[Clang] add emit -Wignored-base-class-qualifiers diagnostic for cv-qualified base classes (#132116)

Split diagnosing base class qualifiers from the ``-Wignored-Qualifiers``
diagnostic group into a new ``-Wignored-base-class-qualifiers``
diagnostic group (which is grouped under ``-Wignored-qualifiers``).

Fixes #131935

Author: lyledean1

clang/docs/ReleaseNotes.rst

@@ -313,6 +313,8 @@ Improvements to Clang's diagnostics
 
   Fixes #GH61635
 
+- Split diagnosing base class qualifiers from the ``-Wignored-Qualifiers`` diagnostic group into a new ``-Wignored-base-class-qualifiers`` diagnostic group (which is grouped under ``-Wignored-qualifiers``). Fixes #GH131935.
+
 Improvements to Clang's time-trace
 ----------------------------------
 

clang/include/clang/Basic/DiagnosticGroups.td

@@ -496,6 +496,7 @@ def GNUImaginaryConstant : DiagGroup<"gnu-imaginary-constant">;
 def IgnoredGCH : DiagGroup<"ignored-gch">;
 def IgnoredReferenceQualifiers : DiagGroup<"ignored-reference-qualifiers">;
 def IgnoredQualifiers : DiagGroup<"ignored-qualifiers", [IgnoredReferenceQualifiers]>;
+def IgnoredBaseClassQualifiers : DiagGroup<"ignored-base-class-qualifiers", [IgnoredQualifiers]>;
 def : DiagGroup<"import">;
 def GNUIncludeNext : DiagGroup<"gnu-include-next">;
 def IncompatibleMSStruct : DiagGroup<"incompatible-ms-struct">;

clang/include/clang/Basic/DiagnosticSemaKinds.td

@@ -545,7 +545,7 @@ def warn_qual_return_type : Warning<
   InGroup<IgnoredQualifiers>, DefaultIgnore;
 def warn_qual_base_type : Warning<
   "'%0' qualifier%s1 on base class type %2 %plural{1:has|:have}1 no effect">,
-  InGroup<IgnoredQualifiers>, DefaultIgnore;
+  InGroup<IgnoredBaseClassQualifiers>, DefaultIgnore;
 
 def warn_deprecated_redundant_constexpr_static_def : Warning<
   "out-of-line definition of constexpr static data member is redundant "

clang/test/SemaCXX/warn-base-type-qualifiers.cpp

@@ -1,4 +1,6 @@
-// RUN: %clang_cc1 %s -std=c++11 -Wignored-qualifiers -verify
+// RUN: %clang_cc1 %s -std=c++11 -Wignored-base-class-qualifiers -verify
+// RUN: %clang_cc1 %s -std=c++11 -Wno-ignored-qualifiers -verify=good
+// good-no-diagnostics
 
 template <typename T> struct add_const {
   using type = const T;