How to reliably detect an alias sequence?

[sighoya]

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.