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| author | Ohad Ravid <ohad.rv@gmail.com> | 2019-11-08 21:40:30 +0100 |
|---|---|---|
| committer | Ohad Ravid <ohad.rv@gmail.com> | 2019-11-09 19:30:04 +0100 |
| commit | 7e94cc37e8d4938da29def5f49ae9fec56ca7dec (patch) | |
| tree | 6f16ed2e50b651533277b047bad15d8eadef1672 | |
| parent | eb981a1da4bcd2d372f0b61b38e6ce3b13a47468 (diff) | |
| download | rust-7e94cc37e8d4938da29def5f49ae9fec56ca7dec.tar.gz rust-7e94cc37e8d4938da29def5f49ae9fec56ca7dec.zip | |
Update E0210 to match RFC 2451
| -rw-r--r-- | src/librustc_typeck/error_codes.rs | 22 |
1 files changed, 16 insertions, 6 deletions
diff --git a/src/librustc_typeck/error_codes.rs b/src/librustc_typeck/error_codes.rs index f21fc2df8b9..9417e78ebfa 100644 --- a/src/librustc_typeck/error_codes.rs +++ b/src/librustc_typeck/error_codes.rs @@ -2058,8 +2058,13 @@ E0210: r##" 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: @@ -2117,12 +2122,17 @@ 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). -For information on the design of the orphan rules, see [RFC 1023]. +Both of the folowing 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]. +[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 "##, |