#14038: TypeApplications regression in GHC HEAD: ‘p0’ is untouchable inside the constraints: () -------------------------------------+------------------------------------- Reporter: RyanGlScott | Owner: (none) Type: bug | Status: new Priority: high | Milestone: 8.4.1 Component: Compiler (Type | Version: 8.3 checker) | Keywords: Resolution: | TypeApplications Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: Blocked By: 14119 | Blocking: Related Tickets: #13877 | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by simonpj): comment:6 says:
The problem is that the App instance for (:~>) gets type-checked with a coercion in its patterns
Can you boil this out into a simple case? I'm lost.
Have TcHsType proceed normally, but rip the coercions out after-the- fact.
That's what happens in Rules. See `DsBinds.decomposeRuleLhs`. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/14038#comment:12 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler