[clang-tools-extra] [clang-tidy] Fix false positive in readability-convert-member-functions-to-static for const overloads (PR #191712)

[Gaurav Dhingra via cfe-commits]

================
@@ -235,3 +235,38 @@ struct NoFixitInMacro {
     return;
   }
 };
+
+
+struct OverloadedMethods {
+  void f() {
+    this->i++;
+  }
+  void f() const {
+    ;
----------------
gxyd wrote:

I think we do actually need the `;`, because in it's absence the function will be declared as having a trivial body. That would mean the matcher (under consideration): https://github.com/llvm/llvm-project/blob/d9c02ffa4d519245903ba8d168b3bafeb1a396af/clang-tools-extra/clang-tidy/readability/ConvertMemberFunctionsToStaticCheck.cpp#L83-L99

would never match. Hence, we'll never be actually testing the `hasNonConstOverload` (the utility I just added).

Let me know if you still think otherwise.

https://github.com/llvm/llvm-project/pull/191712