#15270: TH doesn't verify name types during conversion -------------------------------------+------------------------------------- Reporter: bgamari | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: 8.6.1 Component: Template Haskell | Version: 8.4.3 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by RyanGlScott): Actually, I think your hypothesis wasn't too far off, bgamari. Here's a minimal example which triggers the panic: {{{#!hs {-# LANGUAGE TemplateHaskell #-} module Bug where import Language.Haskell.TH.Lib import Language.Haskell.TH.Syntax main :: IO () main = print $(conE (mkNameG_v "ghc-prim" "GHC.Types" "True")) }}} {{{ $ ghc/inplace/bin/ghc-stage2 Bug2.hs [1 of 1] Compiling Bug ( Bug2.hs, Bug2.o ) ghc-stage2: panic! (the 'impossible' happened) (GHC version 8.5.20180616 for x86_64-unknown-linux): ASSERT failed! True Call stack: CallStack (from HasCallStack): callStackDoc, called at compiler/utils/Outputable.hs:1164:37 in ghc:Outputable pprPanic, called at compiler/utils/Outputable.hs:1223:5 in ghc:Outputable assertPprPanic, called at compiler/typecheck/TcHsSyn.hs:655:67 in ghc:TcHsSyn }}} It turns out that I was using `conE (mkNameG_v "ghc-prim" "GHC.Types" "True")` in `deriving-compat`. Oops! -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/15270#comment:4 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler