Wingman inserts layout-breaking spaces when case-splitting in do block

[isovector]

as reported by @jhrcek:

data Thing = A | B | C

getThing :: IO Thing
getThing = pure A

f :: Int -> IO ()
f i = do
    thing <- getThing
    _

this case splits to

f :: Int -> IO ()
f i = do
    thing <- getThing
     (case thing of
       A -> _
       B -> _
       C -> _
    )

but notice the leading space. In expressions it doesn't matter, but here YIKES.

Seems related to alanz/ghc-exactprint#91, except that we aren't calling addAnnotationsForPretty anymore. Maybe generated splices just need a setPrecedingLine (-1) 0 to get rid of this leading column?

[isovector]

Also this makes it clear I need a better notion than "is top hole" to determine if parentheses are necessary.

[isovector]

Aha! This is the culprit!

haskell-language-server/ghcide/src/Development/IDE/GHC/ExactPrint.hs

Line 402 in 4bcd0c6

let anns' = setPrecedingLines expr' 0 1 anns