```
Using this declaration, it must be called with at least one argument, so
-simply calling `printf()` is illegal. But the following uses are allowed:
+simply calling `printf()` is invalid. But the following uses are allowed:
```
unsafe {
Consider the following erroneous definition of a type for a list of bytes:
```
-// error, illegal recursive struct type
+// error, invalid recursive struct type
struct ListNode {
head: u8,
tail: Option<ListNode>,
"##,
E0117: r##"
-You got this error because because you tried to implement a foreign
-trait for a foreign type (with maybe a foreign type parameter). Erroneous
-code example:
+This error indicates a violation of one of Rust's orphan rules for trait
+implementations. The rule prohibits any implementation of a foreign trait (a
+trait defined in another crate) where
+
+ - the type that is implementing the trait is foreign
+ - all of the parameters being passed to the trait (if there are any) are also
+ foreign.
+
+Here's one example of this error:
```
impl Drop for u32 {}
```
-The type, trait or the type parameter (or all of them) has to be defined
-in your crate. Example:
+To avoid this kind of error, ensure that at least one local type is referenced
+by the `impl`:
```
pub struct Foo; // you define your type in your crate
// code of trait implementation here
}
-trait Bar { // or define your trait in your crate
- fn get(&self) -> usize;
-}
-
-impl Bar for u32 { // and then you implement it on a foreign type
- fn get(&self) -> usize { 0 }
-}
-
impl From<Foo> for i32 { // or you use a type from your crate as
// a type parameter
fn from(i: Foo) -> i32 {
}
}
```
+
+Alternatively, define a trait locally and implement that instead:
+
+```
+trait Bar {
+ fn get(&self) -> usize;
+}
+
+impl Bar for u32 {
+ fn get(&self) -> usize { 0 }
+}
+```
+
+For information on the design of the orphan rules, see [RFC 1023].
+
+[RFC 1023]: https://github.com/rust-lang/rfcs/pull/1023
"##,
E0119: r##"
There are conflicting trait implementations for the same type.
-Erroneous code example:
+Example of erroneous code:
```
trait MyTrait {
}
```
-When you write:
+When looking for the implementation for the trait, the compiler finds
+both the `impl<T> MyTrait for T` where T is all types and the `impl
+MyTrait for Foo`. Since a trait cannot be implemented multiple times,
+this is an error. So, when you write:
```
impl<T> MyTrait for T {
```
"##,
+E0120: r##"
+An attempt was made to implement Drop on a trait, which is not allowed: only
+structs and enums can implement Drop. An example causing this error:
+
+```
+trait MyTrait {}
+
+impl Drop for MyTrait {
+ fn drop(&mut self) {}
+}
+```
+
+A workaround for this problem is to wrap the trait up in a struct, and implement
+Drop on that. An example is shown below:
+
+```
+trait MyTrait {}
+struct MyWrapper<T: MyTrait> { foo: T }
+
+impl <T: MyTrait> Drop for MyWrapper<T> {
+ fn drop(&mut self) {}
+}
+
+```
+
+Alternatively, wrapping trait objects requires something like the following:
+
+```
+trait MyTrait {}
+
+//or Box<MyTrait>, if you wanted an owned trait object
+struct MyWrapper<'a> { foo: &'a MyTrait }
+
+impl <'a> Drop for MyWrapper<'a> {
+ fn drop(&mut self) {}
+}
+```
+"##,
+
E0121: r##"
In order to be consistent with Rust's lack of global type inference, type
placeholders are disallowed by design in item signatures.
```
"##,
+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.
+
+If `ForeignTrait` is a trait defined in some external crate `foo`, then the
+following trait `impl` is an error:
+
+```
+extern crate foo;
+use foo::ForeignTrait;
+
+impl<T> ForeignTrait for T { ... } // error
+```
+
+To work around this, it can be covered with a local type, `MyType`:
+
+```
+struct MyType<T>(T);
+impl<T> ForeignTrait for MyType<T> { ... } // Ok
+```
+
+For another example of an error, suppose there's another trait defined in `foo`
+named `ForeignTrait2` that takes two type parameters. Then this `impl` results
+in the same rule violation:
+
+```
+struct MyType2;
+impl<T> ForeignTrait2<T, MyType<T>> for MyType2 { ... } // error
+```
+
+The reason for this is that there are two appearances of type parameter `T` in
+the `impl` header, both as parameters for `ForeignTrait2`. The first appearance
+is uncovered, and so runs afoul of the orphan rule.
+
+Consider one more example:
+
+```
+impl<T> ForeignTrait2<MyType<T>, T> for MyType2 { ... } // Ok
+```
+
+This only differs from the previous `impl` in that the parameters `T` and
+`MyType<T>` for `ForeignTrait2` have been swapped. This example does *not*
+violate the orphan rule; it is permitted.
+
+To see why that last example was allowed, you need to understand the general
+rule. Unfortunately this rule is a bit tricky to state. Consider an `impl`:
+
+```
+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`.
+
+For information on the design of the orphan rules, see [RFC 1023].
+
+[RFC 1023]: https://github.com/rust-lang/rfcs/pull/1023
+"##,
+
E0211: r##"
You used an intrinsic function which doesn't correspond to its
definition. Erroneous code example:
-lang/rfcs/blob/master/text/0019-opt-in-builtin-traits.md).
"##,
+E0391: r##"
+This error indicates that some types or traits depend on each other
+and therefore cannot be constructed.
+
+The following example contains a circular dependency between two traits:
+
+```
+trait FirstTrait : SecondTrait {
+
+}
+
+trait SecondTrait : FirstTrait {
+
+}
+```
+"##,
+
E0392: r##"
This error indicates that a type or lifetime parameter has been declared
but not actually used. Here is an example that demonstrates the error:
E0103,
E0104,
E0118,
- E0120,
E0122,
E0123,
E0127,
// and only one is supported
E0208,
E0209, // builtin traits can only be implemented on structs or enums
- E0210, // type parameter is not constrained by any local type
E0212, // cannot extract an associated type from a higher-ranked trait bound
E0213, // associated types are not accepted in this context
E0214, // parenthesized parameters may only be used with a trait
- E0215, // angle-bracket notation is not stable with `Fn`
- E0216, // parenthetical notation is only stable with `Fn`
+// E0215, // angle-bracket notation is not stable with `Fn`
+// E0216, // parenthetical notation is only stable with `Fn`
E0217, // ambiguous associated type, defined in multiple supertraits
E0218, // no associated type defined
E0219, // associated type defined in higher-ranked supertrait
E0221, // ambiguous associated type in bounds
- //E0222, // Error code E0045 (variadic function must have C calling
- // convention) duplicate
+// E0222, // Error code E0045 (variadic function must have C calling
+ // convention) duplicate
E0224, // at least one non-builtin train is required for an object type
E0226, // only a single explicit lifetime bound is permitted
E0227, // ambiguous lifetime bound, explicit lifetime bound required
E0241,
E0242, // internal error looking up a definition
E0245, // not a trait
- E0246, // illegal recursive type
+ E0246, // invalid recursive type
E0247, // found module name used as a type
E0248, // found value name used as a type
E0319, // trait impls for defaulted traits allowed just for structs/enums
// between structures with the same definition
E0390, // only a single inherent implementation marked with
// `#[lang = \"{}\"]` is allowed for the `{}` primitive
- E0391, // unsupported cyclic reference between types/traits detected
E0393, // the type parameter `{}` must be explicitly specified in an object
// type because its default value `{}` references the type `Self`"
E0399, // trait items need to be implemented because the associated
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