#9426: ghci triggers 'ASSERT failed! file compiler/ghci/Linker.lhs, line 906' -------------------------------------+------------------------------------- Reporter: slyfox | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.8.2 Resolution: | Keywords: Operating System: | Architecture: Unknown/Multiple Unknown/Multiple | Difficulty: Unknown Type of failure: | Blocked By: None/Unknown | Related Tickets: Test Case: | Blocking: | Differential Revisions: | -------------------------------------+------------------------------------- Comment (by slyfox): Suspicious observation: As in original test case {{{!#hs instance {-# OVERLAPS #-} (HTrue ~ b) => TypeEq x x b instance {-# OVERLAPS #-} (HTrue ~ b) => TypeEq x x b instance {-# OVERLAPS #-} (HFalse ~ b) => TypeEq x y b }}} leads to error {{{ *** Exception: ASSERT failed! file compiler/ghci/Linker.lhs, line 912 }}} (the name failing invariant is '$fTypeEqxxb') If we slightly change free variables: {{{!#hs instance {-# OVERLAPS #-} (HTrue ~ b) => TypeEq x x b instance {-# OVERLAPS #-} (HTrue ~ b) => TypeEq y y b -- changed 'x' to 'y' instance {-# OVERLAPS #-} (HFalse ~ b) => TypeEq x y b }}} there is no assert anymore: {{{ Prelude> :script z.script WARNING: file compiler/simplCore/SimplEnv.lhs, line 539 $fTypeEqyyb WARNING: file compiler/simplCore/SimplEnv.lhs, line 539 $fTypeEqxyb WARNING: file compiler/simplCore/SimplEnv.lhs, line 539 $fTypeEqyyb WARNING: file compiler/simplCore/SimplEnv.lhs, line 539 $fTypeEqxyb }}} Looks like some generated names are not unique emough. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/9426#comment:1 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler