[GHC] #9254: Entered absent argument (again)

#9254: Entered absent argument (again) ------------------------------------+------------------------------------- Reporter: simonpj | Owner: Type: bug | Status: new Priority: normal | Milestone: 7.8.4 Component: Compiler | Version: 7.8.2 Keywords: | Operating System: Unknown/Multiple Architecture: Unknown/Multiple | Type of failure: None/Unknown Difficulty: Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | ------------------------------------+------------------------------------- Consider this program: {{{ {-# LANGUAGE MagicHash, UnboxedTuples #-} module Main where import GHC.Exts f :: (() -> (# Int#, () #)) -> () {-# NOINLINE f #-} -- Strictness signature was (7.8.2) -- -- I.e. calls k, but discards first component of result f k = case k () of (# _, r #) -> r g :: Int -> () g y = f (\n -> (# case y of I# y2 -> h (h (h (h (h (h (h y2)))))), n #)) -- RHS is big enough to force worker/wrapper {-# NOINLINE h #-} h :: Int# -> Int# h n = n +# 1# main = print (g 1) }}} You'll get {{{ bash$ ghc -O -o foo Foo.hs bash$ ./foo foo: Oops! Entered absent arg w_s4vl Int }}} Ugh! This is the bug underlying [https://github.com/bos/vector-binary- instances/issues/4 this bug report]. I know what is going on. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/9254 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler