#6114: ghc: panic! occurred with use of isInstance, newName and a type splice
---------------------------------+------------------------------------------
Reporter: davidmiani | Owner:
Type: bug | Status: closed
Priority: normal | Milestone:
Component: Template Haskell | Version: 7.4.1
Resolution: fixed | Keywords:
Os: MacOS X | Architecture: x86_64 (amd64)
Failure: Compile-time crash | Difficulty: Unknown
Testcase: th/T6114 | Blockedby:
Blocking: | Related:
---------------------------------+------------------------------------------
Changes (by simonpj):
* status: new => closed
* difficulty: => Unknown
* resolution: => fixed
* testcase: => th/T6114
Comment:
The error message is this:
{{{
T6114.hs:6:17:
The exact Name `x_a12K' is not in scope
Probable cause: you used a unique Template Haskell name (NameU),
perhaps via newName, but did not bind it
If that's it, then -ddump-splices might be useful
In the argument of reifyInstances: GHC.Classes.Eq x_0
In the expression:
$(do { xName <- newName "x";
instanceType <- [t| $(varT xName) |];
_ <- reifyInstances ''Eq [instanceType];
.... })
In an equation for `instanceVar':
instanceVar
= $(do { xName <- newName "x";
instanceType <- [t| $(varT xName) |];
.... })
}}}
So the crash is fixed, and the error message does point to the culprit.
The difference between "x_a12K" and "x_0" is unhelpful, but it's not
particularly easy to fix. (The "x_0" comes from applying the TH pretty-
printer, which renames uniques, to the input types; the "x_a12K" is what
the renamer sees.)
So I'm going to close this ticket and wait for someone to complain about
it :-)
--
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/6114#comment:3>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler
_______________________________________________
Glasgow-haskell-bugs mailing list
[email protected]
http://www.haskell.org/mailman/listinfo/glasgow-haskell-bugs
