src/validator/validator_impl.cc - tint - 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 "src/ast/call_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/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::set_error(const Source& src, const std::string& msg) {
   error_ += std::to_string(src.range.begin.line) + ":" +
             std::to_string(src.range.begin.column) + ": " + msg;
 }

 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->IsStruct()) {
       auto* st = ct->AsStruct();
       for (auto* member : st->impl()->members()) {
         if (member->type()->UnwrapAll()->IsArray()) {
           auto* r = member->type()->UnwrapAll()->AsArray();
           if (r->IsRuntimeArray() && member != st->impl()->members().back()) {
             set_error(member->source(),
                       "v-0015: runtime arrays may only appear as the last "
                       "member of a struct: '" +
                           member->name() + "'");
             return false;
           }
         }
       }
     }
   }
   return true;
 }

 bool ValidatorImpl::ValidateGlobalVariables(
     const ast::VariableList& global_vars) {
   for (auto* var : global_vars) {
     if (variable_stack_.has(var->name())) {
       set_error(var->source(),
                 "v-0011: redeclared global identifier '" + var->name() + "'");
       return false;
     }
     if (!var->is_const() && var->storage_class() == ast::StorageClass::kNone) {
       set_error(var->source(),
                 "v-0022: global variables must have a storage class");
       return false;
     }
     if (var->is_const() &&
         !(var->storage_class() == ast::StorageClass::kNone)) {
       set_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())) {
       set_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()) {
         set_error(func->source(),
                   "v-0023: Entry point function must accept no parameters: '" +
                       func->name() + "'");
         return false;
       }

       if (!func->return_type()->IsVoid()) {
         set_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->IsStage()) {
           stage_deco_count++;
         }
       }
       if (stage_deco_count > 1) {
         set_error(
             func->source(),
             "v-0020: only one stage decoration permitted per entry point");
         return false;
       }
     }
   }
   if (!shader_is_present) {
     set_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()->IsVoid()) {
     if (!func->get_last_statement() ||
         !func->get_last_statement()->IsReturn()) {
       set_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()) {
     set_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)) {
     std::string error_number = "v-0014: ";
     if (is_global) {
       error_number = "v-0013: ";
     }
     set_error(decl->source(),
               error_number + "redeclared identifier '" + name + "'");
     return false;
   }
   variable_stack_.set(name, decl->variable());
   if (decl->variable()->type()->UnwrapAll()->IsArray()) {
     if (decl->variable()->type()->UnwrapAll()->AsArray()->IsRuntimeArray()) {
       set_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 (stmt->IsVariableDecl()) {
     auto* v = stmt->AsVariableDecl();
     bool constructor_valid =
         v->variable()->has_constructor()
             ? ValidateExpression(v->variable()->constructor())
             : true;

     return constructor_valid && ValidateDeclStatement(stmt->AsVariableDecl());
   }
   if (stmt->IsAssign()) {
     return ValidateAssign(stmt->AsAssign());
   }
   if (stmt->IsReturn()) {
     return ValidateReturnStatement(stmt->AsReturn());
   }
   if (stmt->IsCall()) {
     return ValidateCallExpr(stmt->AsCall()->expr());
   }
   if (stmt->IsSwitch()) {
     return ValidateSwitch(stmt->AsSwitch());
   }
   if (stmt->IsCase()) {
     return ValidateCase(stmt->AsCase());
   }
   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->IsI32() || cond_type->IsU32())) {
     set_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()) {
         set_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()->IsU32()
                                         ? selector->AsUint()->value()
                                         : selector->AsSint()->value());
       if (selector_set.count(v)) {
         auto v_str = selector->type()->IsU32() ? selector->AsUint()->to_str()
                                                : selector->AsSint()->to_str();
         set_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) {
     set_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->AsCase()->body()->last();
   if (last_stmt_of_last_clause && last_stmt_of_last_clause->IsFallthrough()) {
     set_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 (expr->func()->IsIdentifier()) {
     auto* ident = expr->func()->AsIdentifier();
     auto func_name = ident->name();
     if (ident->IsIntrinsic()) {
       // TODO(sarahM0): validate intrinsics - tied with type-determiner
     } else {
       if (!function_stack_.has(func_name)) {
         set_error(expr->source(),
                   "v-0005: function must be declared before use: '" +
                       func_name + "'");
         return false;
       }
       if (func_name == current_function_->name()) {
         set_error(expr->source(),
                   "v-0004: recursion is not allowed: '" + func_name + "'");
         return false;
       }
     }
   } else {
     set_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 (assign->lhs()->IsIdentifier()) {
     ast::Variable* var;
     auto* ident = assign->lhs()->AsIdentifier();
     if (variable_stack_.get(ident->name(), &var)) {
       if (var->is_const()) {
         set_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()) {
     set_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.
     set_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 (expr->IsIdentifier()) {
     return ValidateIdentifier(expr->AsIdentifier());
   }

   if (expr->IsCall()) {
     return ValidateCallExpr(expr->AsCall());
   }
   return true;
 }

 bool ValidatorImpl::ValidateIdentifier(const ast::IdentifierExpression* ident) {
   ast::Variable* var;
   if (!variable_stack_.get(ident->name(), &var)) {
     set_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 "src/ast/call_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/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::set_error(const Source& src, const std::string& msg) {
	error_ += std::to_string(src.range.begin.line) + ":" +
	std::to_string(src.range.begin.column) + ": " + msg;
	}

