https://issues.dlang.org/show_bug.cgi?id=21452

          Issue ID: 21452
           Summary: isCallable erroneously returns false on function
                    templates
           Product: D
           Version: D2
          Hardware: All
                OS: All
            Status: NEW
          Severity: normal
          Priority: P1
         Component: phobos
          Assignee: nobody@puremagic.com
          Reporter: qs.il.paperinik@gmail.com

https://dlang.org/phobos/std_traits.html#isCallable reads:

Detect whether T is a callable object, which can be called with the function
call operator (...).

However, function templates f that can be called using f!() aren't considered isCallable!f, but certainly can.

The case of function templates that can infer their arguments from run-time arguments won't be easy or even possible.

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