#13775: Type family expansion is too lazy, allows accepting of ill-typed terms -------------------------------------+------------------------------------- Reporter: fizruk | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler (Type | Version: 8.0.2 checker) | Keywords: Resolution: | CustomTypeErrors Operating System: Unknown/Multiple | Architecture: Type of failure: GHC accepts | Unknown/Multiple invalid program | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by fizruk): By the way, if you mistype `Proxy` as `Prox`, you can also get GHC panic: {{{
Prox @ (Head '[]) ghc: panic! (the 'impossible' happened) (GHC version 8.0.2 for x86_64-apple-darwin): initTc: unsolved constraints WC {wc_insol = [W] Prox_a1L4 :: t_a1L3[tau:1] (CHoleCan: Prox) [W] Prox_a1Ls :: t_a1Lr[tau:1] (CHoleCan: Prox)}
Please report this as a GHC bug: http://www.haskell.org/ghc/reportabug }}} But this panic seems to be because of `TypeApplications` and can be reproduced with just two lines in GHCi: {{{
:set -XTypeApplications X @ Int ghc: panic! (the 'impossible' happened) (GHC version 8.0.2 for x86_64-apple-darwin): initTc: unsolved constraints WC {wc_insol = [W] X_a13x :: t_a13w[tau:1] (CHoleCan: X) [W] X_a13V :: t_a13U[tau:1] (CHoleCan: X)}
Please report this as a GHC bug: http://www.haskell.org/ghc/reportabug }}} Should I file this one separately? -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/13775#comment:2 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler