[llvm-bugs] [Bug 25149] New: __kindof type checking breaks sortedArrayUsingFunction: example in Apple docs, in Objective-C++ files.

[via llvm-bugs]

https://llvm.org/bugs/show_bug.cgi?id=25149

            Bug ID: 25149
           Summary: __kindof type checking breaks
                    sortedArrayUsingFunction: example in Apple docs, in
                    Objective-C++ files.
           Product: clang
           Version: trunk
          Hardware: PC
                OS: All
            Status: NEW
          Severity: normal
          Priority: P
         Component: Frontend
          Assignee: unassignedclangbugs at nondot.org
          Reporter: nicolasweber at gmx.de
                CC: llvm-bugs at lists.llvm.org
    Classification: Unclassified

From
https://developer.apple.com/library/prerelease/ios/documentation/Cocoa/Reference/Foundation/Classes/NSArray_Class/index.html#//apple_ref/occ/instm/NSArray/sortedArrayUsingFunction:context:
:

"""
Given anArray (an array of NSNumber objects) and a comparison function of this
type:

NSInteger intSort(id num1, id num2, void *context)
{
    int v1 = [num1 intValue];
    int v2 = [num2 intValue];
    if (v1 < v2)
        return NSOrderedAscending;
    else if (v1 > v2)
        return NSOrderedDescending;
    else
        return NSOrderedSame;
}
A sorted version of anArray is created in this way:

NSArray *sortedArray; sortedArray = [anArray sortedArrayUsingFunction:intSort
context:NULL];
"""

Doing this results in a warning with the 10.11 SDK when used like so (which
quickly happens in practice when passing e.g. [myview subviews] as array):

#import <Foundation/Foundation.h>

NSInteger intSort(id num1, id num2, void* context) {
  int v1 = [num1 intValue];
  int v2 = [num2 intValue];
  if (v1 < v2)
    return NSOrderedAscending;
  else if (v1 > v2)
    return NSOrderedDescending;
  else
    return NSOrderedSame;
}

id f(NSArray<__kindof NSNumber*>* anArray) {
  NSArray* sortedArray =
      [anArray sortedArrayUsingFunction:intSort context:NULL];
  return sortedArray;
}

$ clang -c test.mm 
test.mm:16:41: warning: incompatible pointer types sending 'NSInteger (*)(id,
id, void *)' to parameter of type 'NSInteger (* __nonnull)(__kindof NSNumber *
__nonnull, __kindof NSNumber * __nonnull, void * __nullable)'
[-Wincompatible-pointer-types]
      [anArray sortedArrayUsingFunction:intSort context:NULL];
                                        ^~~~~~~
1 warning generated.



Is this intentional? Or should id typecheck as any __kindof? (works fine in .m
files but not in .mm)

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