[clang-tidy] google-readability-function: skip std::nullptr_t

Parameters of type std::nullptr_t can only have one value, so it doesn't make
sense to name them.

llvm-svn: 221340

clang-tools-extra/clang-tidy/google/NamedParameterCheck.cpp

@@ -65,6 +65,10 @@ void NamedParameterCheck::check(const MatchFinder::MatchResult &Result) {
       if (Typedef->getDecl()->getQualifiedNameAsString() == "testing::Unused")
         continue;
 
+    // Skip std::nullptr_t.
+    if (Parm->getType().getCanonicalType()->isNullPtrType())
+      continue;
+
     // Look for comments. We explicitly want to allow idioms like
     // void foo(int /*unused*/)
     const char *Begin = SM.getCharacterData(Parm->getLocStart());

clang-tools-extra/test/clang-tidy/google-readability-function.cpp

@@ -122,3 +122,9 @@ void MockFunction(Unused, int q, Unused) {
   ++q;
   ++q;
 }
+
+namespace std {
+typedef decltype(nullptr) nullptr_t;
+}
+
+void f(std::nullptr_t) {}