Index: clang/include/clang/Basic/DiagnosticGroups.td
===================================================================
--- clang/include/clang/Basic/DiagnosticGroups.td
+++ clang/include/clang/Basic/DiagnosticGroups.td
@@ -60,6 +60,7 @@
 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",
Index: clang/include/clang/Basic/DiagnosticSemaKinds.td
===================================================================
--- clang/include/clang/Basic/DiagnosticSemaKinds.td
+++ clang/include/clang/Basic/DiagnosticSemaKinds.td
@@ -8543,11 +8543,14 @@
 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=)">;
Index: clang/test/Misc/warning-flags.c
===================================================================
--- clang/test/Misc/warning-flags.c
+++ clang/test/Misc/warning-flags.c
@@ -18,7 +18,7 @@
 
 The list of warnings below should NEVER grow.  It should gradually shrink to 0.
 
-CHECK: Warnings without flags (75):
+CHECK: Warnings without flags (72):
 CHECK-NEXT:   ext_excess_initializers
 CHECK-NEXT:   ext_excess_initializers_in_char_array_initializer
 CHECK-NEXT:   ext_expected_semi_decl_list
@@ -44,9 +44,6 @@
 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