error[E0053]: method `fmt` has an incompatible type for trait
  --> $DIR/trait_type.rs:7:4
   |
LL |    fn fmt(&self, x: &str) -> () { }
   |    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ types differ in mutability
   |
   = note: expected type `fn(&MyType, &mut std::fmt::Formatter<'_>) -> std::result::Result<(), std::fmt::Error>`
              found type `fn(&MyType, &str)`

error[E0050]: method `fmt` has 1 parameter but the declaration in trait `std::fmt::Display::fmt` has 2
  --> $DIR/trait_type.rs:12:11
   |
LL |    fn fmt(&self) -> () { }
   |           ^^^^^ expected 2 parameters, found 1
   |
   = note: `fmt` from trait: `fn(&Self, &mut std::fmt::Formatter<'_>) -> std::result::Result<(), std::fmt::Error>`

error[E0186]: method `fmt` has a `&self` declaration in the trait, but not in the impl
  --> $DIR/trait_type.rs:17:4
   |
LL |    fn fmt() -> () { }
   |    ^^^^^^^^^^^^^^ expected `&self` in impl
   |
   = note: `fmt` from trait: `fn(&Self, &mut std::fmt::Formatter<'_>) -> std::result::Result<(), std::fmt::Error>`

error[E0046]: not all trait items implemented, missing: `fmt`
  --> $DIR/trait_type.rs:21:1
   |
LL | impl std::fmt::Display for MyType4 {}
   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ missing `fmt` in implementation
   |
   = note: `fmt` from trait: `fn(&Self, &mut std::fmt::Formatter<'_>) -> std::result::Result<(), std::fmt::Error>`

error: aborting due to 4 previous errors

Some errors have detailed explanations: E0046, E0050, E0053, E0186.
For more information about an error, try `rustc --explain E0046`.