diff --git a/compiler/rustc_hir_typeck/src/coercion.rs b/compiler/rustc_hir_typeck/src/coercion.rs
index bbf7b81a2cc66..d5f37abb8b455 100644
--- a/compiler/rustc_hir_typeck/src/coercion.rs
+++ b/compiler/rustc_hir_typeck/src/coercion.rs
@@ -1619,6 +1619,7 @@ impl<'tcx, 'exprs, E: AsCoercionSite> CoerceMany<'tcx, 'exprs, E> {
}
}
}
+
fn note_unreachable_loop_return(
&self,
err: &mut Diagnostic,
diff --git a/compiler/rustc_hir_typeck/src/demand.rs b/compiler/rustc_hir_typeck/src/demand.rs
index 665dc8b6a2f2a..3f185dfae0241 100644
--- a/compiler/rustc_hir_typeck/src/demand.rs
+++ b/compiler/rustc_hir_typeck/src/demand.rs
@@ -59,7 +59,8 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
|| self.suggest_copied_or_cloned(err, expr, expr_ty, expected)
|| self.suggest_clone_for_ref(err, expr, expr_ty, expected)
|| self.suggest_into(err, expr, expr_ty, expected)
- || self.suggest_floating_point_literal(err, expr, expected);
+ || self.suggest_floating_point_literal(err, expr, expected)
+ || self.note_result_coercion(err, expr, expected, expr_ty);
if !suggested {
self.point_at_expr_source_of_inferred_type(err, expr, expr_ty, expected);
}
@@ -697,6 +698,56 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
);
}
+ pub(crate) fn note_result_coercion(
+ &self,
+ err: &mut Diagnostic,
+ expr: &hir::Expr<'tcx>,
+ expected: Ty<'tcx>,
+ found: Ty<'tcx>,
+ ) -> bool {
+ let ty::Adt(e, substs_e) = expected.kind() else { return false; };
+ let ty::Adt(f, substs_f) = found.kind() else { return false; };
+ if e.did() != f.did() {
+ return false;
+ }
+ if Some(e.did()) != self.tcx.get_diagnostic_item(sym::Result) {
+ return false;
+ }
+ let map = self.tcx.hir();
+ if let Some(hir::Node::Expr(expr)) = map.find_parent(expr.hir_id)
+ && let hir::ExprKind::Ret(_) = expr.kind
+ {
+ // `return foo;`
+ } else if map.get_return_block(expr.hir_id).is_some() {
+ // Function's tail expression.
+ } else {
+ return false;
+ }
+ let e = substs_e.type_at(1);
+ let f = substs_f.type_at(1);
+ if self
+ .infcx
+ .type_implements_trait(
+ self.tcx.get_diagnostic_item(sym::Into).unwrap(),
+ [f, e],
+ self.param_env,
+ )
+ .must_apply_modulo_regions()
+ {
+ err.multipart_suggestion(
+ "use `?` to coerce and return an appropriate `Err`, and wrap the resulting value \
+ in `Ok` so the expression remains of type `Result`",
+ vec![
+ (expr.span.shrink_to_lo(), "Ok(".to_string()),
+ (expr.span.shrink_to_hi(), "?)".to_string()),
+ ],
+ Applicability::MaybeIncorrect,
+ );
+ return true;
+ }
+ false
+ }
+
/// If the expected type is an enum (Issue #55250) with any variants whose
/// sole field is of the found type, suggest such variants. (Issue #42764)
fn suggest_compatible_variants(
diff --git a/tests/ui/type/type-check/coerce-result-return-value-2.rs b/tests/ui/type/type-check/coerce-result-return-value-2.rs
new file mode 100644
index 0000000000000..23bafa6c5c94c
--- /dev/null
+++ b/tests/ui/type/type-check/coerce-result-return-value-2.rs
@@ -0,0 +1,24 @@
+struct A;
+struct B;
+impl From for B {
+ fn from(_: A) -> Self { B }
+}
