error[E0053]: method `b` has an incompatible type for trait
  --> $DIR/reordered-type-param.rs:16:30
   |
LL |   fn b<C:Clone,D>(&self, x: C) -> C;
   |                             - type in trait
...
LL |   fn b<F:Clone,G>(&self, _x: G) -> G { panic!() }
   |        -       -             ^ expected type parameter `F`, found type parameter `G`
   |        |       |
   |        |       found type parameter
   |        expected type parameter
   |
   = note: expected fn pointer `fn(&E, F) -> F`
              found fn pointer `fn(&E, G) -> G`
   = note: a type parameter was expected, but a different one was found; you might be missing a type parameter or trait bound
   = note: for more information, visit https://doc.rust-lang.org/book/ch10-02-traits.html#traits-as-parameters

error: aborting due to previous error

For more information about this error, try `rustc --explain E0053`.