Name placeholder (like _ in Go)

[vtereshkov]

Would it be possible to add something like _? It can be very useful.

Originally posted by @marekmaskarinec in #70 (comment)

[vtereshkov]

@marekmaskarinec It would not be easy, but I'll consider implementing it.

[skejeton]

If this is limited to declarations, as it usually is then I think I know what to do.

[vtereshkov]

@skejeton Not only declarations. Also assignments, the for...in loop, etc., etc.

Before we start, we need to answer several questions. For example,

1. Do we really need it after Allow variable redeclaration from multiple return function call #329 is done? @marekmaskarinec ?
2. The Go spec has 34 mentions of "blank", i. e., the _. All of them (except those related to generics) may or may not be applicable to Umka.
3. How should it be implemented internally? As an identifier or as a new token kind? If the former, what type should it have? And in how many places should it be treated specially?
4. How to properly skip the right-hand side expressions in a, _, _, b, _, c, d = e, f, g, h, i, j, k? They can have different sizes. And none of them should remain on the stack as garbage.

[marekmaskarinec]

I don't think this issue is worth implementing, since we now have #329. It may be useful in for loops, but it's actually not required thanks to variable shadowing. This works just fine:

fn main() {
        a := []int{ 1, 2, 3 }
        for _,i in a {
                for _,j in a {
                        printf("%d * %d = %d\n", i, j, i * j)
                }
        }
}