Code action: extract expression as where-clause

[Anrock]

Given:

foo x = fmap >(bar . baz . quux)< x

where > and < denotes a selection
running a "extract expression as where clause" code action should produce

foo x = fmap ? x
   where ? = bar . baz . quux

where ? is a placeholder for extracted expression name.

[alanz]

I was thinking exactly the same recently.