Enhance alias to work with elements of a sequence?

[TurkeyMan]

Something like this doesn't work; I think it's because the alias is trying to alias an [] operator expression?

alias seq = AliasSeq!(x, y, z);
alias x = seq[0];

I constantly want to do things like: alias firstParam = Parameters!myFunction[0] when implementing some shim's or function call wrappers.

[WalterBright]

You'll need to be more specific, as:

template AliasSeq(TList...)
{
    alias AliasSeq = TList;
}

alias seq = AliasSeq!(int, uint, long);
alias x = seq[0];

x j = 3;

static assert(is (typeof(j) == int));

compiles without error.

[TurkeyMan]

I'll try and find the problem situations... I always seem to find it when using Parameters!func, or similar functions analysis traits.

[dkorpel]

@TurkeyMan Did you find any?

[TurkeyMan]

I haven't had time at a computer, I'm traveling at the moment.
But most of the situations I encounter problems were when working with Parameters!(), manipulating function args in call shims and stuff.
Also I think when some T... template args have non-type parameters, I think I've seen weird non-uniform failures when trying to alias certain members to simplify introspection logic.

[TurkeyMan]

You'll need to be more specific, as:

template AliasSeq(TList...)
{
    alias AliasSeq = TList;
}

alias seq = AliasSeq!(int, uint, long);
alias x = seq[0];

x j = 3;

static assert(is (typeof(j) == int));

compiles without error.

What about

alias seq = AliasSeq!(1, 2, 3);
alias x = seq[0];

int j = x;

??
I didn't test, I'm just guessing the kind of problem... I need to dig into one of my function adapters.

[ntrel]

alias seq = AliasSeq!(1, 2, 3);
alias x = seq[0];

seqelem.d(3): Error: alias seqelem.x cannot alias an expression 1

alias x = 1; also doesn't work. That's an issue with alias rather than sequences (https://dlang.org/library/std/meta/alias.html).