UDAs and no complaints about "need 'this'"

[Maxim Fomin via Digitalmars-d]

On Thursday, 9 April 2015 at 09:53:15 UTC, John Colvin wrote:
> struct BigLongStructName
> {
> 	int evenLongerMemberName;
> }
>
> struct QN{}
>
> unittest
> {
> 	BigLongStructName bigLongStructName;
>
> 	@(bigLongStructName.evenLongerMemberName)
> 		QN quickName;
> 	
> 	__traits(getAttributes, quickName)[0]++;
> }
>
> Is it just me or is it weird that this works? Once you pull the 
> UDA out from being a storage class and attempt to alias it, you 
> get the usual "need 'this' for 'evenLongerMemberName' of type 
> 'int'" error messages on use.
>
> Why are UDAs so special? I don't believe there's any other way 
> to achieve this sort of effective renaming.

For me it seems to fit into D type system (which is not 
necessarily is a good idea).

struct S
{
	int i;
}

alias S.i si;

void main(){ /*si++;*/}

Behavior of D depends sometimes on it internals, not on 
programmers' expectations. Since D has never been stabilized, the 
boundary between WAT and bugs is partially undefined.