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Unrolled build for rust-lang#117262
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Rollup merge of rust-lang#117262 - celinval:issue-38-norm, r=oli-obk

Create a new ConstantKind variant (ZeroSized) for StableMIR

ZeroSized constants can be represented as `mir::Const::Val` even if their layout is not yet known. In those cases, CrateItem::body() was crashing when trying to convert a `ConstValue::ZeroSized` into its stable counterpart  `ConstantKind::Allocated`.

Instead, we now map `ConstValue::ZeroSized` into a new variant: `ConstantKind::ZeroSized`.

**Note:** I didn't add any new test here since we already have covering tests in our project repository which I manually confirmed that will fix the issue.
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rust-timer authored Oct 27, 2023
2 parents 54e57e6 + 613e618 commit 4bcc366
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Showing 3 changed files with 18 additions and 6 deletions.
19 changes: 14 additions & 5 deletions compiler/rustc_smir/src/rustc_smir/mod.rs
Original file line number Diff line number Diff line change
Expand Up @@ -1283,11 +1283,15 @@ impl<'tcx> Stable<'tcx> for ty::Const<'tcx> {
let kind = match self.kind() {
ty::Value(val) => {
let const_val = tables.tcx.valtree_to_const_val((self.ty(), val));
stable_mir::ty::ConstantKind::Allocated(alloc::new_allocation(
self.ty(),
const_val,
tables,
))
if matches!(const_val, mir::ConstValue::ZeroSized) {
ConstantKind::ZeroSized
} else {
stable_mir::ty::ConstantKind::Allocated(alloc::new_allocation(
self.ty(),
const_val,
tables,
))
}
}
ty::ParamCt(param) => stable_mir::ty::ConstantKind::Param(param.stable(tables)),
ty::ErrorCt(_) => unreachable!(),
Expand Down Expand Up @@ -1401,6 +1405,11 @@ impl<'tcx> Stable<'tcx> for rustc_middle::mir::Const<'tcx> {
let id = tables.intern_const(*self);
Const::new(kind, ty, id)
}
mir::Const::Val(val, ty) if matches!(val, mir::ConstValue::ZeroSized) => {
let ty = ty.stable(tables);
let id = tables.intern_const(*self);
Const::new(ConstantKind::ZeroSized, ty, id)
}
mir::Const::Val(val, ty) => {
let kind = ConstantKind::Allocated(alloc::new_allocation(ty, val, tables));
let ty = ty.stable(tables);
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3 changes: 3 additions & 0 deletions compiler/stable_mir/src/ty.rs
Original file line number Diff line number Diff line change
Expand Up @@ -444,6 +444,9 @@ pub enum ConstantKind {
Allocated(Allocation),
Unevaluated(UnevaluatedConst),
Param(ParamConst),
/// Store ZST constants.
/// We have to special handle these constants since its type might be generic.
ZeroSized,
}

#[derive(Clone, Debug)]
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2 changes: 1 addition & 1 deletion compiler/stable_mir/src/visitor.rs
Original file line number Diff line number Diff line change
Expand Up @@ -50,7 +50,7 @@ impl Visitable for Const {
match &self.kind() {
super::ty::ConstantKind::Allocated(alloc) => alloc.visit(visitor)?,
super::ty::ConstantKind::Unevaluated(uv) => uv.visit(visitor)?,
super::ty::ConstantKind::Param(_) => {}
super::ty::ConstantKind::Param(_) | super::ty::ConstantKind::ZeroSized => {}
}
self.ty().visit(visitor)
}
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