How do i successfully use std.functional.binaryFun in the following example?

import std.stdio;
import std.functional;

class Foo(T, alias greater = "a > b") if (is(typeof(binaryFun!(greater)(T.init, T.init)) == bool))
{
	private alias compare = binaryFun!(greater);

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

void main(string[] args)
{
	auto foo = new Foo!(int, "a < b"); // Works

	auto bar = new Foo!(int, delegate(int a, int b){ return a > b; }); // Linker error.
}

The first instantiation works when using a string but I get a linker error when i try and use a delegate as the compare function. Why is this? and what do i need to do to correct this?

On Monday, 8 December 2014 at 20:08:35 UTC, Gary Willoughby wrote:
> import std.stdio;
> import std.functional;
>
> class Foo(T, alias greater = "a > b") if (is(typeof(binaryFun!(greater)(T.init, T.init)) == bool))
> {
> 	private alias compare = binaryFun!(greater);
>
> 	public this()
> 	{
> 		writefln("%s", this.compare(2, 1));
> 	}
> }
>
> void main(string[] args)
> {
> 	auto foo = new Foo!(int, "a < b"); // Works
>
> 	auto bar = new Foo!(int, delegate(int a, int b){ return a > b; }); // Linker error.
> }

Looks like a compiler bug.

A call without "this." works. When you insert a call without
"this.", other calls with "this." work, too.

A delegate with an implicit parameter type works: `Foo!(int,
delegate(int a, /*!*/ b){ return a > b;})`.

On Tuesday, 9 December 2014 at 01:17:47 UTC, anonymous wrote:
> Looks like a compiler bug.

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