DeriveAnyClass fails on multi-parameter type classes
When I say
{-# LANGUAGE DeriveAnyClass, MultiParamTypeClasses #-}
module Bug where
class C a b
data X
deriving (C Int)
and load that into GHCi, I see this:
*Main> :load "/Users/rae/temp/DeriveAny.hs"
[1 of 1] Compiling Bug ( /Users/rae/temp/DeriveAny.hs, interpreted )
Var/Type length mismatch:
[b_a2YW]
[]
Var/Type length mismatch:
[b_a2YW]
[]
Ok, modules loaded: Bug.
*Bug> :info C
class C a b -- Defined at /Users/rae/temp/DeriveAny.hs:5:1
instance C X -- Defined at /Users/rae/temp/DeriveAny.hs:7:13
It seems my Int
parameter to C
is being dropped. I don't believe I have a debug build in this example, so that debugging output is shipping.
Trac metadata
Trac field | Value |
---|---|
Version | 7.10.1-rc1 |
Type | Bug |
TypeOfFailure | OtherFailure |
Priority | normal |
Resolution | Unresolved |
Component | Compiler |
Test case | |
Differential revisions | |
BlockedBy | |
Related | |
Blocking | |
CC | |
Operating system | |
Architecture |