Objective-C Blocks Don't Check Parameters' Generic Types

Originator:heath.borders
Number:rdar://27014664 Date Originated:25-Jun-2016 02:03 PM
Status:Open Resolved:
Product:Developer Tools Product Version:Version 8.0 beta (8S128d)
Classification:Serious Bug Reproducible:Always
 
Summary:
If a block accepts a parameter that contains a generic type, the block may be assigned to a variable with an incompatible generic type

Steps to Reproduce:
- (void)testExample {
    void (^blockWithNSArrayOfNSStrings)(NSArray<NSString *> *stringArray) = ^(NSArray<NSNumber *> *numberArray)
    {
        NSLog(@"numberArray: %@",
              numberArray);
    };
    blockWithNSArrayOfNSStrings([NSArray<NSString *> arrayWithObjects:
                                 @"foo",
                                 @"bar",
                                 nil]);
}

Expected Results:
The assignment should fail to compile because `blockWithNSArrayOfNSStrings` accepts an `NSArray` containing `NSString`s, but it’s assigned a block accepting an `NSArray` containing `NSNumber`s, and `NSNumber` is not a supertype of `NSString`.

Actual Results:
The assignment compiles without warnings from either clang or the analyzer.

Comments


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