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`.