Broken types in identifiers bound by :print
GHCi, version 8.0.1: http://www.haskell.org/ghc/ :? for help
Prelude> :print show
show = (_t1::Show a => a -> String)
Prelude> :t _t1
<interactive>:1:1: error:
No instance for (Show a) arising from a use of ‘it’
Furthermore:
Prelude> _t1 "foo"
<interactive>:3:5: error:ghc: panic! (the 'impossible' happened)
(GHC version 8.0.1 for x86_64-unknown-linux):
No skolem info: a_a1hz
Please report this as a GHC bug: http://www.haskell.org/ghc/reportabug
Prelude>
Enabling -fprint-explicit-foralls
, I think, reveals the issue:
Prelude> :set -fprint-explicit-foralls
Prelude> :print id
id = (_t2::a1 -> a1)
Prelude> :t id
id :: forall {a}. a -> a
Prelude> :t _t2
_t2 :: a1 -> a1
Similar behavior albeit with a different panic message happens on 7.8.4 and 7.10.3 as verified by bennofs over IRC:
GHCi, version 7.10.3: http://www.haskell.org/ghc/ :? for help
Prelude> :print print
print = (_t1::Show a => a -> IO ())
Prelude> _t1
ghc: panic! (the 'impossible' happened)
(GHC version 7.10.3 for x86_64-unknown-linux):
tcTyVarDetails a_apc
Please report this as a GHC bug: http://www.haskell.org/ghc/reportabug
- 6.3 doesn't exhibit this issue:
GHCi, version 7.6.3: http://www.haskell.org/ghc/ :? for help
Prelude> :print id
id = (_t1::forall a. a -> a)
Trac metadata
Trac field | Value |
---|---|
Version | 8.0.1 |
Type | Bug |
TypeOfFailure | OtherFailure |
Priority | normal |
Resolution | Unresolved |
Component | Compiler |
Test case | |
Differential revisions | |
BlockedBy | |
Related | |
Blocking | |
CC | |
Operating system | |
Architecture |