[GHC] #9175: Bad interaction between Pattern Synonyms and Text

[GHC]

#9175: Bad interaction between Pattern Synonyms and Text
-----------------------------------+---------------------------------------
       Reporter:  emertens         |             Owner:
           Type:  bug              |            Status:  new
       Priority:  normal           |         Milestone:
      Component:  Compiler         |           Version:  7.8.2
       Keywords:                   |  Operating System:  Unknown/Multiple
   Architecture:                   |   Type of failure:  Compile-time crash
  Unknown/Multiple                 |         Test Case:
     Difficulty:  Unknown          |          Blocking:
     Blocked By:                   |
Related Tickets:                   |
-----------------------------------+---------------------------------------
 Compiling this file causes the impossible to happen. It is necessary to
 enable optimizations. The bug did not occur if the Text parameter was
 replaced with ByteString or String.

 {{{
 {-# LANGUAGE PatternSynonyms #-}
 {-# LANGUAGE OverloadedStrings #-}
 module Bug where

 {-
  -  Must compile with optimizations
  -
  -  text-1.1.1.3
  -  ghc-7.8.2
  -  Both Darwin and Linux platforms
  -
  -}

 import Data.Text(Text)

 data T = C Text Bool

 f :: a -> b
 f _ = undefined
 {-# NOINLINE f #-} -- important

 pattern P1 a = C "sh" a -- at least two characters
 pattern P2    = C "x" True -- this pattern has to come last

 g :: Text -> T
 g x = case x of
        "" -> f (P1 undefined) -- this has to be a pattern synonym
 }}}

 {{{
 [1 of 1] Compiling Bug              ( Bug.hs, Bug.o )
 ghc: panic! (the 'impossible' happened)
   (GHC version 7.8.2 for x86_64-apple-darwin):
         StgCmmEnv: variable not found
     lvl_s2Jr{v} [lid]
     local binds for:
     main:Bug.f{v rBS} [gid]
     main:Bug.rewriteRule{v rBV} [gid]
     main:Bug.$mP2{v r17q} [gid]
     main:Bug.$WP2{v r17A} [gid]
     main:Bug.$mP1{v r17E} [gid]
     main:Bug.$WP1{v r17R} [gid]
     main:Bug.$WP3{v r3bq} [gid]
     main:Bug.$WP4{v r3ua} [gid]
     main:Bug.$WP5{v r3ub} [gid]
     main:Bug.$WP2_dt{v r3uc} [gid]
     main:Bug.$WP6{v r3ud} [gid]
     main:Bug.$WP7{v r3ue} [gid]
     main:Bug.$WP8{v r3uf} [gid]
     main:Bug.$w$mP1{v r3ug} [gid]
     main:Bug.$w$mP2{v r3uh} [gid]
     main:Bug.$mP3{v r3ui} [gid]
     main:Bug.$mP4{v r3uj} [gid]
     main:Bug.$mP5{v r3uk} [gid]
     main:Bug.$wrewriteRule{v r3ul} [gid]
     main:Bug.rewriteRule1{v r3um} [gid]
     main:Bug.rewriteRule2{v r3un} [gid]
     main:Bug.rewriteRule3{v r3uo} [gid]
     main:Bug.rewriteRule4{v r3up} [gid]
     main:Bug.rewriteRule5{v r3uq} [gid]
     lvl{v r3ur} [gid]


 Please report this as a GHC bug:  http://www.haskell.org/ghc/reportabug
 }}}

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9175>
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