基于Clang库检查C++类是否满足Concept约束的技术咨询
问题描述
我编写了一段解析C++声明(类、模板类、函数、Concept)的代码,希望判断指定类是否满足某一Concept的约束要求,若不满足则指出未达标的约束项。但自行实现的CheckConceptUsage函数始终返回false,即使类符合Concept要求。现寻求使用Clang Sema分析Concept的示例,以下是我的实现代码:
实现代码
void CheckConceptUsage(Sema &SemaRef, const ConceptDecl *Concept, const CXXRecordDecl *Class) { // Get the type of the class. QualType ClassType = SemaRef.Context.getRecordType(Class); // Create a TemplateArgument representing the class type. TemplateArgument ClassTemplateArg(ClassType); // Prepare the necessary data structures for the constraint check. ConstraintSatisfaction Satisfaction; // Create a MultiLevelTemplateArgumentList MultiLevelTemplateArgumentList TemplateArgs; ArrayRef<TemplateArgument> TemplateArgsRef(ClassTemplateArg); TemplateArgs.addOuterTemplateArguments(const_cast<CXXRecordDecl *>(Class), TemplateArgsRef, /*Final*/ true); // TemplateArgs.addOuterTemplateArguments(ArrayRef<TemplateArgument>(ClassTemplateArg)); // Retrieve the constraint expression associated with the concept const Expr *ConstraintExpr = Concept->getConstraintExpr(); if (!ConstraintExpr) { llvm::outs() << "The concept " << Concept->getNameAsString() << " has no constraints (requires clause) to check.\n"; return; } // Cast the constraint expression to RequiresExpr to access its components if (const RequiresExpr *ReqExpr = llvm::dyn_cast<RequiresExpr>(ConstraintExpr)) { std::cout << "--- CheckConceptUsage if " << std::endl; // Get the list of requirements (constraints) in the requires expression llvm::SmallVector<const Expr*, 4> ConstraintExprs; for (const auto &Requirement : ReqExpr->getRequirements()) { std::cout << "--- CheckConceptUsage for " << std::endl; if (const auto *ExprReq = llvm::dyn_cast<clang::concepts::ExprRequirement>(Requirement)) { // Handle expression requirements std::cout << "--- CheckConceptUsage ExprRequirement" << std::endl; ConstraintExprs.push_back(ExprReq->getExpr()); } else if (const auto *TypeReq = llvm::dyn_cast<clang::concepts::TypeRequirement>(Requirement)) { // Handle type requirements by evaluating the type's instantiation dependency std::cout << "--- CheckConceptUsage TypeRequirement" << std::endl; QualType Type = TypeReq->getType()->getType(); QualType DependentType = TypeReq->getType()->getType(); if (Type->isDependentType()) { std::cout << "--- CheckConceptUsage isDependentType" << std::endl; // Create a pseudo-expression that checks if this type exists // TypeTraitExpr *TraitExpr = TypeTraitExpr::Create( // SemaRef.Context, // DependentType, // SourceLocation(), // UTT_IsCompleteType, // Use a type trait like "is complete type" // ArrayRef<QualType>(DependentType), // SourceLocation(), // SemaRef.Context.BoolTy // ); // ConstraintExprs.push_back(TraitExpr); } } } std::cout << "--- CheckConceptUsage ConstraintExprs size:" << ConstraintExprs.size() << std::endl; // Now use the updated list of constraints in the satisfaction check bool IsSatisfied = SemaRef.CheckConstraintSatisfaction( Concept, ConstraintExprs, TemplateArgs, Class->getSourceRange(), Satisfaction ); if (IsSatisfied) { llvm::outs() << "The class " << Class->getName() << " satisfies the concept " << Concept->getName() << ".\n"; } else { llvm::outs() << "The class " << Class->getName() << " does NOT satisfy the concept " << Concept->getName() << ".\n"; } } else { llvm::outs() << "The concept " << Concept->getNameAsString() << " does not have a valid requires expression.\n"; } }
最小复现示例
template<typename T> concept HasFoo = requires(T t) { t.foo(); typename T::Bar; }; struct GoodClass { void foo() {} using Bar = int; }; struct BadClass { // 缺少foo()成员函数和Bar类型别名 };
内容的提问来源于stack exchange,提问作者Alex
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