error[E0308]: mismatched types --> $DIR/dyn-trait-return-should-be-impl-trait.rs:7:35 | LL | fn fuz() -> (usize, Trait) { (42, Struct) } | ^^^^^^ expected `dyn Trait`, found `Struct` | = note: expected trait object `(dyn Trait + 'static)` found struct `Struct` error[E0277]: the size for values of type `(dyn Trait + 'static)` cannot be known at compilation time --> $DIR/dyn-trait-return-should-be-impl-trait.rs:7:13 | LL | fn fuz() -> (usize, Trait) { (42, Struct) } | ^^^^^^^^^^^^^^ ------------ this returned value is of type `(usize, (dyn Trait + 'static))` | | | doesn't have a size known at compile-time | = help: within `(usize, (dyn Trait + 'static))`, the trait `Sized` is not implemented for `(dyn Trait + 'static)` = note: required because it appears within the type `(usize, dyn Trait)` = note: the return type of a function must have a statically known size error[E0308]: mismatched types --> $DIR/dyn-trait-return-should-be-impl-trait.rs:10:39 | LL | fn bar() -> (usize, dyn Trait) { (42, Struct) } | ^^^^^^ expected `dyn Trait`, found `Struct` | = note: expected trait object `(dyn Trait + 'static)` found struct `Struct` error[E0277]: the size for values of type `(dyn Trait + 'static)` cannot be known at compilation time --> $DIR/dyn-trait-return-should-be-impl-trait.rs:10:13 | LL | fn bar() -> (usize, dyn Trait) { (42, Struct) } | ^^^^^^^^^^^^^^^^^^ ------------ this returned value is of type `(usize, (dyn Trait + 'static))` | | | doesn't have a size known at compile-time | = help: within `(usize, (dyn Trait + 'static))`, the trait `Sized` is not implemented for `(dyn Trait + 'static)` = note: required because it appears within the type `(usize, dyn Trait)` = note: the return type of a function must have a statically known size error[E0746]: return type cannot have an unboxed trait object --> $DIR/dyn-trait-return-should-be-impl-trait.rs:13:13 | LL | fn bap() -> Trait { Struct } | ^^^^^ doesn't have a size known at compile-time | = note: for information on `impl Trait`, see help: use `impl Trait` as the return type, as all return paths are of type `Struct`, which implements `Trait` | LL | fn bap() -> impl Trait { Struct } | ~~~~~~~~~~ error[E0746]: return type cannot have an unboxed trait object --> $DIR/dyn-trait-return-should-be-impl-trait.rs:15:13 | LL | fn ban() -> dyn Trait { Struct } | ^^^^^^^^^ doesn't have a size known at compile-time | = note: for information on `impl Trait`, see help: use `impl Trait` as the return type, as all return paths are of type `Struct`, which implements `Trait` | LL | fn ban() -> impl Trait { Struct } | ~~~~~~~~~~ error[E0746]: return type cannot have an unboxed trait object --> $DIR/dyn-trait-return-should-be-impl-trait.rs:17:13 | LL | fn bak() -> dyn Trait { unimplemented!() } | ^^^^^^^^^ doesn't have a size known at compile-time | 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 | LL | fn bak() -> impl Trait { unimplemented!() } | ~~~~~~~~~~ help: use a boxed trait object if all return paths implement trait `Trait` | LL | fn bak() -> Box { unimplemented!() } | ++++ + error[E0746]: return type cannot have an unboxed trait object --> $DIR/dyn-trait-return-should-be-impl-trait.rs:19:13 | LL | fn bal() -> dyn Trait { | ^^^^^^^^^ doesn't have a size known at compile-time | = note: for information on trait objects, see = note: if all the returned values were of the same type you could use `impl Trait` as the return type = note: for information on `impl Trait`, see = note: you can create a new `enum` with a variant for each returned type help: return a boxed trait object instead | LL | fn bal() -> Box { | ++++ + help: ... and box this value | LL | return Box::new(Struct); | +++++++++ + help: ... and box this value | LL | Box::new(42) | +++++++++ + error[E0308]: `if` and `else` have incompatible types --> $DIR/dyn-trait-return-should-be-impl-trait.rs:29:9 | LL | / if true { LL | | Struct | | ------ expected because of this LL | | } else { LL | | 42 | | ^^ expected `Struct`, found integer LL | | } | |_____- `if` and `else` have incompatible types error[E0746]: return type cannot have an unboxed trait object --> $DIR/dyn-trait-return-should-be-impl-trait.rs:25:13 | LL | fn bax() -> dyn Trait { | ^^^^^^^^^ doesn't have a size known at compile-time | = note: for information on trait objects, see = note: if all the returned values were of the same type you could use `impl Trait` as the return type = note: for information on `impl Trait`, see = note: you can create a new `enum` with a variant for each returned type help: return a boxed trait object instead | LL | fn bax() -> Box { | ++++ + help: ... and box this value | LL | Box::new(Struct) | +++++++++ + help: ... and box this value | LL | Box::new(42) | +++++++++ + error[E0308]: mismatched types --> $DIR/dyn-trait-return-should-be-impl-trait.rs:34:16 | LL | fn bam() -> Box { | -------------- expected `Box<(dyn Trait + 'static)>` because of return type LL | if true { LL | return Struct; | ^^^^^^ expected `Box`, found `Struct` | = note: expected struct `Box<(dyn Trait + 'static)>` found struct `Struct` = 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 help: store this in the heap by calling `Box::new` | LL | return Box::new(Struct); | +++++++++ + error[E0308]: mismatched types --> $DIR/dyn-trait-return-should-be-impl-trait.rs:36:5 | LL | fn bam() -> Box { | -------------- expected `Box<(dyn Trait + 'static)>` because of return type ... LL | 42 | ^^ expected `Box`, found integer | = note: expected struct `Box<(dyn Trait + 'static)>` found type `{integer}` = 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 help: store this in the heap by calling `Box::new` | LL | Box::new(42) | +++++++++ + error[E0308]: mismatched types --> $DIR/dyn-trait-return-should-be-impl-trait.rs:40:16 | LL | fn baq() -> Box { | -------------- expected `Box<(dyn Trait + 'static)>` because of return type LL | if true { LL | return 0; | ^ expected `Box`, found integer | = note: expected struct `Box<(dyn Trait + 'static)>` found type `{integer}` = 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 help: store this in the heap by calling `Box::new` | LL | return Box::new(0); | +++++++++ + error[E0308]: mismatched types --> $DIR/dyn-trait-return-should-be-impl-trait.rs:42:5 | LL | fn baq() -> Box { | -------------- expected `Box<(dyn Trait + 'static)>` because of return type ... LL | 42 | ^^ expected `Box`, found integer | = note: expected struct `Box<(dyn Trait + 'static)>` found type `{integer}` = 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 help: store this in the heap by calling `Box::new` | LL | Box::new(42) | +++++++++ + error[E0308]: mismatched types --> $DIR/dyn-trait-return-should-be-impl-trait.rs:46:9 | LL | fn baz() -> Box { | -------------- expected `Box<(dyn Trait + 'static)>` because of return type LL | if true { LL | Struct | ^^^^^^ expected `Box`, found `Struct` | = note: expected struct `Box<(dyn Trait + 'static)>` found struct `Struct` = 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 help: store this in the heap by calling `Box::new` | LL | Box::new(Struct) | +++++++++ + error[E0308]: mismatched types --> $DIR/dyn-trait-return-should-be-impl-trait.rs:48:9 | LL | fn baz() -> Box { | -------------- expected `Box<(dyn Trait + 'static)>` because of return type ... LL | 42 | ^^ expected `Box`, found integer | = note: expected struct `Box<(dyn Trait + 'static)>` found type `{integer}` = 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 help: store this in the heap by calling `Box::new` | LL | Box::new(42) | +++++++++ + error[E0308]: mismatched types --> $DIR/dyn-trait-return-should-be-impl-trait.rs:53:9 | LL | fn baw() -> Box { | -------------- expected `Box<(dyn Trait + 'static)>` because of return type LL | if true { LL | 0 | ^ expected `Box`, found integer | = note: expected struct `Box<(dyn Trait + 'static)>` found type `{integer}` = 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 help: store this in the heap by calling `Box::new` | LL | Box::new(0) | +++++++++ + error[E0308]: mismatched types --> $DIR/dyn-trait-return-should-be-impl-trait.rs:55:9 | LL | fn baw() -> Box { | -------------- expected `Box<(dyn Trait + 'static)>` because of return type ... LL | 42 | ^^ expected `Box`, found integer | = note: expected struct `Box<(dyn Trait + 'static)>` found type `{integer}` = 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 help: store this in the heap by calling `Box::new` | LL | Box::new(42) | +++++++++ + error[E0746]: return type cannot have an unboxed trait object --> $DIR/dyn-trait-return-should-be-impl-trait.rs:60:13 | LL | fn bat() -> dyn Trait { | ^^^^^^^^^ doesn't have a size known at compile-time | = note: for information on `impl Trait`, see help: use `impl Trait` as the return type, as all return paths are of type `{integer}`, which implements `Trait` | LL | fn bat() -> impl Trait { | ~~~~~~~~~~ error[E0746]: return type cannot have an unboxed trait object --> $DIR/dyn-trait-return-should-be-impl-trait.rs:66:13 | LL | fn bay() -> dyn Trait { | ^^^^^^^^^ doesn't have a size known at compile-time | = note: for information on `impl Trait`, see help: use `impl Trait` as the return type, as all return paths are of type `{integer}`, which implements `Trait` | LL | fn bay() -> impl Trait { | ~~~~~~~~~~ error: aborting due to 20 previous errors Some errors have detailed explanations: E0277, E0308, E0746. For more information about an error, try `rustc --explain E0277`.