}
}
if let (Some(sp), Some(fn_output)) = (fcx.ret_coercion_span.borrow().as_ref(), fn_output) {
- self.add_impl_trait_explanation(&mut err, fcx, expected, *sp, fn_output);
+ self.add_impl_trait_explanation(&mut err, cause, fcx, expected, *sp, fn_output);
}
err
}
fn add_impl_trait_explanation<'a>(
&self,
err: &mut DiagnosticBuilder<'a>,
+ cause: &ObligationCause<'tcx>,
fcx: &FnCtxt<'a, 'tcx>,
expected: Ty<'tcx>,
sp: Span,
],
Applicability::MachineApplicable,
);
+ let sugg = vec![sp, cause.span]
+ .into_iter()
+ .flat_map(|sp| {
+ vec![
+ (sp.shrink_to_lo(), "Box::new(".to_string()),
+ (sp.shrink_to_hi(), ")".to_string()),
+ ]
+ .into_iter()
+ })
+ .collect::<Vec<_>>();
+ err.multipart_suggestion(
+ "if you change the return type to expect trait objects, box the returned \
+ expressions",
+ sugg,
+ Applicability::MaybeIncorrect,
+ );
} else {
err.help(&format!(
"if the trait `{}` were object safe, you could return a boxed trait object",
}
err.note(trait_obj_msg);
}
- err.help("alternatively, create a new `enum` with a variant for each returned type");
+ err.help("you could instead create a new `enum` with a variant for each returned type");
}
fn is_return_ty_unsized(&self, fcx: &FnCtxt<'a, 'tcx>, blk_id: hir::HirId) -> bool {
= note: for information on `impl Trait`, see <https://doc.rust-lang.org/book/ch10-02-traits.html#returning-types-that-implement-traits>
= help: if the trait `NotObjectSafe` were object safe, you could return a boxed trait object
= note: for information on trait objects, see <https://doc.rust-lang.org/book/ch17-02-trait-objects.html#using-trait-objects-that-allow-for-values-of-different-types>
- = help: alternatively, create a new `enum` with a variant for each returned type
+ = help: you could instead create a new `enum` with a variant for each returned type
error[E0308]: mismatched types
--> $DIR/object-unsafe-trait-in-return-position-impl-trait.rs:43:5
= note: to return `impl Trait`, all returned values must be of the same type
= note: for information on `impl Trait`, see <https://doc.rust-lang.org/book/ch10-02-traits.html#returning-types-that-implement-traits>
= note: for information on trait objects, see <https://doc.rust-lang.org/book/ch17-02-trait-objects.html#using-trait-objects-that-allow-for-values-of-different-types>
- = help: alternatively, create a new `enum` with a variant for each returned type
+ = help: you could instead create a new `enum` with a variant for each returned type
help: you could change the return type to be a boxed trait object
|
LL | fn cat() -> Box<dyn ObjectSafe> {
| ^^^^^^^ ^
+help: if you change the return type to expect trait objects, box the returned expressions
+ |
+LL | return Box::new(A);
+LL | }
+LL | Box::new(B)
+ |
error: aborting due to 2 previous errors
= note: to return `impl Trait`, all returned values must be of the same type
= note: for information on `impl Trait`, see <https://doc.rust-lang.org/book/ch10-02-traits.html#returning-types-that-implement-traits>
= note: for information on trait objects, see <https://doc.rust-lang.org/book/ch17-02-trait-objects.html#using-trait-objects-that-allow-for-values-of-different-types>
- = help: alternatively, create a new `enum` with a variant for each returned type
+ = help: you could instead create a new `enum` with a variant for each returned type
help: you could change the return type to be a boxed trait object
|
LL | fn foo() -> Box<dyn std::fmt::Display> {
| ^^^^^^^ ^
+help: if you change the return type to expect trait objects, box the returned expressions
+ |
+LL | return Box::new(0i32);
+LL | }
+LL | Box::new(1u32)
+ |
error[E0308]: mismatched types
--> $DIR/point-to-type-err-cause-on-impl-trait-return.rs:12:16
= note: to return `impl Trait`, all returned values must be of the same type
= note: for information on `impl Trait`, see <https://doc.rust-lang.org/book/ch10-02-traits.html#returning-types-that-implement-traits>
= note: for information on trait objects, see <https://doc.rust-lang.org/book/ch17-02-trait-objects.html#using-trait-objects-that-allow-for-values-of-different-types>
- = help: alternatively, create a new `enum` with a variant for each returned type
+ = help: you could instead create a new `enum` with a variant for each returned type
help: you could change the return type to be a boxed trait object
|
LL | fn bar() -> Box<dyn std::fmt::Display> {
| ^^^^^^^ ^
+help: if you change the return type to expect trait objects, box the returned expressions
+ |
+LL | return Box::new(0i32);
+LL | } else {
