Index: cfe/trunk/lib/AST/ASTContext.cpp
===================================================================
--- cfe/trunk/lib/AST/ASTContext.cpp
+++ cfe/trunk/lib/AST/ASTContext.cpp
@@ -8191,9 +8191,9 @@
   }
 
   if (LHSOPT->isObjCQualifiedIdType() || RHSOPT->isObjCQualifiedIdType())
-    return finish(ObjCQualifiedIdTypesAreCompatible(QualType(LHSOPT,0),
-                                                    QualType(RHSOPT,0),
-                                                    false));
+    return finish(ObjCQualifiedIdTypesAreCompatible(
+        QualType(BlockReturnType ? LHSOPT : RHSOPT, 0),
+        QualType(BlockReturnType ? RHSOPT : LHSOPT, 0), false));
 
   const ObjCInterfaceType* LHS = LHSOPT->getInterfaceType();
   const ObjCInterfaceType* RHS = RHSOPT->getInterfaceType();
Index: cfe/trunk/test/SemaObjC/block-type-safety.m
===================================================================
--- cfe/trunk/test/SemaObjC/block-type-safety.m
+++ cfe/trunk/test/SemaObjC/block-type-safety.m
@@ -133,9 +133,20 @@
 @end
 
 int test5() {
+    // Returned value is used outside of a block, so error on changing
+    // a return type to a more general than expected.
     NSAllArray *(^block)(id);
     id <Foo> (^genericBlock)(id);
     genericBlock = block;
+    block = genericBlock; // expected-error {{incompatible block pointer types assigning to 'NSAllArray *(^)(id)' from 'id<Foo> (^)(id)'}}
+
+    // A parameter is used inside a block, so error on changing a parameter type
+    // to a more specific than an argument type it will be called with.
+    // rdar://problem/52788423
+    void (^blockWithParam)(NSAllArray *);
+    void (^genericBlockWithParam)(id<Foo>);
+    genericBlockWithParam = blockWithParam; // expected-error {{incompatible block pointer types assigning to 'void (^)(id<Foo>)' from 'void (^)(NSAllArray *)'}}
+    blockWithParam = genericBlockWithParam;
     return 0;
 }