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Rollup merge of #78224 - lcnr:repeat-expr, r=varkor

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min_const_generics: allow ty param in repeat expr

implements https://rust-lang.zulipchat.com/#narrow/stream/260443-project-const-generics/topic/repeat.20expressions

Even with `min_const_generics` active, now keeps resulting in future compat warnings instead of hard errors.
Const parameters, for example `[0; N + 1]`, still result in hard errors during resolve.
```rust
#![allow(dead_code)]

fn foo<T>() {
    [0; std::mem::size_of::<*mut T>()];
}

struct Foo<T>(T);

impl<T> Foo<T> {
    const ASSOC: usize = 4;

    fn test() {
        [0; Self::ASSOC];
    }
}
```

r? @varkor cc @petrochenkov
This commit is contained in:
Yuki Okushi 2020-10-29 12:08:40 +09:00 • committed by GitHub
commit 270d2e0c2e
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4
compiler/rustc_hir/src/def.rs
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@ -206,8 +206,10 @@ pub enum Res<Id = hir::HirId> {
/// ```rust
/// impl Foo { fn test() -> [u8; std::mem::size_of::<Self>()] {} }
/// ```
/// We do however allow `Self` in repeat expression even if it is generic to not break code
/// which already works on stable while causing the `const_evaluatable_unchecked` future compat lint.
///
/// FIXME(lazy_normalization_consts): Remove this bodge once this feature is stable.
/// FIXME(lazy_normalization_consts): Remove this bodge once that feature is stable.
SelfTy(Option<DefId> /* trait */, Option<(DefId, bool)> /* impl */),
ToolMod, // e.g., `rustfmt` in `#[rustfmt::skip]`