Rust error E0053: method `foo` has an incompatible type for trait

What rustc prints

error[E0053]: method `foo` has an incompatible type for trait
  --> main.rs:10:15
   |
10 |     fn foo(x: i16) { }
   |               ^^^ expected `u16`, found `i16`
   |
note: type in trait
  --> main.rs:2:15
   |
 2 |     fn foo(x: u16);
   |               ^^^
   = note: expected signature `fn(u16)`
              found signature `fn(i16)`
help: change the parameter type to match the trait
   |
10 -     fn foo(x: i16) { }
10 +     fn foo(x: u16) { }
   |

Real output of rustc 1.99.0 compiling the official example below (2021 edition). Your names and line numbers will differ; the first line is the part to match.

trait Foo {
    fn foo(x: u16);
    fn bar(&self);
}

struct Bar;

impl Foo for Bar {
    // error, expected u16, found i16
    fn foo(x: i16) { }

    // error, types differ in mutability
    fn bar(&mut self) { }
}

Related errors

• E0308mismatched types
• E0277the trait bound is not satisfied
• E0599no method named X found in the current scope
• E0433failed to resolve
• E0049associated function `foo` has 0 type parameters but its trait declaration has 1 type parameter
• E0050method `foo` has 1 parameter but the declaration in trait `Foo::foo` has 2
• E0055reached the recursion limit while auto-dereferencing `Foo`
• E0059type parameter to bare `FnOnce` trait must be a tuple

All 518 Rust error codes · Rust crate data · Glossary