bjoernager/rust
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Rollup merge of #81100 - lcnr:encode_with_shorthand, r=oli-obk

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prevent potential bug in `encode_with_shorthand`.

see https://rust-lang.zulipchat.com/#narrow/stream/233931-t-compiler.2Fmajor-changes/topic/Remove.20PredicateKind.20in.20favor.20of.20only.20Bin.E2.80.A6.20compiler-team.23397/near/223012169
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Ashley Mannix 2021-01-18 21:53:26 +10:00 • committed by GitHub
commit d3ff9ac8e8
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1 changed files with 3 additions and 3 deletions
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6
compiler/rustc_middle/src/ty/codec.rs
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@ -18,7 +18,6 @@ use rustc_data_structures::fx::FxHashMap;
use rustc_hir::def_id::{CrateNum, DefId};
use rustc_serialize::{Decodable, Decoder, Encodable, Encoder};
use rustc_span::Span;
use std::convert::{TryFrom, TryInto};
use std::hash::Hash;
use std::intrinsics;
use std::marker::DiscriminantKind;
@ -81,7 +80,8 @@ where
E: TyEncoder<'tcx>,
M: for<'b> Fn(&'b mut E) -> &'b mut FxHashMap<T, usize>,
T: EncodableWithShorthand<'tcx, E>,
<T::Variant as DiscriminantKind>::Discriminant: Ord + TryFrom<usize>,
// The discriminant and shorthand must have the same size.
T::Variant: DiscriminantKind<Discriminant = isize>,
{
let existing_shorthand = cache(encoder).get(value).copied();
if let Some(shorthand) = existing_shorthand {
@ -97,7 +97,7 @@ where
// The shorthand encoding uses the same usize as the
// discriminant, with an offset so they can't conflict.
let discriminant = intrinsics::discriminant_value(variant);
assert!(discriminant < SHORTHAND_OFFSET.try_into().ok().unwrap());
assert!(SHORTHAND_OFFSET > discriminant as usize);
let shorthand = start + SHORTHAND_OFFSET;