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Descriptive error when users try to combine RPITIT/AFIT with specialization

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This commit is contained in:
Michael Goulet 2023-02-28 02:03:26 +00:00
parent 6290ae92b2
commit ecac8fd5af
7 changed files with 83 additions and 65 deletions
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40
compiler/rustc_hir_analysis/src/check/check.rs
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@ -792,8 +792,10 @@ fn check_impl_items_against_trait<'tcx>(
trait_def.must_implement_one_of.as_deref();
for &trait_item_id in tcx.associated_item_def_ids(impl_trait_ref.def_id) {
let is_implemented = ancestors
.leaf_def(tcx, trait_item_id)
let leaf_def = ancestors.leaf_def(tcx, trait_item_id);
let is_implemented = leaf_def
.as_ref()
.map_or(false, |node_item| node_item.item.defaultness(tcx).has_value());
if !is_implemented && tcx.impl_defaultness(impl_id).is_final() {
@ -801,8 +803,8 @@ fn check_impl_items_against_trait<'tcx>(
}
// true if this item is specifically implemented in this impl
let is_implemented_here = ancestors
.leaf_def(tcx, trait_item_id)
let is_implemented_here = leaf_def
.as_ref()
.map_or(false, |node_item| !node_item.defining_node.is_from_trait());
if !is_implemented_here {
@ -831,6 +833,36 @@ fn check_impl_items_against_trait<'tcx>(
}
}
}
if let Some(leaf_def) = &leaf_def
&& !leaf_def.is_final()
&& let def_id = leaf_def.item.def_id
&& tcx.impl_method_has_trait_impl_trait_tys(def_id)
{
let def_kind = tcx.def_kind(def_id);
let descr = tcx.def_kind_descr(def_kind, def_id);
let (msg, feature) = if tcx.asyncness(def_id).is_async() {
(
format!("async {descr} in trait cannot be specialized"),
sym::async_fn_in_trait,
)
} else {
(
format!(
"{descr} with return-position `impl Trait` in trait cannot be specialized"
),
sym::return_position_impl_trait_in_trait,
)
};
tcx.sess
.struct_span_err(tcx.def_span(def_id), msg)
.note(format!(
"specialization behaves in inconsistent and \
surprising ways with `#![feature({feature})]`, \
and for now is disallowed"
))
.emit();
}
}
if !missing_items.is_empty() {