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Rvalue::Repeat should hold a ty::Const #68567

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varkor opened this issue Jan 27, 2020 · 1 comment · Fixed by #69981
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Rvalue::Repeat should hold a ty::Const #68567

varkor opened this issue Jan 27, 2020 · 1 comment · Fixed by #69981
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@oli-obk @varkor
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A-const-generics Area: const generics (parameters and arguments) A-mir Area: Mid-level IR (MIR) - https://blog.rust-lang.org/2016/04/19/MIR.html C-enhancement Category: An issue proposing an enhancement or a PR with one. F-const_generics `#![feature(const_generics)]` T-compiler Relevant to the compiler team, which will review and decide on the PR/issue.

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@varkor
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varkor commented Jan 27, 2020 

fn test<const N: usize>() {
    let array = [0; N];
}

currently fails with error: array lengths can't depend on generic parameters, because we can't tell what concrete value N should take here. This is an artificial limitation: when producing a Rvalue::Repeat, we currently need to provide the length of the array, which is impossible at this stage.
cc #43408 (comment)
@varkor varkor added T-compiler Relevant to the compiler team, which will review and decide on the PR/issue. A-const-generics Area: const generics (parameters and arguments) F-const_generics `#![feature(const_generics)]` A-mir Area: Mid-level IR (MIR) - https://blog.rust-lang.org/2016/04/19/MIR.html labels Jan 27, 2020
@varkor varkor mentioned this issue Jan 27, 2020
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@eddyb
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eddyb commented Jan 27, 2020

cc @oli-obk @yodaldevoid

@varkor varkor self-assigned this Jan 28, 2020
This was referenced Feb 6, 2020
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@JohnTitor JohnTitor added the C-enhancement Category: An issue proposing an enhancement or a PR with one. label Feb 16, 2020
@oli-obk oli-obk self-assigned this Mar 13, 2020
@oli-obk oli-obk mentioned this issue Mar 13, 2020
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Centril added a commit to Centril/rust that referenced this issue Mar 23, 2020
@Centril
Rollup merge of rust-lang#69981 - oli-obk:const_blocks, r=eddyb
32b6b1e 
Evaluate repeat expression lengths as late as possible

Fixes rust-lang#68567

r? @varkor
@bors bors closed this as completed in a73ed5a Mar 24, 2020
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A-const-generics Area: const generics (parameters and arguments) A-mir Area: Mid-level IR (MIR) - https://blog.rust-lang.org/2016/04/19/MIR.html C-enhancement Category: An issue proposing an enhancement or a PR with one. F-const_generics `#![feature(const_generics)]` T-compiler Relevant to the compiler team, which will review and decide on the PR/issue.
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Evaluate repeat expression lengths as late as possible oli-obk/rust
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@eddyb @oli-obk @varkor @JohnTitor