#11520: GHC falls into a hole if given incorrect kind signature -------------------------------------+------------------------------------- Reporter: bgamari | Owner: Type: bug | Status: new Priority: normal | Milestone: 8.0.1 Component: Compiler (Type | Version: 8.0.1-rc1 checker) | Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: Type of failure: Incorrect | Unknown/Multiple warning at compile-time | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by simonpj): The trouble here is this: * The kind error is indeed found and reported (i.e. collected in the bag of errors in the monad) * But we continue anyway into `checkValidInstance` * The latter calls `fvProv` to check for something like the size of instance * Which fails because the unsolved constraint has left a hole in the type Really we should not even attempt `checkValidInstance` if we fail to kind- check the type. We could use a `checkNoErrs` in `TcHsTye.TcHsClsInstType`. But there are many other uses of `solveEqualities` all of which in principle have the same concern. So I thought about adding `checkNoErrs` to `solveEqualities`. But there I see {{{ -- | Type-check a thing that emits only equality constraints, then -- solve those constraints. Emits errors -- but does not fail -- -- if there is trouble. solveEqualities :: TcM a -> TcM a }}} '''Richard''': why did you want the "...but does not fail..." bit? What goes wrong if it fais on error? In effect it always used to! -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/11520#comment:4 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler

#11520: GHC falls into a hole if given incorrect kind signature -------------------------------------+------------------------------------- Reporter: bgamari | Owner: Type: bug | Status: new Priority: highest | Milestone: 8.0.1 Component: Compiler (Type | Version: 8.0.1-rc1 checker) | Resolution: | Keywords: TypeInType Operating System: Unknown/Multiple | Architecture: Type of failure: Incorrect | Unknown/Multiple warning at compile-time | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by goldfire): The `but does not fail` bit is just to accurately describe the function. As usual, failing is fine, but it means you get fewer error messages at a go. In other words, we can just change the behavior. But I much favor just fixing `fvProv` to do something other than panic on a coercion hole, like return an empty list. There are a bunch of these panics on coercion holes where I thought coercion holes should never be seen. But I've learned that erroneous code can make GHC take paths I hadn't considered. So I'll remove all of these panics and replace them with something that won't crash GHC. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/11520#comment:6 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler

#11520: GHC falls into a hole if given incorrect kind signature -------------------------------------+------------------------------------- Reporter: bgamari | Owner: Type: bug | Status: new Priority: highest | Milestone: 8.0.1 Component: Compiler (Type | Version: 8.0.1-rc1 checker) | Resolution: | Keywords: TypeInType Operating System: Unknown/Multiple | Architecture: Type of failure: Incorrect | Unknown/Multiple warning at compile-time | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by Simon Peyton Jones ): In [changeset:"b565830dda0994d5d67617039db3310f81e831c8/ghc" b565830d/ghc]: {{{ #!CommitTicketReference repository="ghc" revision="b565830dda0994d5d67617039db3310f81e831c8" Wrap solveEqualities in checkNoErrs This simple change fixes Trac #11563, #11520, #11516, #11399. See esp the comments in #11520. See Note [Fail fast on kind errors] in TcSimplify Merge to 8.0 branch }}} -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/11520#comment:8 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler

#11520: GHC falls into a hole if given incorrect kind signature -------------------------------------+------------------------------------- Reporter: bgamari | Owner: Type: bug | Status: closed Priority: highest | Milestone: 8.0.1 Component: Compiler (Type | Version: 8.0.1-rc1 checker) | Resolution: fixed | Keywords: TypeInType Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: Incorrect | Test Case: warning at compile-time | polykinds/T11520 Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Changes (by bgamari): * status: merge => closed * resolution: => fixed Comment: Merged as d0010d749f80b405f991e88e0e953a21d54a744d -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/11520#comment:10 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler