ppx generates badly typed code

[zoggy]

Hello,

Current version of ppx processor generates code for method calls which does not compile.

Example:

$ cat > j.ml
let doc = Dom_html.window##document;;
^D
$ ocamlfind ocamlc -c -package js_of_ocaml.ppx j.ml
File "j.ml", line 1, characters 10-35:
Error: This expression has type
         Dom_html.document Js.t Js.readonly_prop =
           < get : Dom_html.document Js.t > Js.gen_prop
       but an expression was expected of type 'jsoo_32b5ee21 Js.meth

Examples could make use of the ppx extension to detect these problems as soon as possible.

[hhugo]

the ppx syntax for property access is ##. https://github.com/ocsigen/js_of_ocaml/blob/master/lib/ppx/ppx_js.mli#L19

let doc = Dom_html.window##.document

[hhugo]

note that the syntax for method call has changed as well.
camlp4 x##m(a,b,c) translates to ppx x##m a b c or x##(m a b c)