Put microsoft template parameter shadow warning behind separate flag (PR44794)

Differential revision: https://reviews.llvm.org/D75121

Author: zmodem

clang/include/clang/Basic/DiagnosticGroups.td

@@ -1018,7 +1018,8 @@ def MicrosoftExplicitConstructorCall : DiagGroup<
 def MicrosoftEnumValue : DiagGroup<"microsoft-enum-value">;
 def MicrosoftDefaultArgRedefinition :
     DiagGroup<"microsoft-default-arg-redefinition">;
-def MicrosoftTemplate : DiagGroup<"microsoft-template">;
+def MicrosoftTemplateShadow : DiagGroup<"microsoft-template-shadow">;
+def MicrosoftTemplate : DiagGroup<"microsoft-template", [MicrosoftTemplateShadow]>;
 def MicrosoftInconsistentDllImport : DiagGroup<"inconsistent-dllimport">;
 def MicrosoftRedeclareStatic : DiagGroup<"microsoft-redeclare-static">;
 def MicrosoftEnumForwardReference :

clang/include/clang/Basic/DiagnosticSemaKinds.td

@@ -4273,7 +4273,7 @@ def err_ovl_no_viable_literal_operator : Error<
 def err_template_param_shadow : Error<
   "declaration of %0 shadows template parameter">;
 def ext_template_param_shadow : ExtWarn<
-  err_template_param_shadow.Text>, InGroup<MicrosoftTemplate>;
+  err_template_param_shadow.Text>, InGroup<MicrosoftTemplateShadow>;
 def note_template_param_here : Note<"template parameter is declared here">;
 def warn_template_export_unsupported : Warning<
   "exported templates are unsupported">;

clang/test/SemaCXX/microsoft-template-shadow.cpp

@@ -0,0 +1,11 @@
+// RUN: %clang_cc1 %s -triple i686-pc-win32 -fsyntax-only -verify -fms-compatibility -Wno-microsoft -Wmicrosoft-template-shadow
+
+template <typename T> // expected-note {{template parameter is declared here}}
+struct Outmost {
+  template <typename T> // expected-warning {{declaration of 'T' shadows template parameter}}
+  struct Inner {
+    void f() {
+      T *var;
+    }
+  };
+};