Add syntax extension ary![expr, ..N] #14272
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ary![expr, ..N] expands to an array by repeating `expr` N times. This is
in contrast to [expr, ..N] which Copies `expr` N times.
Sample usage:
let x = ary![None::<Vec<u8>>, ..10];
The one limitation is the count needs to be an integral literal, it
cannot be a static or a compile-time expression.
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If this is added, I do not think it should be part of the public API of the compiler. It should either be behind a feature gate or in a separate library because in the ideal world this macro is not as necessary with proper checking for expressions that can be repeated. Our rules for what can be in a static are basically the same for what can be a repeated expression, we just haven't applied the same logic to these expressions. |
True, and that reminds me, I meant to mention the related issues. Although even fixing that won't remove the need for I'm open to feature gating if necessary. Presumably a decision would be made about it after the relevant tickets have been fixed and we can better evaluate how useful this is. Putting it in a separate library might be a bit much, I feel like saying |
| } | ||
| Some(x) => x | ||
| }; | ||
| let exprs = Vec::from_fn(count, |_| val_expr.clone()); |
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This references the same Expr repeatedly in the vector. Is this ok, or should I be calling .duplicate() on it?
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Closing due to inactivity, but feel free to reopen with a rebase! |
ary![expr, ..N]expands to an array by repeatingexprN times. This isin contrast to
[expr, ..N]which CopiesexprN times.Sample usage:
The one limitation is the count needs to be an integral literal, it
cannot be a static or a compile-time expression.
Related to #5244, but is more flexible.