GHC 8.4.1 bug: -O + separate compilation + three list fields + concatenation; core-lint fails
A simple program that works in 8.2.1 fails in 8.4.1 when compiled with -O. (Sorry, haven't tested 8.2.2.) GHC with -dcore-lint reports an error.
See attached files. In one file I declared:
module Sep where
data Sep = Sep
{ bugVanishesWithoutThis :: [()]
, middle :: [String]
, orThis :: [()]
}
catSep :: Sep -> Sep -> Sep
catSep (Sep a b c) (Sep x y z) = Sep (a ++ x) (b ++ y) (c ++ z)
cc :: Sep -> Bool
cc boost = elem "foo" $ middle boost
and in a second file, simple code fails when compiled with -O:
module Main (main) where
import Sep
main :: IO ()
main = print $ cc bb
bb :: Sep
bb = catSep b1 b2
b1 :: Sep
b1 = Sep [] ["foo"] []
b2 :: Sep
b2 = Sep [] ["bar"] []
This should print "True", and does so for GHC 8.2.1, and GHC 8.4.1 without -O, but prints "False" for GHC 8.4.1 with -O.
I was unable to reproduce the bug with a single file.
Trac metadata
Trac field | Value |
---|---|
Version | 8.4.1 |
Type | Bug |
TypeOfFailure | OtherFailure |
Priority | normal |
Resolution | Unresolved |
Component | Compiler |
Test case | |
Differential revisions | |
BlockedBy | |
Related | |
Blocking | |
CC | ben@dfinity.org |
Operating system | |
Architecture |