors()); | 
 |         if (stmt->condition || behaviors.Contains(sem::Behavior::kBreak)) {  // Does the loop exit? | 
 |             behaviors.Add(sem::Behavior::kNext); | 
 |         } else { | 
 |             behaviors.Remove(sem::Behavior::kNext); | 
 |         } | 
 |         behaviors.Remove(sem::Behavior::kBreak, sem::Behavior::kContinue); | 
 |  | 
 |         return validator_.ForLoopStatement(sem); | 
 |     }); | 
 | } | 
 |  | 
 | sem::WhileStatement* Resolver::WhileStatement(const ast::WhileStatement* stmt) { | 
 |     auto* sem = | 
 |         builder_->create<sem::WhileStatement>(stmt, current_compound_statement_, current_function_); | 
 |     return StatementScope(stmt, sem, [&] { | 
 |         auto& behaviors = sem->Behaviors(); | 
 |  | 
 |         auto* cond = Expression(stmt->condition); | 
 |         if (!cond) { | 
 |             return false; | 
 |         } | 
 |         sem->SetCondition(cond); | 
 |         behaviors.Add(cond->Behaviors()); | 
 |  | 
 |         RegisterLoadIfNeeded(cond); | 
 |  | 
 |         Mark(stmt->body); | 
 |  | 
 |         auto* body = builder_->create<sem::LoopBlockStatement>( | 
 |             stmt->body, current_compound_statement_, current_function_); | 
 |         if (!StatementScope(stmt->body, body, [&] { return Statements(stmt->body->statements); })) { | 
 |             return false; | 
 |         } | 
 |  | 
 |         behaviors.Add(body->Behaviors()); | 
 |         // Always consider the while as having a 'next' behaviour because it has | 
 |         // a condition. We don't check if the condition will terminate but it isn't | 
 |         // valid to have an infinite loop in a WGSL program, so a non-terminating | 
 |         // condition is already an invalid program. | 
 |         behaviors.Add(sem::Behavior::kNext); | 
 |         behaviors.Remove(sem::Behavior::kBreak, sem::Behavior::kContinue); | 
 |  | 
 |         return validator_.WhileStatement(sem); | 
 |     }); | 
 | } | 
 |  | 
 | sem::Expression* Resolver::Expression(const ast::Expression* root) { | 
 |     utils::Vector<const ast::Expression*, 64> sorted; | 
 |     constexpr size_t kMaxExpressionDepth = 512U; | 
 |     bool failed = false; | 
 |     if (!ast::TraverseExpressions<ast::TraverseOrder::RightToLeft>( | 
 |             root, diagnostics_, [&](const ast::Expression* expr, size_t depth) { | 
 |                 if (depth > kMaxExpressionDepth) { | 
 |                     AddError( | 
 |                         "reached max expression depth of " + std::to_string(kMaxExpressionDepth), | 
 |                         expr->source); | 
 |                     failed = true; | 
 |                     return ast::TraverseAction::Stop; | 
 |                 } | 
 |                 if (!Mark(expr)) { | 
 |                     failed = true; | 
 |                     return ast::TraverseAction::Stop; | 
 |                 } | 
 |                 if (auto* binary = expr->As<ast::BinaryExpression>(); | 
 |                     binary && binary->IsLogical()) { | 
 |                     // Store potential const-eval short-circuit pair | 
 |                     logical_binary_lhs_to_parent_.Add(binary->lhs, binary); | 
 |                 } | 
 |                 sorted.Push(expr); | 
 |                 return ast::TraverseAction::Descend; | 
 |             })) { | 
 |         return nullptr; | 
 |     } | 
 |  | 
 |     if (failed) { | 
 |         return nullptr; | 
 |     } | 
 |  | 
 |     for (auto* expr : utils::Reverse(sorted)) { | 
 |         auto* sem_expr = Switch( | 
 |             expr, | 
 |             [&](const ast::IndexAccessorExpression* array) -> sem::Expression* { | 
 |                 return IndexAccessor(array); | 
 |             }, | 
 |             [&](const ast::BinaryExpression* bin_op) -> sem::Expression* { return Binary(bin_op); }, | 
 |             [&](const ast::BitcastExpression* bitcast) -> sem::Expression* { | 
 |                 return Bitcast(bitcast); | 
 |             }, | 
 |             [&](const ast::CallExpression* call) -> sem::Expression* { return Call(call); }, | 
 |             [&](const ast::IdentifierExpression* ident) -> sem::Expression* { | 
 |                 return Identifier(ident); | 
 |             }, | 
 |             [&](const ast::LiteralExpression* literal) -> sem::Expression* { | 
 |                 return Literal(literal); | 
 |             }, | 
 |             [&](const ast::MemberAccessorExpression* member) -> sem::Expression* { | 
 |                 return MemberAccessor(member); | 
 |             }, | 
 |             [&](const ast::UnaryOpExpression* unary) -> sem::Expression* { return UnaryOp(unary); }, | 
 |             [&](const ast::PhonyExpression*) -> sem::Expression* { | 
 |                 return builder_->create<sem::Expression>(expr, builder_->create<type::Void>(), | 
 |                                                          sem::EvaluationStage::kRuntime, | 
 |                                                          current_statement_, | 
 |                                                          /* constant_value */ nullptr, | 
 |                                                          /* has_side_effects */ false); | 
 |             }, | 
 |             [&](Default) { | 
 |                 TINT_ICE(Resolver, diagnostics_) | 
 |                     << "unhandled expression type: " << expr->TypeInfo().name; | 
 |                 return nullptr; | 
 |             }); | 
 |         if (!sem_expr) { | 
 |             return nullptr; | 
 |         } | 
 |  | 
 |         if (auto* constraint = expr_eval_stage_constraint_.constraint) { | 
 |             if (!validator_.EvaluationStage(sem_expr, expr_eval_stage_constraint_.stage, | 
 |                                             constraint)) { | 
 |                 return nullptr; | 
 |             } | 
 |         } | 
 |  | 
 |         builder_->Sem().Add(expr, sem_expr); | 
 |         if (expr == root) { | 
 |             return sem_expr; | 
 |         } | 
 |  | 
 |         // If we just processed the lhs of a constexpr logical binary expression, mark the rhs for | 
 |         // short-circuiting. | 
 |         if (sem_expr->ConstantValue()) { | 
 |             if (auto binary = logical_binary_lhs_to_parent_.Find(expr)) { | 
 |                 const bool lhs_is_true = sem_expr->ConstantValue()->ValueAs<bool>(); | 
 |                 if (((*binary)->IsLogicalAnd() && !lhs_is_true) || | 
 |                     ((*binary)->IsLogicalOr() && lhs_is_true)) { | 
 |                     // Mark entire expression tree to not const-evaluate | 
 |                     auto r = ast::TraverseExpressions(  // | 
 |                         (*binary)->rhs, diagnostics_, [&](const ast::Expression* e) { | 
 |                             skip_const_eval_.Add(e); | 
 |                             return ast::TraverseAction::Descend; | 
 |                         }); | 
 |                     if (!r) { | 
 |                         return nullptr; | 
 |                     } | 
 |                 } | 
 |             } | 
 |         } | 
 |     } | 
 |  | 
 |     TINT_ICE(Resolver, diagnostics_) << "Expression() did not find root node"; | 
 |     return nullptr; | 
 | } | 
 |  | 
 | void Resolver::RegisterLoadIfNeeded(const sem::Expression* expr) { | 
 |     if (!expr) { | 
 |         return; | 
 |     } | 
 |     if (!expr->Type()->Is<type::Reference>()) { | 
 |         return; | 
 |     } | 
 |     if (!current_function_) { | 
 |         // There is currently no situation where the Load Rule can be invoked outside of a function. | 
 |         return; | 
 |     } | 
 |     auto& info = alias_analysis_infos_[current_function_]; | 
 |     Switch( | 
 |         expr->RootIdentifier(), | 
 |         [&](const sem::GlobalVariable* global) { | 
 |             info.module_scope_reads.insert({global, expr}); | 
 |         }, | 
 |         [&](const sem::Parameter* param) { info.parameter_reads.insert(param); }); | 
 | } | 
 |  | 
 | void Resolver::RegisterStore(const sem::Expression* expr) { | 
 |     auto& info = alias_analysis_infos_[current_function_]; | 
 |     Switch( | 
 |         expr->RootIdentifier(), | 
 |         [&](const sem::GlobalVariable* global) { | 
 |             info.module_scope_writes.insert({global, expr}); | 
 |         }, | 
 |         [&](const sem::Parameter* param) { info.parameter_writes.insert(param); }); | 
 | } | 
 |  | 
 | bool Resolver::AliasAnalysis(const sem::Call* call) { | 
 |     auto* target = call->Target()->As<sem::Function>(); | 
 |     if (!target) { | 
 |         return true; | 
 |     } | 
 |     if (validator_.IsValidationDisabled(target->Declaration()->attributes, | 
 |                                         ast::DisabledValidation::kIgnorePointerAliasing)) { | 
 |         return true; | 
 |     } | 
 |  | 
 |     // Helper to generate an aliasing error diagnostic. | 
 |     struct Alias { | 
 |         const sem::Expression* expr;          // the "other expression" | 
 |         enum { Argument, ModuleScope } type;  // the type of the "other" expression | 
 |         std::string access;                   // the access performed for the "other" expression | 
 |     }; | 
 |     auto make_error = [&](const sem::Expression* arg, Alias&& var) { | 
 |         // TODO(crbug.com/tint/1675): Switch to error and return false after deprecation period. | 
 |         AddWarning("invalid aliased pointer argument", arg->Declaration()->source); | 
 |         switch (var.type) { | 
 |             case Alias::Argument: | 
 |                 AddNote("aliases with another argument passed here", | 
 |                         var.expr->Declaration()->source); | 
 |                 break; | 
 |             case Alias::ModuleScope: { | 
 |                 auto* func = var.expr->Stmt()->Function(); | 
 |                 auto func_name = builder_->Symbols().NameFor(func->Declaration()->symbol); | 
 |                 AddNote( | 
 |                     "aliases with module-scope variable " + var.access + " in '" + func_name + "'", | 
 |                     var.expr->Declaration()->source); | 
 |                 break; | 
 |             } | 
 |         } | 
 |         return true; | 
 |     }; | 
 |  | 
 |     auto& args = call->Arguments(); | 
 |     auto& target_info = alias_analysis_infos_[target]; | 
 |     auto& caller_info = alias_analysis_infos_[current_function_]; | 
 |  | 
 |     // Track the set of root identifiers that are read and written by arguments passed in this call. | 
 |     std::unordered_map<const sem::Variable*, const sem::Expression*> arg_reads; | 
 |     std::unordered_map<const sem::Variable*, const sem::Expression*> arg_writes; | 
 |     for (size_t i = 0; i < args.Length(); i++) { | 
 |         auto* arg = args[i]; | 
 |         if (!arg->Type()->Is<type::Pointer>()) { | 
 |             continue; | 
 |         } | 
 |  | 
 |         auto* root = arg->RootIdentifier(); | 
 |         if (target_info.parameter_writes.count(target->Parameters()[i])) { | 
 |             // Arguments that are written to can alias with any other argument or module-scope | 
 |             // variable access. | 
 |             if (arg_writes.count(root)) { | 
 |                 return make_error(arg, {arg_writes.at(root), Alias::Argument, "write"}); | 
 |             } | 
 |             if (arg_reads.count(root)) { | 
 |                 return make_error(arg, {arg_reads.at(root), Alias::Argument, "read"}); | 
 |             } | 
 |             if (target_info.module_scope_reads.count(root)) { | 
 |                 return make_error( | 
 |                     arg, {target_info.module_scope_reads.at(root), Alias::ModuleScope, "read"}); | 
 |             } | 
 |             if (target_info.module_scope_writes.count(root)) { | 
 |                 return make_error( | 
 |                     arg, {target_info.module_scope_writes.at(root), Alias::ModuleScope, "write"}); | 
 |             } | 
 |             arg_writes.insert({root, arg}); | 
 |  | 
 |             // Propagate the write access to the caller. | 
 |             Switch( | 
 |                 root, | 
 |                 [&](const sem::GlobalVariable* global) { | 
 |                     caller_info.module_scope_writes.insert({global, arg}); | 
 |                 }, | 
 |                 [&](const sem::Parameter* param) { caller_info.parameter_writes.insert(param); }); | 
 |         } else if (target_info.parameter_reads.count(target->Parameters()[i])) { | 
 |             // Arguments that are read from can alias with arguments or module-scope variables that | 
 |             // are written to. | 
 |             if (arg_writes.count(root)) { | 
 |                 return make_error(arg, {arg_writes.at(root), Alias::Argument, "write"}); | 
 |             } | 
 |             if (target_info.module_scope_writes.count(root)) { | 
 |                 return make_error( | 
 |                     arg, {target_info.module_scope_writes.at(root), Alias::ModuleScope, "write"}); | 
 |             } | 
 |             arg_reads.insert({root, arg}); | 
 |  | 
 |             // Propagate the read access to the caller. | 
 |             Switch( | 
 |                 root, | 
 |                 [&](const sem::GlobalVariable* global) { | 
 |                     caller_info.module_scope_reads.insert({global, arg}); | 
 |                 }, | 
 |                 [&](const sem::Parameter* param) { caller_info.parameter_reads.insert(param); }); | 
 |         } | 
 |     } | 
 |  | 
 |     // Propagate module-scope variable uses to the caller. | 
 |     for (auto read : target_info.module_scope_reads) { | 
 |         caller_info.module_scope_reads.insert({read.first, read.second}); | 
 |     } | 
 |     for (auto write : target_info.module_scope_writes) { | 
 |         caller_info.module_scope_writes.insert({write.first, write.second}); | 
 |     } | 
 |  | 
