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Diffstat (limited to 'compiler/rustc_error_codes/src/error_codes/E0719.md')
-rw-r--r-- | compiler/rustc_error_codes/src/error_codes/E0719.md | 35 |
1 files changed, 35 insertions, 0 deletions
diff --git a/compiler/rustc_error_codes/src/error_codes/E0719.md b/compiler/rustc_error_codes/src/error_codes/E0719.md new file mode 100644 index 000000000..057a0b164 --- /dev/null +++ b/compiler/rustc_error_codes/src/error_codes/E0719.md @@ -0,0 +1,35 @@ +An associated type value was specified more than once. + +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 } // ok! +``` + +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 |