Remove 'do' in 'instance Text ModuleRenaming'

[int-index]

We have this code in Cabal, which I don't believe to be syntactically valid Haskell:

  do fmap ModuleRenaming parseRns
     <++ parseHidingRenaming
     <++ return DefaultRenaming

It works by a fluke. The GHC parser shifts and we parse it as

  do (fmap ModuleRenaming parseRns
     <++ parseHidingRenaming
     <++ return DefaultRenaming)

rather than

  do (fmap ModuleRenaming parseRns)
     (<++ parseHidingRenaming)
     (<++ return DefaultRenaming)

However, this behaviour is hard to support. I'm currently working on a set of changes to the parser that result in no shift in this case -- and then get the latter parse, which results in an error about no LHS for <++.

Furthermore, even in today's GHC such syntax is not fully supported (happens to work for the <++ operator above, but not if the operator is !).

I'd appreciate if we could merge this to both master and the 2.4 branch. (2.4 because that's what the GHC submodule tracks currently).

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[23Skidoo]

Merged, thanks!

[23Skidoo]

Also cherry-picked into 2.4.

[int-index]

Thanks!