#14918: GHC 8.4.1 regression: derived Read instances with field names containing # no longer parse -------------------------------------+------------------------------------- Reporter: RyanGlScott | Owner: (none) Type: bug | Status: new Priority: high | Milestone: 8.4.2 Component: Compiler | Version: 8.4.1 Resolution: | Keywords: deriving Operating System: Unknown/Multiple | Architecture: Type of failure: Incorrect result | Unknown/Multiple at runtime | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Description changed by RyanGlScott: Old description:
(Originally noticed [here](https://github.com/ekmett/transformers- compat/issues/32).)
Consider the following program:
{{{#!hs {-# LANGUAGE MagicHash #-} module Bug where
data T a = MkT { runT# :: a } deriving (Read, Show)
t1, t2 :: T Int t1 = MkT 1 t2 = read $ show t1
main :: IO () main = print t2 }}}
In GHC 8.2.1, this runs without issue:
{{{ $ /opt/ghc/8.2.2/bin/runghc Bug.hs MkT {runT# = 1} }}}
In GHC 8.4.1, however, this produces a runtime error:
{{{ $ ~/Software/ghc-8.4.1/bin/runghc Bug.hs Bug.hs: Prelude.read: no parse }}}
New description: (Originally noticed [https://github.com/ekmett/transformers- compat/issues/32 here].) Consider the following program: {{{#!hs {-# LANGUAGE MagicHash #-} module Bug where data T a = MkT { runT# :: a } deriving (Read, Show) t1, t2 :: T Int t1 = MkT 1 t2 = read $ show t1 main :: IO () main = print t2 }}} In GHC 8.2.1, this runs without issue: {{{ $ /opt/ghc/8.2.2/bin/runghc Bug.hs MkT {runT# = 1} }}} In GHC 8.4.1, however, this produces a runtime error: {{{ $ ~/Software/ghc-8.4.1/bin/runghc Bug.hs Bug.hs: Prelude.read: no parse }}} -- -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/14918#comment:1 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler