Hiding import behaviour

[Malcolm Gooding]

With the prelude changes that people have been discussing recently
I've been wondering is there any reason why importing an identifier
explicitly and unqualified doesn't automatically hide any implicit
imports of the same identifier? Specifically I'm wondering about cases
where you've imported an identifier explicitly from only one module,
like this:

module Foo (x, ...) where { ... }
module Bar (x, ...) where { ... }

import Bar
import Foo (x)

Even if you needed a pragma to enable it I can't think of any sensible
reason why that shouldn't be equivalent to:

import Bar hiding (x)
import Foo (x)

I don't know much of GHC's internals, but it seems like a pretty
minimal change. Typing rules remain the same; explicit imports just
shadow implicits. So importing multiple identifiers both implicitly or
both explicitly would remain ambiguous.