[GHC] #14884: Type holes cause assertion failure in ghc-stage2 compiler during type checking
#14884: Type holes cause assertion failure in ghc-stage2 compiler during type checking -------------------------------------+------------------------------------- Reporter: sighingnow | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: (Type checker) | Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: Compile-time Unknown/Multiple | crash or panic Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- ghc-stage2 panic! due to assertion failure when compiling the following code with `ghc-stage2 Bug.hs` {{{#!hs module Bug where x :: IO () x = _ print "abc" }}} Callstack: {{{ λ inplace\bin\ghc-stage2 Bug.hs [1 of 1] Compiling Bug ( Bug.hs, Bug.o ) ghc-stage2: panic! (the 'impossible' happened) (GHC version 8.5.20180225 for x86_64-unknown-mingw32): ASSERT failed! t_a4ec[tau:2] 2 1 Call stack: CallStack (from HasCallStack): callStackDoc, called at compiler\utils\Outputable.hs:1150:37 in ghc:Outputable pprPanic, called at compiler\utils\Outputable.hs:1206:5 in ghc:Outputable assertPprPanic, called at compiler\\typecheck\\TcType.hs:1187:83 in ghc:TcType CallStack (from -prof): TcInteract.solve_loop (compiler\typecheck\TcInteract.hs:(247,9)-(254,44)) TcInteract.solveSimples (compiler\typecheck\TcInteract.hs:(241,5)-(243,21)) TcRnDriver.simplifyTop (compiler\typecheck\TcRnDriver.hs:408:25-39) TcRnDriver.tcRnSrcDecls (compiler\typecheck\TcRnDriver.hs:254:25-65) }}} The failed assertion is `checkTcLevelInvariant ctxt_tclvl tv_tclvl` in `isTouchableMetaTyVar`: {{{#!hs isTouchableMetaTyVar :: TcLevel -> TcTyVar -> Bool isTouchableMetaTyVar ctxt_tclvl tv | isTyVar tv -- See Note [Coercion variables in free variable lists] = ASSERT2( tcIsTcTyVar tv, ppr tv ) case tcTyVarDetails tv of MetaTv { mtv_tclvl = tv_tclvl } -> ASSERT2( checkTcLevelInvariant ctxt_tclvl tv_tclvl, ppr tv $$ ppr tv_tclvl $$ ppr ctxt_tclvl ) tv_tclvl `sameDepthAs` ctxt_tclvl _ -> False | otherwise = False }}} Notice that the ghc-stage1 compiler doesn't panic and report the type hole correctly. This seems a regression and I have checked that ghc-8.2.2 also works well. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/14884 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler
#14884: Type holes cause assertion failure in ghc-stage2 compiler during type checking -------------------------------------+------------------------------------- Reporter: sighingnow | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler (Type | Version: checker) | Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: Type of failure: Compile-time | Unknown/Multiple crash or panic | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by simonpj): I've seen this before. It arises during error reporting, when the (now quite elaborate) `TcErrors.validSubstitutions` code invokes the constraint solver. To avoid the assertion error we need to set the level correctly, and we aren't doing that yet. It's unsatisfactory, but I think harmless. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/14884#comment:1 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler
#14884: Type holes cause assertion failure in ghc-stage2 compiler during type checking -------------------------------------+------------------------------------- Reporter: sighingnow | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler (Type | Version: checker) | Resolution: | Keywords: TypedHoles Operating System: Unknown/Multiple | Architecture: Type of failure: Compile-time | Unknown/Multiple crash or panic | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Changes (by simonpj): * keywords: => TypedHoles -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/14884#comment:2 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler
#14884: Type holes cause assertion failure in ghc-stage2 compiler during type checking -------------------------------------+------------------------------------- Reporter: sighingnow | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler (Type | Version: checker) | Resolution: | Keywords: TypedHoles Operating System: Unknown/Multiple | Architecture: Type of failure: Compile-time | Unknown/Multiple crash or panic | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by goldfire): My untested hunch is that my recent fix for #14066 fixed this on the way. Will test in a bit. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/14884#comment:3 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler
#14884: Type holes cause assertion failure in ghc-stage2 compiler during type checking -------------------------------------+------------------------------------- Reporter: sighingnow | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler (Type | Version: checker) | Resolution: | Keywords: TypedHoles Operating System: Unknown/Multiple | Architecture: Type of failure: Compile-time | Unknown/Multiple crash or panic | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by simonpj): I somewhat doubt it.. the calls to the constraint solver from `TcErrors.validSubstitutions` are wonky. I discussed this with Mathias, and he is on the case. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/14884#comment:4 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler
#14884: Type holes cause assertion failure in ghc-stage2 compiler during type
checking
-------------------------------------+-------------------------------------
Reporter: sighingnow | Owner: (none)
Type: bug | Status: new
Priority: normal | Milestone:
Component: Compiler (Type | Version:
checker) |
Resolution: | Keywords: TypedHoles
Operating System: Unknown/Multiple | Architecture:
Type of failure: Compile-time | Unknown/Multiple
crash or panic | Test Case:
Blocked By: | Blocking:
Related Tickets: | Differential Rev(s):
Wiki Page: |
-------------------------------------+-------------------------------------
Comment (by Richard Eisenberg
#14884: Type holes cause assertion failure in ghc-stage2 compiler during type checking -------------------------------------+------------------------------------- Reporter: sighingnow | Owner: (none) Type: bug | Status: closed Priority: normal | Milestone: Component: Compiler (Type | Version: checker) | Resolution: fixed | Keywords: TypedHoles Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: Compile-time | Test Case: crash or panic | typecheck/should_fail/T14884 Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Changes (by goldfire): * testcase: => typecheck/should_fail/T14884 * status: new => closed * resolution: => fixed Comment: Yes, they were wonky. I fixed them, as they caused failures in my work on #14066. Sorry to waste Matthias's time! -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/14884#comment:6 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler
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