Re: [GHC] #3382: Panic in tidyNPat when using N+k patterns with overloaded strings
#3382: Panic in tidyNPat when using N+k patterns with overloaded strings
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Reporter: batterseapower|Owner:
Type: bug | Status: closed
Priority: normal|Milestone:
Component: Compiler | Version: 6.10.4
Severity: normal| Resolution: fixed
Keywords:| Difficulty: Unknown
Testcase: deSugar/should_run/T3382 | Os: Unknown/Multiple
Architecture: Unknown/Multiple |
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Changes (by simonpj):
* testcase: => deSugar/should_run/T3382
* difficulty: => Unknown
* status: new => closed
* resolution: => fixed
Comment:
Ah yes, excellent point. Fixed by
{{{
Mon Jul 20 07:12:26 GMT Daylight Time 2009 simo...@microsoft.com
* Fix Trac #3382: desugaring of NPats
Max spotted that the short-cut rules for desugaring NPats (where
we compare against a literal) were wrong now that we have overloaded
strings.
}}}
thanks
Simon
--
Ticket URL:
GHC
[GHC] #3382: Panic in tidyNPat when using N+k patterns with overloaded strings
#3382: Panic in tidyNPat when using N+k patterns with overloaded strings
-+--
Reporter: batterseapower| Owner:
Type: bug | Status: new
Priority: normal| Component: Compiler
Version: 6.10.4| Severity: normal
Keywords:| Testcase:
Os: Unknown/Multiple | Architecture: Unknown/Multiple
-+--
Spotted this while reading the source code to tidyNPat. It looked dubious
to me, and indeed it is:
{{{
{-# OPTIONS_GHC -XOverloadedStrings #-}
module Main where
import Data.String
instance IsString Int where
fromString x = 1337
f :: Int -> String
f "hello" = "correct"
f _ = "false"
main = do
print $ f 1337
print $ f 1338
}}}
Result:
{{{
mbolingbr...@mb566 ~/Programming/Checkouts
$ ghc --make Boog.hs
[1 of 1] Compiling Main ( Boog.hs, Boog.o )
ghc: panic! (the 'impossible' happened)
(GHC version 6.10.3 for i386-apple-darwin):
tidyNPat
}}}
--
Ticket URL:
GHC