 |     return true; | 
 | } | 
 |  | 
 | const type::Type* Resolver::ConcreteType(const type::Type* ty, | 
 |                                          const type::Type* target_ty, | 
 |                                          const Source& source) { | 
 |     auto i32 = [&] { return builder_->create<type::I32>(); }; | 
 |     auto f32 = [&] { return builder_->create<type::F32>(); }; | 
 |     auto i32v = [&](uint32_t width) { return builder_->create<type::Vector>(i32(), width); }; | 
 |     auto f32v = [&](uint32_t width) { return builder_->create<type::Vector>(f32(), width); }; | 
 |     auto f32m = [&](uint32_t columns, uint32_t rows) { | 
 |         return builder_->create<type::Matrix>(f32v(rows), columns); | 
 |     }; | 
 |  | 
 |     return Switch( | 
 |         ty,  // | 
 |         [&](const type::AbstractInt*) { return target_ty ? target_ty : i32(); }, | 
 |         [&](const type::AbstractFloat*) { return target_ty ? target_ty : f32(); }, | 
 |         [&](const type::Vector* v) { | 
 |             return Switch( | 
 |                 v->type(),  // | 
 |                 [&](const type::AbstractInt*) { return target_ty ? target_ty : i32v(v->Width()); }, | 
 |                 [&](const type::AbstractFloat*) { | 
 |                     return target_ty ? target_ty : f32v(v->Width()); | 
 |                 }); | 
 |         }, | 
 |         [&](const type::Matrix* m) { | 
 |             return Switch(m->type(),  // | 
 |                           [&](const type::AbstractFloat*) { | 
 |                               return target_ty ? target_ty : f32m(m->columns(), m->rows()); | 
 |                           }); | 
 |         }, | 
 |         [&](const type::Array* a) -> const type::Type* { | 
 |             const type::Type* target_el_ty = nullptr; | 
 |             if (auto* target_arr_ty = As<type::Array>(target_ty)) { | 
 |                 target_el_ty = target_arr_ty->ElemType(); | 
 |             } | 
 |             if (auto* el_ty = ConcreteType(a->ElemType(), target_el_ty, source)) { | 
 |                 return Array(source, source, el_ty, a->Count(), /* explicit_stride */ 0); | 
 |             } | 
 |             return nullptr; | 
 |         }, | 
 |         [&](const sem::Struct* s) -> const type::Type* { | 
 |             if (auto tys = s->ConcreteTypes(); !tys.IsEmpty()) { | 
 |                 return target_ty ? target_ty : tys[0]; | 
 |             } | 
 |             return nullptr; | 
 |         }); | 
 | } | 
 |  | 
 | const sem::Expression* Resolver::Materialize(const sem::Expression* expr, | 
 |                                              const type::Type* target_type /* = nullptr */) { | 
 |     if (!expr) { | 
 |         // Allow for Materialize(Expression(blah)), where failures pass through Materialize() | 
 |         return nullptr; | 
 |     } | 
 |  | 
 |     auto* decl = expr->Declaration(); | 
 |  | 
 |     auto* concrete_ty = ConcreteType(expr->Type(), target_type, decl->source); | 
 |     if (!concrete_ty) { | 
 |         return expr;  // Does not require materialization | 
 |     } | 
 |  | 
 |     auto* src_ty = expr->Type(); | 
 |     if (!validator_.Materialize(concrete_ty, src_ty, decl->source)) { | 
 |         return nullptr; | 
 |     } | 
 |  | 
 |     const constant::Value* materialized_val = nullptr; | 
 |     if (!skip_const_eval_.Contains(decl)) { | 
 |         auto expr_val = expr->ConstantValue(); | 
 |         if (!expr_val) { | 
 |             TINT_ICE(Resolver, builder_->Diagnostics()) | 
 |                 << decl->source << "Materialize(" << decl->TypeInfo().name | 
 |                 << ") called on expression with no constant value"; | 
 |             return nullptr; | 
 |         } | 
 |  | 
 |         auto val = const_eval_.Convert(concrete_ty, expr_val, decl->source); | 
 |         if (!val) { | 
 |             // Convert() has already failed and raised an diagnostic error. | 
 |             return nullptr; | 
 |         } | 
 |         materialized_val = val.Get(); | 
 |         if (!materialized_val) { | 
 |             TINT_ICE(Resolver, builder_->Diagnostics()) | 
 |                 << decl->source << "ConvertValue(" << builder_->FriendlyName(expr_val->Type()) | 
 |                 << " -> " << builder_->FriendlyName(concrete_ty) << ") returned invalid value"; | 
 |             return nullptr; | 
 |         } | 
 |     } | 
 |  | 
 |     auto* m = | 
 |         builder_->create<sem::Materialize>(expr, current_statement_, concrete_ty, materialized_val); | 
 |     m->Behaviors() = expr->Behaviors(); | 
 |     builder_->Sem().Replace(decl, m); | 
 |     return m; | 
 | } | 
 |  | 
 | template <size_t N> | 
 | bool Resolver::MaybeMaterializeArguments(utils::Vector<const sem::Expression*, N>& args, | 
 |                                          const sem::CallTarget* target) { | 
 |     for (size_t i = 0, n = std::min(args.Length(), target->Parameters().Length()); i < n; i++) { | 
 |         const auto* param_ty = target->Parameters()[i]->Type(); | 
 |         if (ShouldMaterializeArgument(param_ty)) { | 
 |             auto* materialized = Materialize(args[i], param_ty); | 
 |             if (!materialized) { | 
 |                 return false; | 
 |             } | 
 |             args[i] = materialized; | 
 |         } | 
 |     } | 
 |     return true; | 
 | } | 
 |  | 
 | bool Resolver::ShouldMaterializeArgument(const type::Type* parameter_ty) const { | 
 |     const auto* param_el_ty = type::Type::DeepestElementOf(parameter_ty); | 
 |     return param_el_ty && !param_el_ty->Is<type::AbstractNumeric>(); | 
 | } | 
 |  | 
 | bool Resolver::Convert(const constant::Value*& c, | 
 |                        const type::Type* target_ty, | 
 |                        const Source& source) { | 
 |     auto r = const_eval_.Convert(target_ty, c, source); | 
 |     if (!r) { | 
 |         return false; | 
 |     } | 
 |     c = r.Get(); | 
 |     return true; | 
 | } | 
 |  | 
 | template <size_t N> | 
 | utils::Result<utils::Vector<const constant::Value*, N>> Resolver::ConvertArguments( | 
 |     const utils::Vector<const sem::Expression*, N>& args, | 
 |     const sem::CallTarget* target) { | 
 |     auto const_args = utils::Transform(args, [](auto* arg) { return arg->ConstantValue(); }); | 
 |     for (size_t i = 0, n = std::min(args.Length(), target->Parameters().Length()); i < n; i++) { | 
 |         if (!Convert(const_args[i], target->Parameters()[i]->Type(), | 
 |                      args[i]->Declaration()->source)) { | 
 |             return utils::Failure; | 
 |         } | 
 |     } | 
 |     return const_args; | 
 | } | 
 |  | 
 | sem::Expression* Resolver::IndexAccessor(const ast::IndexAccessorExpression* expr) { | 
 |     auto* idx = Materialize(sem_.Get(expr->index)); | 
 |     if (!idx) { | 
 |         return nullptr; | 
 |     } | 
 |     const auto* obj = sem_.Get(expr->object); | 
 |     if (idx->Stage() != sem::EvaluationStage::kConstant) { | 
 |         // If the index is non-constant, then the resulting expression is non-constant, so we'll | 
 |         // have to materialize the object. For example, consider: | 
 |         //     vec2(1, 2)[runtime-index] | 
 |         obj = Materialize(obj); | 
 |     } | 
 |     RegisterLoadIfNeeded(idx); | 
 |     if (!obj) { | 
 |         return nullptr; | 
 |     } | 
 |     auto* obj_raw_ty = obj->Type(); | 
 |     auto* obj_ty = obj_raw_ty->UnwrapRef(); | 
 |     auto* ty = Switch( | 
 |         obj_ty,  // | 
 |         [&](const type::Array* arr) { return arr->ElemType(); }, | 
 |         [&](const type::Vector* vec) { return vec->type(); }, | 
 |         [&](const type::Matrix* mat) { | 
 |             return builder_->create<type::Vector>(mat->type(), mat->rows()); | 
 |         }, | 
 |         [&](Default) { | 
 |             AddError("cannot index type '" + sem_.TypeNameOf(obj_ty) + "'", expr->source); | 
 |             return nullptr; | 
 |         }); | 
 |     if (ty == nullptr) { | 
 |         return nullptr; | 
 |     } | 
 |  | 
 |     auto* idx_ty = idx->Type()->UnwrapRef(); | 
 |     if (!idx_ty->IsAnyOf<type::I32, type::U32>()) { | 
 |         AddError("index must be of type 'i32' or 'u32', found: '" + sem_.TypeNameOf(idx_ty) + "'", | 
 |                  idx->Declaration()->source); | 
 |         return nullptr; | 
 |     } | 
 |  | 
 |     // If we're extracting from a reference, we return a reference. | 
 |     if (auto* ref = obj_raw_ty->As<type::Reference>()) { | 
 |         ty = builder_->create<type::Reference>(ty, ref->AddressSpace(), ref->Access()); | 
 |     } | 
 |  | 
 |     const constant::Value* val = nullptr; | 
 |     auto stage = sem::EarliestStage(obj->Stage(), idx->Stage()); | 
 |     if (stage == sem::EvaluationStage::kConstant && skip_const_eval_.Contains(expr)) { | 
 |         stage = sem::EvaluationStage::kNotEvaluated; | 
 |     } else { | 
 |         if (auto r = const_eval_.Index(obj, idx)) { | 
 |             val = r.Get(); | 
 |         } else { | 
 |             return nullptr; | 
 |         } | 
 |     } | 
 |     bool has_side_effects = idx->HasSideEffects() || obj->HasSideEffects(); | 
 |     auto* sem = builder_->create<sem::IndexAccessorExpression>( | 
 |         expr, ty, stage, obj, idx, current_statement_, std::move(val), has_side_effects, | 
 |         obj->RootIdentifier()); | 
 |     sem->Behaviors() = idx->Behaviors() + obj->Behaviors(); | 
 |     return sem; | 
 | } | 
 |  | 
 | sem::Expression* Resolver::Bitcast(const ast::BitcastExpression* expr) { | 
 |     auto* inner = Materialize(sem_.Get(expr->expr)); | 
 |     if (!inner) { | 
 |         return nullptr; | 
 |     } | 
 |     auto* ty = Type(expr->type); | 
 |     if (!ty) { | 
 |         return nullptr; | 
 |     } | 
 |  | 
 |     RegisterLoadIfNeeded(inner); | 
 |  | 
 |     const constant::Value* val = nullptr; | 
 |     // TODO(crbug.com/tint/1582): short circuit 'expr' once const eval of Bitcast is implemented. | 
 |     if (auto r = const_eval_.Bitcast(ty, inner)) { | 
 |         val = r.Get(); | 
 |     } else { | 
 |         return nullptr; | 
 |     } | 
 |     auto stage = sem::EvaluationStage::kRuntime;  // TODO(crbug.com/tint/1581) | 
 |     auto* sem = builder_->create<sem::Expression>(expr, ty, stage, current_statement_, | 
 |                                                   std::move(val), inner->HasSideEffects()); | 
 |  | 
 |     sem->Behaviors() = inner->Behaviors(); | 
 |  | 
 |     if (!validator_.Bitcast(expr, ty)) { | 
 |         return nullptr; | 
 |     } | 
 |  | 
 |     return sem; | 
 | } | 
 |  | 
 | sem::Call* Resolver::Call(const ast::CallExpression* expr) { | 
 |     // A CallExpression can resolve to one of: | 
 |     // * A function call. | 
 |     // * A builtin call. | 
 |     // * A type initializer. | 
 |     // * A type conversion. | 
 |  | 
 |     // Resolve all of the arguments, their types and the set of behaviors. | 
 |     utils::Vector<const sem::Expression*, 8> args; | 
 |     args.Reserve(expr->args.Length()); | 
 |     auto args_stage = sem::EvaluationStage::kConstant; | 
 |     sem::Behaviors arg_behaviors; | 
 |     for (size_t i = 0; i < expr->args.Length(); i++) { | 
 |         auto* arg = sem_.Get(expr->args[i]); | 
 |         if (!arg) { | 
 |             return nullptr; | 
 |         } | 
 |         args.Push(arg); | 
 |         args_stage = sem::EarliestStage(args_stage, arg->Stage()); | 
 |         arg_behaviors.Add(arg->Behaviors()); | 
 |  | 
 |         RegisterLoadIfNeeded(arg); | 
 |     } | 
 |     arg_behaviors.Remove(sem::Behavior::kNext); | 
 |  | 
 |     // Did any arguments have side effects? | 
 |     bool has_side_effects = | 
 |         std::any_of(args.begin(), args.end(), [](auto* e) { return e->HasSideEffects(); }); | 
 |  | 
 |     // ct_init_or_conv is a helper for building either a sem::TypeInitializer or | 
 |     // sem::TypeConversion call for a InitConvIntrinsic with an optional template argument type. | 
 |     auto ct_init_or_conv = [&](InitConvIntrinsic ty, const type::Type* template_arg) -> sem::Call* { | 
 |         auto arg_tys = utils::Transform(args, [](auto* arg) { return arg->Type(); }); | 
 |         auto ctor_or_conv = | 
 |             intrinsic_table_->Lookup(ty, template_arg, arg_tys, args_stage, expr->source); | 
 |         if (!ctor_or_conv.target) { | 
 |             return nullptr; | 
 |         } | 
 |         if (!MaybeMaterializeArguments(args, ctor_or_conv.target)) { | 
 |             return nullptr; | 
 |         } | 
 |  | 
 |         const constant::Value* value = nullptr; | 
 |         auto stage = sem::EarliestStage(ctor_or_conv.target->Stage(), args_stage); | 
 |         if (stage == sem::EvaluationStage::kConstant && skip_const_eval_.Contains(expr)) { | 
 |             stage = sem::EvaluationStage::kNotEvaluated; | 
 |         } | 
 |         if (stage == sem::EvaluationStage::kConstant) { | 
 |             auto const_args = ConvertArguments(args, ctor_or_conv.target); | 
 |             if (!const_args) { | 
 |                 return nullptr; | 
 |             } | 
 |             if (auto r = (const_eval_.*ctor_or_conv.const_eval_fn)( | 
 |                     ctor_or_conv.target->ReturnType(), const_args.Get(), expr->source)) { | 
 |                 value = r.Get(); | 
 |             } else { | 
 |                 return nullptr; | 
 |             } | 
 |         } | 
 |         return builder_->create<sem::Call>(expr, ctor_or_conv.target, stage, std::move(args), | 
 |                                            current_statement_, value, has_side_effects); | 
 |     }; | 
 |  | 
 |     // arr_or_str_init is a helper for building a sem::TypeInitializer for an array or structure | 
 |     // initializer call target. | 
 |     auto arr_or_str_init = [&](const type::Type* ty, | 
 |                                const sem::CallTarget* call_target) -> sem::Call* { | 
