1 error[E0308]: mismatched types
2 --> $DIR/dyn-trait-return-should-be-impl-trait.rs:7:35
4 LL | fn fuz() -> (usize, Trait) { (42, Struct) }
5 | ^^^^^^ expected trait object `dyn Trait`, found struct `Struct`
7 = note: expected trait object `(dyn Trait + 'static)`
10 error[E0277]: the size for values of type `(dyn Trait + 'static)` cannot be known at compilation time
11 --> $DIR/dyn-trait-return-should-be-impl-trait.rs:7:13
13 LL | fn fuz() -> (usize, Trait) { (42, Struct) }
14 | ^^^^^^^^^^^^^^ ------------ this returned value is of type `(usize, (dyn Trait + 'static))`
16 | doesn't have a size known at compile-time
18 = help: within `(usize, (dyn Trait + 'static))`, the trait `Sized` is not implemented for `(dyn Trait + 'static)`
19 = note: required because it appears within the type `(usize, (dyn Trait + 'static))`
20 = note: the return type of a function must have a statically known size
22 error[E0308]: mismatched types
23 --> $DIR/dyn-trait-return-should-be-impl-trait.rs:10:39
25 LL | fn bar() -> (usize, dyn Trait) { (42, Struct) }
26 | ^^^^^^ expected trait object `dyn Trait`, found struct `Struct`
28 = note: expected trait object `(dyn Trait + 'static)`
31 error[E0277]: the size for values of type `(dyn Trait + 'static)` cannot be known at compilation time
32 --> $DIR/dyn-trait-return-should-be-impl-trait.rs:10:13
34 LL | fn bar() -> (usize, dyn Trait) { (42, Struct) }
35 | ^^^^^^^^^^^^^^^^^^ ------------ this returned value is of type `(usize, (dyn Trait + 'static))`
37 | doesn't have a size known at compile-time
39 = help: within `(usize, (dyn Trait + 'static))`, the trait `Sized` is not implemented for `(dyn Trait + 'static)`
40 = note: required because it appears within the type `(usize, (dyn Trait + 'static))`
41 = note: the return type of a function must have a statically known size
43 error[E0746]: return type cannot have an unboxed trait object
44 --> $DIR/dyn-trait-return-should-be-impl-trait.rs:13:13
46 LL | fn bap() -> Trait { Struct }
47 | ^^^^^ doesn't have a size known at compile-time
49 = note: for information on `impl Trait`, see <https://doc.rust-lang.org/book/ch10-02-traits.html#returning-types-that-implement-traits>
50 help: use `impl Trait` as the return type, as all return paths are of type `Struct`, which implements `Trait`
52 LL | fn bap() -> impl Trait { Struct }
55 error[E0746]: return type cannot have an unboxed trait object
56 --> $DIR/dyn-trait-return-should-be-impl-trait.rs:15:13
58 LL | fn ban() -> dyn Trait { Struct }
59 | ^^^^^^^^^ doesn't have a size known at compile-time
61 = note: for information on `impl Trait`, see <https://doc.rust-lang.org/book/ch10-02-traits.html#returning-types-that-implement-traits>
62 help: use `impl Trait` as the return type, as all return paths are of type `Struct`, which implements `Trait`
64 LL | fn ban() -> impl Trait { Struct }
67 error[E0746]: return type cannot have an unboxed trait object
68 --> $DIR/dyn-trait-return-should-be-impl-trait.rs:17:13
70 LL | fn bak() -> dyn Trait { unimplemented!() }
71 | ^^^^^^^^^ doesn't have a size known at compile-time
73 help: use `impl Trait` as the return type if all return paths have the same type but you want to expose only the trait in the signature
75 LL | fn bak() -> impl Trait { unimplemented!() }
77 help: use a boxed trait object if all return paths implement trait `Trait`
79 LL | fn bak() -> Box<dyn Trait> { unimplemented!() }
82 error[E0746]: return type cannot have an unboxed trait object
83 --> $DIR/dyn-trait-return-should-be-impl-trait.rs:19:13
85 LL | fn bal() -> dyn Trait {
86 | ^^^^^^^^^ doesn't have a size known at compile-time
88 = 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>
89 = note: if all the returned values were of the same type you could use `impl Trait` as the return type
90 = note: for information on `impl Trait`, see <https://doc.rust-lang.org/book/ch10-02-traits.html#returning-types-that-implement-traits>
