Support Java lambda expressions
Will this work for now? The way the fake paren parsing works, we will have (using '[' ']' as fake parens):
[[([a, b]) -> a] + b]
When we really want:
[([a, b]) -> [a + b]]
I think we should directly try to get this right with the fake parentheses. I'll prepare a patch. Feel free to just abandon this patch.