+fn foo4(x: Result<(), A>) -> Result<(), B> {
+ match true {
+ true => x, //~ ERROR mismatched types
+ false => x,
+ }
+}
+fn foo5(x: Result<(), A>) -> Result<(), B> {
+ match true {
+ true => return x, //~ ERROR mismatched types
+ false => return x,
+ }
+}
+fn main() {
+ let _ = foo4(Ok(()));
+ let _ = foo5(Ok(()));
+ let _: Result<(), B> = { //~ ERROR mismatched types
+ Err(A);
+ };
+}
diff --git a/tests/ui/type/type-check/coerce-result-return-value-2.stderr b/tests/ui/type/type-check/coerce-result-return-value-2.stderr
new file mode 100644
index 0000000000000..5992162341e6e
--- /dev/null
+++ b/tests/ui/type/type-check/coerce-result-return-value-2.stderr
@@ -0,0 +1,47 @@
+error[E0308]: mismatched types
+ --> $DIR/coerce-result-return-value-2.rs:8:17
+ |
+LL | fn foo4(x: Result<(), A>) -> Result<(), B> {
+ | ------------- expected `Result<(), B>` because of return type
+LL | match true {
+LL | true => x,
+ | ^ expected struct `B`, found struct `A`
+ |
+ = note: expected enum `Result<_, B>`
+ found enum `Result<_, A>`
+help: use `?` to coerce and return an appropriate `Err`, and wrap the resulting value in `Ok` so the expression remains of type `Result`
+ |
+LL | true => Ok(x?),
+ | +++ ++
+
+error[E0308]: mismatched types
+ --> $DIR/coerce-result-return-value-2.rs:14:24
+ |
+LL | fn foo5(x: Result<(), A>) -> Result<(), B> {
+ | ------------- expected `Result<(), B>` because of return type
+LL | match true {
+LL | true => return x,
+ | ^ expected struct `B`, found struct `A`
+ |
+ = note: expected enum `Result<_, B>`
+ found enum `Result<_, A>`
+help: use `?` to coerce and return an appropriate `Err`, and wrap the resulting value in `Ok` so the expression remains of type `Result`
+ |
+LL | true => return Ok(x?),
+ | +++ ++
+
+error[E0308]: mismatched types
+ --> $DIR/coerce-result-return-value-2.rs:21:28
+ |
+LL | let _: Result<(), B> = {
+ | ____________________________^
+LL | | Err(A);
+LL | | };
+ | |_____^ expected enum `Result`, found `()`
+ |
+ = note: expected enum `Result<(), B>`
+ found unit type `()`
+
+error: aborting due to 3 previous errors
+
+For more information about this error, try `rustc --explain E0308`.
diff --git a/tests/ui/type/type-check/coerce-result-return-value.fixed b/tests/ui/type/type-check/coerce-result-return-value.fixed
new file mode 100644
index 0000000000000..8a05407070dad
--- /dev/null
+++ b/tests/ui/type/type-check/coerce-result-return-value.fixed
@@ -0,0 +1,24 @@
+// run-rustfix
+struct A;
+struct B;
+impl From for B {
+ fn from(_: A) -> Self { B }
+}
+fn foo1(x: Result<(), A>) -> Result<(), B> {
+ Ok(x?) //~ ERROR mismatched types
+}
+fn foo2(x: Result<(), A>) -> Result<(), B> {
+ return Ok(x?); //~ ERROR mismatched types
+}
+fn foo3(x: Result<(), A>) -> Result<(), B> {
+ if true {
+ Ok(x?) //~ ERROR mismatched types
+ } else {
+ Ok(x?) //~ ERROR mismatched types
+ }
+}
+fn main() {
+ let _ = foo1(Ok(()));
+ let _ = foo2(Ok(()));
+ let _ = foo3(Ok(()));
+}
diff --git a/tests/ui/type/type-check/coerce-result-return-value.rs b/tests/ui/type/type-check/coerce-result-return-value.rs
