bjoernager/rust
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type parameters have unit metadata if they are sized

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This commit is contained in:
Michael Goulet 2022-02-13 13:39:07 -08:00
parent 6d7684101a
commit ef0ba1d2ce
3 changed files with 47 additions and 14 deletions
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22
compiler/rustc_middle/src/ty/sty.rs
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@ -2244,12 +2244,13 @@ impl<'tcx> Ty<'tcx> {
}
}
/// Returns the type of metadata for (potentially fat) pointers to this type.
/// Returns the type of metadata for (potentially fat) pointers to this type,
/// and a boolean signifying if this is conditional on this type being `Sized`.
pub fn ptr_metadata_ty(
self,
tcx: TyCtxt<'tcx>,
normalize: impl FnMut(Ty<'tcx>) -> Ty<'tcx>,
) -> Ty<'tcx> {
) -> (Ty<'tcx>, bool) {
let tail = tcx.struct_tail_with_normalize(self, normalize);
match tail.kind() {
// Sized types
@ -2269,28 +2270,31 @@ impl<'tcx> Ty<'tcx> {
| ty::Closure(..)
| ty::Never
| ty::Error(_)
// Extern types have metadata = ().
| ty::Foreign(..)
// If returned by `struct_tail_without_normalization` this is a unit struct
// without any fields, or not a struct, and therefore is Sized.
| ty::Adt(..)
// If returned by `struct_tail_without_normalization` this is the empty tuple,
// a.k.a. unit type, which is Sized
| ty::Tuple(..) => tcx.types.unit,
| ty::Tuple(..) => (tcx.types.unit, false),
ty::Str | ty::Slice(_) => tcx.types.usize,
ty::Str | ty::Slice(_) => (tcx.types.usize, false),
ty::Dynamic(..) => {
let dyn_metadata = tcx.lang_items().dyn_metadata().unwrap();
tcx.type_of(dyn_metadata).subst(tcx, &[tail.into()])
(tcx.type_of(dyn_metadata).subst(tcx, &[self.into()]), false)
},
ty::Projection(_)
| ty::Param(_)
| ty::Opaque(..)
// type parameters only have unit metadata if they're sized, so return true
// to make sure we double check this during confirmation
ty::Param(_) | ty::Projection(_) => (tcx.types.unit, true),
ty::Opaque(..)
| ty::Infer(ty::TyVar(_))
| ty::Bound(..)
| ty::Placeholder(..)
| ty::Infer(ty::FreshTy(_) | ty::FreshIntTy(_) | ty::FreshFloatTy(_)) => {
bug!("`ptr_metadata_ty` applied to unexpected type: {:?}", tail)
bug!("`ptr_metadata_ty` applied to unexpected type: {:?}", self)
}
}
}