#7194: Typechecker allows a skolem to escapt
---+
Reporter: simonpj | Owner:
Type: bug | Status: closed
Priority: normal| Milestone:
Component: Compiler |Version: 7.4.2
Resolution: fixed | Keywords:
Os: Unknown/Multiple | Architecture: Unknown/Multiple
Failure: None/Unknown | Difficulty: Unknown
Testcase:| Blockedby:
Blocking:|Related:
---+
Changes (by igloo):
* status: new = closed
* resolution: = fixed
Comment:
This now gives a type error:
{{{
T7194.hs:18:35:
Couldn't match expected type `b0' with actual type `F a'
because type variable `a' would escape its scope
This (rigid, skolem) type variable is bound by
the type signature for g :: C (F a) = a - Int
at T7194.hs:17:23-41
Relevant bindings include
x :: b0 (bound at T7194.hs:17:9)
g :: a - Int (bound at T7194.hs:18:18)
y :: a (bound at T7194.hs:18:20)
In the return type of a call of `foo'
In the expression: foo y
In the first argument of `length', namely `[x, foo y]'
}}}
--
Ticket URL: http://hackage.haskell.org/trac/ghc/ticket/7194#comment:1
GHC http://www.haskell.org/ghc/
The Glasgow Haskell Compiler
___
Glasgow-haskell-bugs mailing list
Glasgow-haskell-bugs@haskell.org
http://www.haskell.org/mailman/listinfo/glasgow-haskell-bugs
