#16376: GHCi HEAD silently accepts ill-kinded visible type applications with :type -------------------------------------+------------------------------------- Reporter: RyanGlScott | Owner: (none) Type: bug | Status: new Priority: highest | Milestone: Component: GHCi | Version: 8.9 Resolution: | Keywords: 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 RyanGlScott): Combining this with `-fdefer-type-errors` leads to a panic: {{{ GHCi, version 8.9.20190227: https://www.haskell.org/ghc/ :? for help Loaded GHCi configuration from /home/rgscott/.ghci λ> :set -XTypeApplications -fdefer-type-errors λ> f = id @Maybe <interactive>:2:9: warning: [-Wdeferred-type-errors] • Expecting one more argument to ‘Maybe’ Expected a type, but ‘Maybe’ has kind ‘* -> *’ • In the type ‘Maybe’ In the expression: id @Maybe In an equation for ‘f’: f = id @Maybe ghc-stage2: panic! (the 'impossible' happened) (GHC version 8.9.20190227 for x86_64-unknown-linux): nameModule internal f_a1BS Call stack: CallStack (from HasCallStack): callStackDoc, called at compiler/utils/Outputable.hs:1159:37 in ghc:Outputable pprPanic, called at compiler/basicTypes/Name.hs:249:3 in ghc:Name }}} -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/16376#comment:3 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler