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Rollup merge of #110615 - WaffleLapkin:impl_tag, r=cjgillot

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Add `impl_tag!` macro to implement `Tag` for tagged pointer easily

r? `@Nilstrieb`

This should also lifts the need to think about safety from the callers (`impl_tag!` is robust (ish, see the macro issue)) and removes the possibility of making a "weird" `Tag` impl.
This commit is contained in:
Matthias Krüger
2023-04-25 21:06:33 +02:00
committed by GitHub
parent 297b222066 bec7ce4824
commit 8d00a8d11e
6 changed files with 211 additions and 29 deletions
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29
compiler/rustc_middle/src/ty/mod.rs
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@@ -1497,29 +1497,12 @@ struct ParamTag {
constness: hir::Constness,
}
unsafe impl rustc_data_structures::tagged_ptr::Tag for ParamTag {
const BITS: u32 = 2;
#[inline]
fn into_usize(self) -> usize {
match self {
Self { reveal: traits::Reveal::UserFacing, constness: hir::Constness::NotConst } => 0,
Self { reveal: traits::Reveal::All, constness: hir::Constness::NotConst } => 1,
Self { reveal: traits::Reveal::UserFacing, constness: hir::Constness::Const } => 2,
Self { reveal: traits::Reveal::All, constness: hir::Constness::Const } => 3,
}
}
#[inline]
unsafe fn from_usize(ptr: usize) -> Self {
match ptr {
0 => Self { reveal: traits::Reveal::UserFacing, constness: hir::Constness::NotConst },
1 => Self { reveal: traits::Reveal::All, constness: hir::Constness::NotConst },
2 => Self { reveal: traits::Reveal::UserFacing, constness: hir::Constness::Const },
3 => Self { reveal: traits::Reveal::All, constness: hir::Constness::Const },
_ => std::hint::unreachable_unchecked(),
}
}
impl_tag! {
impl Tag for ParamTag;
ParamTag { reveal: traits::Reveal::UserFacing, constness: hir::Constness::NotConst },
ParamTag { reveal: traits::Reveal::All, constness: hir::Constness::NotConst },
ParamTag { reveal: traits::Reveal::UserFacing, constness: hir::Constness::Const },
ParamTag { reveal: traits::Reveal::All, constness: hir::Constness::Const },
}
impl<'tcx> fmt::Debug for ParamEnv<'tcx> {