Regression in parsec-3.1.6

[edsko]

Consider

import Control.Applicative ((<*), (<$>), (<$))
import Text.Parsec
import Text.Parsec.Language (haskellStyle)
import Text.Parsec.String (Parser)
import Text.Parsec.Expr
import qualified Text.Parsec.Token as P

data Expr = Const Integer | Op Expr Expr
  deriving Show

{-------------------------------------------------------------------------------
  Syntax analysis
-------------------------------------------------------------------------------}

parseTopLevel :: Parser Expr
parseTopLevel = parseExpr <* eof

parseExpr :: Parser Expr
parseExpr = buildExpressionParser table (Const <$> integer)
  where
    table = [[ Infix (Op <$ reserved ">>>") AssocLeft ]]

{-------------------------------------------------------------------------------
  Lexical analysis
-------------------------------------------------------------------------------}

lexer = P.makeTokenParser haskellStyle { P.reservedOpNames = [">>>"] }

integer    = P.integer    lexer
reserved   = P.reserved   lexer
reservedOp = P.reservedOp lexer

with parsec-3.1.5 and below we get

*Main> parseTest parseTopLevel "4 >> 5"
parse error at (line 1, column 3):
unexpected '>'
expecting operator or end of input

but with parsec-3.1.6 we get

*Main> parseTest parseTopLevel "4 >> 5"
parse error at (line 1, column 5):
unexpected " "
expecting operator

[kosmikus]

This is caused by 8607649. I think that change should just be reverted for now.

[aslatter]

Thanks for the bug report.

I've reverted the change, and I'll be pushing out 3.1.7 soon.