src/validator/validator_impl.cc - dawn - Git at Google

 // 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/validator/validator_impl.h"

 #include <cassert>
 #include <unordered_set>
 #include <utility>

 #include "src/ast/call_statement.h"
 #include "src/ast/fallthrough_statement.h"
 #include "src/ast/function.h"
 #include "src/ast/int_literal.h"
 #include "src/ast/intrinsic.h"
 #include "src/ast/sint_literal.h"
 #include "src/ast/stage_decoration.h"
 #include "src/ast/struct.h"
 #include "src/ast/switch_statement.h"
 #include "src/ast/type/array_type.h"
 #include "src/ast/type/i32_type.h"
 #include "src/ast/type/struct_type.h"
 #include "src/ast/type/u32_type.h"
 #include "src/ast/type/void_type.h"
 #include "src/ast/uint_literal.h"
 #include "src/ast/variable_decl_statement.h"

 namespace tint {

 ValidatorImpl::ValidatorImpl() = default;

 ValidatorImpl::~ValidatorImpl() = default;

 void ValidatorImpl::add_error(const Source& src,
                               const char* code,
                               const std::string& msg) {
   diag::Diagnostic diag;
   diag.severity = diag::Severity::Error;
   diag.source = src;
   diag.message = msg;
   diag.code = code;
   diags_.add(std::move(diag));
 }

 void ValidatorImpl::add_error(const Source& src, const std::string& msg) {
   diag::Diagnostic diag;
   diag.severity = diag::Severity::Error;
   diag.source = src;
   diag.message = msg;
   diags_.add(std::move(diag));
 }

 bool ValidatorImpl::Validate(const ast::Module* module) {
   if (!module) {
     return false;
   }
   function_stack_.push_scope();
   if (!ValidateGlobalVariables(module->global_variables())) {
     return false;
   }
   if (!ValidateConstructedTypes(module->constructed_types())) {
     return false;
   }
   if (!ValidateFunctions(module->functions())) {
     return false;
   }
   if (!ValidateEntryPoint(module->functions())) {
     return false;
   }
   function_stack_.pop_scope();

   return true;
 }

 bool ValidatorImpl::ValidateConstructedTypes(
     const std::vector<ast::type::Type*>& constructed_types) {
   for (auto* const ct : constructed_types) {
     if (ct->Is<ast::type::StructType>()) {
       auto* st = ct->As<ast::type::StructType>();
       for (auto* member : st->impl()->members()) {
         if (member->type()->UnwrapAll()->Is<ast::type::ArrayType>()) {
           auto* r = member->type()->UnwrapAll()->As<ast::type::ArrayType>();
           if (r->IsRuntimeArray()) {
             if (member != st->impl()->members().back()) {
               add_error(member->source(), "v-0015",
                         "runtime arrays may only appear as the last "
                         "member of a struct: '" +
                             member->name() + "'");
               return false;
             }
             if (!st->IsBlockDecorated()) {
               add_error(member->source(), "v-0031",
                         "a struct containing a runtime-sized array "
                         "must be in the 'storage' storage class: '" +
                             st->name() + "'");
               return false;
             }
           }
         }
       }
     }
   }
   return true;
 }

 bool ValidatorImpl::ValidateGlobalVariables(
     const ast::VariableList& global_vars) {
   for (auto* var : global_vars) {
     if (variable_stack_.has(var->name())) {
       add_error(var->source(), "v-0011",
                 "redeclared global identifier '" + var->name() + "'");
       return false;
     }
     if (!var->is_const() && var->storage_class() == ast::StorageClass::kNone) {
       add_error(var->source(), "v-0022",
                 "global variables must have a storage class");
       return false;
     }
     if (var->is_const() &&
         !(var->storage_class() == ast::StorageClass::kNone)) {
       add_error(var->source(), "v-global01",
                 "global constants shouldn't have a storage class");
       return false;
     }
     variable_stack_.set_global(var->name(), var);
   }
   return true;
 }

 bool ValidatorImpl::ValidateFunctions(const ast::FunctionList& funcs) {
   for (auto* func : funcs) {
     if (function_stack_.has(func->name())) {
       add_error(func->source(), "v-0016",
                 "function names must be unique '" + func->name() + "'");
       return false;
     }

