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 some type `T` that is `T: Sized` as the return type if all return paths have the same type
75 LL | fn bak() -> T { unimplemented!() }
77 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
79 LL | fn bak() -> impl Trait { unimplemented!() }
81 help: use a boxed trait object if all return paths implement trait `Trait`
83 LL | fn bak() -> Box<dyn Trait> { unimplemented!() }
86 error[E0746]: return type cannot have an unboxed trait object
87 --> $DIR/dyn-trait-return-should-be-impl-trait.rs:19:13
89 LL | fn bal() -> dyn Trait {
90 | ^^^^^^^^^ doesn't have a size known at compile-time
92 = 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>
93 = note: if all the returned values were of the same type you could use `impl Trait` as the return type
94 = note: for information on `impl Trait`, see <https://doc.rust-lang.org/book/ch10-02-traits.html#returning-types-that-implement-traits>
95 = note: you can create a new `enum` with a variant for each returned type
96 help: return a boxed trait object instead
98 LL | fn bal() -> Box<dyn Trait> {
100 help: ... and box this value
102 LL | return Box::new(Struct);
104 help: ... and box this value
109 error[E0308]: `if` and `else` have incompatible types
110 --> $DIR/dyn-trait-return-should-be-impl-trait.rs:29:9
114 | | ------ expected because of this
117 | | ^^ expected struct `Struct`, found integer
119 | |_____- `if` and `else` have incompatible types
121 error[E0746]: return type cannot have an unboxed trait object
122 --> $DIR/dyn-trait-return-should-be-impl-trait.rs:25:13
124 LL | fn bax() -> dyn Trait {
125 | ^^^^^^^^^ doesn't have a size known at compile-time
127 = 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>
128 = note: if all the returned values were of the same type you could use `impl Trait` as the return type
129 = note: for information on `impl Trait`, see <https://doc.rust-lang.org/book/ch10-02-traits.html#returning-types-that-implement-traits>
130 = note: you can create a new `enum` with a variant for each returned type
131 help: return a boxed trait object instead
133 LL | fn bax() -> Box<dyn Trait> {
135 help: ... and box this value
137 LL | Box::new(Struct)
139 help: ... and box this value
144 error[E0308]: mismatched types
145 --> $DIR/dyn-trait-return-should-be-impl-trait.rs:34:16
147 LL | fn bam() -> Box<dyn Trait> {
148 | -------------- expected `Box<(dyn Trait + 'static)>` because of return type
151 | ^^^^^^ expected struct `Box`, found struct `Struct`
153 = note: expected struct `Box<(dyn Trait + 'static)>`
154 found struct `Struct`
155 = 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
156 help: store this in the heap by calling `Box::new`
158 LL | return Box::new(Struct);
161 error[E0308]: mismatched types
162 --> $DIR/dyn-trait-return-should-be-impl-trait.rs:36:5
164 LL | fn bam() -> Box<dyn Trait> {
165 | -------------- expected `Box<(dyn Trait + 'static)>` because of return type
168 | ^^ expected struct `Box`, found integer
170 = note: expected struct `Box<(dyn Trait + 'static)>`
171 found type `{integer}`
172 = 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
173 help: store this in the heap by calling `Box::new`
178 error[E0308]: mismatched types
179 --> $DIR/dyn-trait-return-should-be-impl-trait.rs:40:16
181 LL | fn baq() -> Box<dyn Trait> {
182 | -------------- expected `Box<(dyn Trait + 'static)>` because of return type
185 | ^ expected struct `Box`, found integer
187 = note: expected struct `Box<(dyn Trait + 'static)>`
188 found type `{integer}`
189 = 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
190 help: store this in the heap by calling `Box::new`
192 LL | return Box::new(0);
195 error[E0308]: mismatched types
196 --> $DIR/dyn-trait-return-should-be-impl-trait.rs:42:5
198 LL | fn baq() -> Box<dyn Trait> {
199 | -------------- expected `Box<(dyn Trait + 'static)>` because of return type
202 | ^^ expected struct `Box`, found integer
204 = note: expected struct `Box<(dyn Trait + 'static)>`
205 found type `{integer}`
206 = 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
207 help: store this in the heap by calling `Box::new`
212 error[E0308]: mismatched types
213 --> $DIR/dyn-trait-return-should-be-impl-trait.rs:46:9
215 LL | fn baz() -> Box<dyn Trait> {
216 | -------------- expected `Box<(dyn Trait + 'static)>` because of return type
219 | ^^^^^^ expected struct `Box`, found struct `Struct`
221 = note: expected struct `Box<(dyn Trait + 'static)>`
222 found struct `Struct`
223 = 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
224 help: store this in the heap by calling `Box::new`
226 LL | Box::new(Struct)
229 error[E0308]: mismatched types
230 --> $DIR/dyn-trait-return-should-be-impl-trait.rs:48:9
232 LL | fn baz() -> Box<dyn Trait> {
233 | -------------- expected `Box<(dyn Trait + 'static)>` because of return type
236 | ^^ expected struct `Box`, found integer
238 = note: expected struct `Box<(dyn Trait + 'static)>`
239 found type `{integer}`
240 = 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
241 help: store this in the heap by calling `Box::new`
246 error[E0308]: mismatched types
247 --> $DIR/dyn-trait-return-should-be-impl-trait.rs:53:9
249 LL | fn baw() -> Box<dyn Trait> {
250 | -------------- expected `Box<(dyn Trait + 'static)>` because of return type
253 | ^ expected struct `Box`, found integer
255 = note: expected struct `Box<(dyn Trait + 'static)>`
256 found type `{integer}`
257 = 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
258 help: store this in the heap by calling `Box::new`
263 error[E0308]: mismatched types
264 --> $DIR/dyn-trait-return-should-be-impl-trait.rs:55:9
266 LL | fn baw() -> Box<dyn Trait> {
267 | -------------- expected `Box<(dyn Trait + 'static)>` because of return type
270 | ^^ expected struct `Box`, found integer
272 = note: expected struct `Box<(dyn Trait + 'static)>`
273 found type `{integer}`
274 = 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
275 help: store this in the heap by calling `Box::new`
280 error[E0746]: return type cannot have an unboxed trait object
281 --> $DIR/dyn-trait-return-should-be-impl-trait.rs:60:13
283 LL | fn bat() -> dyn Trait {
284 | ^^^^^^^^^ doesn't have a size known at compile-time
286 = note: for information on `impl Trait`, see <https://doc.rust-lang.org/book/ch10-02-traits.html#returning-types-that-implement-traits>
287 help: use `impl Trait` as the return type, as all return paths are of type `{integer}`, which implements `Trait`
289 LL | fn bat() -> impl Trait {
292 error[E0746]: return type cannot have an unboxed trait object
293 --> $DIR/dyn-trait-return-should-be-impl-trait.rs:66:13
295 LL | fn bay() -> dyn Trait {
296 | ^^^^^^^^^ doesn't have a size known at compile-time
298 = note: for information on `impl Trait`, see <https://doc.rust-lang.org/book/ch10-02-traits.html#returning-types-that-implement-traits>
299 help: use `impl Trait` as the return type, as all return paths are of type `{integer}`, which implements `Trait`
301 LL | fn bay() -> impl Trait {
304 error: aborting due to 20 previous errors
306 Some errors have detailed explanations: E0277, E0308, E0746.
307 For more information about an error, try `rustc --explain E0277`.