[Clang-Tidy: modernize] Fix for modernize-redundant-void-arg: complains about variable cast to void

Summary:
Hello, i would like to suggest a fix for one of the checks in clang-tidy.The bug was reported in https://bugs.llvm.org/show_bug.cgi?id=32575 where you can find more information.

For example:
```
template <typename T0>
struct S {
  template <typename T>
  void g() const {
    int a;
    (void)a;
  }
};

void f() {
  S<int>().g<int>();
}
```


this piece of code should not trigger any warning by the check modernize-redundant-void-arg but when we execute the following command


```
clang_tidy -checks=-*,modernize-redundant-void-arg test.cpp -- -std=c++11
```

we obtain the following warning:

/Users/eco419/Desktop/clang-tidy.project/void-redundand_2/test.cpp:6:6: warning: redundant void argument list in function declaration [modernize-redundant-void-arg]
    (void)a;
     ^~~~

Reviewers: aaron.ballman, hokein, alexfh, JonasToth

Reviewed By: aaron.ballman, JonasToth

Subscribers: JonasToth, lebedev.ri, cfe-commits

Tags: #clang-tools-extra

Differential Revision: https://reviews.llvm.org/D52135

llvm-svn: 342388

2 files changed, 62 insertions, 1 deletions

diff --git a/clang-tools-extra/clang-tidy/modernize/RedundantVoidArgCheck.cpp b/clang-tools-extra/clang-tidy/modernize/RedundantVoidArgCheck.cpp
index 51dc5a2cc40..ea49ab7bba3 100644
--- a/clang-tools-extra/clang-tidy/modernize/RedundantVoidArgCheck.cpp
+++ b/clang-tools-extra/clang-tidy/modernize/RedundantVoidArgCheck.cpp
@@ -49,7 +49,7 @@ void RedundantVoidArgCheck::registerMatchers(MatchFinder *Finder) {
     return;
 
   Finder->addMatcher(functionDecl(parameterCountIs(0), unless(isImplicit()),
-                                  unless(isExternC()))
+                                  unless(isInstantiated()), unless(isExternC()))
                          .bind(FunctionId),
                      this);
   Finder->addMatcher(typedefNameDecl().bind(TypedefId), this);
diff --git a/clang-tools-extra/test/clang-tidy/modernize-redundant-void-arg.cpp b/clang-tools-extra/test/clang-tidy/modernize-redundant-void-arg.cpp
index 750e5c1b293..453a4816af0 100644
--- a/clang-tools-extra/test/clang-tidy/modernize-redundant-void-arg.cpp
+++ b/clang-tools-extra/test/clang-tidy/modernize-redundant-void-arg.cpp
@@ -488,3 +488,64 @@ void lambda_expression_with_macro_test(){
   // CHECK-MESSAGES: :[[@LINE-1]]:6: warning: redundant void argument list in lambda expression [modernize-redundant-void-arg]
   // CHECK-FIXES: []() BODY;
 }
+
+struct S_1 {
+  void g_1(void) const {
+    // CHECK-MESSAGES: :[[@LINE-1]]:11: warning: redundant void argument list in function definition [modernize-redundant-void-arg]
+    // CHECK-FIXES: void g_1() const {
+    int a;
+    (void)a;
+  }
+
+  void g_2() const {
+    int a;
+    (void)a;
+  }
+};
+
+template <typename T0>
+struct S_2 {
+  void g_1(void) const {
+    // CHECK-MESSAGES: :[[@LINE-1]]:11: warning: redundant void argument list in function definition [modernize-redundant-void-arg]
+    // CHECK-FIXES: void g_1() const {
+    int a;
+    (void)a;
+  }
+
+  void g_2() const {
+    int a;
+    (void)a;
+  }
+};
+
+template <typename T0>
+struct S_3 {
+  template <typename T1>
+  void g_1(void) const {
+    // CHECK-MESSAGES: :[[@LINE-1]]:11: warning: redundant void argument list in function definition [modernize-redundant-void-arg]
+    // CHECK-FIXES: void g_1() const {
+    int a;
+    (void)a;
+  }
+  template <typename T2>
+  void g_2() const {
+    int a;
+    (void)a;
+  }
+};
+
+template <typename T1>
+void g_3(void) {
+  // CHECK-MESSAGES: :[[@LINE-1]]:10: warning: redundant void argument list in function definition [modernize-redundant-void-arg]
+  // CHECK-FIXES: void g_3(){
+  int a;
+  (void)a;
+}
+
+//Template instantiation
+void f_testTemplate() {
+  S_1();
+  S_2<int>();
+  S_3<int>();
+  g_3<int>();
+}