new file mode 100644
index 0000000000000..442203addb787
--- /dev/null
+++ b/tests/ui/type/type-check/coerce-result-return-value.rs
@@ -0,0 +1,24 @@
+// run-rustfix
+struct A;
+struct B;
+impl From for B {
+ fn from(_: A) -> Self { B }
+}
+fn foo1(x: Result<(), A>) -> Result<(), B> {
+ x //~ ERROR mismatched types
+}
+fn foo2(x: Result<(), A>) -> Result<(), B> {
+ return x; //~ ERROR mismatched types
+}
+fn foo3(x: Result<(), A>) -> Result<(), B> {
+ if true {
+ x //~ ERROR mismatched types
+ } else {
+ x //~ ERROR mismatched types
+ }
+}
+fn main() {
+ let _ = foo1(Ok(()));
+ let _ = foo2(Ok(()));
+ let _ = foo3(Ok(()));
+}
diff --git a/tests/ui/type/type-check/coerce-result-return-value.stderr b/tests/ui/type/type-check/coerce-result-return-value.stderr
new file mode 100644
index 0000000000000..550153520782c
--- /dev/null
+++ b/tests/ui/type/type-check/coerce-result-return-value.stderr
@@ -0,0 +1,65 @@
+error[E0308]: mismatched types
+ --> $DIR/coerce-result-return-value.rs:8:5
+ |
+LL | fn foo1(x: Result<(), A>) -> Result<(), B> {
+ | ------------- expected `Result<(), B>` because of return type
+LL | x
+ | ^ expected struct `B`, found struct `A`
+ |
+ = note: expected enum `Result<_, B>`
+ found enum `Result<_, A>`
+help: use `?` to coerce and return an appropriate `Err`, and wrap the resulting value in `Ok` so the expression remains of type `Result`
+ |
+LL | Ok(x?)
+ | +++ ++
+
+error[E0308]: mismatched types
+ --> $DIR/coerce-result-return-value.rs:11:12
+ |
+LL | fn foo2(x: Result<(), A>) -> Result<(), B> {
+ | ------------- expected `Result<(), B>` because of return type
+LL | return x;
+ | ^ expected struct `B`, found struct `A`
+ |
+ = note: expected enum `Result<_, B>`
+ found enum `Result<_, A>`
+help: use `?` to coerce and return an appropriate `Err`, and wrap the resulting value in `Ok` so the expression remains of type `Result`
+ |
+LL | return Ok(x?);
+ | +++ ++
+
+error[E0308]: mismatched types
+ --> $DIR/coerce-result-return-value.rs:15:9
+ |
+LL | fn foo3(x: Result<(), A>) -> Result<(), B> {
+ | ------------- expected `Result<(), B>` because of return type
+LL | if true {
+LL | x
+ | ^ expected struct `B`, found struct `A`
+ |
+ = note: expected enum `Result<_, B>`
+ found enum `Result<_, A>`
+help: use `?` to coerce and return an appropriate `Err`, and wrap the resulting value in `Ok` so the expression remains of type `Result`
+ |
+LL | Ok(x?)
+ | +++ ++
+
+error[E0308]: mismatched types
+ --> $DIR/coerce-result-return-value.rs:17:9
+ |
+LL | fn foo3(x: Result<(), A>) -> Result<(), B> {
+ | ------------- expected `Result<(), B>` because of return type
+...
+LL | x
+ | ^ expected struct `B`, found struct `A`
+ |
+ = note: expected enum `Result<_, B>`
+ found enum `Result<_, A>`
+help: use `?` to coerce and return an appropriate `Err`, and wrap the resulting value in `Ok` so the expression remains of type `Result`
+ |
+LL | Ok(x?)
+ | +++ ++
+
+error: aborting due to 4 previous errors
+
+For more information about this error, try `rustc --explain E0308`.