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1ac1b63c9c
Introduce co- and contra-variance for Objective-C type parameters, which allows us to express that (for example) an NSArray is covariant in its type parameter. This means that NSArray<NSMutableString *> * is a subtype of NSArray<NSString *> *, which is expected of the immutable Foundation collections. Type parameters can be annotated with __covariant or __contravariant to make them co- or contra-variant, respectively. This feature can be detected by __has_feature(objc_generics_variance). Implements rdar://problem/20217490. llvm-svn: 241549
46 lines
1.4 KiB
Objective-C
46 lines
1.4 KiB
Objective-C
// RUN: %clang_cc1 -emit-pch %s -o %t
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// RUN: %clang_cc1 -include-pch %t -verify %s
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#ifndef HEADER_INCLUDED
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#define HEADER_INCLUDED
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@protocol NSObject
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@end
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__attribute__((objc_root_class))
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@interface NSObject
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@end
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@interface PC1<__covariant T, U : NSObject *> : NSObject
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// expected-note@-2{{type parameter 'U' declared here}}
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@end
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@interface PC1<__covariant T, U : NSObject *> (Cat1)
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@end
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typedef PC1<id, NSObject *> PC1Specialization1;
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typedef PC1Specialization1 <NSObject> PC1Specialization2;
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#else
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@interface PC1<T : NSObject *, // expected-error{{type bound 'NSObject *' for type parameter 'T' conflicts with implicit bound 'id}}
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// expected-note@15{{type parameter 'T' declared here}}
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U : id> (Cat2) // expected-error{{type bound 'id' for type parameter 'U' conflicts with previous bound 'NSObject *'}}
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// expected-note@15{{type parameter 'U' declared here}}
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@end
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typedef PC1Specialization1<id, NSObject *> PC1Specialization3; // expected-error{{type arguments cannot be applied to already-specialized class type 'PC1Specialization1' (aka 'PC1<id,NSObject *>')}}
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typedef PC1Specialization2<id, NSObject *> PC1Specialization4; // expected-error{{already-specialized class type 'PC1Specialization2' (aka 'PC1Specialization1<NSObject>')}}
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@interface NSString : NSObject
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@end
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void testCovariance(PC1<NSObject *, NSObject *> *pc1a,
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PC1<NSString *, NSObject *> *pc1b) {
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pc1a = pc1b;
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}
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#endif
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