bjoernager/rust
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remove a hack that seems to only benefit a few very special cases

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This commit is contained in:
Ralf Jung 2020-10-25 18:06:41 +01:00
parent bd837e899b
commit 99a44ed086
3 changed files with 37 additions and 55 deletions
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58
compiler/rustc_mir/src/transform/promote_consts.rs
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@ -22,7 +22,7 @@ use rustc_middle::ty::cast::CastTy;
use rustc_middle::ty::subst::InternalSubsts;
use rustc_middle::ty::{self, List, TyCtxt, TypeFoldable};
use rustc_span::symbol::sym;
use rustc_span::{Span, DUMMY_SP};
use rustc_span::Span;
use rustc_index::vec::{Idx, IndexVec};
use rustc_target::spec::abi::Abi;
@ -326,41 +326,16 @@ impl<'tcx> Validator<'_, 'tcx> {
if place.projection.contains(&ProjectionElem::Deref) {
return Err(Unpromotable);
}
let mut has_mut_interior =
self.qualif_local::<qualifs::HasMutInterior>(place.local);
// HACK(eddyb) this should compute the same thing as
// `<HasMutInterior as Qualif>::in_projection` from
// `check_consts::qualifs` but without recursion.
if has_mut_interior {
// This allows borrowing fields which don't have
// `HasMutInterior`, from a type that does, e.g.:
// `let _: &'static _ = &(Cell::new(1), 2).1;`
let mut place_projection = &place.projection[..];
// FIXME(eddyb) use a forward loop instead of a reverse one.
while let &[ref proj_base @ .., elem] = place_projection {
// FIXME(eddyb) this is probably excessive, with
// the exception of `union` member accesses.
let ty =
Place::ty_from(place.local, proj_base, self.body, self.tcx)
.projection_ty(self.tcx, elem)
.ty;
if ty.is_freeze(self.tcx.at(DUMMY_SP), self.param_env) {
has_mut_interior = false;
break;
}
place_projection = proj_base;
}
if self.qualif_local::<qualifs::NeedsDrop>(place.local) {
return Err(Unpromotable);
}
// FIXME(eddyb) this duplicates part of `validate_rvalue`.
let has_mut_interior =
self.qualif_local::<qualifs::HasMutInterior>(place.local);
if has_mut_interior {
return Err(Unpromotable);
}
if self.qualif_local::<qualifs::NeedsDrop>(place.local) {
return Err(Unpromotable);
}
if let BorrowKind::Mut { .. } = kind {
let ty = place.ty(self.body, self.tcx).ty;
@ -692,28 +667,7 @@ impl<'tcx> Validator<'_, 'tcx> {
self.validate_place(place)?;
// HACK(eddyb) this should compute the same thing as
// `<HasMutInterior as Qualif>::in_projection` from
// `check_consts::qualifs` but without recursion.
let mut has_mut_interior =
self.qualif_local::<qualifs::HasMutInterior>(place.local);
if has_mut_interior {
let mut place_projection = place.projection;
// FIXME(eddyb) use a forward loop instead of a reverse one.
while let &[ref proj_base @ .., elem] = place_projection {
// FIXME(eddyb) this is probably excessive, with
// the exception of `union` member accesses.
let ty = Place::ty_from(place.local, proj_base, self.body, self.tcx)
.projection_ty(self.tcx, elem)
.ty;
if ty.is_freeze(self.tcx.at(DUMMY_SP), self.param_env) {
has_mut_interior = false;
break;
}
place_projection = proj_base;
}
}
let has_mut_interior = self.qualif_local::<qualifs::HasMutInterior>(place.local);
if has_mut_interior {
return Err(Unpromotable);
}