#15600: Bug while writing a simple parser with Parsec -------------------------------------+------------------------------------- Reporter: roehst | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: 8.6.1 Component: Compiler | Version: 8.0.2 Keywords: | Operating System: Unknown/Multiple Architecture: x86_64 | Type of failure: None/Unknown (amd64) | Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- {{{#!hs module Main where import Control.Monad.Identity import Control.Monad.State import Data.List import Text.ParserCombinators.Parsec type Name = String data Value = VlInt Int | VlBool Bool deriving Show data Term = TmVal Value | TmVar Name | TmLet Name Term Term | TmAdd Term Term deriving Show parseTerm :: Parser Term parseTerm = parseVal <|> parseVar <|> parseLet <|> parseAdd }}} And then I get: GHCi, version 8.0.2: http://www.haskell.org/ghc/ :? for help [1 of 1] Compiling Main ( Main.hs, interpreted ) ghc: panic! (the 'impossible' happened) (GHC version 8.0.2 for x86_64-unknown-linux): initTc: unsolved constraints WC {wc_insol = [W] parseVal_a2YR :: t_a2YQ[tau:1] (CHoleCan: parseVal) [W] parseVar_a2YY :: t_a2YX[tau:1] (CHoleCan: parseVar) [W] parseLet_a2Z5 :: t_a2Z4[tau:1] (CHoleCan: parseLet) [W] parseAdd_a2Z8 :: t_a2Z7[tau:1] (CHoleCan: parseAdd)} Please report this as a GHC bug: http://www.haskell.org/ghc/reportabug -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/15600 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler