Improve the Objective-C common-type computation used by the ternary operator.

The Objective-C common-type computation had a few problems that
required a significant rework, including:
  - Quadradic behavior when finding the common base type; now it's
  linear.
  - Keeping around type arguments when computing the common type
  between a specialized and an unspecialized type
  - Introducing redundant protocol qualifiers.

Part of rdar://problem/6294649. Also fixes rdar://problem/19572837 by
addressing a longstanding bug in
ASTContext::CollectInheritedProtocols().

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@241544 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 32 insertions, 1 deletions

diff --git a/test/SemaObjC/conditional-expr-8.m b/test/SemaObjC/conditional-expr-8.m
index beddd205a9..35f4e75314 100644
--- a/test/SemaObjC/conditional-expr-8.m
+++ b/test/SemaObjC/conditional-expr-8.m
@@ -1,7 +1,7 @@
 // RUN: %clang_cc1 -fsyntax-only -verify %s
 // expected-no-diagnostics
-// rdar://9296866
 
+// rdar://9296866
 @interface NSResponder
 @end
 
@@ -24,3 +24,34 @@
 }
 @end
 
+// rdar://problem/19572837
+@protocol NSObject
+@end
+
+__attribute__((objc_root_class))
+@interface NSObject <NSObject>
+@end
+
+@protocol Goable <NSObject>
+- (void)go;
+@end
+
+@protocol Drivable <Goable>
+- (void)drive;
+@end
+
+@interface Car : NSObject
+- (NSObject <Goable> *)bestGoable:(NSObject <Goable> *)drivable;
+@end
+
+@interface Car(Category) <Drivable>
+@end
+
+@interface Truck : Car
+@end
+
+@implementation Truck
+- (NSObject <Goable> *)bestGoable:(NSObject <Goable> *)drivable value:(int)value{
+    return value > 0 ? self : drivable;
+}
+@end