Index: clang-tidy/performance/UnnecessaryValueParamCheck.cpp =================================================================== --- clang-tidy/performance/UnnecessaryValueParamCheck.cpp +++ clang-tidy/performance/UnnecessaryValueParamCheck.cpp @@ -39,6 +39,14 @@ return true; } +bool isReferencedOutsideOfCallExpr(const FunctionDecl &Function, + ASTContext &Context) { + auto Matches = match(declRefExpr(to(functionDecl(equalsNode(&Function))), + unless(hasAncestor(callExpr()))), + Context); + return !Matches.empty(); +} + } // namespace UnnecessaryValueParamCheck::UnnecessaryValueParamCheck( @@ -118,10 +126,14 @@ "invocation but only used as a const reference; " "consider making it a const reference") << paramNameOrIndex(Param->getName(), Index); - // Do not propose fixes in macros since we cannot place them correctly, or if - // function is virtual as it might break overrides. + // Do not propose fixes when: + // 1. in macros since we cannot place them correctly + // 2. the function is virtual as it might break overrides + // 3. the function is referenced outside of a call expression within the + // compilation unit as the signature change could introduce build errors. const auto *Method = llvm::dyn_cast(Function); - if (Param->getLocStart().isMacroID() || (Method && Method->isVirtual())) + if (Param->getLocStart().isMacroID() || (Method && Method->isVirtual()) || + isReferencedOutsideOfCallExpr(*Function, *Result.Context)) return; for (const auto *FunctionDecl = Function; FunctionDecl != nullptr; FunctionDecl = FunctionDecl->getPreviousDecl()) { Index: test/clang-tidy/performance-unnecessary-value-param.cpp =================================================================== --- test/clang-tidy/performance-unnecessary-value-param.cpp +++ test/clang-tidy/performance-unnecessary-value-param.cpp @@ -237,3 +237,21 @@ ExpensiveToCopyType B; B = A; } + +void PositiveOnlyMessageAsReferencedInCompilationUnit(ExpensiveToCopyType A) { + // CHECK-MESSAGES: [[@LINE-1]]:75: warning: the parameter 'A' is copied + // CHECK-FIXES: void PositiveOnlyMessageAsReferencedInCompilationUnit(ExpensiveToCopyType A) { +} + +void ReferenceFunctionOutsideOfCallExpr() { + void (*ptr)(ExpensiveToCopyType) = &PositiveOnlyMessageAsReferencedInCompilationUnit; +} + +void PositiveMessageAndFixAsFunctionIsCalled(ExpensiveToCopyType A) { + // CHECK-MESSAGES: [[@LINE-1]]:66: warning: the parameter 'A' is copied + // CHECK-FIXES: void PositiveMessageAndFixAsFunctionIsCalled(const ExpensiveToCopyType& A) { +} + +void ReferenceFunctionByCallingIt() { + PositiveMessageAndFixAsFunctionIsCalled(ExpensiveToCopyType()); +}