Rust error E0643: method `foo` has incompatible signature for trait

What rustc prints

error[E0643]: method `foo` has incompatible signature for trait
 --> main.rs:5:12
  |
2 |     fn foo(&self, _: &impl Iterator);
  |                       ------------- declaration in trait here
...
5 |     fn foo<U: Iterator>(&self, _: &U) { } // error method `foo` has incompatible
  |            ^ expected `impl Trait`, found generic parameter
  |
help: try removing the generic parameter and using `impl Trait` instead
  |
5 -     fn foo<U: Iterator>(&self, _: &U) { } // error method `foo` has incompatible
5 +     fn foo(&self, _: &impl Iterator) { } // error method `foo` has incompatible
  |

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(&self, _: &impl Iterator);
}
impl Foo for () {
    fn foo<U: Iterator>(&self, _: &U) { } // error method `foo` has incompatible
                                          // signature for trait
}

Related errors

• E0308mismatched types
• E0277the trait bound is not satisfied
• E0599no method named X found in the current scope
• E0433failed to resolve
• E0634type has conflicting packed representation hints
• E0642patterns aren't allowed in functions without bodies
• E0644closure/coroutine type that references itself
• E0665`#[derive(Default)]` on enum with no `#[default]`

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