 |         if (!MaybeMaterializeArguments(args, call_target)) { | 
 |             return nullptr; | 
 |         } | 
 |  | 
 |         auto stage = args_stage;                    // The evaluation stage of the call | 
 |         const constant::Value* value = nullptr;     // The constant value for the call | 
 |         if (stage == sem::EvaluationStage::kConstant) { | 
 |             if (auto r = const_eval_.ArrayOrStructInit(ty, args)) { | 
 |                 value = r.Get(); | 
 |             } else { | 
 |                 return nullptr; | 
 |             } | 
 |             if (!value) { | 
 |                 // Constant evaluation failed. | 
 |                 // Can happen for expressions that will fail validation (later). | 
 |                 // Use the kRuntime EvaluationStage, as kConstant will trigger an assertion in | 
 |                 // the sem::Expression initializer, which checks that kConstant is paired with a | 
 |                 // constant value. | 
 |                 stage = sem::EvaluationStage::kRuntime; | 
 |             } | 
 |         } | 
 |  | 
 |         return builder_->create<sem::Call>(expr, call_target, stage, std::move(args), | 
 |                                            current_statement_, value, has_side_effects); | 
 |     }; | 
 |  | 
 |     // ty_init_or_conv is a helper for building either a sem::TypeInitializer or | 
 |     // sem::TypeConversion call for the given semantic type. | 
 |     auto ty_init_or_conv = [&](const type::Type* ty) { | 
 |         return Switch( | 
 |             ty,  // | 
 |             [&](const type::Vector* v) { | 
 |                 return ct_init_or_conv(VectorInitConvIntrinsic(v->Width()), v->type()); | 
 |             }, | 
 |             [&](const type::Matrix* m) { | 
 |                 return ct_init_or_conv(MatrixInitConvIntrinsic(m->columns(), m->rows()), m->type()); | 
 |             }, | 
 |             [&](const type::I32*) { return ct_init_or_conv(InitConvIntrinsic::kI32, nullptr); }, | 
 |             [&](const type::U32*) { return ct_init_or_conv(InitConvIntrinsic::kU32, nullptr); }, | 
 |             [&](const type::F16*) { | 
 |                 return validator_.CheckF16Enabled(expr->source) | 
 |                            ? ct_init_or_conv(InitConvIntrinsic::kF16, nullptr) | 
 |                            : nullptr; | 
 |             }, | 
 |             [&](const type::F32*) { return ct_init_or_conv(InitConvIntrinsic::kF32, nullptr); }, | 
 |             [&](const type::Bool*) { return ct_init_or_conv(InitConvIntrinsic::kBool, nullptr); }, | 
 |             [&](const type::Array* arr) -> sem::Call* { | 
 |                 auto* call_target = array_inits_.GetOrCreate( | 
 |                     ArrayInitializerSig{{arr, args.Length(), args_stage}}, | 
 |                     [&]() -> sem::TypeInitializer* { | 
 |                         auto params = utils::Transform(args, [&](auto, size_t i) { | 
 |                             return builder_->create<sem::Parameter>( | 
 |                                 nullptr,                   // declaration | 
 |                                 static_cast<uint32_t>(i),  // index | 
 |                                 arr->ElemType(),           // type | 
 |                                 ast::AddressSpace::kNone,  // address_space | 
 |                                 ast::Access::kUndefined); | 
 |                         }); | 
 |                         return builder_->create<sem::TypeInitializer>(arr, std::move(params), | 
 |                                                                       args_stage); | 
 |                     }); | 
 |  | 
 |                 auto* call = arr_or_str_init(arr, call_target); | 
 |                 if (!call) { | 
 |                     return nullptr; | 
 |                 } | 
 |  | 
 |                 // Validation must occur after argument materialization in arr_or_str_init(). | 
 |                 if (!validator_.ArrayInitializer(expr, arr)) { | 
 |                     return nullptr; | 
 |                 } | 
 |                 return call; | 
 |             }, | 
 |             [&](const sem::Struct* str) -> sem::Call* { | 
 |                 auto* call_target = struct_inits_.GetOrCreate( | 
 |                     StructInitializerSig{{str, args.Length(), args_stage}}, | 
 |                     [&]() -> sem::TypeInitializer* { | 
 |                         utils::Vector<const sem::Parameter*, 8> params; | 
 |                         params.Resize(std::min(args.Length(), str->Members().Length())); | 
 |                         for (size_t i = 0, n = params.Length(); i < n; i++) { | 
 |                             params[i] = builder_->create<sem::Parameter>( | 
 |                                 nullptr,                    // declaration | 
 |                                 static_cast<uint32_t>(i),   // index | 
 |                                 str->Members()[i]->Type(),  // type | 
 |                                 ast::AddressSpace::kNone,   // address_space | 
 |                                 ast::Access::kUndefined);   // access | 
 |                         } | 
 |                         return builder_->create<sem::TypeInitializer>(str, std::move(params), | 
 |                                                                       args_stage); | 
 |                     }); | 
 |  | 
 |                 auto* call = arr_or_str_init(str, call_target); | 
 |                 if (!call) { | 
 |                     return nullptr; | 
 |                 } | 
 |  | 
 |                 // Validation must occur after argument materialization in arr_or_str_init(). | 
 |                 if (!validator_.StructureInitializer(expr, str)) { | 
 |                     return nullptr; | 
 |                 } | 
 |                 return call; | 
 |             }, | 
 |             [&](Default) { | 
 |                 AddError("type is not constructible", expr->source); | 
 |                 return nullptr; | 
 |             }); | 
 |     }; | 
 |  | 
 |     // ast::CallExpression has a target which is either an ast::Type or an | 
 |     // ast::IdentifierExpression | 
 |     sem::Call* call = nullptr; | 
 |     if (expr->target.type) { | 
 |         // ast::CallExpression has an ast::Type as the target. | 
 |         // This call is either a type initializer or type conversion. | 
 |         call = Switch( | 
 |             expr->target.type, | 
 |             [&](const ast::Vector* v) -> sem::Call* { | 
 |                 Mark(v); | 
 |                 // vector element type must be inferred if it was not specified. | 
 |                 type::Type* template_arg = nullptr; | 
 |                 if (v->type) { | 
 |                     template_arg = Type(v->type); | 
 |                     if (!template_arg) { | 
 |                         return nullptr; | 
 |                     } | 
 |                 } | 
 |                 if (auto* c = ct_init_or_conv(VectorInitConvIntrinsic(v->width), template_arg)) { | 
 |                     builder_->Sem().Add(expr->target.type, c->Target()->ReturnType()); | 
 |                     return c; | 
 |                 } | 
 |                 return nullptr; | 
 |             }, | 
 |             [&](const ast::Matrix* m) -> sem::Call* { | 
 |                 Mark(m); | 
 |                 // matrix element type must be inferred if it was not specified. | 
 |                 type::Type* template_arg = nullptr; | 
 |                 if (m->type) { | 
 |                     template_arg = Type(m->type); | 
 |                     if (!template_arg) { | 
 |                         return nullptr; | 
 |                     } | 
 |                 } | 
 |                 if (auto* c = ct_init_or_conv(MatrixInitConvIntrinsic(m->columns, m->rows), | 
 |                                               template_arg)) { | 
 |                     builder_->Sem().Add(expr->target.type, c->Target()->ReturnType()); | 
 |                     return c; | 
 |                 } | 
 |                 return nullptr; | 
 |             }, | 
 |             [&](const ast::Array* a) -> sem::Call* { | 
 |                 Mark(a); | 
 |                 // array element type must be inferred if it was not specified. | 
 |                 const type::ArrayCount* el_count = nullptr; | 
 |                 const type::Type* el_ty = nullptr; | 
 |                 if (a->type) { | 
 |                     el_ty = Type(a->type); | 
 |                     if (!el_ty) { | 
 |                         return nullptr; | 
 |                     } | 
 |                     if (!a->count) { | 
 |                         AddError("cannot construct a runtime-sized array", expr->source); | 
 |                         return nullptr; | 
 |                     } | 
 |                     el_count = ArrayCount(a->count); | 
 |                     if (!el_count) { | 
 |                         return nullptr; | 
 |                     } | 
 |                     // Note: validation later will detect any mismatches between explicit array | 
 |                     // size and number of initializer expressions. | 
 |                 } else { | 
 |                     el_count = builder_->create<type::ConstantArrayCount>( | 
 |                         static_cast<uint32_t>(args.Length())); | 
 |                     auto arg_tys = | 
 |                         utils::Transform(args, [](auto* arg) { return arg->Type()->UnwrapRef(); }); | 
 |                     el_ty = type::Type::Common(arg_tys); | 
 |                     if (!el_ty) { | 
 |                         AddError( | 
 |                             "cannot infer common array element type from initializer arguments", | 
 |                             expr->source); | 
 |                         utils::Hashset<const type::Type*, 8> types; | 
 |                         for (size_t i = 0; i < args.Length(); i++) { | 
 |                             if (types.Add(args[i]->Type())) { | 
 |                                 AddNote("argument " + std::to_string(i) + " is of type '" + | 
 |                                             sem_.TypeNameOf(args[i]->Type()) + "'", | 
 |                                         args[i]->Declaration()->source); | 
 |                             } | 
 |                         } | 
 |                         return nullptr; | 
 |                     } | 
 |                 } | 
 |                 uint32_t explicit_stride = 0; | 
 |                 if (!ArrayAttributes(a->attributes, el_ty, explicit_stride)) { | 
 |                     return nullptr; | 
 |                 } | 
 |  | 
 |                 auto* arr = Array(a->type ? a->type->source : a->source, | 
 |                                   a->count ? a->count->source : a->source,  // | 
 |                                   el_ty, el_count, explicit_stride); | 
 |                 if (!arr) { | 
 |                     return nullptr; | 
 |                 } | 
 |                 builder_->Sem().Add(a, arr); | 
 |  | 
 |                 return ty_init_or_conv(arr); | 
 |             }, | 
 |             [&](const ast::Type* ast) -> sem::Call* { | 
 |                 // Handler for AST types that do not have an optional element type. | 
 |                 if (auto* ty = Type(ast)) { | 
 |                     return ty_init_or_conv(ty); | 
 |                 } | 
 |                 return nullptr; | 
 |             }, | 
 |             [&](Default) { | 
 |                 TINT_ICE(Resolver, diagnostics_) | 
 |                     << expr->source << " unhandled CallExpression target:\n" | 
 |                     << "type: " | 
 |                     << (expr->target.type ? expr->target.type->TypeInfo().name : "<null>"); | 
 |                 return nullptr; | 
 |             }); | 
 |     } else { | 
 |         // ast::CallExpression has an ast::IdentifierExpression as the target. | 
 |         // This call is either a function call, builtin call, type initializer or type | 
 |         // conversion. | 
 |         auto* ident = expr->target.name; | 
 |         Mark(ident); | 
 |         if (auto* resolved = sem_.ResolvedSymbol<type::Type>(ident)) { | 
 |             // A type initializer or conversions. | 
 |             // Note: Unlike the code path where we're resolving the call target from an | 
 |             // ast::Type, all types must already have the element type explicitly specified, | 
 |             // so there's no need to infer element types. | 
 |             return ty_init_or_conv(resolved); | 
 |         } | 
 |  | 
 |         auto* resolved = sem_.ResolvedSymbol<sem::Node>(ident); | 
 |         call = Switch<sem::Call*>( | 
 |             resolved,  // | 
 |             [&](sem::Function* func) { return FunctionCall(expr, func, args, arg_behaviors); }, | 
 |             [&](sem::Variable* var) { | 
 |                 auto name = builder_->Symbols().NameFor(var->Declaration()->symbol); | 
 |                 AddError("cannot call variable '" + name + "'", ident->source); | 
 |                 AddNote("'" + name + "' declared here", var->Declaration()->source); | 
 |                 return nullptr; | 
 |             }, | 
 |             [&](Default) -> sem::Call* { | 
 |                 auto name = builder_->Symbols().NameFor(ident->symbol); | 
 |                 if (auto builtin_type = sem::ParseBuiltinType(name); | 
 |                     builtin_type != sem::BuiltinType::kNone) { | 
 |                     return BuiltinCall(expr, builtin_type, args); | 
 |                 } | 
 |                 if (auto* alias = ShortName(ident->symbol, ident->source)) { | 
 |                     return ty_init_or_conv(alias); | 
 |                 } | 
 |                 return nullptr; | 
 |             }); | 
 |     } | 
 |  | 
 |     if (!call) { | 
 |         return nullptr; | 
 |     } | 
 |  | 
