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implement PlaceBuilder::try_ty

This commit is contained in:
b-naber 2022-11-02 13:37:37 +01:00
parent 80b3c6dbde
commit ac31d52324
2 changed files with 75 additions and 35 deletions

View file

@ -323,6 +323,64 @@ impl<'tcx> PlaceBuilder<'tcx> {
projection: Vec::from_iter(self.projection.iter().copied().chain([elem])),
}
}
pub fn try_ty<D>(&self, local_decls: &D, cx: &Builder<'_, 'tcx>) -> Option<Ty<'tcx>>
where
D: HasLocalDecls<'tcx>,
{
let tcx = cx.tcx;
let project_ty = |ty: Ty<'tcx>, elem: &PlaceElem<'tcx>| -> Ty<'tcx> {
match elem {
ProjectionElem::Deref => {
ty.builtin_deref(true)
.unwrap_or_else(|| {
bug!("deref projection of non-dereferenceable ty {:?}", ty)
})
.ty
}
ProjectionElem::Index(_) | ProjectionElem::ConstantIndex { .. } => {
ty.builtin_index().unwrap()
}
ProjectionElem::Subslice { from, to, from_end } => match ty.kind() {
ty::Slice(..) => ty,
ty::Array(inner, _) if !from_end => tcx.mk_array(*inner, (to - from) as u64),
ty::Array(inner, size) if *from_end => {
let size = size.eval_usize(tcx, ty::ParamEnv::empty());
let len = size - (*from as u64) - (*to as u64);
tcx.mk_array(*inner, len)
}
_ => bug!("cannot subslice non-array type: `{:?}`", ty),
},
ProjectionElem::Downcast(..) => ty,
ProjectionElem::Field(_, ty) | ProjectionElem::OpaqueCast(ty) => *ty,
}
};
match self.base {
PlaceBase::Local(local) => {
let base_ty = local_decls.local_decls()[local].ty;
Some(self.projection.iter().fold(base_ty, |ty, &elem| project_ty(ty, &elem)))
}
PlaceBase::Upvar { .. } => {
match to_upvars_resolved_place_builder(self.clone(), cx) {
Ok(resolved_place_builder) => {
// `base` is guaranteed to be `PlaceBase::Local` now, so recursive call is ok
resolved_place_builder.try_ty(local_decls, cx)
}
Err(place_builder) => {
match &place_builder.projection[..] {
&[ProjectionElem::OpaqueCast(base_ty), ref projections @ ..] => Some(
projections.iter().fold(base_ty, |ty, &elem| project_ty(ty, &elem)),
),
_ => None, // would need a base `Ty` for these
}
}
}
}
}
}
}
impl<'tcx> From<Local> for PlaceBuilder<'tcx> {