Injective type family syntax accepted without TypeFamilyDependencies

This program compiles fine although it names the result type variable, which is a piece of syntax that should only be available with TypeFamilyDependencies (injective type families):

{-# LANGUAGE TypeFamilies #-}

module Foo where

type family F a = r where
    F a = a

If I say:

type family F a = r | r -> a where
    F a = a

only then the definition is rejected.

Trac metadata

Trac field	Value
Version	8.0.1
Type	Bug
TypeOfFailure	OtherFailure
Priority	low
Resolution	Unresolved
Component	Compiler (Parser)
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