 |     return validator_.Call(call, current_statement_) ? call : nullptr; | 
 | } | 
 |  | 
 | template <size_t N> | 
 | sem::Call* Resolver::BuiltinCall(const ast::CallExpression* expr, | 
 |                                  sem::BuiltinType builtin_type, | 
 |                                  utils::Vector<const sem::Expression*, N>& args) { | 
 |     auto arg_stage = sem::EvaluationStage::kConstant; | 
 |     for (auto* arg : args) { | 
 |         arg_stage = sem::EarliestStage(arg_stage, arg->Stage()); | 
 |     } | 
 |  | 
 |     IntrinsicTable::Builtin builtin; | 
 |     { | 
 |         auto arg_tys = utils::Transform(args, [](auto* arg) { return arg->Type(); }); | 
 |         builtin = intrinsic_table_->Lookup(builtin_type, arg_tys, arg_stage, expr->source); | 
 |         if (!builtin.sem) { | 
 |             return nullptr; | 
 |         } | 
 |     } | 
 |  | 
 |     if (builtin_type == sem::BuiltinType::kTintMaterialize) { | 
 |         args[0] = Materialize(args[0]); | 
 |         if (!args[0]) { | 
 |             return nullptr; | 
 |         } | 
 |     } else { | 
 |         // Materialize arguments if the parameter type is not abstract | 
 |         if (!MaybeMaterializeArguments(args, builtin.sem)) { | 
 |             return nullptr; | 
 |         } | 
 |     } | 
 |  | 
 |     if (builtin.sem->IsDeprecated()) { | 
 |         AddWarning("use of deprecated builtin", expr->source); | 
 |     } | 
 |  | 
 |     // If the builtin is @const, and all arguments have constant values, evaluate the builtin | 
 |     // now. | 
 |     const constant::Value* value = nullptr; | 
 |     auto stage = sem::EarliestStage(arg_stage, builtin.sem->Stage()); | 
 |     if (stage == sem::EvaluationStage::kConstant && skip_const_eval_.Contains(expr)) { | 
 |         stage = sem::EvaluationStage::kNotEvaluated; | 
 |     } | 
 |     if (stage == sem::EvaluationStage::kConstant) { | 
 |         auto const_args = ConvertArguments(args, builtin.sem); | 
 |         if (!const_args) { | 
 |             return nullptr; | 
 |         } | 
 |  | 
 |         if (auto r = (const_eval_.*builtin.const_eval_fn)(builtin.sem->ReturnType(), | 
 |                                                           const_args.Get(), expr->source)) { | 
 |             value = r.Get(); | 
 |         } else { | 
 |             return nullptr; | 
 |         } | 
 |     } | 
 |  | 
 |     bool has_side_effects = | 
 |         builtin.sem->HasSideEffects() || | 
 |         std::any_of(args.begin(), args.end(), [](auto* e) { return e->HasSideEffects(); }); | 
 |     auto* call = builder_->create<sem::Call>(expr, builtin.sem, stage, std::move(args), | 
 |                                              current_statement_, value, has_side_effects); | 
 |  | 
 |     if (current_function_) { | 
 |         current_function_->AddDirectlyCalledBuiltin(builtin.sem); | 
 |         current_function_->AddDirectCall(call); | 
 |     } | 
 |  | 
 |     if (!validator_.RequiredExtensionForBuiltinFunction(call)) { | 
 |         return nullptr; | 
 |     } | 
 |  | 
 |     if (IsTextureBuiltin(builtin_type)) { | 
 |         if (!validator_.TextureBuiltinFunction(call)) { | 
 |             return nullptr; | 
 |         } | 
 |         CollectTextureSamplerPairs(builtin.sem, call->Arguments()); | 
 |     } | 
 |  | 
 |     if (!validator_.BuiltinCall(call)) { | 
 |         return nullptr; | 
 |     } | 
 |  | 
 |     return call; | 
 | } | 
 |  | 
 | type::Type* Resolver::ShortName(Symbol sym, const Source& source) const { | 
 |     auto name = builder_->Symbols().NameFor(sym); | 
 |     auto& b = *builder_; | 
 |     auto vec_f32 = [&](uint32_t n) { return b.create<type::Vector>(b.create<type::F32>(), n); }; | 
 |     auto vec_f16 = [&](uint32_t n) { return b.create<type::Vector>(b.create<type::F16>(), n); }; | 
 |  | 
 |     switch (type::ParseShortName(name)) { | 
 |         case type::ShortName::kMat2X2F: | 
 |             return b.create<type::Matrix>(vec_f32(2u), 2u); | 
 |         case type::ShortName::kMat2X3F: | 
 |             return b.create<type::Matrix>(vec_f32(3u), 2u); | 
 |         case type::ShortName::kMat2X4F: | 
 |             return b.create<type::Matrix>(vec_f32(4u), 2u); | 
 |         case type::ShortName::kMat3X2F: | 
 |             return b.create<type::Matrix>(vec_f32(2u), 3u); | 
 |         case type::ShortName::kMat3X3F: | 
 |             return b.create<type::Matrix>(vec_f32(3u), 3u); | 
 |         case type::ShortName::kMat3X4F: | 
 |             return b.create<type::Matrix>(vec_f32(4u), 3u); | 
 |         case type::ShortName::kMat4X2F: | 
 |             return b.create<type::Matrix>(vec_f32(2u), 4u); | 
 |         case type::ShortName::kMat4X3F: | 
 |             return b.create<type::Matrix>(vec_f32(3u), 4u); | 
 |         case type::ShortName::kMat4X4F: | 
 |             return b.create<type::Matrix>(vec_f32(4u), 4u); | 
 |         case type::ShortName::kMat2X2H: | 
 |             return validator_.CheckF16Enabled(source) ? b.create<type::Matrix>(vec_f16(2u), 2u) | 
 |                                                       : nullptr; | 
 |         case type::ShortName::kMat2X3H: | 
 |             return validator_.CheckF16Enabled(source) ? b.create<type::Matrix>(vec_f16(3u), 2u) | 
 |                                                       : nullptr; | 
 |         case type::ShortName::kMat2X4H: | 
 |             return validator_.CheckF16Enabled(source) ? b.create<type::Matrix>(vec_f16(4u), 2u) | 
 |                                                       : nullptr; | 
 |         case type::ShortName::kMat3X2H: | 
 |             return validator_.CheckF16Enabled(source) ? b.create<type::Matrix>(vec_f16(2u), 3u) | 
 |                                                       : nullptr; | 
 |         case type::ShortName::kMat3X3H: | 
 |             return validator_.CheckF16Enabled(source) ? b.create<type::Matrix>(vec_f16(3u), 3u) | 
 |                                                       : nullptr; | 
 |         case type::ShortName::kMat3X4H: | 
 |             return validator_.CheckF16Enabled(source) ? b.create<type::Matrix>(vec_f16(4u), 3u) | 
 |                                                       : nullptr; | 
 |         case type::ShortName::kMat4X2H: | 
 |             return validator_.CheckF16Enabled(source) ? b.create<type::Matrix>(vec_f16(2u), 4u) | 
 |                                                       : nullptr; | 
 |         case type::ShortName::kMat4X3H: | 
 |             return validator_.CheckF16Enabled(source) ? b.create<type::Matrix>(vec_f16(3u), 4u) | 
 |                                                       : nullptr; | 
 |         case type::ShortName::kMat4X4H: | 
 |             return validator_.CheckF16Enabled(source) ? b.create<type::Matrix>(vec_f16(4u), 4u) | 
 |                                                       : nullptr; | 
 |         case type::ShortName::kVec2F: | 
 |             return vec_f32(2u); | 
 |         case type::ShortName::kVec3F: | 
 |             return vec_f32(3u); | 
 |         case type::ShortName::kVec4F: | 
 |             return vec_f32(4u); | 
 |         case type::ShortName::kVec2H: | 
 |             return validator_.CheckF16Enabled(source) ? vec_f16(2u) : nullptr; | 
 |         case type::ShortName::kVec3H: | 
 |             return validator_.CheckF16Enabled(source) ? vec_f16(3u) : nullptr; | 
 |         case type::ShortName::kVec4H: | 
 |             return validator_.CheckF16Enabled(source) ? vec_f16(4u) : nullptr; | 
 |         case type::ShortName::kVec2I: | 
 |             return b.create<type::Vector>(b.create<type::I32>(), 2u); | 
 |         case type::ShortName::kVec3I: | 
 |             return b.create<type::Vector>(b.create<type::I32>(), 3u); | 
 |         case type::ShortName::kVec4I: | 
 |             return b.create<type::Vector>(b.create<type::I32>(), 4u); | 
 |         case type::ShortName::kVec2U: | 
 |             return b.create<type::Vector>(b.create<type::U32>(), 2u); | 
 |         case type::ShortName::kVec3U: | 
 |             return b.create<type::Vector>(b.create<type::U32>(), 3u); | 
 |         case type::ShortName::kVec4U: | 
 |             return b.create<type::Vector>(b.create<type::U32>(), 4u); | 
 |         case type::ShortName::kUndefined: | 
 |             break; | 
 |     } | 
 |  | 
 |     TINT_ICE(Resolver, diagnostics_) << source << " unhandled type short name '" << name << "'"; | 
 |     return nullptr; | 
 | } | 
 |  | 
 | void Resolver::CollectTextureSamplerPairs(const sem::Builtin* builtin, | 
 |                                           utils::VectorRef<const sem::Expression*> args) const { | 
 |     // Collect a texture/sampler pair for this builtin. | 
 |     const auto& signature = builtin->Signature(); | 
 |     int texture_index = signature.IndexOf(sem::ParameterUsage::kTexture); | 
 |     if (texture_index == -1) { | 
 |         TINT_ICE(Resolver, diagnostics_) << "texture builtin without texture parameter"; | 
 |     } | 
 |     if (auto* user = args[static_cast<size_t>(texture_index)]->As<sem::VariableUser>()) { | 
 |         auto* texture = user->Variable(); | 
 |         if (!texture->Type()->UnwrapRef()->Is<type::StorageTexture>()) { | 
 |             int sampler_index = signature.IndexOf(sem::ParameterUsage::kSampler); | 
 |             const sem::Variable* sampler = | 
 |                 sampler_index != -1 | 
 |                     ? args[static_cast<size_t>(sampler_index)]->As<sem::VariableUser>()->Variable() | 
 |                     : nullptr; | 
 |             current_function_->AddTextureSamplerPair(texture, sampler); | 
 |         } | 
 |     } | 
 | } | 
 |  | 
 | template <size_t N> | 
 | sem::Call* Resolver::FunctionCall(const ast::CallExpression* expr, | 
 |                                   sem::Function* target, | 
 |                                   utils::Vector<const sem::Expression*, N>& args, | 
 |                                   sem::Behaviors arg_behaviors) { | 
 |     auto sym = expr->target.name->symbol; | 
 |     auto name = builder_->Symbols().NameFor(sym); | 
 |  | 
 |     if (!MaybeMaterializeArguments(args, target)) { | 
 |         return nullptr; | 
 |     } | 
 |  | 
 |     // TODO(crbug.com/tint/1420): For now, assume all function calls have side | 
 |     // effects. | 
 |     bool has_side_effects = true; | 
 |     auto* call = builder_->create<sem::Call>(expr, target, sem::EvaluationStage::kRuntime, | 
 |                                              std::move(args), current_statement_, | 
 |                                              /* constant_value */ nullptr, has_side_effects); | 
 |  | 
 |     target->AddCallSite(call); | 
 |  | 
 |     call->Behaviors() = arg_behaviors + target->Behaviors(); | 
 |  | 
 |     if (!validator_.FunctionCall(call, current_statement_)) { | 
 |         return nullptr; | 
 |     } | 
 |  | 
 |     if (current_function_) { | 
 |         // Note: Requires called functions to be resolved first. | 
 |         // This is currently guaranteed as functions must be declared before | 
 |         // use. | 
 |         current_function_->AddTransitivelyCalledFunction(target); | 
 |         current_function_->AddDirectCall(call); | 
 |         for (auto* transitive_call : target->TransitivelyCalledFunctions()) { | 
 |             current_function_->AddTransitivelyCalledFunction(transitive_call); | 
 |         } | 
 |  | 
 |         // We inherit any referenced variables from the callee. | 
 |         for (auto* var : target->TransitivelyReferencedGlobals()) { | 
 |             current_function_->AddTransitivelyReferencedGlobal(var); | 
 |         } | 
 |  | 
 |         if (!AliasAnalysis(call)) { | 
 |             return nullptr; | 
 |         } | 
 |  | 
 |         // Note: Validation *must* be performed before calling this method. | 
 |         CollectTextureSamplerPairs(target, call->Arguments()); | 
 |     } | 
 |  | 
 |     return call; | 
 | } | 
 |  | 
 | void Resolver::CollectTextureSamplerPairs(sem::Function* func, | 
 |                                           utils::VectorRef<const sem::Expression*> args) const { | 
 |     // Map all texture/sampler pairs from the target function to the | 
 |     // current function. These can only be global or parameter | 
 |     // variables. Resolve any parameter variables to the corresponding | 
 |     // argument passed to the current function. Leave global variables | 
 |     // as-is. Then add the mapped pair to the current function's list of | 
 |     // texture/sampler pairs. | 
 |     for (sem::VariablePair pair : func->TextureSamplerPairs()) { | 
 |         const sem::Variable* texture = pair.first; | 
 |         const sem::Variable* sampler = pair.second; | 
 |         if (auto* param = texture->As<sem::Parameter>()) { | 
 |             texture = args[param->Index()]->As<sem::VariableUser>()->Variable(); | 
 |         } | 
 |         if (sampler) { | 
 |             if (auto* param = sampler->As<sem::Parameter>()) { | 
 |                 sampler = args[param->Index()]->As<sem::VariableUser>()->Variable(); | 
 |             } | 
 |         } | 
 |         current_function_->AddTextureSamplerPair(texture, sampler); | 
 |     } | 
 | } | 
 |  | 
 | sem::Expression* Resolver::Literal(const ast::LiteralExpression* literal) { | 
 |     auto* ty = Switch( | 
 |         literal, | 
 |         [&](const ast::IntLiteralExpression* i) -> type::Type* { | 
 |             switch (i->suffix) { | 
 |                 case ast::IntLiteralExpression::Suffix::kNone: | 
 |                     return builder_->create<type::AbstractInt>(); | 
 |                 case ast::IntLiteralExpression::Suffix::kI: | 
 |                     return builder_->create<type::I32>(); | 
 |                 case ast::IntLiteralExpression::Suffix::kU: | 
 |                     return builder_->create<type::U32>(); | 
 |             } | 
 |             TINT_UNREACHABLE(Resolver, builder_->Diagnostics()) | 
