Bad warning from quoted instance

This quoted instance gives a bogus warning; from #4127 (closed).

$ ghc -XTemplateHaskell
GHCi, version 6.13.20100704: http://www.haskell.org/ghc/  :? for help
Loading package ghc-prim ... linking ... done.
Loading package integer-gmp ... linking ... done.
Loading package base ... linking ... done.
Loading package ffi-1.0 ... linking ... done.
Prelude> :m + Language.Haskell.TH
Prelude Language.Haskell.TH> runQ $ [d| f = undefined; class Foo x where { f :: x -> x }; instance Foo Int where { f = id } |]
Loading package array-0.3.0.0 ... linking ... done.
Loading package containers-0.3.0.0 ... linking ... done.
Loading package pretty-1.0.1.1 ... linking ... done.
Loading package template-haskell ... linking ... done.

<interactive>:1:71:
    Warning: No explicit method nor default method for `f'
    In the instance declaration for `Foo Int'
    In the Template Haskell quotation
      [d| f = undefined
          
          class Foo x where { f :: x -> x; }
          
          instance Foo Int where
              { f = id } |]
    In the second argument of `($)', namely
        `[d| f = undefined
             
             class Foo x where { f :: x -> x; }
             
             instance Foo Int where
                 { f = id } |]'
[ValD (VarP f) (NormalB (VarE GHC.Err.undefined)) [],ClassD [] Foo [PlainTV x_0] [] [SigD f (AppT (AppT ArrowT (VarT x_0)) (VarT x_0))],InstanceD [] (AppT (ConT Foo) (ConT GHC.Types.Int)) [ValD (VarP f) (NormalB (VarE GHC.Base.id)) []]]
Prelude Language.Haskell.TH> 

Trac metadata

Trac field	Value
Version	6.13
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Template Haskell
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