Introduce `hsExprType :: HsExpr GhcTc -> Type` in the new modulewip/hsExprType

`GHC.Hs.Syn.Type`

The existing `hsPatType`, `hsLPatType` and `hsLitType` functions have also been
moved to this module

This is a less ambitious take on the same problem that !2182 and !3866
attempt to solve. Rather than have the `hsExprType` function attempt to
efficiently compute the `Type` of every subexpression in an `HsExpr`, this
simply computes the overall `Type` of a single `HsExpr`.

- Explicitly forbids the `SplicePat` `HsIPVar`, `HsBracket`, `HsRnBracketOut`
  and `HsTcBracketOut` constructors during the typechecking phase by using
  `Void` as the TTG extension field
- Also introduces `dataConCantHappen` as a domain specific alternative to `absurd`
  to handle cases where the TTG extension points forbid a constructor.
- Turns HIE file generation into a pure function that doesn't need access to the
  `DsM` monad to compute types, but uses `hsExprType` instead.
- Computes a few more types during HIE file generation
- Makes GHCi's `:set +c` command also use `hsExprType` instead of going through
  the desugarer to compute types.

Updates haddock submodule

Co-authored-by: Zubin Duggal <zubin.duggal@gmail.com>

1 files changed, 6 insertions, 5 deletions

diff --git a/compiler/GHC/Tc/Gen/Splice.hs b/compiler/GHC/Tc/Gen/Splice.hs
index 056855469d..72fc259e83 100644
--- a/compiler/GHC/Tc/Gen/Splice.hs
+++ b/compiler/GHC/Tc/Gen/Splice.hs
@@ -210,12 +210,13 @@ tcTypedBracket rn_expr brack@(TExpBr _ expr) res_ty
        ; let rep = getRuntimeRep expr_ty
        ; meta_ty <- tcTExpTy m_var expr_ty
        ; ps' <- readMutVar ps_ref
-       ; texpco <- tcLookupId unsafeCodeCoerceName
+       ; codeco <- tcLookupId unsafeCodeCoerceName
+       ; bracket_ty <- mkAppTy m_var <$> tcMetaTy expTyConName
        ; tcWrapResultO (Shouldn'tHappenOrigin "TExpBr")
                        rn_expr
                        (unLoc (mkHsApp (mkLHsWrap (applyQuoteWrapper wrapper)
-                                                  (nlHsTyApp texpco [rep, expr_ty]))
-                                      (noLocA (HsTcBracketOut noExtField (Just wrapper) brack ps'))))
+                                                  (nlHsTyApp codeco [rep, expr_ty]))
+                                      (noLocA (HsTcBracketOut bracket_ty (Just wrapper) brack ps'))))
                        meta_ty res_ty }
 tcTypedBracket _ other_brack _
   = pprPanic "tcTypedBracket" (ppr other_brack)
@@ -244,7 +245,7 @@ tcUntypedBracket rn_expr brack ps res_ty
        -- Unify the overall type of the bracket with the expected result
        -- type
        ; tcWrapResultO BracketOrigin rn_expr
-            (HsTcBracketOut noExtField brack_info brack ps')
+            (HsTcBracketOut expected_type brack_info brack ps')
             expected_type res_ty
 
        }
@@ -690,7 +691,7 @@ runTopSplice (DelayedSplice lcl_env orig_expr res_ty q_expr)
        ; mod_finalizers <- readTcRef modfinalizers_ref
        ; addModFinalizersWithLclEnv $ ThModFinalizers mod_finalizers
        -- We use orig_expr here and not q_expr when tracing as a call to
-       -- unsafeTExpCoerce is added to the original expression by the
+       -- unsafeCodeCoerce is added to the original expression by the
        -- typechecker when typed quotes are type checked.
        ; traceSplice (SpliceInfo { spliceDescription = "expression"
                                  , spliceIsDecl      = False