     function_stack_.set(func->name(), func);
     current_function_ = func;
     if (!ValidateFunction(func)) {
       return false;
     }
     current_function_ = nullptr;
   }

   return true;
 }

 bool ValidatorImpl::ValidateEntryPoint(const ast::FunctionList& funcs) {
   auto shader_is_present = false;
   for (auto* func : funcs) {
     if (func->IsEntryPoint()) {
       shader_is_present = true;
       if (!func->params().empty()) {
         add_error(func->source(), "v-0023",
                   "Entry point function must accept no parameters: '" +
                       func->name() + "'");
         return false;
       }

       if (!func->return_type()->Is<ast::type::VoidType>()) {
         add_error(
             func->source(), "v-0024",
             "Entry point function must return void: '" + func->name() + "'");
         return false;
       }
       auto stage_deco_count = 0;
       for (auto* deco : func->decorations()) {
         if (deco->Is<ast::StageDecoration>()) {
           stage_deco_count++;
         }
       }
       if (stage_deco_count > 1) {
         add_error(func->source(), "v-0020",
                   "only one stage decoration permitted per entry point");
         return false;
       }
     }
   }
   if (!shader_is_present) {
     add_error(Source{}, "v-0003",
               "At least one of vertex, fragment or compute shader must "
               "be present");
     return false;
   }
   return true;
 }

 bool ValidatorImpl::ValidateFunction(const ast::Function* func) {
   variable_stack_.push_scope();

   for (auto* param : func->params()) {
     variable_stack_.set(param->name(), param);
   }
   if (!ValidateStatements(func->body())) {
     return false;
   }
   variable_stack_.pop_scope();

   if (!current_function_->return_type()->Is<ast::type::VoidType>()) {
     if (!func->get_last_statement() ||
         !func->get_last_statement()->Is<ast::ReturnStatement>()) {
       add_error(func->source(), "v-0002",
                 "non-void function must end with a return statement");
       return false;
     }
   }
   return true;
 }

 bool ValidatorImpl::ValidateReturnStatement(const ast::ReturnStatement* ret) {
   // TODO(sarahM0): update this when this issue resolves:
   // https://github.com/gpuweb/gpuweb/issues/996
   ast::type::Type* func_type = current_function_->return_type();

   ast::type::VoidType void_type;
   auto* ret_type =
       ret->has_value() ? ret->value()->result_type()->UnwrapAll() : &void_type;

   if (func_type->type_name() != ret_type->type_name()) {
     add_error(ret->source(), "v-000y",
               "return statement type must match its function return "
               "type, returned '" +
                   ret_type->type_name() + "', expected '" +
                   func_type->type_name() + "'");
     return false;
   }

   return true;
 }

 bool ValidatorImpl::ValidateStatements(const ast::BlockStatement* block) {
   if (!block) {
     return false;
   }
   for (auto* stmt : *block) {
     if (!ValidateStatement(stmt)) {
       return false;
     }
   }
   return true;
 }

 bool ValidatorImpl::ValidateDeclStatement(
     const ast::VariableDeclStatement* decl) {
   auto name = decl->variable()->name();
   bool is_global = false;
   if (variable_stack_.get(name, nullptr, &is_global)) {
     const char* error_code = "v-0014";
     if (is_global) {
       error_code = "v-0013";
     }
     add_error(decl->source(), error_code,
               "redeclared identifier '" + name + "'");
     return false;
   }
   variable_stack_.set(name, decl->variable());
   if (decl->variable()->type()->UnwrapAll()->Is<ast::type::ArrayType>()) {
     if (decl->variable()
             ->type()
             ->UnwrapAll()
             ->As<ast::type::ArrayType>()
             ->IsRuntimeArray()) {
       add_error(decl->source(), "v-0015",
                 "runtime arrays may only appear as the last "
                 "member of a struct: '" +
                     decl->variable()->name() + "'");
       return false;
     }
   }
   return true;
 }

 bool ValidatorImpl::ValidateStatement(const ast::Statement* stmt) {
   if (!stmt) {
     return false;
   }
   if (auto* v = stmt->As<ast::VariableDeclStatement>()) {
     bool constructor_valid =
         v->variable()->has_constructor()
             ? ValidateExpression(v->variable()->constructor())
             : true;

