Require structs to use newtype form or have at least one field

[nikomatsakis]

Per this thread on the mailing list, structs should be required to either be written struct Foo; or to have at least one field. This avoids various ambiguities when parsing.

[thomaslee]

Is this as simple as modifying the parser to prevent the "struct Foo {}" syntax (i.e. a struct with no fields) & modifying it to support the braceless syntax, or is more work needed to make it a newtype? And if so, what?

[huonw]

@thomaslee, this seems to have been done already:

$ cat empty-struct.rs
struct A {}
fn main() {}

$ rustc empty-struct.rs
empty-struct.rs:1:10: 1:11 error: Unit-like struct should be written as: struct A;
empty-struct.rs:1 struct A {}
                            ^

(ping @nikomatsakis, you can probably close this.)

[thomaslee]

Ah good catch @dbaupp -- thanks.