rust

trait M<A> {}
impl<A, B> M<A> for (A, B) {}
impl<A, B> M<B> for (A, B) {}
fn main() {}

error[E0119]: conflicting implementations of trait `M<_>` for type `(_, _)`:
 --> 845880507/source.rs:3:1
  |
2 | impl<A, B> M<A> for (A, B) {}
  | -------------------------- first implementation here
3 | impl<A, B> M<B> for (A, B) {}
  | ^^^^^^^^^^^^^^^^^^^^^^^^^^ conflicting implementation for `(_, _)`

error: aborting due to previous error

For more information about this error, try `rustc --explain E0119`.