Merge pull request swiftlang#30252 from nkcsgexi/add-enum-case-break

APIChecker: adding enum cases are source breaking changes

Author: nkcsgexi

include/swift/AST/DiagnosticsModuleDiffer.def

@@ -102,6 +102,8 @@ ERROR(added_invisible_designated_init,none,"%0 has new designated initializers t
 
 ERROR(not_inheriting_convenience_inits,none,"%0 no longer inherits convenience inits from its superclass", (StringRef))
 
+ERROR(enum_case_added,none,"%0 has been added as a new enum case", (StringRef))
+
 #ifndef DIAG_NO_UNDEF
 # if defined(DIAG)
 #  undef DIAG

test/api-digester/Outputs/Cake.txt

@@ -46,6 +46,7 @@ cake: Func S1.foo1() has self access kind changing from NonMutating to Mutating
 cake: Func S1.foo3() is now static
 cake: Var C1.CIIns1 changes from weak to strong
 cake: Var C1.CIIns2 changes from strong to weak
+cake: EnumElement FrozenKind.AddedCase has been added as a new enum case
 
 /* Conformance changes */
 cake: Func ObjCProtocol.removeOptional() is no longer an optional requirement

tools/swift-api-digester/ModuleDiagsConsumer.cpp

@@ -55,6 +55,7 @@ static StringRef getCategoryName(uint32_t ID) {
     return "/* RawRepresentable Changes */";
   case LocalDiagID::generic_sig_change:
     return "/* Generic Signature Changes */";
+  case LocalDiagID::enum_case_added:
   case LocalDiagID::decl_added:
   case LocalDiagID::decl_reorder:
   case LocalDiagID::var_has_fixed_order_change:

tools/swift-api-digester/swift-api-digester.cpp

@@ -1179,7 +1179,14 @@ class PrunePass : public MatchedNodeListener, public SDKTreeDiffPass {
           }
         }
       }
-
+      // Adding an enum case is source-breaking.
+      if (!Ctx.checkingABI()) {
+        if (auto *Var = dyn_cast<SDKNodeDeclVar>(Right)) {
+          if (Var->getDeclKind() == DeclKind::EnumElement) {
+            Var->emitDiag(Var->getLoc(), diag::enum_case_added);
+          }
+        }
+      }
       return;
     case NodeMatchReason::Removed:
       assert(!Right);