Warn when an intended Objective-C specialization was actually a useless protocol qualification.

Warn in cases where one has provided redundant protocol qualification
that might be a typo for a specialization, e.g., NSArray<NSObject>,
which is pointless (NSArray declares that it conforms to NSObject) and
is likely to be a typo for NSArray<NSObject *>, i.e., an array of
NSObject pointers. This warning is very narrow, only applying when the
base type being qualified is parameterized, has the same number of
parameters as their are protocols listed, all of the names can also
refer to types (including Objective-C class types, of course), and at
least one of those types is an Objective-C class (making this a typo
for a missing '*'). The limitations are partly for performance reasons
(we don't want to do redundant name lookup unless we really need to),
and because we want the warning to apply in very limited cases to
limit false positives.

Part of rdar://problem/6294649.

llvm-svn: 241547

1 files changed, 9 insertions, 1 deletions

diff --git a/clang/test/SemaObjC/parameterized_classes_subst.m b/clang/test/SemaObjC/parameterized_classes_subst.m
index 979053bfa78..6804bdc7955 100644
--- a/clang/test/SemaObjC/parameterized_classes_subst.m
+++ b/clang/test/SemaObjC/parameterized_classes_subst.m
@@ -3,8 +3,11 @@
 // Test the substitution of type arguments for type parameters when
 // using parameterized classes in Objective-C.
 
+@protocol NSObject
+@end
+
 __attribute__((objc_root_class))
-@interface NSObject
+@interface NSObject <NSObject>
 + (instancetype)alloc;
 - (instancetype)init;
 @end
@@ -376,3 +379,8 @@ void test_ternary_operator(NSArray<NSString *> *stringArray,
   ip = [super array]; // expected-warning{{from 'NSArray<NSString *> *'}}
 }
 @end
+
+// --------------------------------------------------------------------------
+// warning about likely protocol/class name typos.
+// --------------------------------------------------------------------------
+typedef NSArray<NSObject> ArrayOfNSObjectWarning; // expected-warning{{parameterized class 'NSArray' already conforms to the protocols listed; did you forget a '*'?}}