================
@@ -0,0 +1,93 @@
+// RUN: %check_clang_tidy -std=c++14-or-later %s
performance-unnecessary-value-param %t
+
+struct ExpensiveToCopyType {
+ virtual ~ExpensiveToCopyType();
+};
+
+template <typename T> void templateWithNonTemplatizedParameter(const
ExpensiveToCopyType S, T V) {
+ // CHECK-MESSAGES: [[@LINE-1]]:90: warning: the const qualified parameter 'S'
+ // CHECK-MESSAGES: [[@LINE-2]]:95: warning: the parameter 'V'
+ // CHECK-FIXES: template <typename T> void
templateWithNonTemplatizedParameter(const ExpensiveToCopyType& S, const T& V) {
+}
+
+void instantiatedWithExpensiveValue() {
+ templateWithNonTemplatizedParameter(
+ ExpensiveToCopyType(), ExpensiveToCopyType());
+ templateWithNonTemplatizedParameter(ExpensiveToCopyType(), 5);
+}
+
+template <typename T> void
templateWithNonTemplatizedParameterCheapTemplate(const ExpensiveToCopyType S, T
V) {
+ // CHECK-MESSAGES: [[@LINE-1]]:103: warning: the const qualified parameter
'S'
+ // CHECK-FIXES: template <typename T> void
templateWithNonTemplatizedParameterCheapTemplate(const ExpensiveToCopyType& S,
T V) {
+}
+
+void instantiatedWithCheapValue() {
+ templateWithNonTemplatizedParameterCheapTemplate(ExpensiveToCopyType(), 5);
+}
+
+template <typename T> void nonInstantiatedTemplateWithConstValue(const T S) {}
+template <typename T> void nonInstantiatedTemplateWithNonConstValue(T S) {}
+
+template <typename T> void instantiatedTemplateSpecialization(T NoSpecS) {}
+template <>
+void instantiatedTemplateSpecialization<ExpensiveToCopyType>(
+ ExpensiveToCopyType SpecS) {
+ // CHECK-MESSAGES: [[@LINE-1]]:25: warning: the parameter 'SpecS'
+ // When updating a template specialization, we also update the main template.
----------------
5chmidti wrote:
I don't think that we need to do that. The specialization can specialize for
the specific type, and the base template can be `const&`-ed when an
instantiation contains a type that is not cheap to copy. WDYT?
https://github.com/llvm/llvm-project/pull/97767
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