tests/ui/union/union-fields-2.rs

union U {
    a: u8,
    b: u16,
}

fn main() {
    let u = U {}; //~ ERROR union expressions should have exactly one field
    let u = U { a: 0 }; // OK
    let u = U { a: 0, b: 1 }; //~ ERROR union expressions should have exactly one field
    let u = U { a: 0, b: 1, c: 2 }; //~ ERROR union expressions should have exactly one field
                                    //~^ ERROR union `U` has no field named `c`
    let u = U { ..u }; //~ ERROR union expressions should have exactly one field
                       //~^ ERROR functional record update syntax requires a struct

    let U {} = u; //~ ERROR union patterns should have exactly one field
    let U { a } = u; // OK
    let U { a, b } = u; //~ ERROR union patterns should have exactly one field
    let U { a, b, c } = u; //~ ERROR union patterns should have exactly one field
                           //~^ ERROR union `U` does not have a field named `c`
    let U { .. } = u; //~ ERROR union patterns should have exactly one field
                      //~^ ERROR `..` cannot be used in union patterns
    let U { a, .. } = u; //~ ERROR `..` cannot be used in union patterns
}