Possible type inference regression: "Expected a type, but 'a' has kind 'k0'"

The following program causes GHC HEAD to give an error:

{-# LANGUAGE ScopedTypeVariables #-}
module Foo where

foo (_ :: p a) = [] :: [a]

[1 of 1] Compiling Foo              ( kind.hs, kind.o )

kind.hs:4:25: error:
    • Expected a type, but ‘a’ has kind ‘k0’
    • In an expression type signature: [a]
      In the expression: [] :: [a]
      In an equation for ‘foo’: foo (_ :: p a) = [] :: [a]

GHC 7.10.1 compiles it fine, and infers the type foo :: p a -> [a].

Trac metadata

Trac field	Value
Version	8.1
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Compiler (Type checker)
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