     return constructor_valid && ValidateDeclStatement(v);
   }
   if (auto* a = stmt->As<ast::AssignmentStatement>()) {
     return ValidateAssign(a);
   }
   if (auto* r = stmt->As<ast::ReturnStatement>()) {
     return ValidateReturnStatement(r);
   }
   if (auto* c = stmt->As<ast::CallStatement>()) {
     return ValidateCallExpr(c->expr());
   }
   if (auto* s = stmt->As<ast::SwitchStatement>()) {
     return ValidateSwitch(s);
   }
   if (auto* c = stmt->As<ast::CaseStatement>()) {
     return ValidateCase(c);
   }
   return true;
 }

 bool ValidatorImpl::ValidateSwitch(const ast::SwitchStatement* s) {
   if (!ValidateExpression(s->condition())) {
     return false;
   }

   auto* cond_type = s->condition()->result_type()->UnwrapAll();
   if (!(cond_type->Is<ast::type::I32Type>() ||
         cond_type->Is<ast::type::U32Type>())) {
     add_error(s->condition()->source(), "v-0025",
               "switch statement selector expression must be of a "
               "scalar integer type");
     return false;
   }

   int default_counter = 0;
   std::unordered_set<int32_t> selector_set;
   for (auto* case_stmt : s->body()) {
     if (!ValidateStatement(case_stmt)) {
       return false;
     }

     if (case_stmt->IsDefault()) {
       default_counter++;
     }

     for (auto* selector : case_stmt->selectors()) {
       if (cond_type != selector->type()) {
         add_error(case_stmt->source(), "v-0026",
                   "the case selector values must have the same "
                   "type as the selector expression.");
         return false;
       }

       auto v =
           static_cast<int32_t>(selector->type()->Is<ast::type::U32Type>()
                                    ? selector->As<ast::UintLiteral>()->value()
                                    : selector->As<ast::SintLiteral>()->value());
       if (selector_set.count(v)) {
         auto v_str = selector->type()->Is<ast::type::U32Type>()
                          ? selector->As<ast::UintLiteral>()->to_str()
                          : selector->As<ast::SintLiteral>()->to_str();
         add_error(case_stmt->source(), "v-0027",
                   "a literal value must not appear more than once in "
                   "the case selectors for a switch statement: '" +
                       v_str + "'");
         return false;
       }
       selector_set.emplace(v);
     }
   }

   if (default_counter != 1) {
     add_error(s->source(), "v-0008",
               "switch statement must have exactly one default clause");
     return false;
   }

   auto* last_clause = s->body().back();
   auto* last_stmt_of_last_clause =
       last_clause->As<ast::CaseStatement>()->body()->last();
   if (last_stmt_of_last_clause &&
       last_stmt_of_last_clause->Is<ast::FallthroughStatement>()) {
     add_error(last_stmt_of_last_clause->source(), "v-0028",
               "a fallthrough statement must not appear as "
               "the last statement in last clause of a switch");
     return false;
   }
   return true;
 }

 bool ValidatorImpl::ValidateCase(const ast::CaseStatement* c) {
   if (!ValidateStatement(c->body())) {
     return false;
   }
   return true;
 }

 bool ValidatorImpl::ValidateCallExpr(const ast::CallExpression* expr) {
   if (!expr) {
     // TODO(sarahM0): Here and other Validate.*: figure out whether return
     // false or true
     return false;
   }

   if (auto* ident = expr->func()->As<ast::IdentifierExpression>()) {
     auto func_name = ident->name();
     if (ident->IsIntrinsic()) {
       // TODO(sarahM0): validate intrinsics - tied with type-determiner
     } else {
       if (!function_stack_.has(func_name)) {
         add_error(expr->source(), "v-0005",
                   "function must be declared before use: '" + func_name + "'");
         return false;
       }
       if (func_name == current_function_->name()) {
         add_error(expr->source(), "v-0004",
                   "recursion is not allowed: '" + func_name + "'");
         return false;
       }
     }
   } else {
     add_error(expr->source(), "Invalid function call expression");
     return false;
   }

