Enum mapping giving 'Sum types without js.* attribute not supported in this context'

[nickbetteridge]

I've suddenly run into issues with enums -

Given a file with one line containing type t = [`foo | `bar [@js 42] | `Baz] [@@js.enum], when I run ocamlfind gen_js_api/gen_js_api test.mli I get Error: Sum types without js.* attribute not supported in this context.

I'm pretty sure this was working in the not too distant past - I'm running with ocaml 4.07.0, opam2 and gen_js_api 1.0.5 - gen_js_api is compiling without error on everything else I have.

[nickbetteridge]

Ah - it's a matter of ampersands - polymorphic variants require just one ampersand - [@js.enum] whereas normal variants require two - [@@js.enum]