clang-bug-or-pebkac?

gistfile1.m

/*
$ clang test.m 
test.m:24:17: warning: incomplete implementation [-Wincomplete-implementation]
@implementation Test (TestCategory)
                ^
test.m:24:17: warning: method in protocol not implemented [-Wprotocol]
test.m:17:1: note: method declared here
- (id)testMethod;
^
test.m:21:12: note: required for direct or indirect protocol 'TestProtocol'
@interface Test (TestCategory) <TestProtocol>
           ^
2 warnings generated
*/

#import <Foundation/Foundation.h>

@interface Test : NSObject
- (id)testMethod;
@end

@implementation Test

- (id)testMethod;
{
  return nil;
}

@end

@protocol TestProtocol <NSObject>
- (id)testMethod;
- (id)secondMethod;
@end

@interface Test (TestCategory) <TestProtocol>
@end

@implementation Test (TestCategory)

- (id)secondMethod;
{
  return nil;
}

@end