[Issue 13843] New: Issue when passing a delegate as an class alias template parameter

[via Digitalmars-d-bugs]

https://issues.dlang.org/show_bug.cgi?id=13843

          Issue ID: 13843
           Summary: Issue when passing a delegate as an class alias
                    template parameter
           Product: D
           Version: D2
          Hardware: x86_64
                OS: Linux
            Status: NEW
          Severity: normal
          Priority: P1
         Component: DMD
          Assignee: nobody at puremagic.com
          Reporter: dev at nomad.so

There is an issue when passing a delegate as an class alias template parameter
to be used with std.functional.binaryFun. Look at this code:

import std.stdio;
import std.functional;

class Foo(T, alias greater = "a > b")
{
    private alias compare = binaryFun!(greater);

    public this()
    {
        writefln("%s", compare(2, 1));
    }
}

void main(string[] args)
{
    // These work:
    auto foo1 = new Foo!(int, "a > b");
    auto foo2 = new Foo!(int, (a, b) => a > b);
    auto foo4 = new Foo!(int, delegate(a, b){return a > b;});

    // The following works when the delegate method is called without 'this.' 
    // otherwise they generate linker Errors:
    auto foo3 = new Foo!(int, (int a, int b) => a > b);
    auto foo5 = new Foo!(int, delegate(int a, int b){return a > b;});
}

If i remove the 'this.' from the compare method call, all works fine. After
that call, i can call compare *with* 'this.' and all works. But there has to be
an initial call made without the 'this.' for it to work from then on.

If i leave the 'this.' in place and pass a delegate as the compare function
using types in the parameter list, a linker error occurs when calling the
delegate.

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