TTG: TH brackets finishing touches

Rewrite the critical notes and fix outdated ones,

use `HsQuote GhcRn` (in `HsBracketTc`) for desugaring regardless of the
bracket being typed or untyped,

remove unused `EpAnn` from `Hs*Bracket GhcRn`,

zonkExpr factor out common brackets code,

ppr_expr factor out common brackets code,

and fix tests,

to finish MR https://gitlab.haskell.org/ghc/ghc/-/merge_requests/4782.

-------------------------
Metric Decrease:
    hard_hole_fits
-------------------------

1 files changed, 20 insertions, 28 deletions

diff --git a/compiler/GHC/Tc/Utils/Zonk.hs b/compiler/GHC/Tc/Utils/Zonk.hs
index 45e6ec9a02..b0af88d813 100644
--- a/compiler/GHC/Tc/Utils/Zonk.hs
+++ b/compiler/GHC/Tc/Utils/Zonk.hs
@@ -778,34 +778,11 @@ zonkExpr env (HsAppType ty e t)
        return (HsAppType new_ty new_e t)
        -- NB: the type is an HsType; can't zonk that!
 
--- romes TODO: refactor common
-zonkExpr env (HsTypedBracket (HsBracketTc hsb_thing ty wrap bs) body)
-  = do wrap' <- traverse zonkQuoteWrap wrap
-       bs' <- mapM (zonk_b env) bs
-       new_ty <- zonkTcTypeToTypeX env ty
-       return (HsTypedBracket (HsBracketTc hsb_thing new_ty wrap' bs') body)
-  where
-    zonkQuoteWrap (QuoteWrapper ev ty) = do
-        let ev' = zonkIdOcc env ev
-        ty' <- zonkTcTypeToTypeX env ty
-        return (QuoteWrapper ev' ty')
-
-    zonk_b env' (PendingTcSplice n e) = do e' <- zonkLExpr env' e
-                                           return (PendingTcSplice n e')
-
-zonkExpr env (HsUntypedBracket (HsBracketTc hsb_thing ty wrap bs) body)
-  = do wrap' <- traverse zonkQuoteWrap wrap
-       bs' <- mapM (zonk_b env) bs
-       new_ty <- zonkTcTypeToTypeX env ty
-       return (HsUntypedBracket (HsBracketTc hsb_thing new_ty wrap' bs') body)
-  where
-    zonkQuoteWrap (QuoteWrapper ev ty) = do
-        let ev' = zonkIdOcc env ev
-        ty' <- zonkTcTypeToTypeX env ty
-        return (QuoteWrapper ev' ty')
+zonkExpr env (HsTypedBracket hsb_tc body)
+  = (\x -> HsTypedBracket x body) <$> zonkBracket env hsb_tc
 
-    zonk_b env' (PendingTcSplice n e) = do e' <- zonkLExpr env' e
-                                           return (PendingTcSplice n e')
+zonkExpr env (HsUntypedBracket hsb_tc body)
+  = (\x -> HsUntypedBracket x body) <$> zonkBracket env hsb_tc
 
 zonkExpr env (HsSpliceE _ (XSplice (HsSplicedT s))) =
   runTopSplice s >>= zonkExpr env
@@ -1102,6 +1079,22 @@ zonkOverLit env lit@(OverLit {ol_ext = x@OverLitTc { ol_witness = e, ol_type = t
                                    , ol_type = ty' } }) }
 
 -------------------------------------------------------------------------
+zonkBracket :: ZonkEnv -> HsBracketTc -> TcM HsBracketTc
+zonkBracket env (HsBracketTc hsb_thing ty wrap bs)
+  = do wrap' <- traverse zonkQuoteWrap wrap
+       bs' <- mapM (zonk_b env) bs
+       new_ty <- zonkTcTypeToTypeX env ty
+       return (HsBracketTc hsb_thing new_ty wrap' bs')
+  where
+    zonkQuoteWrap (QuoteWrapper ev ty) = do
+        let ev' = zonkIdOcc env ev
+        ty' <- zonkTcTypeToTypeX env ty
+        return (QuoteWrapper ev' ty')
+
+    zonk_b env' (PendingTcSplice n e) = do e' <- zonkLExpr env' e
+                                           return (PendingTcSplice n e')
+
+-------------------------------------------------------------------------
 zonkArithSeq :: ZonkEnv -> ArithSeqInfo GhcTc -> TcM (ArithSeqInfo GhcTc)
 
 zonkArithSeq env (From e)
@@ -1124,7 +1117,6 @@ zonkArithSeq env (FromThenTo e1 e2 e3)
        new_e3 <- zonkLExpr env e3
        return (FromThenTo new_e1 new_e2 new_e3)
 
-
 -------------------------------------------------------------------------
 zonkStmts :: Anno (StmtLR GhcTc GhcTc (LocatedA (body GhcTc))) ~ SrcSpanAnnA
           => ZonkEnv