   return true;
 }

 bool ValidatorImpl::ValidateAssign(const ast::AssignmentStatement* a) {
   if (!a) {
     return false;
   }
   if (!(ValidateConstant(a))) {
     return false;
   }
   if (!(ValidateExpression(a->lhs()) && ValidateExpression(a->rhs()))) {
     return false;
   }
   if (!ValidateResultTypes(a)) {
     return false;
   }

   return true;
 }

 bool ValidatorImpl::ValidateConstant(const ast::AssignmentStatement* assign) {
   if (!assign) {
     return false;
   }

   if (auto* ident = assign->lhs()->As<ast::IdentifierExpression>()) {
     ast::Variable* var;
     if (variable_stack_.get(ident->name(), &var)) {
       if (var->is_const()) {
         add_error(assign->source(), "v-0021",
                   "cannot re-assign a constant: '" + ident->name() + "'");
         return false;
       }
     }
   }
   return true;
 }

 bool ValidatorImpl::ValidateResultTypes(const ast::AssignmentStatement* a) {
   if (!a->lhs()->result_type() || !a->rhs()->result_type()) {
     add_error(a->source(), "result_type() is nullptr");
     return false;
   }

   auto* lhs_result_type = a->lhs()->result_type()->UnwrapAll();
   auto* rhs_result_type = a->rhs()->result_type()->UnwrapAll();
   if (lhs_result_type != rhs_result_type) {
     // TODO(sarahM0): figur out what should be the error number.
     add_error(a->source(), "v-000x",
               "invalid assignment of '" + lhs_result_type->type_name() +
                   "' to '" + rhs_result_type->type_name() + "'");
     return false;
   }
   return true;
 }

 bool ValidatorImpl::ValidateExpression(const ast::Expression* expr) {
   if (!expr) {
     return false;
   }
   if (auto* i = expr->As<ast::IdentifierExpression>()) {
     return ValidateIdentifier(i);
   }

   if (auto* c = expr->As<ast::CallExpression>()) {
     return ValidateCallExpr(c);
   }
   return true;
 }

 bool ValidatorImpl::ValidateIdentifier(const ast::IdentifierExpression* ident) {
   ast::Variable* var;
   if (!variable_stack_.get(ident->name(), &var)) {
     add_error(ident->source(), "v-0006",
               "'" + ident->name() + "' is not declared");
     return false;
   }
   return true;
 }

 }  // namespace tint
	// 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/validator/validator_impl.h"

	#include <cassert>
	#include <unordered_set>
	#include <utility>

	#include "src/ast/call_statement.h"
	#include "src/ast/fallthrough_statement.h"
	#include "src/ast/function.h"
	#include "src/ast/int_literal.h"
	#include "src/ast/intrinsic.h"
	#include "src/ast/sint_literal.h"
	#include "src/ast/stage_decoration.h"
	#include "src/ast/struct.h"
	#include "src/ast/switch_statement.h"
	#include "src/ast/type/array_type.h"
	#include "src/ast/type/i32_type.h"
	#include "src/ast/type/struct_type.h"
	#include "src/ast/type/u32_type.h"
	#include "src/ast/type/void_type.h"
	#include "src/ast/uint_literal.h"
	#include "src/ast/variable_decl_statement.h"

	namespace tint {

	ValidatorImpl::ValidatorImpl() = default;

	ValidatorImpl::~ValidatorImpl() = default;

	void ValidatorImpl::add_error(const Source& src,
	const char* code,
	const std::string& msg) {
	diag::Diagnostic diag;
	diag.severity = diag::Severity::Error;
	diag.source = src;
	diag.message = msg;
	diag.code = code;
	diags_.add(std::move(diag));
	}

	void ValidatorImpl::add_error(const Source& src, const std::string& msg) {
	diag::Diagnostic diag;
	diag.severity = diag::Severity::Error;
	diag.source = src;
	diag.message = msg;
	diags_.add(std::move(diag));
	}

	bool ValidatorImpl::Validate(const ast::Module* module) {
	if (!module) {
	return false;
	}
	function_stack_.push_scope();
	if (!ValidateGlobalVariables(module->global_variables())) {
	return false;
	}
	if (!ValidateConstructedTypes(module->constructed_types())) {
	return false;
	}
	if (!ValidateFunctions(module->functions())) {
	return false;
	}
	if (!ValidateEntryPoint(module->functions())) {
	return false;
	}
	function_stack_.pop_scope();