+LL | return Box::new(1u32);
+ |
error[E0308]: mismatched types
--> $DIR/point-to-type-err-cause-on-impl-trait-return.rs:20:9
= note: to return `impl Trait`, all returned values must be of the same type
= note: for information on `impl Trait`, see <https://doc.rust-lang.org/book/ch10-02-traits.html#returning-types-that-implement-traits>
= note: for information on trait objects, see <https://doc.rust-lang.org/book/ch17-02-trait-objects.html#using-trait-objects-that-allow-for-values-of-different-types>
- = help: alternatively, create a new `enum` with a variant for each returned type
+ = help: you could instead create a new `enum` with a variant for each returned type
help: you could change the return type to be a boxed trait object
|
LL | fn baz() -> Box<dyn std::fmt::Display> {
| ^^^^^^^ ^
+help: if you change the return type to expect trait objects, box the returned expressions
+ |
+LL | return Box::new(0i32);
+LL | } else {
+LL | Box::new(1u32)
+ |
error[E0308]: `if` and `else` have incompatible types
--> $DIR/point-to-type-err-cause-on-impl-trait-return.rs:28:9
|
LL | fn qux() -> Box<dyn std::fmt::Display> {
| ^^^^^^^ ^
-help: if you change the return type to expect trait objects box the returned expressions
+help: if you change the return type to expect trait objects, box the returned expressions
|
LL | Box::new(0i32)
LL | } else {
= note: to return `impl Trait`, all returned values must be of the same type
= note: for information on `impl Trait`, see <https://doc.rust-lang.org/book/ch10-02-traits.html#returning-types-that-implement-traits>
= note: for information on trait objects, see <https://doc.rust-lang.org/book/ch17-02-trait-objects.html#using-trait-objects-that-allow-for-values-of-different-types>
- = help: alternatively, create a new `enum` with a variant for each returned type
+ = help: you could instead create a new `enum` with a variant for each returned type
help: you could change the return type to be a boxed trait object
|
LL | fn bat() -> Box<dyn std::fmt::Display> {
| ^^^^^^^ ^
+help: if you change the return type to expect trait objects, box the returned expressions
+ |
+LL | 0 => return Box::new(0i32),
+LL | _ => Box::new(1u32),
+ |
error[E0308]: mismatched types
--> $DIR/point-to-type-err-cause-on-impl-trait-return.rs:40:5
= note: to return `impl Trait`, all returned values must be of the same type
= note: for information on `impl Trait`, see <https://doc.rust-lang.org/book/ch10-02-traits.html#returning-types-that-implement-traits>
= note: for information on trait objects, see <https://doc.rust-lang.org/book/ch17-02-trait-objects.html#using-trait-objects-that-allow-for-values-of-different-types>
- = help: alternatively, create a new `enum` with a variant for each returned type
+ = help: you could instead create a new `enum` with a variant for each returned type
help: you could change the return type to be a boxed trait object
|
LL | fn can() -> Box<dyn std::fmt::Display> {
| ^^^^^^^ ^
+help: if you change the return type to expect trait objects, box the returned expressions
+ |
+LL | Box::new(match 13 {
+LL | 0 => return Box::new(0i32),
+LL | 1 => 1u32,
+LL | _ => 2u32,
+LL | })
+ |
error[E0308]: mismatched types
--> $DIR/point-to-type-err-cause-on-impl-trait-return.rs:53:13
= note: to return `impl Trait`, all returned values must be of the same type
= note: for information on `impl Trait`, see <https://doc.rust-lang.org/book/ch10-02-traits.html#returning-types-that-implement-traits>
= note: for information on trait objects, see <https://doc.rust-lang.org/book/ch17-02-trait-objects.html#using-trait-objects-that-allow-for-values-of-different-types>
- = help: alternatively, create a new `enum` with a variant for each returned type
+ = help: you could instead create a new `enum` with a variant for each returned type
help: you could change the return type to be a boxed trait object
|
LL | fn cat() -> Box<dyn std::fmt::Display> {
| ^^^^^^^ ^
+help: if you change the return type to expect trait objects, box the returned expressions
+ |
+LL | return Box::new(0i32);
+LL | }
+LL | _ => {
+LL | Box::new(1u32)
+ |
error[E0308]: `match` arms have incompatible types
--> $DIR/point-to-type-err-cause-on-impl-trait-return.rs:61:14
|
LL | fn dog() -> Box<dyn std::fmt::Display> {
| ^^^^^^^ ^
-help: if you change the return type to expect trait objects box the returned expressions
+help: if you change the return type to expect trait objects, box the returned expressions
|
LL | 0 => Box::new(0i32),
LL | 1 => Box::new(1u32),