Proposal: Add IsString instance for (Maybe a) to base

[Simon Hengel]

Hi,
what about adding

    instance IsString a => IsString (Maybe a) where
      fromString = Just . fromString

It makes specifying optional String/Text/... values more convenient.
Here is an example that uses System.Process.shell:

Use

    shell "ls -l" { cwd = "/home/me" }

instead of

    shell "ls -l" { cwd = Just "/home/me" }

I'm not yet sure how essential it is.  But I somehow can't see any
issues with it.  So why not?

Cheers,
Simon