parsing long single-line array literals fails

[lue-bird]

Slightly obscure edge case

• Long list formatted all on one line causes a parser error (trailing comma) elm/compiler#2281

[morteako]

Seems like the issue is underflow coming from the fact that the line length is larger than the range of Word16 (2^16 = 65536), which is used in

data Position
  = Position
      {-# UNPACK #-} !Word16
      {-# UNPACK #-} !Word16
  deriving (Eq, Show)

Should be fixable by using Word32 (or something else larger), but I guess it has to be weighed up against the performance/memory cost.

[robinheghan]

Pretty certain we'd do fine with Word32.

Thanks for looking into this! :)