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Rollup merge of #99011 - oli-obk:UnsoundCell, r=eddyb

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`UnsafeCell` blocks niches inside its nested type from being available outside

fixes #87341

This implements the plan by `@eddyb` in https://github.com/rust-lang/rust/issues/87341#issuecomment-886083646

Somewhat related PR (not strictly necessary, but that cleanup made this PR simpler): #94527
This commit is contained in:
Dylan DPC 2022-07-13 19:32:34 +05:30 • committed by GitHub
commit 1e7d04b23b
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22 changed files with 139 additions and 513 deletions
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2
compiler/rustc_const_eval/src/interpret/intern.rs
View file

@ -217,7 +217,7 @@ impl<'rt, 'mir, 'tcx: 'mir, M: CompileTimeMachine<'mir, 'tcx, const_eval::Memory
}
if let Some(def) = mplace.layout.ty.ty_adt_def() {
if Some(def.did()) == self.ecx.tcx.lang_items().unsafe_cell_type() {
if def.is_unsafe_cell() {
// We are crossing over an `UnsafeCell`, we can mutate again. This means that
// References we encounter inside here are interned as pointing to mutable
// allocations.

2
compiler/rustc_const_eval/src/interpret/validity.rs
View file

@ -821,7 +821,7 @@ impl<'rt, 'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> ValueVisitor<'mir, 'tcx, M>
// Special check preventing `UnsafeCell` in the inner part of constants
if let Some(def) = op.layout.ty.ty_adt_def() {
if matches!(self.ctfe_mode, Some(CtfeValidationMode::Const { inner: true, .. }))
&& Some(def.did()) == self.ecx.tcx.lang_items().unsafe_cell_type()
&& def.is_unsafe_cell()
{
throw_validation_failure!(self.path, { "`UnsafeCell` in a `const`" });
}

4
compiler/rustc_const_eval/src/transform/check_consts/qualifs.rs
View file

@ -96,13 +96,13 @@ impl Qualif for HasMutInterior {
}
fn in_adt_inherently<'tcx>(
cx: &ConstCx<'_, 'tcx>,
_cx: &ConstCx<'_, 'tcx>,
adt: AdtDef<'tcx>,
_: SubstsRef<'tcx>,
) -> bool {
// Exactly one type, `UnsafeCell`, has the `HasMutInterior` qualif inherently.
// It arises structurally for all other types.
Some(adt.did()) == cx.tcx.lang_items().unsafe_cell_type()
adt.is_unsafe_cell()
}
}