GHC in -haddock mode can't handle docstrings on unnamed constructor fields

Summary

GHC is broken in various ways on declarations like this:

data Foo
  = -- | Bar
    Bar
      -- | Field 1
      Int

Steps to reproduce

Exhibit A, parse error on a valid docstring

data Foo
  = -- | Bar
    Bar
      -- | Field 1
      Int

$ ghc -haddock /tmp/x.hs
[1 of 1] Compiling Foo              ( /tmp/x.hs, /tmp/x.o )

/tmp/x.hs:7:7: error: parse error on input ‘Int’
  |
7 |       Int
  |       ^^^

Exhibit B, docstring missing from parse tree

data Foo
  = -- | Bar
    Bar
      Int -- ^ Field 1

ghc -haddock /tmp/x.hs -fforce-recomp -ddump-parsed
[1 of 1] Compiling Foo              ( /tmp/x.hs, /tmp/x.o )

==================== Parser ====================
module Foo where
data Foo = " Bar" Bar Int

Expected behavior

Case (A) should parse successfully. Case (B) should retain the docstring for the field in the parse tree.

Environment

• GHC version used: HEAD as of Oct 30 (commit 01ef3e1f)