Auto merge of #77087 - estebank:issue-45817, r=matthewjasper
Provide structured suggestions when finding structs when expecting a trait When finding an ADT in a trait object definition provide some solutions. Fix #45817. Given `<Param as Trait>::Assoc: Ty` suggest `Param: Trait<Assoc = Ty>`. Fix #75829.
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08764ad163
7 changed files with 524 additions and 23 deletions
19
src/test/ui/traits/assoc_type_bound_with_struct.rs
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19
src/test/ui/traits/assoc_type_bound_with_struct.rs
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@ -0,0 +1,19 @@
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trait Bar {
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type Baz;
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}
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struct Foo<T> where T: Bar, <T as Bar>::Baz: String { //~ ERROR expected trait, found struct
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t: T,
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}
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struct Qux<'a, T> where T: Bar, <&'a T as Bar>::Baz: String { //~ ERROR expected trait, found struct
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t: &'a T,
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}
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fn foo<T: Bar>(_: T) where <T as Bar>::Baz: String { //~ ERROR expected trait, found struct
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}
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fn qux<'a, T: Bar>(_: &'a T) where <&'a T as Bar>::Baz: String { //~ ERROR expected trait, found
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}
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fn main() {}
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83
src/test/ui/traits/assoc_type_bound_with_struct.stderr
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83
src/test/ui/traits/assoc_type_bound_with_struct.stderr
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error[E0404]: expected trait, found struct `String`
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--> $DIR/assoc_type_bound_with_struct.rs:5:46
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LL | struct Foo<T> where T: Bar, <T as Bar>::Baz: String {
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| ^^^^^^ not a trait
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::: $SRC_DIR/alloc/src/string.rs:LL:COL
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LL | pub trait ToString {
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| ------------------ similarly named trait `ToString` defined here
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help: constrain the associated type to `String`
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LL | struct Foo<T> where T: Bar, T: Bar<Baz = String> {
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| ^^^^^^^^^^^^^^^^^^^^
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help: a trait with a similar name exists
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LL | struct Foo<T> where T: Bar, <T as Bar>::Baz: ToString {
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| ^^^^^^^^
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error[E0404]: expected trait, found struct `String`
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--> $DIR/assoc_type_bound_with_struct.rs:9:54
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LL | struct Qux<'a, T> where T: Bar, <&'a T as Bar>::Baz: String {
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| ^^^^^^ not a trait
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::: $SRC_DIR/alloc/src/string.rs:LL:COL
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LL | pub trait ToString {
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| ------------------ similarly named trait `ToString` defined here
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help: constrain the associated type to `String`
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LL | struct Qux<'a, T> where T: Bar, &'a T: Bar<Baz = String> {
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| ^^^^^^^^^^^^^^^^^^^^^^^^
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help: a trait with a similar name exists
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LL | struct Qux<'a, T> where T: Bar, <&'a T as Bar>::Baz: ToString {
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| ^^^^^^^^
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error[E0404]: expected trait, found struct `String`
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--> $DIR/assoc_type_bound_with_struct.rs:13:45
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LL | fn foo<T: Bar>(_: T) where <T as Bar>::Baz: String {
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| ^^^^^^ not a trait
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::: $SRC_DIR/alloc/src/string.rs:LL:COL
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LL | pub trait ToString {
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| ------------------ similarly named trait `ToString` defined here
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help: constrain the associated type to `String`
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LL | fn foo<T: Bar>(_: T) where T: Bar<Baz = String> {
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| ^^^^^^^^^^^^^^^^^^^^
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help: a trait with a similar name exists
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LL | fn foo<T: Bar>(_: T) where <T as Bar>::Baz: ToString {
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| ^^^^^^^^
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error[E0404]: expected trait, found struct `String`
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--> $DIR/assoc_type_bound_with_struct.rs:16:57
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LL | fn qux<'a, T: Bar>(_: &'a T) where <&'a T as Bar>::Baz: String {
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| ^^^^^^ not a trait
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::: $SRC_DIR/alloc/src/string.rs:LL:COL
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LL | pub trait ToString {
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| ------------------ similarly named trait `ToString` defined here
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help: constrain the associated type to `String`
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LL | fn qux<'a, T: Bar>(_: &'a T) where &'a T: Bar<Baz = String> {
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| ^^^^^^^^^^^^^^^^^^^^^^^^
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help: a trait with a similar name exists
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LL | fn qux<'a, T: Bar>(_: &'a T) where <&'a T as Bar>::Baz: ToString {
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| ^^^^^^^^
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error: aborting due to 4 previous errors
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For more information about this error, try `rustc --explain E0404`.
