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Allow dyn* upcasting

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This commit is contained in:
bjorn3 2022-10-23 15:09:11 +02:00
parent 7a9abf5ab2
commit 2470ad30e6
1 changed files with 28 additions and 6 deletions
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34
src/unsize.rs
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@ -25,7 +25,12 @@ pub(crate) fn unsized_info<'tcx>(
.bcx
.ins()
.iconst(fx.pointer_type, len.eval_usize(fx.tcx, ParamEnv::reveal_all()) as i64),
(&ty::Dynamic(ref data_a, ..), &ty::Dynamic(ref data_b, ..)) => {
(
&ty::Dynamic(ref data_a, _, src_dyn_kind),
&ty::Dynamic(ref data_b, _, target_dyn_kind),
) => {
assert_eq!(src_dyn_kind, target_dyn_kind);
let old_info =
old_info.expect("unsized_info: missing old info for trait upcasting coercion");
if data_a.principal_def_id() == data_b.principal_def_id() {
@ -101,6 +106,21 @@ fn unsize_ptr<'tcx>(
}
}
/// Coerces `src` to `dst_ty` which is guaranteed to be a `dyn*` type.
pub(crate) fn cast_to_dyn_star<'tcx>(
fx: &mut FunctionCx<'_, '_, 'tcx>,
src: Value,
src_ty_and_layout: TyAndLayout<'tcx>,
dst_ty: Ty<'tcx>,
old_info: Option<Value>,
) -> (Value, Value) {
assert!(
matches!(dst_ty.kind(), ty::Dynamic(_, _, ty::DynStar)),
"destination type must be a dyn*"
);
(src, unsized_info(fx, src_ty_and_layout.ty, dst_ty, old_info))
}
/// Coerce `src`, which is a reference to a value of type `src_ty`,
/// to a value of type `dst_ty` and store the result in `dst`
pub(crate) fn coerce_unsized_into<'tcx>(
@ -152,14 +172,16 @@ pub(crate) fn coerce_dyn_star<'tcx>(
src: CValue<'tcx>,
dst: CPlace<'tcx>,
) {
let data = src.load_scalar(fx);
let vtable = if let ty::Dynamic(data, _, ty::DynStar) = dst.layout().ty.kind() {
crate::vtable::get_vtable(fx, src.layout().ty, data.principal())
let (data, extra) = if let ty::Dynamic(_, _, ty::DynStar) = src.layout().ty.kind() {
let (data, vtable) = src.load_scalar_pair(fx);
(data, Some(vtable))
} else {
bug!("Only valid to do a DynStar cast into a DynStar type")
let data = src.load_scalar(fx);
(data, None)
};
let (data, vtable) = cast_to_dyn_star(fx, data, src.layout(), dst.layout().ty, extra);
dst.write_cvalue(fx, CValue::by_val_pair(data, vtable, dst.layout()));
}