Clang with ARC bug: Incorrect substitution for pointer template parameters. This bug report is suitable to be posted to http://bugreport.apple.com

gistfile1.txt

Summary:
When ARC is enabled, C++ candidate templates' pointer template parameters are not correctly substituted for objective-C object pointers.


Steps to reproduce:
Compile the following main.mm file, with and without ARC:

#import <Foundation/Foundation.h>

template <typename T>
void testing(const T & whoCares) {
    NSLog(@"================> Non pointer template");
}

template <typename T>
void testing(T * const & whoCares) {
    NSLog(@"================> Pointer template");
}

int main(int argc, const char * argv[])
{
    NSString *stringObject = @"hi";
    char *cString = "abc";
    testing(1);
    testing(cString);
    testing(stringObject);
    testing<NSString>(stringObject);
    return 0;
}


Expected Results:
The template with the pointer parameter should be instantiated for cString and stringObject, without needing to parameterize the template explicitly, as demonstrated by the output when compiled without ARC:

================> Non pointer template
================> Pointer template
================> Pointer template
================> Pointer template


Actual Results:
When ARC is enabled and the template is not parameterized explicitly, the non-pointer template is instantiated if the pointer is an objective-c type, as demonstrated by the output when compiled with ARC:

================> Non pointer template
================> Pointer template
================> Non pointer template         <== WRONG
================> Pointer template


Regression:

Notes:
It seems clear that the substitution is incorrect since there is a more specialized template for T * const, which should be elected instead of const T for NSString *.