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Rollup merge of #119975 - lukas-code:inferring-return-types-and-opaque-types-do-mix-sometimes, r=compiler-errors

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Don't ICE if TAIT-defining fn contains a closure with `_` in return type

The `delay_span_bug` got added in https://github.com/rust-lang/rust/pull/119803/commits/0e82aaeb6799041991c54fb9ff37b5c20a5c6146 to reduce the amount of errors emitted for functions that have `_` in their return type, because inference doesn't apply to function items. But this logic shouldn't apply to closures, because their return types *can* be inferred.

Fixes https://github.com/rust-lang/rust/issues/119916.
This commit is contained in:
Matthias Krüger 2024-01-17 20:21:20 +01:00 • committed by GitHub
commit 22f19130df
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4 changed files with 69 additions and 13 deletions
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31
compiler/rustc_hir_analysis/src/collect/type_of/opaque.rs
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@ -135,18 +135,25 @@ impl TaitConstraintLocator<'_> {
return;
}
if let Some(hir_sig) = self.tcx.hir_node_by_def_id(item_def_id).fn_decl() {
if hir_sig.output.get_infer_ret_ty().is_some() {
let guar = self.tcx.dcx().span_delayed_bug(
hir_sig.output.span(),
"inferring return types and opaque types do not mix well",
);
self.found = Some(ty::OpaqueHiddenType {
span: DUMMY_SP,
ty: Ty::new_error(self.tcx, guar),
});
return;
}
// Function items with `_` in their return type already emit an error, skip any
// "non-defining use" errors for them.
// Note that we use `Node::fn_sig` instead of `Node::fn_decl` here, because the former
// excludes closures, which are allowed to have `_` in their return type.
let hir_node = self.tcx.hir_node_by_def_id(item_def_id);
debug_assert!(
!matches!(hir_node, Node::ForeignItem(..)),
"foreign items cannot constrain opaque types",
);
if let Some(hir_sig) = hir_node.fn_sig()
&& hir_sig.decl.output.get_infer_ret_ty().is_some()
{
let guar = self.tcx.dcx().span_delayed_bug(
hir_sig.decl.output.span(),
"inferring return types and opaque types do not mix well",
);
self.found =
Some(ty::OpaqueHiddenType { span: DUMMY_SP, ty: Ty::new_error(self.tcx, guar) });
return;
}
// Calling `mir_borrowck` can lead to cycle errors through