Objective-C qoi. When Objective-C pointer mismatches with

a qualified-id type because pointer is object of a forward
class declaration, include this info in a diagnostic note.
// rdar://10751015


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@211324 91177308-0d34-0410-b5e6-96231b3b80d8

include/clang/Basic/DiagnosticSemaKinds.td

@@ -5491,6 +5491,8 @@ def err_typecheck_missing_return_type_incompatible : Error<
   "return type must match previous return type}0,1 when %select{block "
   "literal|lambda expression}2 has unspecified explicit return type">;
 
+def not_incomplete_class_and_qualified_id : Note<
+  "conformance of forward class %0 to protocol %1 can not be confirmed">;
 def warn_incompatible_qualified_id : Warning<
   "%select{%diff{assigning to $ from incompatible type $|"
   "assigning to type from incompatible type}0,1"

lib/Sema/SemaExpr.cpp

@@ -10832,6 +10832,8 @@ bool Sema::DiagnoseAssignmentResult(AssignConvertType ConvTy,
   ConversionFixItGenerator ConvHints;
   bool MayHaveConvFixit = false;
   bool MayHaveFunctionDiff = false;
+  const ObjCInterfaceDecl *IFace = nullptr;
+  const ObjCProtocolDecl *PDecl = nullptr;
   switch (ConvTy) {
   case Compatible:
@@ -10913,11 +10915,32 @@ bool Sema::DiagnoseAssignmentResult(AssignConvertType ConvTy,
   case IncompatibleBlockPointer:
     DiagKind = diag::err_typecheck_convert_incompatible_block_pointer;
     break;
-  case IncompatibleObjCQualifiedId:
-    // FIXME: Diagnose the problem in ObjCQualifiedIdTypesAreCompatible, since
-    // it can give a more specific diagnostic.
+  case IncompatibleObjCQualifiedId: {
+    if (SrcType->isObjCQualifiedIdType()) {
+      const ObjCObjectPointerType *srcOPT =
+                SrcType->getAs<ObjCObjectPointerType>();
+      for (auto *srcProto : srcOPT->quals()) {
+        PDecl = srcProto;
+        break;
+      }
+      if (const ObjCInterfaceType *IFaceT =
+            DstType->getAs<ObjCObjectPointerType>()->getInterfaceType())
+        IFace = IFaceT->getDecl();
+    }
+    else if (DstType->isObjCQualifiedIdType()) {
+      const ObjCObjectPointerType *dstOPT =
+        DstType->getAs<ObjCObjectPointerType>();
+      for (auto *dstProto : dstOPT->quals()) {
+        PDecl = dstProto;
+        break;
+      }
+      if (const ObjCInterfaceType *IFaceT =
+            SrcType->getAs<ObjCObjectPointerType>()->getInterfaceType())
+        IFace = IFaceT->getDecl();
+    }
     DiagKind = diag::warn_incompatible_qualified_id;
     break;
+  }
   case IncompatibleVectors:
     DiagKind = diag::warn_incompatible_vectors;
     break;
@@ -10975,7 +10998,11 @@ bool Sema::DiagnoseAssignmentResult(AssignConvertType ConvTy,
     HandleFunctionTypeMismatch(FDiag, SecondType, FirstType);
   Diag(Loc, FDiag);
-
+  if (DiagKind == diag::warn_incompatible_qualified_id &&
+      PDecl && IFace && !IFace->hasDefinition())
+      Diag(IFace->getLocation(), diag::not_incomplete_class_and_qualified_id)
+        << IFace->getName() << PDecl->getName();
+    
   if (SecondType == Context.OverloadTy)
     NoteAllOverloadCandidates(OverloadExpr::find(SrcExpr).Expression,
                               FirstType);

test/SemaObjC/comptypes-legal.m

@@ -35,3 +35,20 @@ void foo(void)
   // Since registerFunc: expects a Derived object as it's second argument, I don't know why this would be legal.
   [Derived registerFunc: ExternFunc];  // expected-warning{{incompatible pointer types sending 'NSObject *(NSObject *, NSObject *)' to parameter of type 'FuncSignature *'}}
 }
+
+// rdar://10751015
+@protocol NSCopying @end
+@interface I
+- (void) Meth : (id <NSCopying>)aKey; // expected-note {{passing argument to parameter 'aKey' here}}
+@end
+
+@class ForwarClass; // expected-note 3 {{conformance of forward class ForwarClass to protocol NSCopying can not be confirmed}}
+
+ForwarClass *Test10751015 (I* pi, ForwarClass *ns_forward) {
+
+  [pi Meth : ns_forward ]; // expected-warning {{sending 'ForwarClass *' to parameter of incompatible type 'id<NSCopying>'}}
+
+  id <NSCopying> id_ns = ns_forward; // expected-warning {{initializing 'id<NSCopying>' with an expression of incompatible type 'ForwarClass *'}}
+
+  return id_ns; // expected-warning {{returning 'id<NSCopying>' from a function with incompatible result type 'ForwarClass *'}}
+}