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Rollup of 7 pull requests #69643

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doc(librustc_error_codes): add long error explanation for E0719
Progresses #61137
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thekuom committed Mar 1, 2020

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commit 275dac7bfb6cfadd02c12edacbd4fdf529269424
2 changes: 1 addition & 1 deletion src/librustc_error_codes/error_codes.rs
Original file line number Diff line number Diff line change
@@ -395,6 +395,7 @@ E0714: include_str!("./error_codes/E0714.md"),
E0715: include_str!("./error_codes/E0715.md"),
E0716: include_str!("./error_codes/E0716.md"),
E0718: include_str!("./error_codes/E0718.md"),
E0719: include_str!("./error_codes/E0719.md"),
E0720: include_str!("./error_codes/E0720.md"),
E0723: include_str!("./error_codes/E0723.md"),
E0725: include_str!("./error_codes/E0725.md"),
@@ -604,7 +605,6 @@ E0747: include_str!("./error_codes/E0747.md"),
E0710, // an unknown tool name found in scoped lint
E0711, // a feature has been declared with conflicting stability attributes
E0717, // rustc_promotable without stability attribute
E0719, // duplicate values for associated type binding
// E0721, // `await` keyword
E0722, // Malformed `#[optimize]` attribute
E0724, // `#[ffi_returns_twice]` is only allowed in foreign functions
35 changes: 35 additions & 0 deletions src/librustc_error_codes/error_codes/E0719.md
Original file line number Diff line number Diff line change
@@ -0,0 +1,35 @@
The value for an associated type has already been specified.

Erroneous code example:

```compile_fail,E0719
#![feature(associated_type_bounds)]

trait FooTrait {}
trait BarTrait {}

// error: associated type `Item` in trait `Iterator` is specified twice
struct Foo<T: Iterator<Item: FooTrait, Item: BarTrait>> { f: T }
```

`Item` in trait `Iterator` cannot be specified multiple times for struct `Foo`.
To fix this, create a new trait that is a combination of the desired traits and
specify the associated type with the new trait.

Corrected example:

```
#![feature(associated_type_bounds)]

trait FooTrait {}
trait BarTrait {}
trait FooBarTrait: FooTrait + BarTrait {}

struct Foo<T: Iterator<Item: FooBarTrait>> { f: T }
```

For more information about associated types, see [the book][bk-at]. For more
information on associated type bounds, see [RFC 2289][rfc-2289].

[bk-at]: https://doc.rust-lang.org/book/ch19-03-advanced-traits.html#specifying-placeholder-types-in-trait-definitions-with-associated-types
[rfc-2289]: https://rust-lang.github.io/rfcs/2289-associated-type-bounds.html
1 change: 1 addition & 0 deletions src/test/ui/associated-type-bounds/duplicate.stderr
Original file line number Diff line number Diff line change
@@ -728,3 +728,4 @@ LL | type TADyn3 = dyn Iterator<Item: 'static, Item: 'static>;

error: aborting due to 96 previous errors

For more information about this error, try `rustc --explain E0719`.
1 change: 1 addition & 0 deletions src/test/ui/error-codes/E0719.stderr
Original file line number Diff line number Diff line change
@@ -16,3 +16,4 @@ LL | fn test() -> Box<dyn Iterator<Item = (), Item = Unit>> {

error: aborting due to 2 previous errors

For more information about this error, try `rustc --explain E0719`.