Allow discards in foreach

[adamyakes]

I was writing some code that randomized some input for testing. I wanted to test it a bunch of times, so I threw it in a loop. Much to my surprise, this doesn't work:

foreach (_ in Enumerable.Range(0, 100)
{
    // ...
}

I think it would be nice to allow discards here. You can of course still use var _, but then _ becomes a variable and you effectively can't use discards within that block. Note, this silly thing works:

foreach (var (_, _) in Enumerable.Range(0, 100).Zip(Enumerable.Range(0, 100)))
{
    // ...
}

I recognize this is an incredibly niche use case, and only really applies to this one scenario.

[TahirAhmadov]

foreach (_ in Enumerable.Range(0, 100)
{
    // ...
}

Why not do:

for(int i = 0; i < 100; ++i)
{
  // ...
}

PS. Or:

100.Repeat(() =>
{
  // ...
});

public static void Repeat(this int This, Action action) { ... }

[adamyakes]

The first loop is still introducing a local variable. The second is a little better, but the lambda syntax is ugly IMO and requires an extension method. If we allow some discards in loop variables, what is the restriction to allow all of them?

[TahirAhmadov]

What's wrong with a local variable?
The issue with the foreach (_ in Enumerable.Range(0, 100)) is inefficiency - you're creating an enumerable, there are method calls, etc. Look at this SharpLab

[TahirAhmadov]

While it's still an extremely low priority item, I would rather see something like:

do(100) // any size integer expression goes inside the parens
{
}

[HaloFour]

See: #7888

[adamyakes]

Thanks - I searched for foreach discard and for some reason this did not come up. I've closed this as duplicate.