91 = note: you can create a new `enum` with a variant for each returned type
92 help: return a boxed trait object instead
94 LL | fn bal() -> Box<dyn Trait> {
96 help: ... and box this value
98 LL | return Box::new(Struct);
100 help: ... and box this value
105 error[E0308]: `if` and `else` have incompatible types
106 --> $DIR/dyn-trait-return-should-be-impl-trait.rs:29:9
110 | | ------ expected because of this
113 | | ^^ expected struct `Struct`, found integer
115 | |_____- `if` and `else` have incompatible types
117 error[E0746]: return type cannot have an unboxed trait object
118 --> $DIR/dyn-trait-return-should-be-impl-trait.rs:25:13
120 LL | fn bax() -> dyn Trait {
121 | ^^^^^^^^^ doesn't have a size known at compile-time
123 = 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>
124 = note: if all the returned values were of the same type you could use `impl Trait` as the return type
125 = note: for information on `impl Trait`, see <https://doc.rust-lang.org/book/ch10-02-traits.html#returning-types-that-implement-traits>
126 = note: you can create a new `enum` with a variant for each returned type
127 help: return a boxed trait object instead
129 LL | fn bax() -> Box<dyn Trait> {
131 help: ... and box this value
133 LL | Box::new(Struct)
135 help: ... and box this value
140 error[E0308]: mismatched types
141 --> $DIR/dyn-trait-return-should-be-impl-trait.rs:34:16
143 LL | fn bam() -> Box<dyn Trait> {
144 | -------------- expected `Box<(dyn Trait + 'static)>` because of return type
147 | ^^^^^^ expected struct `Box`, found struct `Struct`
149 = note: expected struct `Box<(dyn Trait + 'static)>`
150 found struct `Struct`
151 = note: for more on the distinction between the stack and the heap, read https://doc.rust-lang.org/book/ch15-01-box.html, https://doc.rust-lang.org/rust-by-example/std/box.html, and https://doc.rust-lang.org/std/boxed/index.html
152 help: store this in the heap by calling `Box::new`
154 LL | return Box::new(Struct);
157 error[E0308]: mismatched types
158 --> $DIR/dyn-trait-return-should-be-impl-trait.rs:36:5
160 LL | fn bam() -> Box<dyn Trait> {
161 | -------------- expected `Box<(dyn Trait + 'static)>` because of return type
164 | ^^ expected struct `Box`, found integer
166 = note: expected struct `Box<(dyn Trait + 'static)>`
167 found type `{integer}`
168 = note: for more on the distinction between the stack and the heap, read https://doc.rust-lang.org/book/ch15-01-box.html, https://doc.rust-lang.org/rust-by-example/std/box.html, and https://doc.rust-lang.org/std/boxed/index.html
169 help: store this in the heap by calling `Box::new`
174 error[E0308]: mismatched types
175 --> $DIR/dyn-trait-return-should-be-impl-trait.rs:40:16
177 LL | fn baq() -> Box<dyn Trait> {
178 | -------------- expected `Box<(dyn Trait + 'static)>` because of return type
181 | ^ expected struct `Box`, found integer
183 = note: expected struct `Box<(dyn Trait + 'static)>`
184 found type `{integer}`
185 = note: for more on the distinction between the stack and the heap, read https://doc.rust-lang.org/book/ch15-01-box.html, https://doc.rust-lang.org/rust-by-example/std/box.html, and https://doc.rust-lang.org/std/boxed/index.html
186 help: store this in the heap by calling `Box::new`
188 LL | return Box::new(0);
191 error[E0308]: mismatched types
192 --> $DIR/dyn-trait-return-should-be-impl-trait.rs:42:5
194 LL | fn baq() -> Box<dyn Trait> {
195 | -------------- expected `Box<(dyn Trait + 'static)>` because of return type
198 | ^^ expected struct `Box`, found integer
200 = note: expected struct `Box<(dyn Trait + 'static)>`
201 found type `{integer}`
202 = note: for more on the distinction between the stack and the heap, read https://doc.rust-lang.org/book/ch15-01-box.html, https://doc.rust-lang.org/rust-by-example/std/box.html, and https://doc.rust-lang.org/std/boxed/index.html
