#10764: GHC panic (no skolem info) -------------------------------------+------------------------------------- Reporter: zardoz | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.10.2 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: Type of failure: Compile-time | Unknown/Multiple crash | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Revisions: -------------------------------------+------------------------------------- Changes (by bgamari): * failure: None/Unknown => Compile-time crash Old description:

The attached program causes GHC 7.10.2 to panic with the following output:

bug.hs:6:19: Found hole ‘_’ with type: t1 → t2 → m1 a1 → m1 a1 Where: ‘t1’ is a rigid type variable bound by the inferred type of whenMultipleOf ∷ MonadPlus m1 ⇒ t1 → t2 → m1 a1 → m1 a1 at bug.hs:7:1 ‘a1’ is a rigid type variable bound by the inferred type of whenMultipleOf ∷ MonadPlus m1 ⇒ t1 → t2 → m1 a1 → m1 a1 at bug.hs:7:1 ‘m1’ is a rigid type variable bound by the inferred type of whenMultipleOf ∷ MonadPlus m1 ⇒ t1 → t2 → m1 a1 → m1 a1 at bug.hs:7:1 ‘t2’ is a rigid type variable bound by the inferred type of whenMultipleOf ∷ MonadPlus m1 ⇒ t1 → t2 → m1 a1 → m1 a1 at bug.hs:7:1 To use the inferred type, enable PartialTypeSignatures In the type signature for ‘whenMultipleOf’: _

bug.hs:7:1: No instance for (MonadPlus m) When checking that ‘whenMultipleOf’ has the specified type whenMultipleOf ∷ ∀ t a (m ∷ * → *) t1. t → t1 → m a → m a Probable cause: the inferred type is ambiguous

bug.hs:10:62: Couldn't match type ‘a1’ with ‘t’ ‘a1’ is a rigid type variable bound by the type signature for sumOfMultiples ∷ Integral a1 ⇒ [a1] → a1 → [a1] at bug.hs:9:19ghci-ng: panic! (the 'impossible' happened) (GHC version 7.10.2 for x86_64-unknown-linux): No skolem info: t_a7vV[sk]

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

New description: The attached program causes GHC 7.10.2 to panic with the following output: {{{ bug.hs:6:19: Found hole ‘_’ with type: t1 → t2 → m1 a1 → m1 a1 Where: ‘t1’ is a rigid type variable bound by the inferred type of whenMultipleOf ∷ MonadPlus m1 ⇒ t1 → t2 → m1 a1 → m1 a1 at bug.hs:7:1 ‘a1’ is a rigid type variable bound by the inferred type of whenMultipleOf ∷ MonadPlus m1 ⇒ t1 → t2 → m1 a1 → m1 a1 at bug.hs:7:1 ‘m1’ is a rigid type variable bound by the inferred type of whenMultipleOf ∷ MonadPlus m1 ⇒ t1 → t2 → m1 a1 → m1 a1 at bug.hs:7:1 ‘t2’ is a rigid type variable bound by the inferred type of whenMultipleOf ∷ MonadPlus m1 ⇒ t1 → t2 → m1 a1 → m1 a1 at bug.hs:7:1 To use the inferred type, enable PartialTypeSignatures In the type signature for ‘whenMultipleOf’: _ bug.hs:7:1: No instance for (MonadPlus m) When checking that ‘whenMultipleOf’ has the specified type whenMultipleOf ∷ ∀ t a (m ∷ * → *) t1. t → t1 → m a → m a Probable cause: the inferred type is ambiguous bug.hs:10:62: Couldn't match type ‘a1’ with ‘t’ ‘a1’ is a rigid type variable bound by the type signature for sumOfMultiples ∷ Integral a1 ⇒ [a1] → a1 → [a1] at bug.hs:9:19ghci-ng: panic! (the 'impossible' happened) (GHC version 7.10.2 for x86_64-unknown-linux): No skolem info: t_a7vV[sk] Please report this as a GHC bug: http://www.haskell.org/ghc/reportabug }}} -- Comment: Could you describe how you invoke GHC? I'm afraid I get no such error when I build your testcase with 7.10.2. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/10764#comment:1 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler