Panic: Template variable unbound in rewrite rule

Installing singletons-1.0 with GHC 7.8.2 on both OS X 10.9.2 and Ubuntu 2014.04 fails:

ghc: panic! (the 'impossible' happened)
  (GHC version 7.8.2 for x86_64-apple-darwin):
        Template variable unbound in rewrite rule

This seems to be an issue with the optimizer, as the bug only appears with optimization level 2, using the following line in ~/.cabal/config:

optimization: 2

See also goldfirere/singletons#83

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Attached file singletons-1.0.log (download).

Build log

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Related	→ #4524 (closed)

Attached file ghc.info (download).

ghc --info

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Operating system	MacOS X → Unknown/Multiple

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mentioned in commit b637585d

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Test case	→ indexed_types/should_fail/T9160

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changed milestone to %7.8.3

closed

Merged into 7.8.3.

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Resolution	Unresolved → ResolvedFixed

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reopened

I'm seeing the same symptoms with 7.8.3:

$ ghc --version
The Glorious Glasgow Haskell Compilation System, version 7.8.3

Only with -O2 set, again.

$ cd singletons-1.0/
$ runghc Setup.hs configure --user -O2
Configuring singletons-1.0...
$ runghc Setup.hs build
...
[39 of 45] Compiling Data.Singletons.Prelude.List ( src/Data/Singletons/Prelude/List.hs, dist/build/Data/Singletons/Prelude/List.o )
ghc: panic! (the 'impossible' happened)
  (GHC version 7.8.3 for x86_64-unknown-linux):
	Template variable unbound in rewrite rule

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Resolution	ResolvedFixed → Unresolved

Attached file singletons-1.0-build.log (download).

Attached file ghc-info.txt (download).

I should also mention that the test cases passes, i.e. fails:

$ ghc T9160.hs
[1 of 1] Compiling T9160            ( T9160.hs, T9160.o )
Loading package ghc-prim ... linking ... done.
Loading package integer-gmp ... linking ... done.
Loading package base ... linking ... done.
Loading package array-0.5.0.0 ... linking ... done.
Loading package deepseq-1.3.0.2 ... linking ... done.
Loading package containers-0.5.5.1 ... linking ... done.
Loading package pretty-1.1.1.1 ... linking ... done.
Loading package template-haskell ... linking ... done.

T9160.hs:18:8:
    Type indexes must match class instance head
    Found ‘* -> *’ but expected ‘*’
    In the type instance declaration for ‘F’
    In the instance declaration for ‘C (a :: *)’

Same thing happens with -O2.

I am also seeing this on ghc 7.10.1, not sure if this is another instance of this bug:

cabal install bitmap [ 3 of 10] Compiling Data.Bitmap.IO ( Data/Bitmap/IO.hs, dist/build/Data/Bitmap/IO.o )

Data/Bitmap/IO.hs:1248:1: Warning:

SPECIALISE pragma for non-overloaded function ‘myPlusPtr’

Data/Bitmap/IO.hs:1249:1: Warning:

SPECIALISE pragma for non-overloaded function ‘myPlusPtr’

ghc: panic! (the 'impossible' happened)

(GHC version 7.10.1 for x86_64-apple-darwin):

Template variable unbound in rewrite rule

$fPixelComponentFloat3_X2Rc [$fPixelComponentFloat3_X2Rc] [$fPixelComponentFloat3_X2Rc] [] []

Please report this as a GHC bug: http://www.haskell.org/ghc/reportabug

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CC	jstolarek, slyfox → george, jstolarek, slyfox

Replying to [ticket:9160#comment:97896 George]:

I am also seeing this on ghc 7.10.1, not sure if this is another instance of this bug:

cabal install bitmap [ 3 of 10] Compiling Data.Bitmap.IO ( Data/Bitmap/IO.hs, dist/build/Data/Bitmap/IO.o )

I've distilled it a bit to a selfcontained test:

-- sf 9160 # cat B.hs 
{-# LANGUAGE NoImplicitPrelude #-}
{-# OPTIONS_GHC -O2 #-}
module B (bug) where

data D = D
data E = E

class Storable a where
    poke2 :: a -> E
instance Storable D where
    poke2 = poke2 -- undefined

class Foo a where
instance Foo D where

class (Foo t, Storable t) => FooStorable t where

instance FooStorable D where
    {-# SPECIALIZE instance FooStorable D #-}

{-# SPECIALIZE bug :: D -> E #-}

bug
  :: FooStorable t
  => t
  -> E
bug = poke2
{-
sf 9160 # ghc -c -fforce-recomp -Wall B.hs 

B.hs:5:10: Warning: Defined but not used: data constructor ‘D’

B.hs:6:10: Warning: Defined but not used: data constructor ‘E’
ghc: panic! (the 'impossible' happened)
  (GHC version 7.10.1 for x86_64-unknown-linux):
        Template variable unbound in rewrite rule
  $fFooStorableD_XU
  [$fFooStorableD_XU]
  [$fFooStorableD_XU]
  []
  []

Please report this as a GHC bug:  http://www.haskell.org/ghc/reportabug
-}

mentioned in issue #10251 (closed)

Good report, but ticket:9160#comment:97918 and #9160 (closed) are definitely a different bug to #9160 (closed). I've opened #10251 (closed).

Simon

Should we re-close this ticket then?

closed

Well, ticket:9160#comment:89989 claims that GHC 7.8.3 couldn't compile singletons. However I've confirmed that HEAD can compile singletons-1.1, so yes, I'll close this.

Simon

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Resolution	Unresolved → ResolvedFixed

mentioned in issue #12212 (closed)

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