	return true;
	}

	bool ValidatorImpl::ValidateConstructedTypes(
	const std::vector<ast::type::Type*>& constructed_types) {
	for (auto* const ct : constructed_types) {
	if (ct->Is<ast::type::StructType>()) {
	auto* st = ct->As<ast::type::StructType>();
	for (auto* member : st->impl()->members()) {
	if (member->type()->UnwrapAll()->Is<ast::type::ArrayType>()) {
	auto* r = member->type()->UnwrapAll()->As<ast::type::ArrayType>();
	if (r->IsRuntimeArray()) {
	if (member != st->impl()->members().back()) {
	add_error(member->source(), "v-0015",
	"runtime arrays may only appear as the last "
	"member of a struct: '" +
	member->name() + "'");
	return false;
	}
	if (!st->IsBlockDecorated()) {
	add_error(member->source(), "v-0031",
	"a struct containing a runtime-sized array "
	"must be in the 'storage' storage class: '" +
	st->name() + "'");
	return false;
	}
	}
	}
	}
	}
	}
	return true;
	}

	bool ValidatorImpl::ValidateGlobalVariables(
	const ast::VariableList& global_vars) {
	for (auto* var : global_vars) {
	if (variable_stack_.has(var->name())) {
	add_error(var->source(), "v-0011",
	"redeclared global identifier '" + var->name() + "'");
	return false;
	}
	if (!var->is_const() && var->storage_class() == ast::StorageClass::kNone) {
	add_error(var->source(), "v-0022",
	"global variables must have a storage class");
	return false;
	}
	if (var->is_const() &&
	!(var->storage_class() == ast::StorageClass::kNone)) {
	add_error(var->source(), "v-global01",
	"global constants shouldn't have a storage class");
	return false;
	}
	variable_stack_.set_global(var->name(), var);
	}
	return true;
	}

	bool ValidatorImpl::ValidateFunctions(const ast::FunctionList& funcs) {
	for (auto* func : funcs) {
	if (function_stack_.has(func->name())) {
	add_error(func->source(), "v-0016",
	"function names must be unique '" + func->name() + "'");
	return false;
	}

	function_stack_.set(func->name(), func);
	current_function_ = func;
	if (!ValidateFunction(func)) {
	return false;
	}
	current_function_ = nullptr;
	}

	return true;
	}

	bool ValidatorImpl::ValidateEntryPoint(const ast::FunctionList& funcs) {
	auto shader_is_present = false;
	for (auto* func : funcs) {
	if (func->IsEntryPoint()) {
	shader_is_present = true;
	if (!func->params().empty()) {
	add_error(func->source(), "v-0023",
	"Entry point function must accept no parameters: '" +
	func->name() + "'");
	return false;
	}

	if (!func->return_type()->Is<ast::type::VoidType>()) {
	add_error(
	func->source(), "v-0024",
	"Entry point function must return void: '" + func->name() + "'");
	return false;
	}
	auto stage_deco_count = 0;
	for (auto* deco : func->decorations()) {
	if (deco->Is<ast::StageDecoration>()) {
	stage_deco_count++;
	}
	}
	if (stage_deco_count > 1) {
	add_error(func->source(), "v-0020",
	"only one stage decoration permitted per entry point");
	return false;
	}
	}
	}
	if (!shader_is_present) {
	add_error(Source{}, "v-0003",
	"At least one of vertex, fragment or compute shader must "
	"be present");
	return false;
	}
	return true;
	}

	bool ValidatorImpl::ValidateFunction(const ast::Function* func) {
	variable_stack_.push_scope();

	for (auto* param : func->params()) {
	variable_stack_.set(param->name(), param);
	}
	if (!ValidateStatements(func->body())) {
	return false;
	}
	variable_stack_.pop_scope();

	if (!current_function_->return_type()->Is<ast::type::VoidType>()) {
	if (!func->get_last_statement() \|\|
	!func->get_last_statement()->Is<ast::ReturnStatement>()) {
	add_error(func->source(), "v-0002",
	"non-void function must end with a return statement");
	return false;
	}
	}
	return true;
	}

	bool ValidatorImpl::ValidateReturnStatement(const ast::ReturnStatement* ret) {
	// TODO(sarahM0): update this when this issue resolves:
	// https://github.com/gpuweb/gpuweb/issues/996
	ast::type::Type* func_type = current_function_->return_type();

