Sema: track and emit un-deserialized members

This adds tracking of the vtable holes due to a failure to deserialize
vtable entries.  This allows for the user to be able to identify what
member failed to be deserialied and can aid in understanding why an
`open` class may not be subclassed.

Future improvements here would allow tracing the XRefPath which failed
to be deserialied.  However, this still provides an improvement over the
existing experience where there is no available information on why the
class cannot be inherited from.

Author: compnerd

include/swift/AST/DiagnosticsSema.def

@@ -2781,6 +2781,8 @@ ERROR(inheritance_from_class_with_missing_vtable_entries,none,
       "cannot inherit from class %0 because it has overridable members that "
       "could not be loaded",
       (Identifier))
+NOTE(inheritance_from_class_with_missing_vtable_entry, none,
+     "could not deserialize %0", (DeclName))
 ERROR(inheritance_from_class_with_missing_vtable_entries_versioned,none,
       "cannot inherit from class %0 (compiled with Swift %1) because it has "
       "overridable members that could not be loaded in Swift %2",

lib/Sema/TypeCheckDeclPrimary.cpp

@@ -2553,6 +2553,10 @@ class DeclChecker : public DeclVisitor<DeclChecker> {
         if (!isInvalidSuperclass) {
           CD->diagnose(diag::inheritance_from_class_with_missing_vtable_entries,
                        Super->getName());
+          for (const auto &member : Super->getMembers())
+            if (const auto *MMD = dyn_cast<MissingMemberDecl>(member))
+              CD->diagnose(diag::inheritance_from_class_with_missing_vtable_entry,
+                           MMD->getName());
           isInvalidSuperclass = true;
         }
       }

test/Serialization/Inputs/CLibrary.h

@@ -0,0 +1,7 @@
+
+#ifndef CLibrary_h
+#define CLibrary_h
+
+typedef struct __attribute__((__objc_bridge__(Object))) CObject *CObjectRef;
+
+#endif

test/Serialization/Inputs/module.modulemap

@@ -0,0 +1,4 @@
+
+module CLibrary {
+  header "CLibrary.h"
+}

test/Serialization/Recovery/typedefs.swift

@@ -87,7 +87,19 @@ public class UserDynamicConvenienceSub: UserDynamicConvenience {
 }
 _ = UserDynamicConvenienceSub(conveniently: 0)
 
-public class UserSub : User {} // expected-error {{cannot inherit from class 'User' because it has overridable members that could not be loaded}}
+public class UserSub : User {}
+// expected-error@-1 {{cannot inherit from class 'User' because it has overridable members that could not be loaded}}
+// expected-note@-2 {{could not deserialize 'wrappedProp'}}
+// expected-note@-3 {{could not deserialize 'returnsWrappedMethod()'}}
+// expected-note@-4 {{could not deserialize 'constrainedWrapped'}}
+// expected-note@-5 {{could not deserialize 'subscript(_:)'}}
+// expected-note@-6 {{could not deserialize 'subscript(_:)'}}
+// expected-note@-7 {{could not deserialize 'init(wrapped:)'}}
+// expected-note@-8 {{could not deserialize 'init(generic:)'}}
+// expected-note@-9 {{could not deserialize 'init(wrappedRequired:)'}}
+// expected-note@-10 {{could not deserialize 'init(wrappedRequiredInSub:)'}}
+// expected-note@-11 {{could not deserialize 'init(wrappedDynamic:)'}}
+// expected-note@-12 {{could not deserialize 'init(wrappedRequiredDynamic:)'}}
 
 #endif // VERIFY
 

test/Serialization/implementation-only-open.swift

@@ -0,0 +1,25 @@
+// RUN: %empty-directory(%t)
+// RUN: %empty-directory(%t/swift)
+// RUN: %target-swift-frontend -emit-module -emit-module-path %t/swift/SwiftLibrary.swiftmodule %s -module-name SwiftLibrary -I%S/Inputs
+// RUN: %target-typecheck-verify-swift -DCLIENT -c %s -module-name client -I%t/swift
+
+#if CLIENT
+import SwiftLibrary
+
+public class MyObject: Object {
+// expected-error@-1 {{cannot inherit from class 'Object' because it has overridable members that could not be loaded}}
+// expected-note@-2 {{could not deserialize 'raw'}}
+// expected-note@-3 {{could not deserialize 'init(object:)'}}
+}
+#else
+@_implementationOnly import CLibrary
+
+open class Object {
+  internal var storage: AnyObject
+  internal var raw: CObject { unsafeBitCast(storage, to: CObject.self) }
+
+  fileprivate init(object: CObject) {
+    self.storage = object
+  }
+}
+#endif