203 help: store this in the heap by calling `Box::new`
208 error[E0308]: mismatched types
209 --> $DIR/dyn-trait-return-should-be-impl-trait.rs:46:9
211 LL | fn baz() -> Box<dyn Trait> {
212 | -------------- expected `Box<(dyn Trait + 'static)>` because of return type
215 | ^^^^^^ expected struct `Box`, found struct `Struct`
217 = note: expected struct `Box<(dyn Trait + 'static)>`
218 found struct `Struct`
219 = note: for more on the distinction between the stack and the heap, read https://doc.rust-lang.org/book/ch15-01-box.html, https://doc.rust-lang.org/rust-by-example/std/box.html, and https://doc.rust-lang.org/std/boxed/index.html
220 help: store this in the heap by calling `Box::new`
222 LL | Box::new(Struct)
225 error[E0308]: mismatched types
226 --> $DIR/dyn-trait-return-should-be-impl-trait.rs:48:9
228 LL | fn baz() -> Box<dyn Trait> {
229 | -------------- expected `Box<(dyn Trait + 'static)>` because of return type
232 | ^^ expected struct `Box`, found integer
234 = note: expected struct `Box<(dyn Trait + 'static)>`
235 found type `{integer}`
236 = note: for more on the distinction between the stack and the heap, read https://doc.rust-lang.org/book/ch15-01-box.html, https://doc.rust-lang.org/rust-by-example/std/box.html, and https://doc.rust-lang.org/std/boxed/index.html
237 help: store this in the heap by calling `Box::new`
242 error[E0308]: mismatched types
243 --> $DIR/dyn-trait-return-should-be-impl-trait.rs:53:9
245 LL | fn baw() -> Box<dyn Trait> {
246 | -------------- expected `Box<(dyn Trait + 'static)>` because of return type
249 | ^ expected struct `Box`, found integer
251 = note: expected struct `Box<(dyn Trait + 'static)>`
252 found type `{integer}`
253 = note: for more on the distinction between the stack and the heap, read https://doc.rust-lang.org/book/ch15-01-box.html, https://doc.rust-lang.org/rust-by-example/std/box.html, and https://doc.rust-lang.org/std/boxed/index.html
254 help: store this in the heap by calling `Box::new`
259 error[E0308]: mismatched types
260 --> $DIR/dyn-trait-return-should-be-impl-trait.rs:55:9
262 LL | fn baw() -> Box<dyn Trait> {
263 | -------------- expected `Box<(dyn Trait + 'static)>` because of return type
266 | ^^ expected struct `Box`, found integer
268 = note: expected struct `Box<(dyn Trait + 'static)>`
269 found type `{integer}`
270 = note: for more on the distinction between the stack and the heap, read https://doc.rust-lang.org/book/ch15-01-box.html, https://doc.rust-lang.org/rust-by-example/std/box.html, and https://doc.rust-lang.org/std/boxed/index.html
271 help: store this in the heap by calling `Box::new`
276 error[E0746]: return type cannot have an unboxed trait object
277 --> $DIR/dyn-trait-return-should-be-impl-trait.rs:60:13
279 LL | fn bat() -> dyn Trait {
280 | ^^^^^^^^^ doesn't have a size known at compile-time
282 = note: for information on `impl Trait`, see <https://doc.rust-lang.org/book/ch10-02-traits.html#returning-types-that-implement-traits>
283 help: use `impl Trait` as the return type, as all return paths are of type `{integer}`, which implements `Trait`
285 LL | fn bat() -> impl Trait {
288 error[E0746]: return type cannot have an unboxed trait object
289 --> $DIR/dyn-trait-return-should-be-impl-trait.rs:66:13
291 LL | fn bay() -> dyn Trait {
292 | ^^^^^^^^^ doesn't have a size known at compile-time
294 = note: for information on `impl Trait`, see <https://doc.rust-lang.org/book/ch10-02-traits.html#returning-types-that-implement-traits>
295 help: use `impl Trait` as the return type, as all return paths are of type `{integer}`, which implements `Trait`
297 LL | fn bay() -> impl Trait {
300 error: aborting due to 20 previous errors
302 Some errors have detailed explanations: E0277, E0308, E0746.
303 For more information about an error, try `rustc --explain E0277`.