ApplicativeDo causes GHC panic on irrefutable list pattern match
So this just happened:
{-# language ApplicativeDo #-}
module Main where
main :: IO ()
main = do
[_] <- pure []
pure ()
Compiling (under Stack) with stack exec -- ghc --make src/Main.hs
yields
[1 of 1] Compiling Main ( src/Main.hs, src/Main.o )
ghc: panic! (the 'impossible' happened)
(GHC version 8.2.1 for x86_64-unknown-linux):
isStrictPattern
Please report this as a GHC bug: http://www.haskell.org/ghc/reportabug
This does not happen on GHC-8.0.2. It does not happen when ApplicativeDo
is not activated. It also does not happen when the pattern match line is changed to
[] <- pure []
For completeness, the compiler used by stack
is that which comes with nightly-2017-08-10
. I am on Linux x64 (Ubuntu).
Trac metadata
Trac field | Value |
---|---|
Version | 8.2.1 |
Type | Bug |
TypeOfFailure | OtherFailure |
Priority | normal |
Resolution | Unresolved |
Component | Compiler |
Test case | |
Differential revisions | |
BlockedBy | |
Related | |
Blocking | |
CC | |
Operating system | |
Architecture |