E0069

Warning name: declaration_implemented

Declaration is already implemented.

This warning is emitted when a declare item already has a matching implementation in the same package. At that point the declaration is redundant: the implementation itself is enough for the compiler to know the API.

This warning is useful when declarations were added during a refactor and should be removed after the implementation has landed.

Erroneous example

declare fn f() -> Unit

fn f() -> Unit {
  println("only")
}

Suggestion

Remove the redundant declaration and keep the implementation:

fn f() -> Unit {
  println("only")
}