	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->IsStruct()) {
	auto* st = ct->AsStruct();
	for (auto* member : st->impl()->members()) {
	if (member->type()->UnwrapAll()->IsArray()) {
	auto* r = member->type()->UnwrapAll()->AsArray();
	if (r->IsRuntimeArray() && member != st->impl()->members().back()) {
	set_error(member->source(),
	"v-0015: runtime arrays may only appear as the last "
	"member of a struct: '" +
	member->name() + "'");
	return false;
	}
	}
	}
	}
	}
	return true;
	}

	bool ValidatorImpl::ValidateGlobalVariables(
	const ast::VariableList& global_vars) {
	for (auto* var : global_vars) {
	if (variable_stack_.has(var->name())) {
	set_error(var->source(),
	"v-0011: redeclared global identifier '" + var->name() + "'");
	return false;
	}
	if (!var->is_const() && var->storage_class() == ast::StorageClass::kNone) {
	set_error(var->source(),
	"v-0022: global variables must have a storage class");
	return false;
	}
	if (var->is_const() &&
	!(var->storage_class() == ast::StorageClass::kNone)) {
	set_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())) {
	set_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()) {
	set_error(func->source(),
	"v-0023: Entry point function must accept no parameters: '" +
	func->name() + "'");
	return false;
	}

	if (!func->return_type()->IsVoid()) {
	set_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->IsStage()) {
	stage_deco_count++;
	}
	}
	if (stage_deco_count > 1) {
	set_error(
	func->source(),
	"v-0020: only one stage decoration permitted per entry point");
	return false;
	}
	}
	}
	if (!shader_is_present) {
	set_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()->IsVoid()) {
	if (!func->get_last_statement() \|\|
	!func->get_last_statement()->IsReturn()) {
	set_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()) {
	set_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)) {
	std::string error_number = "v-0014: ";
	if (is_global) {
	error_number = "v-0013: ";
	}
	set_error(decl->source(),
	error_number + "redeclared identifier '" + name + "'");
	return false;
	}
	variable_stack_.set(name, decl->variable());
	if (decl->variable()->type()->UnwrapAll()->IsArray()) {
	if (decl->variable()->type()->UnwrapAll()->AsArray()->IsRuntimeArray()) {
	set_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 (stmt->IsVariableDecl()) {
	auto* v = stmt->AsVariableDecl();
	bool constructor_valid =
	v->variable()->has_constructor()
	? ValidateExpression(v->variable()->constructor())
	: true;

	return constructor_valid && ValidateDeclStatement(stmt->AsVariableDecl());
	}
	if (stmt->IsAssign()) {
	return ValidateAssign(stmt->AsAssign());
	}
	if (stmt->IsReturn()) {
	return ValidateReturnStatement(stmt->AsReturn());
	}
	if (stmt->IsCall()) {
	return ValidateCallExpr(stmt->AsCall()->expr());
	}
	if (stmt->IsSwitch()) {
	return ValidateSwitch(stmt->AsSwitch());
	}
	if (stmt->IsCase()) {
	return ValidateCase(stmt->AsCase());
	}
	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->IsI32() \|\| cond_type->IsU32())) {
	set_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()) {
	set_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()->IsU32()
	? selector->AsUint()->value()
	: selector->AsSint()->value());
	if (selector_set.count(v)) {
	auto v_str = selector->type()->IsU32() ? selector->AsUint()->to_str()
	: selector->AsSint()->to_str();
	set_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) {
	set_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->AsCase()->body()->last();
	if (last_stmt_of_last_clause && last_stmt_of_last_clause->IsFallthrough()) {
	set_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 (expr->func()->IsIdentifier()) {
	auto* ident = expr->func()->AsIdentifier();
	auto func_name = ident->name();
	if (ident->IsIntrinsic()) {
	// TODO(sarahM0): validate intrinsics - tied with type-determiner
	} else {
	if (!function_stack_.has(func_name)) {
	set_error(expr->source(),
	"v-0005: function must be declared before use: '" +
	func_name + "'");
	return false;
	}
	if (func_name == current_function_->name()) {
	set_error(expr->source(),
	"v-0004: recursion is not allowed: '" + func_name + "'");
	return false;
	}
	}
	} else {
	set_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 (assign->lhs()->IsIdentifier()) {
	ast::Variable* var;
	auto* ident = assign->lhs()->AsIdentifier();
	if (variable_stack_.get(ident->name(), &var)) {
	if (var->is_const()) {
	set_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()) {
	set_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.
	set_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 (expr->IsIdentifier()) {
	return ValidateIdentifier(expr->AsIdentifier());
	}

	if (expr->IsCall()) {
	return ValidateCallExpr(expr->AsCall());
	}
	return true;
	}

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

	} // namespace tint