	ast::type::VoidType void_type;
	auto* ret_type =
	ret->has_value() ? ret->value()->result_type()->UnwrapAll() : &void_type;

	if (func_type->type_name() != ret_type->type_name()) {
	add_error(ret->source(), "v-000y",
	"return statement type must match its function return "
	"type, returned '" +
	ret_type->type_name() + "', expected '" +
	func_type->type_name() + "'");
	return false;
	}

	return true;
	}

	bool ValidatorImpl::ValidateStatements(const ast::BlockStatement* block) {
	if (!block) {
	return false;
	}
	for (auto* stmt : *block) {
	if (!ValidateStatement(stmt)) {
	return false;
	}
	}
	return true;
	}

	bool ValidatorImpl::ValidateDeclStatement(
	const ast::VariableDeclStatement* decl) {
	auto name = decl->variable()->name();
	bool is_global = false;
	if (variable_stack_.get(name, nullptr, &is_global)) {
	const char* error_code = "v-0014";
	if (is_global) {
	error_code = "v-0013";
	}
	add_error(decl->source(), error_code,
	"redeclared identifier '" + name + "'");
	return false;
	}
	variable_stack_.set(name, decl->variable());
	if (decl->variable()->type()->UnwrapAll()->Is<ast::type::ArrayType>()) {
	if (decl->variable()
	->type()
	->UnwrapAll()
	->As<ast::type::ArrayType>()
	->IsRuntimeArray()) {
	add_error(decl->source(), "v-0015",
	"runtime arrays may only appear as the last "
	"member of a struct: '" +
	decl->variable()->name() + "'");
	return false;
	}
	}
	return true;
	}

	bool ValidatorImpl::ValidateStatement(const ast::Statement* stmt) {
	if (!stmt) {
	return false;
	}
	if (auto* v = stmt->As<ast::VariableDeclStatement>()) {
	bool constructor_valid =
	v->variable()->has_constructor()
	? ValidateExpression(v->variable()->constructor())
	: true;

	return constructor_valid && ValidateDeclStatement(v);
	}
	if (auto* a = stmt->As<ast::AssignmentStatement>()) {
	return ValidateAssign(a);
	}
	if (auto* r = stmt->As<ast::ReturnStatement>()) {
	return ValidateReturnStatement(r);
	}
	if (auto* c = stmt->As<ast::CallStatement>()) {
	return ValidateCallExpr(c->expr());
	}
	if (auto* s = stmt->As<ast::SwitchStatement>()) {
	return ValidateSwitch(s);
	}
	if (auto* c = stmt->As<ast::CaseStatement>()) {
	return ValidateCase(c);
	}
	return true;
	}

	bool ValidatorImpl::ValidateSwitch(const ast::SwitchStatement* s) {
	if (!ValidateExpression(s->condition())) {
	return false;
	}

	auto* cond_type = s->condition()->result_type()->UnwrapAll();
	if (!(cond_type->Is<ast::type::I32Type>() \|\|
	cond_type->Is<ast::type::U32Type>())) {
	add_error(s->condition()->source(), "v-0025",
	"switch statement selector expression must be of a "
	"scalar integer type");
	return false;
	}

	int default_counter = 0;
	std::unordered_set<int32_t> selector_set;
	for (auto* case_stmt : s->body()) {
	if (!ValidateStatement(case_stmt)) {
	return false;
	}

	if (case_stmt->IsDefault()) {
	default_counter++;
	}

	for (auto* selector : case_stmt->selectors()) {
	if (cond_type != selector->type()) {
	add_error(case_stmt->source(), "v-0026",
	"the case selector values must have the same "
	"type as the selector expression.");
	return false;
	}

	auto v =
	static_cast<int32_t>(selector->type()->Is<ast::type::U32Type>()
	? selector->As<ast::UintLiteral>()->value()
	: selector->As<ast::SintLiteral>()->value());
	if (selector_set.count(v)) {
	auto v_str = selector->type()->Is<ast::type::U32Type>()
	? selector->As<ast::UintLiteral>()->to_str()
	: selector->As<ast::SintLiteral>()->to_str();
	add_error(case_stmt->source(), "v-0027",
	"a literal value must not appear more than once in "
	"the case selectors for a switch statement: '" +
	v_str + "'");
	return false;
	}
	selector_set.emplace(v);
	}
	}

