#5959: GHC Panic: nameModule
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Reporter: mightybyte | Owner: pcapriotti
Type: bug | Status: new
Priority: high | Milestone: 7.4.2
Component: Compiler | Version: 7.4.1
Keywords: | Os: Linux
Architecture: x86_64 (amd64) | Failure: Compile-time crash
Difficulty: Unknown | Testcase:
Blockedby: | Blocking:
Related: |
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Comment(by pcapriotti):
The problem here is when we have `Exact` names in what should be an
implicit forall type. After TH splicing, we get
{{{
Lens app b_aIy
}}}
where b_aIy is an Exact name (out of scope). The renamer implicitly
assumes that all exact names are in scope in a type signature, so the type
checker panics.
The error here is actually in the Lens library, since it generates a type
signature with incorrectly qualified type variables, when the record is
existentially qualified. However, GHC should report a "type variable not
in scope" error.
I'm not sure how this can fixed. The local renamer environment doesn't
keep track of exact names, so there's no way it can determine whether a
type variable with an Exact name is in scope or not. Maybe we should add
exact names to the environment? Any other ideas?
--
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/5959#comment:5>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler
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