#7354: Panic with recursion-schemes package and unit
-------------------------------+--------------------------------------------
Reporter: amplitwist | Owner:
Type: bug | Status: new
Priority: normal | Milestone:
Component: GHCi | Version: 7.6.1
Keywords: | Os: Linux
Architecture: x86_64 (amd64) | Failure: GHCi crash
Difficulty: Unknown | Testcase:
Blockedby: | Blocking:
Related: |
-------------------------------+--------------------------------------------
Changes (by simonpj):
* difficulty: => Unknown
Old description:
> Steps to reproduce:
>
> 1. Install GHC 7.6.1 and recursion-schemes
> ([http://hackage.haskell.org/package/recursion-schemes])
> 2. Create a new .hs file with the following
> --------------
> import Data.Functor.Foldable
>
> foo = embed ()
> --------------
> 3. Load the file into GHCI
> 4. Evaluate foo
>
> *Main> foo
>
> <interactive>:162:1:
> Can't find interface-file declaration for variable foo
> Probable cause: bug in .hi-boot file, or inconsistent .hi file
> Use -ddump-if-trace to get an idea of which file caused the error
> In the expression: foo
> In an equation for `it': it = foo
> *Main> :t foo
>
> <interactive>:1:1:
> Can't find interface-file declaration for variable foo
> Probable cause: bug in .hi-boot file, or inconsistent .hi file
> Use -ddump-if-trace to get an idea of which file caused the error
> In the expression: foo
>
> 5. Evaluate ``embed ()'' directly at the REPL
> *Main> embed ()
> ghc: panic! (the 'impossible' happened)
> (GHC version 7.6.1 for x86_64-unknown-linux):
> nameModule
> <<details unavailable>>
>
> Please report this as a GHC bug: http://www.haskell.org/ghc/reportabug
> --------------
>
> System Information:
>
> [andy@vanir ~]$ uname -a
> Linux vanir 3.5.6-1-ARCH #1 SMP PREEMPT Sun Oct 7 19:30:49 CEST 2012
> x86_64 GNU/Linux
> [andy@vanir ~]$ ls asdf.hi # the would-be .hi file
> ls: cannot access asdf.hi: No such file or directory
New description:
Steps to reproduce:
1. Install GHC 7.6.1 and recursion-schemes
([http://hackage.haskell.org/package/recursion-schemes])
2. Create a new .hs file with the following
{{{
import Data.Functor.Foldable
foo = embed ()
}}}
3. Load the file into GHCI
4. Evaluate foo
{{{
*Main> foo
<interactive>:162:1:
Can't find interface-file declaration for variable foo
Probable cause: bug in .hi-boot file, or inconsistent .hi file
Use -ddump-if-trace to get an idea of which file caused the error
In the expression: foo
In an equation for `it': it = foo
*Main> :t foo
<interactive>:1:1:
Can't find interface-file declaration for variable foo
Probable cause: bug in .hi-boot file, or inconsistent .hi file
Use -ddump-if-trace to get an idea of which file caused the error
In the expression: foo
}}}
5. Evaluate `embed ()' directly at the REPL
{{{
*Main> embed ()
ghc: panic! (the 'impossible' happened)
(GHC version 7.6.1 for x86_64-unknown-linux):
nameModule
<<details unavailable>>
}}}
System Information:
{{{
[andy@vanir ~]$ uname -a
Linux vanir 3.5.6-1-ARCH #1 SMP PREEMPT Sun Oct 7 19:30:49 CEST 2012
x86_64 GNU/Linux
[andy@vanir ~]$ ls asdf.hi # the would-be .hi file
ls: cannot access asdf.hi: No such file or directory
}}}
--
Comment:
Right. I can reproduce this failure with 7.6.1. Happily HEAD says:
{{{
$ ~/5builds/HEAD/inplace/bin/ghc-stage2 --interactive T7354.hs
GHCi, version 7.7: http://www.haskell.org/ghc/ :? for help
Loading package ghc-prim ... linking ... done.
Loading package integer-gmp ... linking ... done.
Loading package base ... linking ... done.
[1 of 1] Compiling T7354 ( T7354.hs, interpreted )
Ok, modules loaded: T7354.
*T7354> ana alg
<interactive>:2:5:
Occurs check: cannot construct the infinite type:
a ~ Base t (Prim [a] a)
Expected type: Prim [a] a -> Base t (Prim [a] a)
Actual type: Prim [a] a -> a
Relevant bindings include
it :: Prim [a] a -> t (bound at <interactive>:2:1)
In the first argument of `ana', namely `alg'
In the expression: ana alg
In an equation for `it': it = ana alg
}}}
which looks right.
Next is to try `recursion-schemes` with HEAD.
--
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/7354#comment:3>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler
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