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Move E0210 to new error location

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Guillaume Gomez 2019-11-14 13:08:23 +01:00
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src/librustc_error_codes/error_codes/E0210.md
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@ -1,8 +1,13 @@
This error indicates a violation of one of Rust's orphan rules for trait
implementations. The rule concerns the use of type parameters in an
implementation of a foreign trait (a trait defined in another crate), and
states that type parameters must be "covered" by a local type. To understand
what this means, it is perhaps easiest to consider a few examples.
states that type parameters must be "covered" by a local type.
When implementing a foreign trait for a foreign type,
the trait must have one or more type parameters.
A type local to your crate must appear before any use of any type parameters.
To understand what this means, it is perhaps easier to consider a few examples.
If `ForeignTrait` is a trait defined in some external crate `foo`, then the
following trait `impl` is an error:
@ -60,10 +65,18 @@ impl<P1, ..., Pm> ForeignTrait<T1, ..., Tn> for T0 { ... }
where `P1, ..., Pm` are the type parameters of the `impl` and `T0, ..., Tn`
are types. One of the types `T0, ..., Tn` must be a local type (this is another
orphan rule, see the explanation for E0117). Let `i` be the smallest integer
such that `Ti` is a local type. Then no type parameter can appear in any of the
`Tj` for `j < i`.
orphan rule, see the explanation for E0117).
Both of the following must be true:
1. At least one of the types `T0..=Tn` must be a local type.
Let `Ti` be the first such type.
2. No uncovered type parameters `P1..=Pm` may appear in `T0..Ti`
(excluding `Ti`).
For information on the design of the orphan rules,
see [RFC 2451] and [RFC 1023].
For information on the design of the orphan rules, see [RFC 1023].
[RFC 2451]: https://rust-lang.github.io/rfcs/2451-re-rebalancing-coherence.html
[RFC 1023]: https://github.com/rust-lang/rfcs/blob/master/text/1023-rebalancing-coherence.md