Fast pipe and local open

[alex35mil]

Compiler yells when I fast-pipe into local open.

Repro: https://reasonml.github.io/en/try.html?rrjsx=true&reason=LYewJgrgNgpgBAMTgXjgbwFBzrALnAMxTgAoAPALjgEsA7XAGjgE8qBnXAJzoHMBKFAD5SfANwYAvuIwB6AFRwAmjAAOcOTIwBGOAB9hCAHQkCJAPpMARFst8xGWQuVqNGIyR27DhEtdv3HOAA5EBV4V09vd1M-O3EgA

[strega-nil]

It seems like it should be a compiler error if one does x |. <expr> where <expr> is not a (possibly parenthesized) function-call-expression.

[chenglou]

cc @bobzhang

[bobzhang]

feel free to close it, moved to bucklescript repo