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// We don't need those errors. Ideally we would silence them, but to do so we need to move the
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// lint from being an early-lint during parsing to a late-lint, because it needs to be aware of
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// the types involved.
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#![allow(bare_trait_objects)]
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struct Foo;
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fn foo(_x: Box<Foo + Send>) { } //~ ERROR expected trait, found struct `Foo`
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type A<T> = Box<dyn Vec<T>>; //~ ERROR expected trait, found struct `Vec`
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type TypeAlias<T> = Box<dyn Vec<T>>; //~ ERROR expected trait, found struct `Vec`
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fn main() { }
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struct A;
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fn a() -> A + 'static { //~ ERROR expected trait, found
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A
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}
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fn b<'a,T,E>(iter: Iterator<Item=Result<T,E> + 'a>) { //~ ERROR expected trait, found
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panic!()
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}
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fn c() -> 'static + A { //~ ERROR expected trait, found
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A
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}
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fn d<'a,T,E>(iter: Iterator<Item='a + Result<T,E>>) { //~ ERROR expected trait, found
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panic!()
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}
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fn e() -> 'static + A + 'static { //~ ERROR expected trait, found
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//~^ ERROR only a single explicit lifetime bound is permitted
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A
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}
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fn f<'a,T,E>(iter: Iterator<Item='a + Result<T,E> + 'a>) { //~ ERROR expected trait, found
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//~^ ERROR only a single explicit lifetime bound is permitted
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panic!()
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}
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struct Traitor;
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trait Trait {}
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fn g() -> Traitor + 'static { //~ ERROR expected trait, found struct `Traitor`
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A
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}
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fn main() {}
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error[E0226]: only a single explicit lifetime bound is permitted
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--> $DIR/trait-bounds-not-on-struct.rs:25:25
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LL | fn e() -> 'static + A + 'static {
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| ^^^^^^^
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error[E0226]: only a single explicit lifetime bound is permitted
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--> $DIR/trait-bounds-not-on-struct.rs:29:53
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LL | fn f<'a,T,E>(iter: Iterator<Item='a + Result<T,E> + 'a>) {
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| ^^
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error[E0404]: expected trait, found struct `Foo`
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--> $DIR/trait-bounds-not-on-struct.rs:5:16
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--> $DIR/trait-bounds-not-on-struct.rs:8:16
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LL | fn foo(_x: Box<Foo + Send>) { }
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| ^^^ not a trait
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help: `+` is used to constrain a "trait object" type with lifetimes or auto-traits; structs and enums can't be bound in that way
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--> $DIR/trait-bounds-not-on-struct.rs:8:22
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LL | fn foo(_x: Box<Foo + Send>) { }
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| --- ^^^^ ...because of this bound
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| |
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| expected this type to be a trait...
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error[E0404]: expected trait, found struct `Vec`
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--> $DIR/trait-bounds-not-on-struct.rs:7:21
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--> $DIR/trait-bounds-not-on-struct.rs:10:29
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LL | type A<T> = Box<dyn Vec<T>>;
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| ^^^^^^ not a trait
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LL | type TypeAlias<T> = Box<dyn Vec<T>>;
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| ^^^^^^ not a trait
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error: aborting due to 2 previous errors
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error[E0404]: expected trait, found struct `A`
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--> $DIR/trait-bounds-not-on-struct.rs:13:11
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LL | fn a() -> A + 'static {
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| ^ not a trait
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help: `+` is used to constrain a "trait object" type with lifetimes or auto-traits; structs and enums can't be bound in that way
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--> $DIR/trait-bounds-not-on-struct.rs:13:15
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LL | fn a() -> A + 'static {
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| - ^^^^^^^ ...because of this bound
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| |
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| expected this type to be a trait...
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help: if you meant to use a type and not a trait here, remove the bounds
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LL | fn a() -> A {
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| --
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For more information about this error, try `rustc --explain E0404`.
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error[E0404]: expected trait, found enum `Result`
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--> $DIR/trait-bounds-not-on-struct.rs:16:34
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LL | fn b<'a,T,E>(iter: Iterator<Item=Result<T,E> + 'a>) {
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| ^^^^^^^^^^^ not a trait
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help: `+` is used to constrain a "trait object" type with lifetimes or auto-traits; structs and enums can't be bound in that way
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--> $DIR/trait-bounds-not-on-struct.rs:16:48
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LL | fn b<'a,T,E>(iter: Iterator<Item=Result<T,E> + 'a>) {
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| ----------- ^^ ...because of this bound
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| |
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| expected this type to be a trait...
