Pipeline + arrow function grammar

[littledan]

In the explained and babel implementation, cases like x |> y => z are permitted. The current grammar does not permit these, throwing a syntax error. It seems like a useful case, but I haven't figured out how to spec it.

[littledan]

Cc @waldemarhowat @jridgewell @hzoo @gilbert

[jridgewell]

Is this the parenthesis vs no parenthesis thing we talked about? If so we can lock down how Babylon parses it.

[danny-andrews]

Not sure if there's an issue for this already, or if this is a bug with babel, but I'm having an issue with the opposite. This:

const RightReaderPromise = a => (a |> Either.Right |> ReaderPromise.of);

Gives:

  return a |> _monet.Either.Right |> _readerPromise2.default.of;
            ^

SyntaxError: Unexpected token >

[jridgewell]

It's a bug with your babel setup, you have to enable the transform. This is not the right thread for that.

[tabatkins]

Closing this issue, as the proposal has advanced to stage 2 with Hack-style syntax. We're still working on the precise details of some precedence issues, but at least putting arrow functions in pipe bodies is a lot less common of a thing to do now, so it's a much smaller issue.