UnnecessaryCopyInitializationCheck.h

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//===----------------------------------------------------------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
 
#ifndef LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_PERFORMANCE_UNNECESSARYCOPYINITIALIZATIONCHECK_H
#define LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_PERFORMANCE_UNNECESSARYCOPYINITIALIZATIONCHECK_H
 
#include "../ClangTidyCheck.h"
#include "clang/AST/Decl.h"
 
namespace clang::tidy::performance {
 
// The check detects local variable declarations that are copy initialized with
// the const reference of a function call or the const reference of a method
// call whose object is guaranteed to outlive the variable's scope and suggests
// to use a const reference.
//
// The check currently only understands a subset of variables that are
// guaranteed to outlive the const reference returned, namely: const variables,
// const references, and const pointers to const.
//
// For the user-facing documentation see:
// https://clang.llvm.org/extra/clang-tidy/checks/performance/unnecessary-copy-initialization.html
class UnnecessaryCopyInitializationCheck : public ClangTidyCheck {
public:
  UnnecessaryCopyInitializationCheck(StringRef Name, ClangTidyContext *Context);
  bool isLanguageVersionSupported(const LangOptions &LangOpts) const override {
    return LangOpts.CPlusPlus;
  }
  void registerMatchers(ast_matchers::MatchFinder *Finder) override;
  void check(const ast_matchers::MatchFinder::MatchResult &Result) override;
  void storeOptions(ClangTidyOptions::OptionMap &Opts) override;
 
protected:
  // A helper to manipulate the state common to
  // `CopyFromMethodReturn` and `CopyFromLocalVar`.
  struct CheckContext {
    const VarDecl &Var;
    const Stmt &BlockStmt;
    const DeclStmt &VarDeclStmt;
    clang::ASTContext &ASTCtx;
    const bool IssueFix;
    const bool IsVarUnused;
    const bool IsVarOnlyUsedAsConst;
  };
 
  // Create diagnostics. These are virtual so that derived classes can change
  // behaviour.
  virtual void diagnoseCopyFromMethodReturn(const CheckContext &Ctx);
  virtual void diagnoseCopyFromLocalVar(const CheckContext &Ctx,
                                        const VarDecl &OldVar);
 
private:
  void handleCopyFromMethodReturn(const CheckContext &Ctx,
                                  const VarDecl *ObjectArg);
  void handleCopyFromLocalVar(const CheckContext &Ctx, const VarDecl &OldVar);
 
  void maybeIssueFixes(const CheckContext &Ctx, DiagnosticBuilder &Diagnostic);
 
  const std::vector<StringRef> AllowedTypes;
  const std::vector<StringRef> ExcludedContainerTypes;
};
 
} // namespace clang::tidy::performance
 
#endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_PERFORMANCE_UNNECESSARYCOPYINITIALIZATIONCHECK_H