[GHC] #15325: GHCi panic in getIdFromTrivialExpr with -fdefer-type-errors

[GHC]

#15325: GHCi panic in getIdFromTrivialExpr with -fdefer-type-errors
-------------------------------------+-------------------------------------
        Reporter:  dramforever       |                Owner:  (none)
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:  8.6.1
       Component:  Compiler          |              Version:  8.4.3
      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 monoidal):

 Confirmed in master, here's a simpler case:

 {{{
 #!hs
 module T15325 where

 class PolyList e where
     polyList :: e -> ()

 f :: PolyList e => e -> ()
 f x = polyList x

 plh :: ()
 plh = f 0
 }}}

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15325#comment:2>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler