Allow unnecessary-value-param to match templated functions including …

…lambdas with auto.

Clang-Tidy unnecessary-value-param value param will be triggered for
templated functions if at least one instantiontion with expensive to
copy type is present in translation unit.

It is relatively common mistake to write lambda functions with auto
arguments for expensive to copy types.

Example:
Copy of the vectors will happen on every comparison.

void SortBySize(std::vector<std::vector<int>>& a) {
  std::sort(
      a.begin(), a.end(),
      [](auto x, auto y) { return a.size() < b.size()});
}

clang-tools-extra/clang-tidy/performance/UnnecessaryValueParamCheck.cpp

@@ -75,7 +75,7 @@ void UnnecessaryValueParamCheck::registerMatchers(MatchFinder *Finder) {
           functionDecl(hasBody(stmt()), isDefinition(), unless(isImplicit()),
                        unless(cxxMethodDecl(anyOf(isOverride(), isFinal()))),
                        has(typeLoc(forEach(ExpensiveValueParamDecl))),
-                       unless(isInstantiated()), decl().bind("functionDecl"))),
+                       decl().bind("functionDecl"))),
       this);
 }
 
@@ -133,12 +133,9 @@ void UnnecessaryValueParamCheck::check(const MatchFinder::MatchResult &Result) {
   // 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.
-  // 4. the function is a primary template or an explicit template
-  // specialization.
   const auto *Method = llvm::dyn_cast<CXXMethodDecl>(Function);
   if (Param->getBeginLoc().isMacroID() || (Method && Method->isVirtual()) ||
-      isReferencedOutsideOfCallExpr(*Function, *Result.Context) ||
-      (Function->getTemplatedKind() != FunctionDecl::TK_NonTemplate))
+      isReferencedOutsideOfCallExpr(*Function, *Result.Context))
     return;
   for (const auto *FunctionDecl = Function; FunctionDecl != nullptr;
        FunctionDecl = FunctionDecl->getPreviousDecl()) {

clang-tools-extra/test/clang-tidy/checkers/performance/unnecessary-value-param.cpp

@@ -107,19 +107,6 @@ struct PositiveConstValueConstructor {
   // CHECK-FIXES: PositiveConstValueConstructor(const ExpensiveToCopyType& ConstCopy) {}
 };
 
-template <typename T> void templateWithNonTemplatizedParameter(const ExpensiveToCopyType S, T V) {
-  // CHECK-MESSAGES: [[@LINE-1]]:90: warning: the const qualified parameter 'S'
-  // CHECK-FIXES-NOT: template <typename T> void templateWithNonTemplatizedParameter(const ExpensiveToCopyType& S, T V) {
-}
-
-void instantiated() {
-  templateWithNonTemplatizedParameter(ExpensiveToCopyType(), ExpensiveToCopyType());
-  templateWithNonTemplatizedParameter(ExpensiveToCopyType(), 5);
-}
-
-template <typename T> void negativeTemplateType(const T V) {
-}
-
 void negativeArray(const ExpensiveToCopyType[]) {
 }
 
@@ -370,35 +357,3 @@ void fun() {
   ExpensiveToCopyType E;
   NegativeUsingConstructor S(E);
 }
-
-template<typename T>
-void templateFunction(T) {
-}
-
-template<>
-void templateFunction<ExpensiveToCopyType>(ExpensiveToCopyType E) {
-  // CHECK-MESSAGES: [[@LINE-1]]:64: warning: the parameter 'E' is copied
-  // CHECK-FIXES: void templateFunction<ExpensiveToCopyType>(ExpensiveToCopyType E) {
-  E.constReference();
-}
-
-template <class T>
-T templateSpecializationFunction(ExpensiveToCopyType E) {
-  // CHECK-MESSAGES: [[@LINE-1]]:54: warning: the parameter 'E' is copied
-  // CHECK-FIXES-NOT: T templateSpecializationFunction(const ExpensiveToCopyType& E) {
-  return T();
-}
-
-template <>
-bool templateSpecializationFunction(ExpensiveToCopyType E) {
-  // CHECK-MESSAGES: [[@LINE-1]]:57: warning: the parameter 'E' is copied
-  // CHECK-FIXES-NOT: bool templateSpecializationFunction(const ExpensiveToCopyType& E) {
-  return true;
-}
-
-template <>
-int templateSpecializationFunction(ExpensiveToCopyType E) {
-  // CHECK-MESSAGES: [[@LINE-1]]:56: warning: the parameter 'E' is copied
-  // CHECK-FIXES-NOT: int templateSpecializationFunction(const ExpensiveToCopyType& E) {
-  return 0;
-}