RecordWildCards undocumented behavior

Summary

https://downloads.haskell.org/ghc/latest/docs/html/users_guide/exts/record_wildcards.html

There are two behaviors of RecordWildCards (RWC) undocumented or documented unclearly.

1. Unclear qualified names

For both pattern and expression wildcards, the “..” expands to the missing in-scope record fields...

The record field f is in scope somehow (either qualified or unqualified).

module M where
  data R = R { a,b,c :: Int }
module X where
  import M( R(R,a,c) )
  f a b = R { .. }

The R{..} expands to R{a=a}

There should be an example of qualified in-scope presence, which I find very useful

module M where
  data R = R{a, b, c :: Int}

module X where
  import M (R (R))
  import M qualified
  f a b = R{..}

The R{..} expands to R{M.a = a, M.b = b}, so you can use fields without messing with getters.

2. RWC interferes with NamedFieldPuns

With NamedFieldPuns (NFP) enabled and RWC disabled:

import M (R (R))
import M qualified
f foo = R{foo} -- use of NFP syntax, not RWC

error:
    Not in scope: ‘foo’
    Perhaps you want to add ‘foo’ to the import list in the import of

With RWC additionally enabled, the same code is compiled successfully!

So, RWC desugars NFP syntax R{foo} to R{M.foo = foo}, which must be documented.

Proposed improvements or changes

I'm not sure about specific wording.

Environment

• GHC version used: 8.10.4