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Compute bound vars correctly

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This commit is contained in:
Michael Goulet
2023-03-10 21:41:11 +00:00
parent 773e8a5ad1
commit 0308d4ad18
2 changed files with 108 additions and 17 deletions
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71
compiler/rustc_hir_analysis/src/astconv/mod.rs
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@@ -1088,7 +1088,7 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
// TODO: rtn comment goes here
let associated_return_type_bound =
binding.gen_args.parenthesized && self.tcx().features().associated_return_type_bounds;
binding.gen_args.parenthesized && tcx.features().associated_return_type_bounds;
let candidate = if return_type_notation {
if self.trait_defines_associated_item_named(
@@ -1156,7 +1156,7 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
dup_bindings
.entry(assoc_item.def_id)
.and_modify(|prev_span| {
self.tcx().sess.emit_err(ValueOfAssociatedStructAlreadySpecified {
tcx.sess.emit_err(ValueOfAssociatedStructAlreadySpecified {
span: binding.span,
prev_span: *prev_span,
item_name: binding.item_name,
@@ -1166,14 +1166,53 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
.or_insert(binding.span);
}
let projection_ty = if associated_return_type_bound {
let generics = self.tcx().generics_of(assoc_item.def_id);
if !generics.params.is_empty() {
todo!();
}
let output = self.tcx().fn_sig(assoc_item.def_id).skip_binder().output();
let fn_bound_vars = output.bound_vars();
let projection_ty = if return_type_notation {
// If we have an method return type bound, then we need to substitute
// the method's early bound params with suitable late-bound params.
let mut num_bound_vars = candidate.bound_vars().len();
let substs =
candidate.skip_binder().substs.extend_to(tcx, assoc_item.def_id, |param, _| {
let subst = match param.kind {
GenericParamDefKind::Lifetime => tcx
.mk_re_late_bound(
ty::INNERMOST,
ty::BoundRegion {
var: ty::BoundVar::from_usize(num_bound_vars),
kind: ty::BoundRegionKind::BrNamed(param.def_id, param.name),
},
)
.into(),
GenericParamDefKind::Type { .. } => tcx
.mk_bound(
ty::INNERMOST,
ty::BoundTy {
var: ty::BoundVar::from_usize(num_bound_vars),
kind: ty::BoundTyKind::Param(param.def_id, param.name),
},
)
.into(),
GenericParamDefKind::Const { .. } => {
let ty = tcx
.type_of(param.def_id)
.no_bound_vars()
.expect("ct params cannot have early bound vars");
tcx.mk_const(
ty::ConstKind::Bound(
ty::INNERMOST,
ty::BoundVar::from_usize(num_bound_vars),
),
ty,
)
.into()
}
};
num_bound_vars += 1;
subst
});
// Next, we need to check that the return-type notation is being used on
// an RPITIT (return-position impl trait in trait) or AFIT (async fn in trait).
let output = tcx.fn_sig(assoc_item.def_id).skip_binder().output();
let output = if let ty::Alias(ty::Projection, alias_ty) = *output.skip_binder().kind()
&& tcx.def_kind(alias_ty.def_id) == DefKind::ImplTraitPlaceholder
{
@@ -1182,13 +1221,13 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
todo!("found return type of {output:?}");
};
let trait_bound_vars = candidate.bound_vars();
let shifted_output = tcx.shift_bound_var_indices(trait_bound_vars.len(), output);
let subst_output =
ty::EarlyBinder(shifted_output).subst(tcx, candidate.skip_binder().substs);
let bound_vars =
tcx.mk_bound_variable_kinds_from_iter(trait_bound_vars.iter().chain(fn_bound_vars));
// Finally, move the fn return type's bound vars over to account for the early bound
// params (and trait ref's late bound params). This logic is very similar to
// `Predicate::subst_supertrait`, and it's no coincidence why.
let shifted_output = tcx.shift_bound_var_indices(num_bound_vars, output);
let subst_output = ty::EarlyBinder(shifted_output).subst(tcx, substs);
let bound_vars = tcx.late_bound_vars(binding.hir_id);
ty::Binder::bind_with_vars(subst_output, bound_vars)
} else {
// Include substitutions for generic parameters of associated types
@@ -1211,7 +1250,7 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
debug!(?substs_trait_ref_and_assoc_item);
self.tcx().mk_alias_ty(assoc_item.def_id, substs_trait_ref_and_assoc_item)
tcx.mk_alias_ty(assoc_item.def_id, substs_trait_ref_and_assoc_item)
})
};