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There are conflicting trait implementations for the same type.
Erroneous code example:
```compile_fail,E0119
trait MyTrait {
fn get(&self) -> usize;
}
impl<T> MyTrait for T {
fn get(&self) -> usize { 0 }
}
struct Foo {
value: usize
}
impl MyTrait for Foo { // error: conflicting implementations of trait
// `MyTrait` for type `Foo`
fn get(&self) -> usize { self.value }
}
```
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:
```
trait MyTrait {
fn get(&self) -> usize;
}
impl<T> MyTrait for T {
fn get(&self) -> usize { 0 }
}
```
This makes the trait implemented on all types in the scope. So if you
try to implement it on another one after that, the implementations will
conflict. Example:
```
trait MyTrait {
fn get(&self) -> usize;
}
impl<T> MyTrait for T {
fn get(&self) -> usize { 0 }
}
struct Foo;
fn main() {
let f = Foo;
f.get(); // the trait is implemented so we can use it
}
```
|
