Standalone deriving of an unsupported class panics GHC
Using standalone deriving on a non-standard class, without GeneralizedNewtypeDeriving, causes GHC to panic. Here is an example:
{-# LANGUAGE StandaloneDeriving #-}
class C a
instance C Int
newtype T = T Int
deriving instance C T
Output:
ghc: panic! (the 'impossible' happened)
(GHC version 6.12.1 for x86_64-unknown-linux):
genDerivBinds: bad derived class main:Main.C{tc rdh}
Trac metadata
Trac field | Value |
---|---|
Version | 6.12.1 |
Type | Bug |
TypeOfFailure | OtherFailure |
Priority | normal |
Resolution | Unresolved |
Component | Compiler |
Test case | |
Differential revisions | |
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Blocking | |
CC | |
Operating system | |
Architecture |