INLINEing top-level patterns causes ghc to emit 'arity missing' traces

When an INLINE pragma is specified on a pattern, ghc-7.6.1 shows some internal trace messages.

module Foo where

{-# INLINE widths #-}

widths :: [Int]
widthMonth, widthYear :: Int

widths@[widthMonth, widthYear] = [1,2]

~/Downloads$ ghc --version
The Glorious Glasgow Haskell Compilation System, version 7.6.1
~/Downloads$ ghc Foo.hs -O
[1 of 1] Compiling Foo              ( Foo.hs, Foo.o )
makeCorePair: arity missing widths{v aeJ} [lid]

I'm not certain that specifying an INLINE pragma in this context even makes sense, in which case perhaps a more useful warning could be produced.

Trac metadata

Trac field	Value
Version	7.6.1
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Compiler
Test case
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CC	jwlato@gmail.com
Operating system
Architecture