Create a warning flag for 'warn_conv_*_not_used'

[rdwampler]

Summary

These warnings are grouped under '-Wclass-conversion' to be compatiable with GCC 9.

[rdwampler]

Ping.

[rdwampler]

Rebase

[rdwampler]

Rebase.

[rdwampler]

Ping.

[rdwampler]

Ping.

[ASDenysPetrov]

I suddenly discovered you unnoticed revision. I'd advise you to add more reviewers or subscribers here.

[rdwampler]

Ping.

[rdwampler]

Ping.

[lebedev.ri]

Sorry for the delay, LG.

clang/test/Misc/warning-flags.c

21–22

Right, it's a good change regardless of whether or not that improves gcc compatibility.

clang/include/clang/Basic/DiagnosticGroups.td

 def LiteralConversion : DiagGroup<"literal-conversion">;
 def StringConversion : DiagGroup<"string-conversion">;
 def SignConversion : DiagGroup<"sign-conversion">;
 def PointerBoolConversion : DiagGroup<"pointer-bool-conversion">;
 def UndefinedBoolConversion : DiagGroup<"undefined-bool-conversion">;
 def BoolConversion : DiagGroup<"bool-conversion", [PointerBoolConversion,
                                                    UndefinedBoolConversion]>;
 def IntConversion : DiagGroup<"int-conversion">;
+def ClassConversion: DiagGroup<"class-conversion">;
 def DeprecatedEnumCompareConditional :
   DiagGroup<"deprecated-enum-compare-conditional">;
 def EnumCompareConditional : DiagGroup<"enum-compare-conditional",
                                        [DeprecatedEnumCompareConditional]>;
 def EnumCompareSwitch : DiagGroup<"enum-compare-switch">;
 def DeprecatedEnumCompare : DiagGroup<"deprecated-enum-compare">;
 def EnumCompare : DiagGroup<"enum-compare", [EnumCompareSwitch,
                                              DeprecatedEnumCompare]>;

clang/include/clang/Basic/DiagnosticSemaKinds.td

def err_conv_function_with_complex_decl : Error<
   "%select{"
   "; put the complete type after 'operator'|"
   "; use a typedef to declare a conversion to %1|"
   "; use an alias template to declare a conversion to %1|"
   "}0">;
 def err_conv_function_redeclared : Error<
   "conversion function cannot be redeclared">;
 def warn_conv_to_self_not_used : Warning<
-  "conversion function converting %0 to itself will never be used">;
+  "conversion function converting %0 to itself will never be used">,
+  InGroup<ClassConversion>;
 def warn_conv_to_base_not_used : Warning<
-  "conversion function converting %0 to its base class %1 will never be used">;
+  "conversion function converting %0 to its base class %1 will never be used">,
+  InGroup<ClassConversion>;
 def warn_conv_to_void_not_used : Warning<
-  "conversion function converting %0 to %1 will never be used">;
+  "conversion function converting %0 to %1 will never be used">,
+  InGroup<ClassConversion>;
 
 def warn_not_compound_assign : Warning<
   "use of unary operator that may be intended as compound assignment (%0=)">;
 
 // C++11 explicit conversion operators
 def ext_explicit_conversion_functions : ExtWarn<
   "explicit conversion functions are a C++11 extension">, InGroup<CXX11>;
 def warn_cxx98_compat_explicit_conversion_functions : Warning<

clang/test/Misc/warning-flags.c

(2) It prevents us adding new warnings to Clang that have no -W flag.  All
     new warnings should have -W flags.
 
     If you add a new warning without a flag, this test will fail.  To fix
     this test, simply add a warning group to that warning.
 
 
 The list of warnings below should NEVER grow.  It should gradually shrink to 0.
 
-CHECK: Warnings without flags (72):
+CHECK: Warnings without flags (69):
+
 CHECK-NEXT:   ext_expected_semi_decl_list
 CHECK-NEXT:   ext_explicit_specialization_storage_class
 CHECK-NEXT:   ext_missing_declspec
 CHECK-NEXT:   ext_missing_whitespace_after_macro_name
 CHECK-NEXT:   ext_new_paren_array_nonconst
 CHECK-NEXT:   ext_plain_complex
 CHECK-NEXT:   ext_template_arg_extra_parens
 CHECK-NEXT:   ext_typecheck_cond_incompatible_operands
 CHECK-NEXT:   ext_typecheck_ordered_comparison_of_pointer_integer
 CHECK-NEXT:   ext_using_undefined_std
 CHECK-NEXT:   pp_invalid_string_literal
 CHECK-NEXT:   pp_out_of_date_dependency
 CHECK-NEXT:   pp_poisoning_existing_macro
 CHECK-NEXT:   warn_accessor_property_type_mismatch
 CHECK-NEXT:   warn_arcmt_nsalloc_realloc
 CHECK-NEXT:   warn_asm_label_on_auto_decl
 CHECK-NEXT:   warn_c_kext
 CHECK-NEXT:   warn_call_wrong_number_of_arguments
 CHECK-NEXT:   warn_case_empty_range
 CHECK-NEXT:   warn_char_constant_too_large
 CHECK-NEXT:   warn_collection_expr_type
 CHECK-NEXT:   warn_conflicting_variadic
-CHECK-NEXT:   warn_conv_to_base_not_used
-CHECK-NEXT:   warn_conv_to_self_not_used
-CHECK-NEXT:   warn_conv_to_void_not_used
 CHECK-NEXT:   warn_delete_array_type
 CHECK-NEXT:   warn_double_const_requires_fp64
 CHECK-NEXT:   warn_drv_assuming_mfloat_abi_is
 CHECK-NEXT:   warn_drv_clang_unsupported
 CHECK-NEXT:   warn_drv_pch_not_first_include
 CHECK-NEXT:   warn_dup_category_def
 CHECK-NEXT:   warn_enum_value_overflow
 CHECK-NEXT:   warn_expected_qualified_after_typename