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Rollup merge of #100239 - RalfJung:const-prop-uninit, r=oli-obk

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remove an ineffective check in const_prop

Based on https://github.com/rust-lang/rust/pull/100043, only the last two commits are new.

ConstProp has a special check when reading from a local that prevents reading uninit locals. However, if that local flows into `force_allocation`, then no check fires and evaluation proceeds. So this check is not really effective at preventing accesses to uninit locals.

With https://github.com/rust-lang/rust/pull/100043, `read_immediate` and friends always fail when reading uninit locals, so I don't see why ConstProp would need a separate check. Thus I propose we remove it. This is needed to be able to do https://github.com/rust-lang/rust/pull/100085.
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Dylan DPC 2022-08-29 16:49:40 +05:30 • committed by GitHub
commit 3ea5456366
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8 changed files with 64 additions and 58 deletions
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3
compiler/rustc_const_eval/src/interpret/eval_context.rs
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@ -187,9 +187,6 @@ pub enum LocalValue<Prov: Provenance = AllocId> {
impl<'tcx, Prov: Provenance + 'static> LocalState<'tcx, Prov> {
/// Read the local's value or error if the local is not yet live or not live anymore.
///
/// Note: This may only be invoked from the `Machine::access_local` hook and not from
/// anywhere else. You may be invalidating machine invariants if you do!
#[inline]
pub fn access(&self) -> InterpResult<'tcx, &Operand<Prov>> {
match &self.value {