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

[hans]

Summary

This puts the warning behind a separate -Wmicrosoft-template-shadow flag as suggested on the bug.

[rnk]

code lgtm

Should we have a standalone test for this? Something that compiles with clang -cc1 -Wno-microsoft -Wmicrosoft-template-shadow and looks for the shadowing warnings?

[hans]

In D75121#1891879, @rnk wrote:

code lgtm

Should we have a standalone test for this? Something that compiles with clang -cc1 -Wno-microsoft -Wmicrosoft-template-shadow and looks for the shadowing warnings?

Adding one before committing.

clang/include/clang/Basic/DiagnosticGroups.td

 def MicrosoftPureDefinition : DiagGroup<"microsoft-pure-definition">;
 def MicrosoftUnionMemberReference : DiagGroup<
     "microsoft-union-member-reference">;
 def MicrosoftExplicitConstructorCall : DiagGroup<
     "microsoft-explicit-constructor-call">;
 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 :
     DiagGroup<"microsoft-enum-forward-reference">;
 def MicrosoftGoto : DiagGroup<"microsoft-goto">;
 def MicrosoftFlexibleArray : DiagGroup<"microsoft-flexible-array">;
 def MicrosoftExtraQualification : DiagGroup<"microsoft-extra-qualification">;
 def MicrosoftCast : DiagGroup<"microsoft-cast">;

clang/include/clang/Basic/DiagnosticSemaKinds.td

def err_ovl_no_viable_literal_operator : Error<
   "%select{| with argument of type %2| with arguments of types %2 and %3}1"
   "%select{| or 'const char *'}4"
   "%select{|, and no matching literal operator template}5">;
 
 // C++ Template Declarations
 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">;
 def err_template_outside_namespace_or_class_scope : Error<
   "templates can only be declared in namespace or class scope">;
 def err_template_inside_local_class : Error<
   "templates cannot be declared inside of a local class">;
 def err_template_linkage : Error<"templates must have C++ linkage">;

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

+// 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;
+    }
+  };
+};