swift-module-digester: removing super classes is API breaking.

Author: nkcsgexi

include/swift/AST/DiagnosticsModuleDiffer.def

@@ -68,6 +68,8 @@ ERROR(default_associated_type_removed,none,"%0 has removed default type %1", (St
 
 ERROR(protocol_req_added,none,"%0 has been added as a protocol requirement", (StringRef))
 
+ERROR(super_class_removed,none,"%0 has removed its super class %1", (StringRef, StringRef))
+
 #ifndef DIAG_NO_UNDEF
 # if defined(DIAG)
 #  undef DIAG

test/api-digester/Inputs/cake1.swift

@@ -89,3 +89,5 @@ public protocol RequiementChanges {
   associatedtype removedType
   var removedVar: Int {get}
 }
+
+public class SuperClassRemoval: C3 {}

test/api-digester/Inputs/cake2.swift

@@ -96,3 +96,5 @@ public protocol RequiementChanges {
   func addedFunc()
   var addedVar: Int { get }
 }
+
+public class SuperClassRemoval {}

test/api-digester/Outputs/Cake-abi.txt

@@ -59,3 +59,6 @@ cake1: AssociatedType AssociatedTypePro.T1 has removed default type Int
 cake2: AssociatedType RequiementChanges.addedTypeWithoutDefault has been added as a protocol requirement
 cake2: Func RequiementChanges.addedFunc() has been added as a protocol requirement
 cake2: Var RequiementChanges.addedVar has been added as a protocol requirement
+
+/* Class Inheritance Change */
+cake1: Class SuperClassRemoval has removed its super class C3

test/api-digester/Outputs/Cake.txt

@@ -44,4 +44,7 @@ cake1: Struct fixedLayoutStruct has removed conformance to P1
 cake1: AssociatedType AssociatedTypePro.T1 has removed default type Int
 cake2: AssociatedType RequiementChanges.addedTypeWithoutDefault has been added as a protocol requirement
 cake2: Func RequiementChanges.addedFunc() has been added as a protocol requirement
-cake2: Var RequiementChanges.addedVar has been added as a protocol requirement
+cake2: Var RequiementChanges.addedVar has been added as a protocol requirement
+
+/* Class Inheritance Change */
+cake1: Class SuperClassRemoval has removed its super class C3

tools/swift-api-digester/ModuleDiagsConsumer.cpp

@@ -58,6 +58,8 @@ static StringRef getCategoryName(uint32_t ID) {
   case LocalDiagID::default_associated_type_removed:
   case LocalDiagID::protocol_req_added:
     return "/* Protocol Requirement Change */";
+  case LocalDiagID::super_class_removed:
+    return "/* Class Inheritance Change */";
   default:
     return StringRef();
   }

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

@@ -694,6 +694,14 @@ static void diagnoseNominalTypeDeclChange(SDKNodeDeclType *L, SDKNodeDeclType *R
                      Name);
     });
   }
+  auto LSuperClass = L->getSuperClassName();
+  auto RSuperClass = R->getSuperClassName();
+  if (!LSuperClass.empty()) {
+    if (RSuperClass.empty()) {
+      Diags.diagnose(SourceLoc(), diag::super_class_removed, L->getScreenInfo(),
+                     LSuperClass);
+    }
+  }
 }
 
 static void detectDeclChange(NodePtr L, NodePtr R, SDKContext &Ctx) {