Bug in D type inferencing

[John Colvin via Digitalmars-d]

On Saturday, 2 July 2016 at 01:20:35 UTC, Hiemlick Hiemlicker 
wrote:
> public struct Foo
> {
> 	public void Create(T)(uint delegate(T) c, T param)
> 	{	
> 	}
> }
>
> Foo f;
>
> f.Create((x) { }, "asdf");
>
> cannot deduce arguments compiler error.
>
> Surely D can figure out that T is a string?
>
> If one simply changes this to
>
> public struct Foo(T)
> {
> 	public void Create(uint delegate(T) c, T param)
> 	{	
> 	}
> }
>
> and
>
> Foo!string f;
>
> everything works.
>
> The second parameter is a string so why not infer that T is a 
> string?
>
> Also, if one does
>
> f.Create((string x) { }, "asdf");
>
> Then it works. Seems like a blatant limitation in D's type 
> inferencing system.

Those lambdas don't return uint, they return void, so they could 
never match anyway.

Here's a simple example showing the problem I think you are 
getting at:

void create(T)(void delegate(T) c, T param) {}

void main()
{
//  create((x){}, "fdsa"); // can't deduce
     create!string((x){},"fdsa"); // OK
     create((string x){},"fdsa"); // OK
}

I don't know how difficult it would be to make this work, but you 
could definitely file an enhancement request for it at 
issues.dlang.org