From 1e9b58bdf8dcb88ee21fbb8b0d2e86cba2b4cbb6 Mon Sep 17 00:00:00 2001
From: Camille GILLOT <gillot.camille@gmail.com>
Date: Sun, 5 Mar 2023 14:49:33 +0000
Subject: [PATCH] Use the correct bound vars in return type suggestion.
---
.../src/fn_ctxt/suggestions.rs | 45 +++++++++----------
tests/ui/suggestions/issue-107860.rs | 6 +++
tests/ui/suggestions/issue-107860.stderr | 12 +++++
3 files changed, 39 insertions(+), 24 deletions(-)
create mode 100644 tests/ui/suggestions/issue-107860.rs
create mode 100644 tests/ui/suggestions/issue-107860.stderr
diff --git a/compiler/rustc_hir_typeck/src/fn_ctxt/suggestions.rs b/compiler/rustc_hir_typeck/src/fn_ctxt/suggestions.rs
index c49621b7c2488..2c9d908166fa3 100644
--- a/compiler/rustc_hir_typeck/src/fn_ctxt/suggestions.rs
+++ b/compiler/rustc_hir_typeck/src/fn_ctxt/suggestions.rs
@@ -669,6 +669,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
/// This routine checks if the return type is left as default, the method is not part of an
/// `impl` block and that it isn't the `main` method. If so, it suggests setting the return
/// type.
+ #[instrument(level = "trace", skip(self, err))]
pub(in super::super) fn suggest_missing_return_type(
&self,
err: &mut Diagnostic,
@@ -705,28 +706,24 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
return true
}
}
- hir::FnRetTy::Return(ty) => {
- let span = ty.span;
-
- if let hir::TyKind::OpaqueDef(item_id, ..) = ty.kind
- && let hir::Node::Item(hir::Item {
- kind: hir::ItemKind::OpaqueTy(op_ty),
- ..
- }) = self.tcx.hir().get(item_id.hir_id())
- && let hir::OpaqueTy {
- bounds: [bound], ..
- } = op_ty
- && let hir::GenericBound::LangItemTrait(
- hir::LangItem::Future, _, _, generic_args) = bound
- && let hir::GenericArgs { bindings: [ty_binding], .. } = generic_args
- && let hir::TypeBinding { kind, .. } = ty_binding
- && let hir::TypeBindingKind::Equality { term } = kind
- && let hir::Term::Ty(term_ty) = term {
+ hir::FnRetTy::Return(hir_ty) => {
+ let span = hir_ty.span;
+
+ if let hir::TyKind::OpaqueDef(item_id, ..) = hir_ty.kind
+ && let hir::Node::Item(hir::Item {
+ kind: hir::ItemKind::OpaqueTy(op_ty),
+ ..
+ }) = self.tcx.hir().get(item_id.hir_id())
+ && let [hir::GenericBound::LangItemTrait(
+ hir::LangItem::Future, _, _, generic_args)] = op_ty.bounds
+ && let hir::GenericArgs { bindings: [ty_binding], .. } = generic_args
+ && let hir::TypeBindingKind::Equality { term: hir::Term::Ty(term) } = ty_binding.kind
+ {
// Check if async function's return type was omitted.
// Don't emit suggestions if the found type is `impl Future<...>`.
- debug!("suggest_missing_return_type: found = {:?}", found);
+ debug!(?found);
if found.is_suggestable(self.tcx, false) {
- if term_ty.span.is_empty() {
+ if term.span.is_empty() {
err.subdiagnostic(AddReturnTypeSuggestion::Add { span, found: found.to_string() });
return true;
} else {
@@ -737,11 +734,11 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
// Only point to return type if the expected type is the return type, as if they
// are not, the expectation must have been caused by something else.
- debug!("suggest_missing_return_type: return type {:?} node {:?}", ty, ty.kind);
- let ty = self.astconv().ast_ty_to_ty(ty);
- debug!("suggest_missing_return_type: return type {:?}", ty);
- debug!("suggest_missing_return_type: expected type {:?}", ty);
- let bound_vars = self.tcx.late_bound_vars(fn_id);
+ debug!("return type {:?}", hir_ty);
+ let ty = self.astconv().ast_ty_to_ty(hir_ty);
+ debug!("return type {:?}", ty);
+ debug!("expected type {:?}", expected);
+ let bound_vars = self.tcx.late_bound_vars(hir_ty.hir_id.owner.into());
let ty = Binder::bind_with_vars(ty, bound_vars);
let ty = self.normalize(span, ty);
let ty = self.tcx.erase_late_bound_regions(ty);
diff --git a/tests/ui/suggestions/issue-107860.rs b/tests/ui/suggestions/issue-107860.rs
new file mode 100644
index 0000000000000..a6449cd44d0f8
--- /dev/null
+++ b/tests/ui/suggestions/issue-107860.rs
@@ -0,0 +1,6 @@
+// edition: 2021
+
+async fn str<T>(T: &str) -> &str { &str }
+//~^ ERROR mismatched types
+
+fn main() {}
diff --git a/tests/ui/suggestions/issue-107860.stderr b/tests/ui/suggestions/issue-107860.stderr
new file mode 100644
index 0000000000000..92e3cf8c43b3b
--- /dev/null
+++ b/tests/ui/suggestions/issue-107860.stderr
@@ -0,0 +1,12 @@
+error[E0308]: mismatched types
+ --> $DIR/issue-107860.rs:3:36
+ |
+LL | async fn str<T>(T: &str) -> &str { &str }
+ | ^^^^ expected `&str`, found `&fn(&str) -> ... {str::<...>}`
+ |
+ = note: expected reference `&str`
+ found reference `&for<'a> fn(&'a str) -> impl Future<Output = &'a str> {str::<_>}`
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0308`.