GHC panic: MkExternalCore died: make_lit

[audunska]

Compiling the attached example with -fext-core crashes ghc with the following text:

$ ghc -fext-core min.hs
[1 of 1] Compiling Main             ( min.hs, min.o )
ghc: panic! (the 'impossible' happened)
  (GHC version 7.4.1 for x86_64-unknown-linux):
	MkExternalCore died: make_lit

Replacing the data declaration with a newtype or a library type such as Complex or Ratio gives the same crash. An empty .hcr file is created.

Replacing the "main" action with "return ()" or removing one of the type synonym declarations makes the crash go away.

This is using the ghc package distributed with ubuntu 12.04.

[audunska]

Minimal triggering example

[simonpj]

Fixed by

commit 7b8a17ad3c0792f06ffa991e9e587f5458610a3c
Author: Simon Peyton Jones <simonpj@microsoft.com>
Date:   Sat Sep 15 23:12:23 2012 +0100

    Print literal integers in External Core.

>---------------------------------------------------------------

 compiler/coreSyn/MkExternalCore.lhs |    3 ++-
 1 files changed, 2 insertions(+), 1 deletions(-)

diff --git a/compiler/coreSyn/MkExternalCore.lhs b/compiler/coreSyn/MkExternalCore.lhs
index d05da2a..2103708 100644
--- a/compiler/coreSyn/MkExternalCore.lhs
+++ b/compiler/coreSyn/MkExternalCore.lhs
@@ -229,7 +229,8 @@ make_lit dflags l =
     MachWord64 i -> C.Lint i t
     MachFloat r -> C.Lrational r t
     MachDouble r -> C.Lrational r t
-    _ -> error "MkExternalCore died: make_lit"
+    LitInteger i _ -> C.Lint i t
+    _ -> pprPanic "MkExternalCore died: make_lit" (ppr l)
   where 
     t = make_ty dflags (literalType l)

[simonpj]

Test added.

[igloo]

Merged as 8a767d8be37e6ab437dfcb92bfe543e9f4901c99