 |                 << "Unhandled integer literal suffix: " << i->suffix; | 
 |             return nullptr; | 
 |         }, | 
 |         [&](const ast::FloatLiteralExpression* f) -> type::Type* { | 
 |             switch (f->suffix) { | 
 |                 case ast::FloatLiteralExpression::Suffix::kNone: | 
 |                     return builder_->create<type::AbstractFloat>(); | 
 |                 case ast::FloatLiteralExpression::Suffix::kF: | 
 |                     return builder_->create<type::F32>(); | 
 |                 case ast::FloatLiteralExpression::Suffix::kH: | 
 |                     return validator_.CheckF16Enabled(literal->source) | 
 |                                ? builder_->create<type::F16>() | 
 |                                : nullptr; | 
 |             } | 
 |             TINT_UNREACHABLE(Resolver, builder_->Diagnostics()) | 
 |                 << "Unhandled float literal suffix: " << f->suffix; | 
 |             return nullptr; | 
 |         }, | 
 |         [&](const ast::BoolLiteralExpression*) { return builder_->create<type::Bool>(); }, | 
 |         [&](Default) { | 
 |             TINT_UNREACHABLE(Resolver, builder_->Diagnostics()) | 
 |                 << "Unhandled literal type: " << literal->TypeInfo().name; | 
 |             return nullptr; | 
 |         }); | 
 |  | 
 |     if (ty == nullptr) { | 
 |         return nullptr; | 
 |     } | 
 |  | 
 |     const constant::Value* val = nullptr; | 
 |     if (auto r = const_eval_.Literal(ty, literal)) { | 
 |         val = r.Get(); | 
 |     } else { | 
 |         return nullptr; | 
 |     } | 
 |     return builder_->create<sem::Expression>(literal, ty, sem::EvaluationStage::kConstant, | 
 |                                              current_statement_, std::move(val), | 
 |                                              /* has_side_effects */ false); | 
 | } | 
 |  | 
 | sem::Expression* Resolver::Identifier(const ast::IdentifierExpression* expr) { | 
 |     auto symbol = expr->symbol; | 
 |     auto* sem_resolved = sem_.ResolvedSymbol<sem::Node>(expr); | 
 |     if (auto* variable = As<sem::Variable>(sem_resolved)) { | 
 |         auto* user = builder_->create<sem::VariableUser>(expr, current_statement_, variable); | 
 |  | 
 |         if (current_statement_) { | 
 |             // If identifier is part of a loop continuing block, make sure it | 
 |             // doesn't refer to a variable that is bypassed by a continue statement | 
 |             // in the loop's body block. | 
 |             if (auto* continuing_block = | 
 |                     current_statement_->FindFirstParent<sem::LoopContinuingBlockStatement>()) { | 
 |                 auto* loop_block = continuing_block->FindFirstParent<sem::LoopBlockStatement>(); | 
 |                 if (loop_block->FirstContinue()) { | 
 |                     // If our identifier is in loop_block->decls, make sure its index is | 
 |                     // less than first_continue | 
 |                     if (auto decl = loop_block->Decls().Find(symbol)) { | 
 |                         if (decl->order >= loop_block->NumDeclsAtFirstContinue()) { | 
 |                             AddError("continue statement bypasses declaration of '" + | 
 |                                          builder_->Symbols().NameFor(symbol) + "'", | 
 |                                      loop_block->FirstContinue()->source); | 
 |                             AddNote("identifier '" + builder_->Symbols().NameFor(symbol) + | 
 |                                         "' declared here", | 
 |                                     decl->variable->Declaration()->source); | 
 |                             AddNote("identifier '" + builder_->Symbols().NameFor(symbol) + | 
 |                                         "' referenced in continuing block here", | 
 |                                     expr->source); | 
 |                             return nullptr; | 
 |                         } | 
 |                     } | 
 |                 } | 
 |             } | 
 |         } | 
 |  | 
 |         auto* global = variable->As<sem::GlobalVariable>(); | 
 |         if (current_function_) { | 
 |             if (global) { | 
 |                 current_function_->AddDirectlyReferencedGlobal(global); | 
 |                 auto* refs = builder_->Sem().TransitivelyReferencedOverrides(global); | 
 |                 if (refs) { | 
 |                     for (auto* var : *refs) { | 
 |                         current_function_->AddTransitivelyReferencedGlobal(var); | 
 |                     } | 
 |                 } | 
 |             } | 
 |         } else if (variable->Declaration()->Is<ast::Override>()) { | 
 |             if (resolved_overrides_) { | 
 |                 // Track the reference to this pipeline-overridable constant and any other | 
 |                 // pipeline-overridable constants that it references. | 
 |                 resolved_overrides_->Add(global); | 
 |                 auto* refs = builder_->Sem().TransitivelyReferencedOverrides(global); | 
 |                 if (refs) { | 
 |                     for (auto* var : *refs) { | 
 |                         resolved_overrides_->Add(var); | 
 |                     } | 
 |                 } | 
 |             } | 
 |         } else if (variable->Declaration()->Is<ast::Var>()) { | 
 |             // Use of a module-scope 'var' outside of a function. | 
 |             // Note: The spec is currently vague around the rules here. See | 
 |             // https://github.com/gpuweb/gpuweb/issues/3081. Remove this comment when resolved. | 
 |             std::string desc = "var '" + builder_->Symbols().NameFor(symbol) + "' "; | 
 |             AddError(desc + "cannot be referenced at module-scope", expr->source); | 
 |             AddNote(desc + "declared here", variable->Declaration()->source); | 
 |             return nullptr; | 
 |         } | 
 |  | 
 |         variable->AddUser(user); | 
 |         return user; | 
 |     } | 
 |  | 
 |     if (Is<sem::Function>(sem_resolved)) { | 
 |         AddError("missing '(' for function call", expr->source.End()); | 
 |         return nullptr; | 
 |     } | 
 |  | 
 |     if (IsBuiltin(symbol)) { | 
 |         AddError("missing '(' for builtin call", expr->source.End()); | 
 |         return nullptr; | 
 |     } | 
 |  | 
 |     if (sem_.ResolvedSymbol<type::Type>(expr)) { | 
 |         AddError("missing '(' for type initializer or cast", expr->source.End()); | 
 |         return nullptr; | 
 |     } | 
 |  | 
 |     TINT_ICE(Resolver, diagnostics_) | 
 |         << expr->source << " unresolved identifier:\n" | 
 |         << "resolved: " << (sem_resolved ? sem_resolved->TypeInfo().name : "<null>") << "\n" | 
 |         << "name: " << builder_->Symbols().NameFor(symbol); | 
 |     return nullptr; | 
 | } | 
 |  | 
 | sem::Expression* Resolver::MemberAccessor(const ast::MemberAccessorExpression* expr) { | 
 |     auto* structure = sem_.TypeOf(expr->structure); | 
 |     auto* storage_ty = structure->UnwrapRef(); | 
 |     auto* object = sem_.Get(expr->structure); | 
 |     auto* root_ident = object->RootIdentifier(); | 
 |  | 
 |     const type::Type* ty = nullptr; | 
 |  | 
 |     // Object may be a side-effecting expression (e.g. function call). | 
 |     bool has_side_effects = object && object->HasSideEffects(); | 
 |  | 
 |     return Switch( | 
 |         storage_ty,  // | 
 |         [&](const sem::Struct* str) -> sem::Expression* { | 
 |             Mark(expr->member); | 
 |             auto symbol = expr->member->symbol; | 
 |  | 
 |             const sem::StructMember* member = nullptr; | 
 |             for (auto* m : str->Members()) { | 
 |                 if (m->Name() == symbol) { | 
 |                     member = m; | 
 |                     break; | 
 |                 } | 
 |             } | 
 |  | 
 |             // TODO(crbug.com/tint/1757): Remove | 
 |             if (utils::HasPrefix(builder_->Symbols().NameFor(str->Name()), "__frexp_result")) { | 
 |                 if (builder_->Symbols().NameFor(symbol) == "sig") { | 
 |                     AddWarning( | 
 |                         "use of deprecated language feature: 'sig' has been renamed to 'fract'", | 
 |                         expr->member->source); | 
 |                     member = str->Members()[0]; | 
 |                 } | 
 |             } | 
 |  | 
 |             if (member == nullptr) { | 
 |                 AddError("struct member " + builder_->Symbols().NameFor(symbol) + " not found", | 
 |                          expr->source); | 
 |                 return nullptr; | 
 |             } | 
 |  | 
 |             ty = member->Type(); | 
 |  | 
 |             // If we're extracting from a reference, we return a reference. | 
 |             if (auto* ref = structure->As<type::Reference>()) { | 
 |                 ty = builder_->create<type::Reference>(ty, ref->AddressSpace(), ref->Access()); | 
 |             } | 
 |  | 
 |             auto val = const_eval_.MemberAccess(object, member); | 
 |             if (!val) { | 
 |                 return nullptr; | 
 |             } | 
 |             return builder_->create<sem::StructMemberAccess>(expr, ty, current_statement_, | 
 |                                                              val.Get(), object, member, | 
 |                                                              has_side_effects, root_ident); | 
 |         }, | 
 |  | 
 |         [&](const type::Vector* vec) -> sem::Expression* { | 
 |             Mark(expr->member); | 
 |             std::string s = builder_->Symbols().NameFor(expr->member->symbol); | 
 |             auto size = s.size(); | 
 |             utils::Vector<uint32_t, 4> swizzle; | 
 |             swizzle.Reserve(s.size()); | 
 |  | 
 |             for (auto c : s) { | 
 |                 switch (c) { | 
 |                     case 'x': | 
 |                     case 'r': | 
 |                         swizzle.Push(0u); | 
 |                         break; | 
 |                     case 'y': | 
 |                     case 'g': | 
 |                         swizzle.Push(1u); | 
 |                         break; | 
 |                     case 'z': | 
 |                     case 'b': | 
 |                         swizzle.Push(2u); | 
 |                         break; | 
 |                     case 'w': | 
 |                     case 'a': | 
 |                         swizzle.Push(3u); | 
 |                         break; | 
 |                     default: | 
 |                         AddError("invalid vector swizzle character", | 
 |                                  expr->member->source.Begin() + swizzle.Length()); | 
 |                         return nullptr; | 
 |                 } | 
 |  | 
 |                 if (swizzle.Back() >= vec->Width()) { | 
 |                     AddError("invalid vector swizzle member", expr->member->source); | 
 |                     return nullptr; | 
 |                 } | 
 |             } | 
 |  | 
 |             if (size < 1 || size > 4) { | 
 |                 AddError("invalid vector swizzle size", expr->member->source); | 
 |                 return nullptr; | 
 |             } | 
 |  | 
 |             // All characters are valid, check if they're being mixed | 
 |             auto is_rgba = [](char c) { return c == 'r' || c == 'g' || c == 'b' || c == 'a'; }; | 
 |             auto is_xyzw = [](char c) { return c == 'x' || c == 'y' || c == 'z' || c == 'w'; }; | 
 |             if (!std::all_of(s.begin(), s.end(), is_rgba) && | 
 |                 !std::all_of(s.begin(), s.end(), is_xyzw)) { | 
 |                 AddError("invalid mixing of vector swizzle characters rgba with xyzw", | 
 |                          expr->member->source); | 
 |                 return nullptr; | 
 |             } | 
 |  | 
 |             if (size == 1) { | 
 |                 // A single element swizzle is just the type of the vector. | 
 |                 ty = vec->type(); | 
 |                 // If we're extracting from a reference, we return a reference. | 
 |                 if (auto* ref = structure->As<type::Reference>()) { | 
 |                     ty = builder_->create<type::Reference>(ty, ref->AddressSpace(), ref->Access()); | 
 |                 } | 
 |             } else { | 
 |                 // The vector will have a number of components equal to the length of | 
 |                 // the swizzle. | 
 |                 ty = builder_->create<type::Vector>(vec->type(), static_cast<uint32_t>(size)); | 
 |             } | 
 |             auto val = const_eval_.Swizzle(ty, object, swizzle); | 
 |             if (!val) { | 
 |                 return nullptr; | 
 |             } | 
 |             return builder_->create<sem::Swizzle>(expr, ty, current_statement_, val.Get(), object, | 
 |                                                   std::move(swizzle), has_side_effects, root_ident); | 
 |         }, | 
 |  | 
 |         [&](Default) { | 
 |             AddError("invalid member accessor expression. Expected vector or struct, got '" + | 
 |                          sem_.TypeNameOf(storage_ty) + "'", | 
 |                      expr->structure->source); | 
 |             return nullptr; | 
 |         }); | 
 | } | 
 |  | 
 | sem::Expression* Resolver::Binary(const ast::BinaryExpression* expr) { | 
 |     const auto* lhs = sem_.Get(expr->lhs); | 
 |     const auto* rhs = sem_.Get(expr->rhs); | 
 |     auto* lhs_ty = lhs->Type()->UnwrapRef(); | 
 |     auto* rhs_ty = rhs->Type()->UnwrapRef(); | 
 |  | 
 |     auto stage = sem::EarliestStage(lhs->Stage(), rhs->Stage()); | 
 |     auto op = intrinsic_table_->Lookup(expr->op, lhs_ty, rhs_ty, stage, expr->source, false); | 
 |     if (!op.result) { | 
 |         return nullptr; | 
 |     } | 
 |     if (ShouldMaterializeArgument(op.lhs)) { | 
 |         lhs = Materialize(lhs, op.lhs); | 
 |         if (!lhs) { | 
 |             return nullptr; | 
 |         } | 
 |     } | 
 |     if (ShouldMaterializeArgument(op.rhs)) { | 
 |         rhs = Materialize(rhs, op.rhs); | 
 |         if (!rhs) { | 
 |             return nullptr; | 
 |         } | 
 |     } | 
 |  | 
 |     RegisterLoadIfNeeded(lhs); | 
 |     RegisterLoadIfNeeded(rhs); | 
 |  | 
 |     const constant::Value* value = nullptr; | 
 |     if (stage == sem::EvaluationStage::kConstant) { | 
 |         if (op.const_eval_fn) { | 
 |             if (skip_const_eval_.Contains(expr)) { | 
 |                 stage = sem::EvaluationStage::kNotEvaluated; | 
 |             } else if (skip_const_eval_.Contains(expr->rhs)) { | 
 |                 // Only the rhs should be short-circuited, use the lhs value | 
 |                 value = lhs->ConstantValue(); | 
 |             } else { | 
 |                 auto const_args = utils::Vector{lhs->ConstantValue(), rhs->ConstantValue()}; | 
 |                 // Implicit conversion (e.g. AInt -> AFloat) | 
 |                 if (!Convert(const_args[0], op.lhs, lhs->Declaration()->source)) { | 
 |                     return nullptr; | 
 |                 } | 
 |                 if (!Convert(const_args[1], op.rhs, rhs->Declaration()->source)) { | 
 |                     return nullptr; | 
 |                 } | 
 |                 if (auto r = (const_eval_.*op.const_eval_fn)(op.result, const_args, expr->source)) { | 
 |                     value = r.Get(); | 
 |                 } else { | 
 |                     return nullptr; | 
 |                 } | 
 |             } | 
 |         } else { | 
 |             stage = sem::EvaluationStage::kRuntime; | 
 |         } | 
 |     } | 
 |  | 
 |     bool has_side_effects = lhs->HasSideEffects() || rhs->HasSideEffects(); | 
 |     auto* sem = builder_->create<sem::Expression>(expr, op.result, stage, current_statement_, value, | 
 |                                                   has_side_effects); | 
 |     sem->Behaviors() = lhs->Behaviors() + rhs->Behaviors(); | 
 |  | 
 |     return sem; | 
 | } | 
 |  | 
 | sem::Expression* Resolver::UnaryOp(const ast::UnaryOpExpression* unary) { | 
 |     const auto* expr = sem_.Get(unary->expr); | 
 |     auto* expr_ty = expr->Type(); | 
 |     if (!expr_ty) { | 
 |         return nullptr; | 
 |     } | 
 |  | 
 |     const type::Type* ty = nullptr; | 
 |     const sem::Variable* root_ident = nullptr; | 
 |     const constant::Value* value = nullptr; | 
 |     auto stage = sem::EvaluationStage::kRuntime; | 
 |  | 
 |     switch (unary->op) { | 
 |         case ast::UnaryOp::kAddressOf: | 
 |             if (auto* ref = expr_ty->As<type::Reference>()) { | 
 |                 if (ref->StoreType()->UnwrapRef()->is_handle()) { | 
 |                     AddError("cannot take the address of expression in handle address space", | 
 |                              unary->expr->source); | 
 |                     return nullptr; | 
 |                 } | 
 |  | 
 |                 auto* array = unary->expr->As<ast::IndexAccessorExpression>(); | 
 |                 auto* member = unary->expr->As<ast::MemberAccessorExpression>(); | 
 |                 if ((array && sem_.TypeOf(array->object)->UnwrapRef()->Is<type::Vector>()) || | 
 |                     (member && sem_.TypeOf(member->structure)->UnwrapRef()->Is<type::Vector>())) { | 
 |                     AddError("cannot take the address of a vector component", unary->expr->source); | 
 |                     return nullptr; | 
 |                 } | 
 |  | 
 |                 ty = builder_->create<type::Pointer>(ref->StoreType(), ref->AddressSpace(), | 
 |                                                      ref->Access()); | 
 |  | 
 |                 root_ident = expr->RootIdentifier(); | 
 |             } else { | 
 |                 AddError("cannot take the address of expression", unary->expr->source); | 
 |                 return nullptr; | 
 |             } | 
 |             break; | 
 |  | 
 |         case ast::UnaryOp::kIndirection: | 
 |             if (auto* ptr = expr_ty->As<type::Pointer>()) { | 
 |                 ty = builder_->create<type::Reference>(ptr->StoreType(), ptr->AddressSpace(), | 
 |                                                        ptr->Access()); | 
 |                 root_ident = expr->RootIdentifier(); | 
 |             } else { | 
 |                 AddError("cannot dereference expression of type '" + sem_.TypeNameOf(expr_ty) + "'", | 
 |                          unary->expr->source); | 
 |                 return nullptr; | 
 |             } | 
 |             break; | 
 |  | 
 |         default: { | 
 |             stage = expr->Stage(); | 
 |             auto op = intrinsic_table_->Lookup(unary->op, expr_ty, stage, unary->source); | 
 |             if (!op.result) { | 
 |                 return nullptr; | 
 |             } | 
 |             ty = op.result; | 
 |             if (ShouldMaterializeArgument(op.parameter)) { | 
 |                 expr = Materialize(expr, op.parameter); | 
 |                 if (!expr) { | 
 |                     return nullptr; | 
 |                 } | 
 |             } | 
 |             if (stage == sem::EvaluationStage::kConstant) { | 
 |                 if (op.const_eval_fn) { | 
 |                     if (auto r = (const_eval_.*op.const_eval_fn)( | 
 |                             ty, utils::Vector{expr->ConstantValue()}, | 
 |                             expr->Declaration()->source)) { | 
 |                         value = r.Get(); | 
 |                     } else { | 
 |                         return nullptr; | 
 |                     } | 
 |                 } else { | 
 |                     stage = sem::EvaluationStage::kRuntime; | 
 |                 } | 
 |             } | 
 |             RegisterLoadIfNeeded(expr); | 
 |             break; | 
 |         } | 
 |     } | 
 |  | 
 |     auto* sem = builder_->create<sem::Expression>(unary, ty, stage, current_statement_, value, | 
 |                                                   expr->HasSideEffects(), root_ident); | 
 |     sem->Behaviors() = expr->Behaviors(); | 
 |     return sem; | 
 | } | 
 |  | 
 | bool Resolver::Enable(const ast::Enable* enable) { | 
 |     enabled_extensions_.Add(enable->extension); | 
 |     return true; | 
 | } | 
 |  | 
 | type::Type* Resolver::TypeDecl(const ast::TypeDecl* named_type) { | 
 |     type::Type* result = nullptr; | 
 |     if (auto* alias = named_type->As<ast::Alias>()) { | 
 |         result = Alias(alias); | 
 |     } else if (auto* str = named_type->As<ast::Struct>()) { | 
 |         result = Structure(str); | 
 |     } else { | 
 |         TINT_UNREACHABLE(Resolver, diagnostics_) << "Unhandled TypeDecl"; | 
 |     } | 
 |  | 
 |     if (!result) { | 
 |         return nullptr; | 
 |     } | 
 |  | 
 |     builder_->Sem().Add(named_type, result); | 
 |     return result; | 
 | } | 
 |  | 
 | type::Array* Resolver::Array(const ast::Array* arr) { | 
 |     if (!arr->type) { | 
 |         AddError("missing array element type", arr->source.End()); | 
 |         return nullptr; | 
 |     } | 
 |  | 
 |     utils::UniqueVector<const sem::GlobalVariable*, 4> transitively_referenced_overrides; | 
 |     TINT_SCOPED_ASSIGNMENT(resolved_overrides_, &transitively_referenced_overrides); | 
 |  | 
 |     auto* el_ty = Type(arr->type); | 
 |     if (!el_ty) { | 
 |         return nullptr; | 
 |     } | 
 |  | 
 |     // Look for explicit stride via @stride(n) attribute | 
 |     uint32_t explicit_stride = 0; | 
 |     if (!ArrayAttributes(arr->attributes, el_ty, explicit_stride)) { | 
 |         return nullptr; | 
 |     } | 
 |  | 
 |     const type::ArrayCount* el_count = nullptr; | 
 |  | 
 |     // Evaluate the constant array count expression. | 
 |     if (auto* count_expr = arr->count) { | 
 |         el_count = ArrayCount(count_expr); | 
 |         if (!el_count) { | 
 |             return nullptr; | 
 |         } | 
 |     } else { | 
 |         el_count = builder_->create<type::RuntimeArrayCount>(); | 
 |     } | 
 |  | 
 |     auto* out = Array(arr->type->source,                              // | 
 |                       arr->count ? arr->count->source : arr->source,  // | 
 |                       el_ty, el_count, explicit_stride); | 
 |     if (out == nullptr) { | 
 |         return nullptr; | 
 |     } | 
 |  | 
 |     if (el_ty->Is<type::Atomic>()) { | 
 |         atomic_composite_info_.Add(out, &arr->type->source); | 
 |     } else { | 
 |         if (auto found = atomic_composite_info_.Get(el_ty)) { | 
 |             atomic_composite_info_.Add(out, *found); | 
 |         } | 
 |     } | 
 |  | 
 |     // Track the pipeline-overridable constants that are transitively referenced by this array | 
 |     // type. | 
 |     for (auto* var : transitively_referenced_overrides) { | 
 |         builder_->Sem().AddTransitivelyReferencedOverride(out, var); | 
 |     } | 
 |  | 
 |     return out; | 
 | } | 
 |  | 
 | const type::ArrayCount* Resolver::ArrayCount(const ast::Expression* count_expr) { | 
 |     // Evaluate the constant array count expression. | 
 |     const auto* count_sem = Materialize(Expression(count_expr)); | 
 |     if (!count_sem) { | 
 |         return nullptr; | 
 |     } | 
 |  | 
 |     if (count_sem->Stage() == sem::EvaluationStage::kOverride) { | 
 |         // array count is an override expression. | 
 |         // Is the count a named 'override'? | 
 |         if (auto* user = count_sem->UnwrapMaterialize()->As<sem::VariableUser>()) { | 
 |             if (auto* global = user->Variable()->As<sem::GlobalVariable>()) { | 
 |                 return builder_->create<sem::NamedOverrideArrayCount>(global); | 
 |             } | 
 |         } | 
 |         return builder_->create<sem::UnnamedOverrideArrayCount>(count_sem); | 
 |     } | 
 |  | 
 |     auto* count_val = count_sem->ConstantValue(); | 
 |     if (!count_val) { | 
 |         AddError("array count must evaluate to a constant integer expression or override variable", | 
 |                  count_expr->source); | 
 |         return nullptr; | 
 |     } | 
 |  | 
 |     if (auto* ty = count_val->Type(); !ty->is_integer_scalar()) { | 
 |         AddError("array count must evaluate to a constant integer expression, but is type '" + | 
 |                      builder_->FriendlyName(ty) + "'", | 
 |                  count_expr->source); | 
 |         return nullptr; | 
 |     } | 
 |  | 
 |     int64_t count = count_val->ValueAs<AInt>(); | 
 |     if (count < 1) { | 
 |         AddError("array count (" + std::to_string(count) + ") must be greater than 0", | 
 |                  count_expr->source); | 
 |         return nullptr; | 
 |     } | 
 |  | 
 |     return builder_->create<type::ConstantArrayCount>(static_cast<uint32_t>(count)); | 
 | } | 
 |  | 
 | bool Resolver::ArrayAttributes(utils::VectorRef<const ast::Attribute*> attributes, | 
 |                                const type::Type* el_ty, | 
 |                                uint32_t& explicit_stride) { | 
 |     if (!validator_.NoDuplicateAttributes(attributes)) { | 
 |         return false; | 
 |     } | 
 |  | 
 |     for (auto* attr : attributes) { | 
 |         Mark(attr); | 
 |         if (auto* sd = attr->As<ast::StrideAttribute>()) { | 
 |             // If the element type is not plain, then el_ty->Align() may be 0, in which case we | 
 |             // could get a DBZ in ArrayStrideAttribute(). In this case, validation will error | 
 |             // about the invalid array element type (which is tested later), so this is just a | 
 |             // seatbelt. | 
 |             if (IsPlain(el_ty)) { | 
 |                 explicit_stride = sd->stride; | 
 |                 if (!validator_.ArrayStrideAttribute(sd, el_ty->Size(), el_ty->Align())) { | 
 |                     return false; | 
 |                 } | 
 |             } | 
 |             continue; | 
 |         } | 
 |  | 
 |         AddError("attribute is not valid for array types", attr->source); | 
 |         return false; | 
 |     } | 
 |  | 
 |     return true; | 
 | } | 
 |  | 
 | type::Array* Resolver::Array(const Source& el_source, | 
 |                              const Source& count_source, | 
 |                              const type::Type* el_ty, | 
 |                              const type::ArrayCount* el_count, | 
 |                              uint32_t explicit_stride) { | 
 |     uint32_t el_align = el_ty->Align(); | 
 |     uint32_t el_size = el_ty->Size(); | 
 |     uint64_t implicit_stride = el_size ? utils::RoundUp<uint64_t>(el_align, el_size) : 0; | 
 |     uint64_t stride = explicit_stride ? explicit_stride : implicit_stride; | 
 |     uint64_t size = 0; | 
 |  | 
 |     if (auto const_count = el_count->As<type::ConstantArrayCount>()) { | 
 |         size = const_count->value * stride; | 
 |         if (size > std::numeric_limits<uint32_t>::max()) { | 
 |             std::stringstream msg; | 
 |             msg << "array byte size (0x" << std::hex << size | 
 |                 << ") must not exceed 0xffffffff bytes"; | 
 |             AddError(msg.str(), count_source); | 
 |             return nullptr; | 
 |         } | 
 |     } else if (el_count->Is<type::RuntimeArrayCount>()) { | 
 |         size = stride; | 
 |     } | 
 |     auto* out = builder_->create<type::Array>( | 
 |         el_ty, el_count, el_align, static_cast<uint32_t>(size), static_cast<uint32_t>(stride), | 
 |         static_cast<uint32_t>(implicit_stride)); | 
 |  | 
 |     if (!validator_.Array(out, el_source)) { | 
 |         return nullptr; | 
 |     } | 
 |  | 
 |     return out; | 
 | } | 
 |  | 
 | type::Type* Resolver::Alias(const ast::Alias* alias) { | 
 |     auto* ty = Type(alias->type); | 
 |     if (!ty) { | 
 |         return nullptr; | 
 |     } | 
 |     if (!validator_.Alias(alias)) { | 
 |         return nullptr; | 
 |     } | 
 |     return ty; | 
 | } | 
 |  | 
 | sem::Struct* Resolver::Structure(const ast::Struct* str) { | 
 |     if (!validator_.NoDuplicateAttributes(str->attributes)) { | 
 |         return nullptr; | 
 |     } | 
 |     for (auto* attr : str->attributes) { | 
 |         Mark(attr); | 
 |     } | 
 |  | 
 |     utils::Vector<const sem::StructMember*, 8> sem_members; | 
 |     sem_members.Reserve(str->members.Length()); | 
 |  | 
 |     // Calculate the effective size and alignment of each field, and the overall size of the | 
 |     // structure. For size, use the size attribute if provided, otherwise use the default size | 
 |     // for the type. For alignment, use the alignment attribute if provided, otherwise use the | 
 |     // default alignment for the member type. Diagnostic errors are raised if a basic rule is | 
 |     // violated. Validation of storage-class rules requires analyzing the actual variable usage | 
 |     // of the structure, and so is performed as part of the variable validation. | 
 |     uint64_t struct_size = 0; | 
 |     uint64_t struct_align = 1; | 
 |     utils::Hashmap<Symbol, const ast::StructMember*, 8> member_map; | 
 |  | 
 |     for (auto* member : str->members) { | 
 |         Mark(member); | 
 |         if (auto added = member_map.Add(member->symbol, member); !added) { | 
 |             AddError("redefinition of '" + builder_->Symbols().NameFor(member->symbol) + "'", | 
 |                      member->source); | 
 |             AddNote("previous definition is here", (*added.value)->source); | 
 |             return nullptr; | 
 |         } | 
 |  | 
 |         // Resolve member type | 
 |         auto* type = Type(member->type); | 
 |         if (!type) { | 
 |             return nullptr; | 
 |         } | 
 |  | 
 |         // validator_.Validate member type | 
 |         if (!validator_.IsPlain(type)) { | 
 |             AddError(sem_.TypeNameOf(type) + " cannot be used as the type of a structure member", | 
 |                      member->source); | 
 |             return nullptr; | 
 |         } | 
 |  | 
 |         uint64_t offset = struct_size; | 
 |         uint64_t align = type->Align(); | 
 |         uint64_t size = type->Size(); | 
 |  | 
 |         if (!validator_.NoDuplicateAttributes(member->attributes)) { | 
 |             return nullptr; | 
 |         } | 
 |  | 
 |         bool has_offset_attr = false; | 
 |         bool has_align_attr = false; | 
 |         bool has_size_attr = false; | 
 |         std::optional<uint32_t> location; | 
 |         for (auto* attr : member->attributes) { | 
 |             Mark(attr); | 
 |             bool ok = Switch( | 
 |                 attr,  // | 
 |                 [&](const ast::StructMemberOffsetAttribute* o) { | 
 |                     // Offset attributes are not part of the WGSL spec, but are emitted | 
 |                     // by the SPIR-V reader. | 
 |                     ExprEvalStageConstraint constraint{sem::EvaluationStage::kConstant, | 
 |                                                        "@offset value"}; | 
 |                     TINT_SCOPED_ASSIGNMENT(expr_eval_stage_constraint_, constraint); | 
 |  | 
 |                     auto* materialized = Materialize(Expression(o->expr)); | 
 |                     if (!materialized) { | 
 |                         return false; | 
 |                     } | 
 |                     auto const_value = materialized->ConstantValue(); | 
 |                     if (!const_value) { | 
 |                         AddError("@offset must be constant expression", o->expr->source); | 
 |                         return false; | 
 |                     } | 
 |                     offset = const_value->ValueAs<uint64_t>(); | 
 |  | 
 |                     if (offset < struct_size) { | 
 |                         AddError("offsets must be in ascending order", o->source); | 
 |                         return false; | 
 |                     } | 
 |                     has_offset_attr = true; | 
 |                     return true; | 
 |                 }, | 
 |                 [&](const ast::StructMemberAlignAttribute* a) { | 
 |                     ExprEvalStageConstraint constraint{sem::EvaluationStage::kConstant, "@align"}; | 
 |                     TINT_SCOPED_ASSIGNMENT(expr_eval_stage_constraint_, constraint); | 
 |  | 
 |                     auto* materialized = Materialize(Expression(a->expr)); | 
 |                     if (!materialized) { | 
 |                         return false; | 
 |                     } | 
 |                     if (!materialized->Type()->IsAnyOf<type::I32, type::U32>()) { | 
 |                         AddError("@align must be an i32 or u32 value", a->source); | 
 |                         return false; | 
 |                     } | 
 |  | 
 |                     auto const_value = materialized->ConstantValue(); | 
 |                     if (!const_value) { | 
 |                         AddError("@align must be constant expression", a->source); | 
 |                         return false; | 
 |                     } | 
 |                     auto value = const_value->ValueAs<AInt>(); | 
 |  | 
 |                     if (value <= 0 || !utils::IsPowerOfTwo(value)) { | 
 |                         AddError("@align value must be a positive, power-of-two integer", | 
 |                                  a->source); | 
 |                         return false; | 
 |                     } | 
 |                     align = u32(value); | 
 |                     has_align_attr = true; | 
 |                     return true; | 
 |                 }, | 
 |                 [&](const ast::StructMemberSizeAttribute* s) { | 
 |                     ExprEvalStageConstraint constraint{sem::EvaluationStage::kConstant, "@size"}; | 
 |                     TINT_SCOPED_ASSIGNMENT(expr_eval_stage_constraint_, constraint); | 
 |  | 
 |                     auto* materialized = Materialize(Expression(s->expr)); | 
 |                     if (!materialized) { | 
 |                         return false; | 
 |                     } | 
 |                     if (!materialized->Type()->IsAnyOf<type::U32, type::I32>()) { | 
 |                         AddError("@size must be an i32 or u32 value", s->source); | 
 |                         return false; | 
 |                     } | 
 |  | 
 |                     auto const_value = materialized->ConstantValue(); | 
 |                     if (!const_value) { | 
 |                         AddError("@size must be constant expression", s->expr->source); | 
 |                         return false; | 
 |                     } | 
 |                     { | 
 |                         auto value = const_value->ValueAs<AInt>(); | 
 |                         if (value <= 0) { | 
 |                             AddError("@size must be a positive integer", s->source); | 
 |                             return false; | 
 |                         } | 
 |                     } | 
 |                     auto value = const_value->ValueAs<uint64_t>(); | 
 |                     if (value < size) { | 
 |                         AddError("@size must be at least as big as the type's size (" + | 
 |                                      std::to_string(size) + ")", | 
 |                                  s->source); | 
 |                         return false; | 
 |                     } | 
 |                     size = u32(value); | 
 |                     has_size_attr = true; | 
 |                     return true; | 
 |                 }, | 
 |                 [&](const ast::LocationAttribute* loc_attr) { | 
 |                     auto value = LocationAttribute(loc_attr); | 
 |                     if (!value) { | 
 |                         return false; | 
 |                     } | 
 |                     location = value.Get(); | 
 |                     return true; | 
 |                 }, | 
 |                 [&](Default) { | 
 |                     // The validator will check attributes can be applied to the struct member. | 
 |                     return true; | 
 |                 }); | 
 |             if (!ok) { | 
 |                 return nullptr; | 
 |             } | 
 |         } | 
 |  | 
 |         if (has_offset_attr && (has_align_attr || has_size_attr)) { | 
 |             AddError("@offset cannot be used with @align or @size", member->source); | 
 |             return nullptr; | 
 |         } | 
 |  | 
 |         offset = utils::RoundUp(align, offset); | 
 |         if (offset > std::numeric_limits<uint32_t>::max()) { | 
 |             std::stringstream msg; | 
 |             msg << "struct member offset (0x" << std::hex << offset << ") must not exceed 0x" | 
 |                 << std::hex << std::numeric_limits<uint32_t>::max() << " bytes"; | 
 |             AddError(msg.str(), member->source); | 
 |             return nullptr; | 
 |         } | 
 |  | 
 |         auto* sem_member = builder_->create<sem::StructMember>( | 
 |             member, member->source, member->symbol, type, | 
 |             static_cast<uint32_t>(sem_members.Length()), static_cast<uint32_t>(offset), | 
 |             static_cast<uint32_t>(align), static_cast<uint32_t>(size), location); | 
 |         builder_->Sem().Add(member, sem_member); | 
 |         sem_members.Push(sem_member); | 
 |  | 
 |         struct_size = offset + size; | 
 |         struct_align = std::max(struct_align, align); | 
 |     } | 
 |  | 
 |     uint64_t size_no_padding = struct_size; | 
 |     struct_size = utils::RoundUp(struct_align, struct_size); | 
 |  | 
 |     if (struct_size > std::numeric_limits<uint32_t>::max()) { | 
 |         std::stringstream msg; | 
 |         msg << "struct size (0x" << std::hex << struct_size << ") must not exceed 0xffffffff bytes"; | 
 |         AddError(msg.str(), str->source); | 
 |         return nullptr; | 
 |     } | 
 |     if (struct_align > std::numeric_limits<uint32_t>::max()) { | 
 |         TINT_ICE(Resolver, diagnostics_) << "calculated struct stride exceeds uint32"; | 
 |         return nullptr; | 
 |     } | 
 |  | 
 |     auto* out = builder_->create<sem::Struct>( | 
 |         str, str->source, str->name, std::move(sem_members), static_cast<uint32_t>(struct_align), | 
 |         static_cast<uint32_t>(struct_size), static_cast<uint32_t>(size_no_padding)); | 
 |  | 
 |     for (size_t i = 0; i < sem_members.Length(); i++) { | 
 |         auto* mem_type = sem_members[i]->Type(); | 
 |         if (mem_type->Is<type::Atomic>()) { | 
 |             atomic_composite_info_.Add(out, &sem_members[i]->Source()); | 
 |             break; | 
 |         } else { | 
 |             if (auto found = atomic_composite_info_.Get(mem_type)) { | 
 |                 atomic_composite_info_.Add(out, *found); | 
 |                 break; | 
 |             } | 
 |         } | 
 |  | 
 |         const_cast<sem::StructMember*>(sem_members[i])->SetStruct(out); | 
 |     } | 
 |  | 
 |     auto stage = current_function_ ? current_function_->Declaration()->PipelineStage() | 
 |                                    : ast::PipelineStage::kNone; | 
 |     if (!validator_.Structure(out, stage)) { | 
 |         return nullptr; | 
 |     } | 
 |  | 
 |     return out; | 
 | } | 
 |  | 
 | sem::Statement* Resolver::ReturnStatement(const ast::ReturnStatement* stmt) { | 
 |     auto* sem = | 
 |         builder_->create<sem::Statement>(stmt, current_compound_statement_, current_function_); | 
 |     return StatementScope(stmt, sem, [&] { | 
 |         auto& behaviors = current_statement_->Behaviors(); | 
 |         behaviors = sem::Behavior::kReturn; | 
 |  | 
 |         const type::Type* value_ty = nullptr; | 
 |         if (auto* value = stmt->value) { | 
 |             const auto* expr = Expression(value); | 
 |             if (!expr) { | 
 |                 return false; | 
 |             } | 
 |             if (auto* ret_ty = current_function_->ReturnType(); !ret_ty->Is<type::Void>()) { | 
 |                 expr = Materialize(expr, ret_ty); | 
 |                 if (!expr) { | 
 |                     return false; | 
 |                 } | 
 |             } | 
 |             behaviors.Add(expr->Behaviors() - sem::Behavior::kNext); | 
 |             value_ty = expr->Type()->UnwrapRef(); | 
 |  | 
 |             RegisterLoadIfNeeded(expr); | 
 |         } else { | 
 |             value_ty = builder_->create<type::Void>(); | 
 |         } | 
 |  | 
 |         // Validate after processing the return value expression so that its type | 
 |         // is available for validation. | 
 |         return validator_.Return(stmt, current_function_->ReturnType(), value_ty, | 
 |                                  current_statement_); | 
 |     }); | 
 | } | 
 |  | 
 | sem::SwitchStatement* Resolver::SwitchStatement(const ast::SwitchStatement* stmt) { | 
 |     auto* sem = builder_->create<sem::SwitchStatement>(stmt, current_compound_statement_, | 
 |                                                        current_function_); | 
 |     return StatementScope(stmt, sem, [&] { | 
 |         auto& behaviors = sem->Behaviors(); | 
 |  | 
 |         const auto* cond = Expression(stmt->condition); | 
 |         if (!cond) { | 
 |             return false; | 
 |         } | 
 |         behaviors = cond->Behaviors() - sem::Behavior::kNext; | 
 |  | 
 |         RegisterLoadIfNeeded(cond); | 
 |  | 
 |         auto* cond_ty = cond->Type()->UnwrapRef(); | 
 |  | 
 |         // Determine the common type across all selectors and the switch expression | 
 |         // This must materialize to an integer scalar (non-abstract). | 
 |         utils::Vector<const type::Type*, 8> types; | 
 |         types.Push(cond_ty); | 
 |         for (auto* case_stmt : stmt->body) { | 
 |             for (auto* sel : case_stmt->selectors) { | 
 |                 if (sel->IsDefault()) { | 
 |                     continue; | 
 |                 } | 
 |                 auto* sem_expr = Expression(sel->expr); | 
 |                 if (!sem_expr) { | 
 |                     return false; | 
 |                 } | 
 |                 types.Push(sem_expr->Type()->UnwrapRef()); | 
 |             } | 
 |         } | 
 |         auto* common_ty = type::Type::Common(types); | 
 |         if (!common_ty || !common_ty->is_integer_scalar()) { | 
 |             // No common type found or the common type was abstract. | 
 |             // Pick i32 and let validation deal with any mismatches. | 
 |             common_ty = builder_->create<type::I32>(); | 
 |         } | 
 |         cond = Materialize(cond, common_ty); | 
 |         if (!cond) { | 
 |             return false; | 
 |         } | 
 |  | 
 |         utils::Vector<sem::CaseStatement*, 4> cases; | 
 |         cases.Reserve(stmt->body.Length()); | 
 |         for (auto* case_stmt : stmt->body) { | 
 |             Mark(case_stmt); | 
 |             auto* c = CaseStatement(case_stmt, common_ty); | 
 |             if (!c) { | 
 |                 return false; | 
 |             } | 
 |             cases.Push(c); | 
 |             behaviors.Add(c->Behaviors()); | 
 |             sem->Cases().emplace_back(c); | 
 |         } | 
 |  | 
 |         if (behaviors.Contains(sem::Behavior::kBreak)) { | 
 |             behaviors.Add(sem::Behavior::kNext); | 
 |         } | 
 |         behaviors.Remove(sem::Behavior::kBreak); | 
 |  | 
 |         return validator_.SwitchStatement(stmt); | 
 |     }); | 
 | } | 
 |  | 
 | sem::Statement* Resolver::VariableDeclStatement(const ast::VariableDeclStatement* stmt) { | 
 |     auto* sem = | 
 |         builder_->create<sem::Statement>(stmt, current_compound_statement_, current_function_); | 
 |     return StatementScope(stmt, sem, [&] { | 
 |         Mark(stmt->variable); | 
 |  | 
 |         auto* variable = Variable(stmt->variable, /* is_global */ false); | 
 |         if (!variable) { | 
 |             return false; | 
 |         } | 
 |  | 
 |         for (auto* attr : stmt->variable->attributes) { | 
 |             Mark(attr); | 
 |             if (!attr->Is<ast::InternalAttribute>()) { | 
 |                 AddError("attributes are not valid on local variables", attr->source); | 
 |                 return false; | 
 |             } | 
 |         } | 
 |  | 
 |         current_compound_statement_->AddDecl(variable->As<sem::LocalVariable>()); | 
 |  | 
 |         if (auto* ctor = variable->Initializer()) { | 
 |             sem->Behaviors() = ctor->Behaviors(); | 
 |         } | 
 |  | 
 |         return validator_.LocalVariable(variable); | 
 |     }); | 
 | } | 
 |  | 
 | sem::Statement* Resolver::AssignmentStatement(const ast::AssignmentStatement* stmt) { | 
 |     auto* sem = | 
 |         builder_->create<sem::Statement>(stmt, current_compound_statement_, current_function_); | 
 |     return StatementScope(stmt, sem, [&] { | 
 |         auto* lhs = Expression(stmt->lhs); | 
 |         if (!lhs) { | 
 |             return false; | 
 |         } | 
 |  | 
 |         const bool is_phony_assignment = stmt->lhs->Is<ast::PhonyExpression>(); | 
 |  | 
 |         const auto* rhs = Expression(stmt->rhs); | 
 |         if (!rhs) { | 
 |             return false; | 
 |         } | 
 |  | 
 |         if (!is_phony_assignment) { | 
 |             rhs = Materialize(rhs, lhs->Type()->UnwrapRef()); | 
 |             if (!rhs) { | 
 |                 return false; | 
 |             } | 
 |         } | 
 |  | 
 |         RegisterLoadIfNeeded(rhs); | 
 |  | 
 |         auto& behaviors = sem->Behaviors(); | 
 |         behaviors = rhs->Behaviors(); | 
 |         if (!is_phony_assignment) { | 
 |             behaviors.Add(lhs->Behaviors()); | 
 |         } | 
 |  | 
 |         if (!is_phony_assignment) { | 
 |             RegisterStore(lhs); | 
 |         } | 
 |  | 
 |         return validator_.Assignment(stmt, sem_.TypeOf(stmt->rhs)); | 
 |     }); | 
 | } | 
 |  | 
 | sem::Statement* Resolver::BreakStatement(const ast::BreakStatement* stmt) { | 
 |     auto* sem = | 
 |         builder_->create<sem::Statement>(stmt, current_compound_statement_, current_function_); | 
 |     return StatementScope(stmt, sem, [&] { | 
 |         sem->Behaviors() = sem::Behavior::kBreak; | 
 |  | 
 |         return validator_.BreakStatement(sem, current_statement_); | 
 |     }); | 
 | } | 
 |  | 
 | sem::Statement* Resolver::BreakIfStatement(const ast::BreakIfStatement* stmt) { | 
 |     auto* sem = builder_->create<sem::BreakIfStatement>(stmt, current_compound_statement_, | 
 |                                                         current_function_); | 
 |     return StatementScope(stmt, sem, [&] { | 
 |         auto* cond = Expression(stmt->condition); | 
 |         if (!cond) { | 
 |             return false; | 
 |         } | 
 |         sem->SetCondition(cond); | 
 |         sem->Behaviors() = cond->Behaviors(); | 
 |         sem->Behaviors().Add(sem::Behavior::kBreak); | 
 |  | 
 |         RegisterLoadIfNeeded(cond); | 
 |  | 
 |         return validator_.BreakIfStatement(sem, current_statement_); | 
 |     }); | 
 | } | 
 |  | 
 | sem::Statement* Resolver::CallStatement(const ast::CallStatement* stmt) { | 
 |     auto* sem = | 
 |         builder_->create<sem::Statement>(stmt, current_compound_statement_, current_function_); | 
 |     return StatementScope(stmt, sem, [&] { | 
 |         if (auto* expr = Expression(stmt->expr)) { | 
 |             sem->Behaviors() = expr->Behaviors(); | 
 |             return true; | 
 |         } | 
 |         return false; | 
 |     }); | 
 | } | 
 |  | 
 | sem::Statement* Resolver::CompoundAssignmentStatement( | 
 |     const ast::CompoundAssignmentStatement* stmt) { | 
 |     auto* sem = | 
 |         builder_->create<sem::Statement>(stmt, current_compound_statement_, current_function_); | 
 |     return StatementScope(stmt, sem, [&] { | 
 |         auto* lhs = Expression(stmt->lhs); | 
 |         if (!lhs) { | 
 |             return false; | 
 |         } | 
 |  | 
 |         auto* rhs = Expression(stmt->rhs); | 
 |         if (!rhs) { | 
 |             return false; | 
 |         } | 
 |  | 
 |         RegisterLoadIfNeeded(rhs); | 
 |         RegisterStore(lhs); | 
 |  | 
 |         sem->Behaviors() = rhs->Behaviors() + lhs->Behaviors(); | 
 |  | 
 |         auto* lhs_ty = lhs->Type()->UnwrapRef(); | 
 |         auto* rhs_ty = rhs->Type()->UnwrapRef(); | 
 |         auto stage = sem::EarliestStage(lhs->Stage(), rhs->Stage()); | 
 |         auto* ty = | 
 |             intrinsic_table_->Lookup(stmt->op, lhs_ty, rhs_ty, stage, stmt->source, true).result; | 
 |         if (!ty) { | 
 |             return false; | 
 |         } | 
 |         return validator_.Assignment(stmt, ty); | 
 |     }); | 
 | } | 
 |  | 
 | sem::Statement* Resolver::ContinueStatement(const ast::ContinueStatement* stmt) { | 
 |     auto* sem = | 
 |         builder_->create<sem::Statement>(stmt, current_compound_statement_, current_function_); | 
 |     return StatementScope(stmt, sem, [&] { | 
 |         sem->Behaviors() = sem::Behavior::kContinue; | 
 |  | 
 |         // Set if we've hit the first continue statement in our parent loop | 
 |         if (auto* block = sem->FindFirstParent<sem::LoopBlockStatement>()) { | 
 |             if (!block->FirstContinue()) { | 
 |                 const_cast<sem::LoopBlockStatement*>(block)->SetFirstContinue( | 
 |                     stmt, block->Decls().Count()); | 
 |             } | 
 |         } | 
 |  | 
 |         return validator_.ContinueStatement(sem, current_statement_); | 
 |     }); | 
 | } | 
 |  | 
 | sem::Statement* Resolver::DiscardStatement(const ast::DiscardStatement* stmt) { | 
 |     auto* sem = | 
 |         builder_->create<sem::Statement>(stmt, current_compound_statement_, current_function_); | 
 |     return StatementScope(stmt, sem, [&] { | 
 |         current_function_->SetDiscardStatement(sem); | 
 |         return true; | 
 |     }); | 
 | } | 
 |  | 
 | sem::Statement* Resolver::IncrementDecrementStatement( | 
 |     const ast::IncrementDecrementStatement* stmt) { | 
 |     auto* sem = | 
 |         builder_->create<sem::Statement>(stmt, current_compound_statement_, current_function_); | 
 |     return StatementScope(stmt, sem, [&] { | 
 |         auto* lhs = Expression(stmt->lhs); | 
 |         if (!lhs) { | 
 |             return false; | 
 |         } | 
 |         sem->Behaviors() = lhs->Behaviors(); | 
 |  | 
 |         RegisterLoadIfNeeded(lhs); | 
 |         RegisterStore(lhs); | 
 |  | 
 |         return validator_.IncrementDecrementStatement(stmt); | 
 |     }); | 
 | } | 
 |  | 
 | bool Resolver::ApplyAddressSpaceUsageToType(ast::AddressSpace address_space, | 
 |                                             type::Type* ty, | 
 |                                             const Source& usage) { | 
 |     ty = const_cast<type::Type*>(ty->UnwrapRef()); | 
 |  | 
 |     if (auto* str = ty->As<sem::Struct>()) { | 
 |         if (str->AddressSpaceUsage().count(address_space)) { | 
 |             return true;  // Already applied | 
 |         } | 
 |  | 
 |         str->AddUsage(address_space); | 
 |  | 
 |         for (auto* member : str->Members()) { | 
 |             auto decl = member->Declaration(); | 
 |             if (decl && | 
 |                 !ApplyAddressSpaceUsageToType( | 
 |                     address_space, const_cast<type::Type*>(member->Type()), decl->type->source)) { | 
 |                 std::stringstream err; | 
 |                 err << "while analyzing structure member " << sem_.TypeNameOf(str) << "." | 
 |                     << builder_->Symbols().NameFor(member->Name()); | 
 |                 AddNote(err.str(), member->Source()); | 
 |                 return false; | 
 |             } | 
 |         } | 
 |         return true; | 
 |     } | 
 |  | 
 |     if (auto* arr = ty->As<type::Array>()) { | 
 |         if (address_space != ast::AddressSpace::kStorage) { | 
 |             if (arr->Count()->Is<type::RuntimeArrayCount>()) { | 
 |                 AddError("runtime-sized arrays can only be used in the <storage> address space", | 
 |                          usage); | 
 |                 return false; | 
 |             } | 
 |  | 
 |             auto count = arr->ConstantCount(); | 
 |             if (count.has_value() && count.value() >= kMaxArrayElementCount) { | 
 |                 AddError("array count (" + std::to_string(count.value()) + ") must be less than " + | 
 |                              std::to_string(kMaxArrayElementCount), | 
 |                          usage); | 
 |                 return false; | 
 |             } | 
 |         } | 
 |         return ApplyAddressSpaceUsageToType(address_space, const_cast<type::Type*>(arr->ElemType()), | 
 |                                             usage); | 
 |     } | 
 |  | 
 |     if (ast::IsHostShareable(address_space) && !validator_.IsHostShareable(ty)) { | 
 |         std::stringstream err; | 
 |         err << "Type '" << sem_.TypeNameOf(ty) << "' cannot be used in address space '" | 
 |             << address_space << "' as it is non-host-shareable"; | 
 |         AddError(err.str(), usage); | 
 |         return false; | 
 |     } | 
 |  | 
 |     return true; | 
 | } | 
 |  | 
 | template <typename SEM, typename F> | 
 | SEM* Resolver::StatementScope(const ast::Statement* ast, SEM* sem, F&& callback) { | 
 |     builder_->Sem().Add(ast, sem); | 
 |  | 
 |     auto* as_compound = As<sem::CompoundStatement, CastFlags::kDontErrorOnImpossibleCast>(sem); | 
 |  | 
 |     TINT_SCOPED_ASSIGNMENT(current_statement_, sem); | 
 |     TINT_SCOPED_ASSIGNMENT(current_compound_statement_, | 
 |                            as_compound ? as_compound : current_compound_statement_); | 
 |     TINT_SCOPED_ASSIGNMENT(current_scoping_depth_, current_scoping_depth_ + 1); | 
 |  | 
 |     if (current_scoping_depth_ > kMaxStatementDepth) { | 
 |         AddError("statement nesting depth / chaining length exceeds limit of " + | 
 |                      std::to_string(kMaxStatementDepth), | 
 |                  ast->source); | 
 |         return nullptr; | 
 |     } | 
 |  | 
 |     if (!callback()) { | 
 |         return nullptr; | 
 |     } | 
 |  | 
 |     return sem; | 
 | } | 
 |  | 
 | bool Resolver::Mark(const ast::Node* node) { | 
 |     if (node == nullptr) { | 
 |         TINT_ICE(Resolver, diagnostics_) << "Resolver::Mark() called with nullptr"; | 
 |         return false; | 
 |     } | 
 |     auto marked_bit_ref = marked_[node->node_id.value]; | 
 |     if (!marked_bit_ref) { | 
 |         marked_bit_ref = true; | 
 |         return true; | 
 |     } | 
 |     TINT_ICE(Resolver, diagnostics_) << "AST node '" << node->TypeInfo().name | 
 |                                      << "' was encountered twice in the same AST of a Program\n" | 
 |                                      << "At: " << node->source << "\n" | 
 |                                      << "Pointer: " << node; | 
 |     return false; | 
 | } | 
 |  | 
 | void Resolver::AddError(const std::string& msg, const Source& source) const { | 
 |     diagnostics_.add_error(diag::System::Resolver, msg, source); | 
 | } | 
 |  | 
 | void Resolver::AddWarning(const std::string& msg, const Source& source) const { | 
 |     diagnostics_.add_warning(diag::System::Resolver, msg, source); | 
 | } | 
 |  | 
 | void Resolver::AddNote(const std::string& msg, const Source& source) const { | 
 |     diagnostics_.add_note(diag::System::Resolver, msg, source); | 
 | } | 
 |  | 
 | bool Resolver::IsBuiltin(Symbol symbol) const { | 
 |     std::string name = builder_->Symbols().NameFor(symbol); | 
 |     return sem::ParseBuiltinType(name) != sem::BuiltinType::kNone; | 
 | } | 
 |  | 
 | }  // namespace tint::resolver |