	if (default_counter != 1) {
	add_error(s->source(), "v-0008",
	"switch statement must have exactly one default clause");
	return false;
	}

	auto* last_clause = s->body().back();
	auto* last_stmt_of_last_clause =
	last_clause->As<ast::CaseStatement>()->body()->last();
	if (last_stmt_of_last_clause &&
	last_stmt_of_last_clause->Is<ast::FallthroughStatement>()) {
	add_error(last_stmt_of_last_clause->source(), "v-0028",
	"a fallthrough statement must not appear as "
	"the last statement in last clause of a switch");
	return false;
	}
	return true;
	}

	bool ValidatorImpl::ValidateCase(const ast::CaseStatement* c) {
	if (!ValidateStatement(c->body())) {
	return false;
	}
	return true;
	}

	bool ValidatorImpl::ValidateCallExpr(const ast::CallExpression* expr) {
	if (!expr) {
	// TODO(sarahM0): Here and other Validate.*: figure out whether return
	// false or true
	return false;
	}

	if (auto* ident = expr->func()->As<ast::IdentifierExpression>()) {
	auto func_name = ident->name();
	if (ident->IsIntrinsic()) {
	// TODO(sarahM0): validate intrinsics - tied with type-determiner
	} else {
	if (!function_stack_.has(func_name)) {
	add_error(expr->source(), "v-0005",
	"function must be declared before use: '" + func_name + "'");
	return false;
	}
	if (func_name == current_function_->name()) {
	add_error(expr->source(), "v-0004",
	"recursion is not allowed: '" + func_name + "'");
	return false;
	}
	}
	} else {
	add_error(expr->source(), "Invalid function call expression");
	return false;
	}

	return true;
	}

	bool ValidatorImpl::ValidateAssign(const ast::AssignmentStatement* a) {
	if (!a) {
	return false;
	}
	if (!(ValidateConstant(a))) {
	return false;
	}
	if (!(ValidateExpression(a->lhs()) && ValidateExpression(a->rhs()))) {
	return false;
	}
	if (!ValidateResultTypes(a)) {
	return false;
	}

	return true;
	}

	bool ValidatorImpl::ValidateConstant(const ast::AssignmentStatement* assign) {
	if (!assign) {
	return false;
	}

	if (auto* ident = assign->lhs()->As<ast::IdentifierExpression>()) {
	ast::Variable* var;
	if (variable_stack_.get(ident->name(), &var)) {
	if (var->is_const()) {
	add_error(assign->source(), "v-0021",
	"cannot re-assign a constant: '" + ident->name() + "'");
	return false;
	}
	}
	}
	return true;
	}

	bool ValidatorImpl::ValidateResultTypes(const ast::AssignmentStatement* a) {
	if (!a->lhs()->result_type() \|\| !a->rhs()->result_type()) {
	add_error(a->source(), "result_type() is nullptr");
	return false;
	}

	auto* lhs_result_type = a->lhs()->result_type()->UnwrapAll();
	auto* rhs_result_type = a->rhs()->result_type()->UnwrapAll();
	if (lhs_result_type != rhs_result_type) {
	// TODO(sarahM0): figur out what should be the error number.
	add_error(a->source(), "v-000x",
	"invalid assignment of '" + lhs_result_type->type_name() +
	"' to '" + rhs_result_type->type_name() + "'");
	return false;
	}
	return true;
	}

	bool ValidatorImpl::ValidateExpression(const ast::Expression* expr) {
	if (!expr) {
	return false;
	}
	if (auto* i = expr->As<ast::IdentifierExpression>()) {
	return ValidateIdentifier(i);
	}

	if (auto* c = expr->As<ast::CallExpression>()) {
	return ValidateCallExpr(c);
	}
	return true;
	}

	bool ValidatorImpl::ValidateIdentifier(const ast::IdentifierExpression* ident) {
	ast::Variable* var;
	if (!variable_stack_.get(ident->name(), &var)) {
	add_error(ident->source(), "v-0006",
	"'" + ident->name() + "' is not declared");
	return false;
	}
	return true;
	}

	} // namespace tint