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help: if you meant to use a type and not a trait here, remove the bounds
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LL | fn b<'a,T,E>(iter: Iterator<Item=Result<T,E>>) {
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| --
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error[E0404]: expected trait, found struct `A`
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--> $DIR/trait-bounds-not-on-struct.rs:19:21
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LL | fn c() -> 'static + A {
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| ^ not a trait
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help: `+` is used to constrain a "trait object" type with lifetimes or auto-traits; structs and enums can't be bound in that way
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--> $DIR/trait-bounds-not-on-struct.rs:19:11
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LL | fn c() -> 'static + A {
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| ^^^^^^^ - expected this type to be a trait...
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| |
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| ...because of this bound
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help: if you meant to use a type and not a trait here, remove the bounds
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LL | fn c() -> A {
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| --
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error[E0404]: expected trait, found enum `Result`
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--> $DIR/trait-bounds-not-on-struct.rs:22:39
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LL | fn d<'a,T,E>(iter: Iterator<Item='a + Result<T,E>>) {
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| ^^^^^^^^^^^ not a trait
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help: `+` is used to constrain a "trait object" type with lifetimes or auto-traits; structs and enums can't be bound in that way
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--> $DIR/trait-bounds-not-on-struct.rs:22:34
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LL | fn d<'a,T,E>(iter: Iterator<Item='a + Result<T,E>>) {
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| ^^ ----------- expected this type to be a trait...
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| |
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| ...because of this bound
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help: if you meant to use a type and not a trait here, remove the bounds
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LL | fn d<'a,T,E>(iter: Iterator<Item=Result<T,E>>) {
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| --
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error[E0404]: expected trait, found struct `A`
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--> $DIR/trait-bounds-not-on-struct.rs:25:21
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LL | fn e() -> 'static + A + 'static {
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| ^ not a trait
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help: `+` is used to constrain a "trait object" type with lifetimes or auto-traits; structs and enums can't be bound in that way
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--> $DIR/trait-bounds-not-on-struct.rs:25:11
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LL | fn e() -> 'static + A + 'static {
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| ^^^^^^^ - ^^^^^^^ ...because of these bounds
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| |
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| expected this type to be a trait...
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help: if you meant to use a type and not a trait here, remove the bounds
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LL | fn e() -> A {
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| ---
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error[E0404]: expected trait, found enum `Result`
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--> $DIR/trait-bounds-not-on-struct.rs:29:39
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LL | fn f<'a,T,E>(iter: Iterator<Item='a + Result<T,E> + 'a>) {
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| ^^^^^^^^^^^ not a trait
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help: `+` is used to constrain a "trait object" type with lifetimes or auto-traits; structs and enums can't be bound in that way
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--> $DIR/trait-bounds-not-on-struct.rs:29:34
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LL | fn f<'a,T,E>(iter: Iterator<Item='a + Result<T,E> + 'a>) {
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| ^^ ----------- ^^ ...because of these bounds
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| |
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| expected this type to be a trait...
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help: if you meant to use a type and not a trait here, remove the bounds
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LL | fn f<'a,T,E>(iter: Iterator<Item=Result<T,E>>) {
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| -- --
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error[E0404]: expected trait, found struct `Traitor`
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--> $DIR/trait-bounds-not-on-struct.rs:35:11
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LL | trait Trait {}
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| ----------- similarly named trait `Trait` defined here
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LL | fn g() -> Traitor + 'static {
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| ^^^^^^^ not a trait
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help: `+` is used to constrain a "trait object" type with lifetimes or auto-traits; structs and enums can't be bound in that way
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--> $DIR/trait-bounds-not-on-struct.rs:35:21
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LL | fn g() -> Traitor + 'static {
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| ------- ^^^^^^^ ...because of this bound
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| |
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| expected this type to be a trait...
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help: if you meant to use a type and not a trait here, remove the bounds
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LL | fn g() -> Traitor {
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| --
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help: a trait with a similar name exists
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LL | fn g() -> Trait + 'static {
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| ^^^^^
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error: aborting due to 11 previous errors
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Some errors have detailed explanations: E0226, E0404.
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For more information about an error, try `rustc --explain E0226`.
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