Error on REPL with implicit parens

[TrevorBurnham]

The code

a(b) -> c

is perfectly legit, equivalent to a(b)(-> c). But on the REPL, it fails with the message

Error: In repl, too many ) on line 2

(as of the current master; error message is on line 1 on 1.1.1). Note that this is the same error that was happening in #1398 with comments (since fixed by Michael).

To be clear,

func ->

works fine, but

func() ->

fails.

[michaelficarra]

It doesn't look like it's the REPL's fault: (fn() ->) fails to compile, but I see nothing wrong with it. Take away the trailing right-parenthesis and it still complains (as it should this time).

edit: It looks like pretty much everything that's similar but slightly different compiles fine. So it's a bug, but definitely not the REPL's fault.

[TrevorBurnham]

Ah, so the root cause of the problem is that

(fn() ->)

gives you an error. Gotcha.

Any idea how the unbalance is happening? These all work:

(fn() (->))
(fn() a, ->)

and this gets the same error:

(fn()->)

So the major commonality in all the error cases is that () immediately precedes ->. I'm guessing some part of the lexer is mistakenly seeing the () as an argument list.

[michaelficarra]

A little debugging output:

$;coffee -te "(fn() a)" (a normal token stream):

tokens: 
 [ [ '(', '(', 0 ],
  [ 'IDENTIFIER', 'fn', 0 ],
  [ 'CALL_START', '(', 0 ],
  [ 'CALL_END', ')', 0, spaced: true ],
  [ 'CALL_START', '(', 0 ],
  [ 'IDENTIFIER', 'a', 0 ],
  [ 'CALL_END', ')', 0 ],
  [ ')', ')', 0 ],
  [ 'TERMINATOR', '\n', 0 ] ]
pair counts: 
 { '(': 0,
  '[': 0,
  '{': 0,
  INDENT: 0,
  CALL_START: 0,
  PARAM_START: 0,
  INDEX_START: 0 }
[( (] [IDENTIFIER fn] [CALL_START (] [CALL_END )] [CALL_START (] [IDENTIFIER a] [CALL_END )] [) )] [TERMINATOR \n]

So everything gets paired up at the end (all the counts end at zero and never dip below zero).

$;coffee -te "(fn() ->)" (our errant case):

coffee -te "(fn() ->)"
tokens: 
 [ [ 'PARAM_START', '(', 0 ],
  [ 'IDENTIFIER', 'fn', 0 ],
  [ 'CALL_START', '(', 0 ],
  [ 'CALL_END', ')', 0, spaced: true ],
  [ 'CALL_START', '(', 0 ],
  [ '->', '->', 0 ],
  [ 'INDENT', 2, 0, generated: true ],
  [ 'OUTDENT', 2, 0, generated: true ],
  [ 'CALL_END', ')', 0 ],
  [ ')', ')', 0 ],
  [ 'TERMINATOR', '\n', 0 ] ]
pair counts: 
 { '(': -1,
  '[': 0,
  '{': 0,
  INDENT: 0,
  CALL_START: 0,
  PARAM_START: 1,
  INDEX_START: 0 }
Error: too many ) on line 1

Here, we see a PARAM_START as the first token (at the time of the ensureBalance rewriting phase) instead of (, so the final ) causes the ( count to dip below zero, triggering the error. Now we just need to see what's putting that PARAM_START token there... probably the lexer, since the rewriter hardly mentions it..

update: the problem is definitely in the lexer, most likely the tagParameters method.

[michaelficarra]

@TrevorBurnham: should be fixed by the above commit.