E4193

Compiler diagnostic name: declare_body_not_empty.

Declaration body is not empty.

A declaration describes an item without providing its implementation body. For function declarations, the declaration must not contain a { ... } block. For type declarations, the declared type must be abstract rather than a concrete struct, enum, or tuple struct definition.

Erroneous example

#declaration_only
fn declared_answer() -> Int {
  42
}

The #declaration_only attribute marks declared_answer as a declaration, but the function still provides an implementation body.

Suggestion

Remove the declaration marker when the item is already implemented, or keep the declaration body empty and provide a matching implementation elsewhere.

fn declared_answer() -> Int {
  42
}