Thread overview
How to reliably detect an alias sequence?
Dec 27
sighoya
December 27
Given a name bound to an alias sequence, what is a reliable way to detect that?

import std.meta: AliasSeq;

alias a = AliasSeq!int;

static if (<is a an AliasSeq>) {

}

__traits(isSame, a, AliasSeq!a) could work but doesn't, because it flattens singletons, which means __traits(isSame, int, AliasSeq!int) is true. (A bug/bad design, IMO. If the intended behavior is not to flatten tuples passed to __traits, there is no reason to make a special case for singletons).
December 27
On Sunday, 27 December 2020 at 12:23:26 UTC, Max Samukha wrote:
> Given a name bound to an alias sequence, what is a reliable way to detect that?
>
> import std.meta: AliasSeq;
>
> alias a = AliasSeq!int;
>
> static if (<is a an AliasSeq>) {
>
> }
>
> __traits(isSame, a, AliasSeq!a) could work but doesn't, because it flattens singletons, which means __traits(isSame, int, AliasSeq!int) is true. (A bug/bad design, IMO. If the intended behavior is not to flatten tuples passed to __traits, there is no reason to make a special case for singletons).

This should work:
```
static assert(is(int == AliasSeq!int));
Drepl: static assert:  `is(int == (int))` is false
```

The most appropriate solution would be:
```
AliasSeq!int.stringof == (int);
```

But it wouldn't exclude false positives.
December 28
On Sunday, 27 December 2020 at 18:25:10 UTC, sighoya wrote:
>
> This should work:
> ```
> static assert(is(int == AliasSeq!int));
> Drepl: static assert:  `is(int == (int))` is false
> ```
>

That will only work for type tuples. We need a general solution that would work for any alias tuple.

> The most appropriate solution would be:
> ```
> AliasSeq!int.stringof == (int);
> ```
>
> But it wouldn't exclude false positives

Yes, stringof is inadequate.