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>

5 files changed, 13 insertions, 15 deletions

diff --git a/compiler/GHC/HsToCore/Arrows.hs b/compiler/GHC/HsToCore/Arrows.hs
index cad3e82154..4a31b9fc8d 100644
--- a/compiler/GHC/HsToCore/Arrows.hs
+++ b/compiler/GHC/HsToCore/Arrows.hs
@@ -20,7 +20,7 @@ import GHC.HsToCore.Utils
 import GHC.HsToCore.Monad
 
 import GHC.Hs
-import GHC.Tc.Utils.Zonk
+import GHC.Hs.Syn.Type
 
 -- NB: The desugarer, which straddles the source and Core worlds, sometimes
 --     needs to see source types (newtypes etc), and sometimes not
diff --git a/compiler/GHC/HsToCore/Expr.hs b/compiler/GHC/HsToCore/Expr.hs
index bd84e21ace..602950bf3e 100644
--- a/compiler/GHC/HsToCore/Expr.hs
+++ b/compiler/GHC/HsToCore/Expr.hs
@@ -71,7 +71,6 @@ import GHC.Utils.Panic
 import GHC.Utils.Panic.Plain
 import GHC.Core.PatSyn
 import Control.Monad
-import Data.Void( absurd )
 
 {-
 ************************************************************************
@@ -262,10 +261,10 @@ dsExpr (HsUnboundVar (HER ref _ _) _)  = dsEvTerm =<< readMutVar ref
 dsExpr (HsPar _ _ e _)        = dsLExpr e
 dsExpr (ExprWithTySig _ e _)  = dsLExpr e
 
-dsExpr (HsIPVar {})           = panic "dsExpr: HsIPVar"
+dsExpr (HsIPVar x _)          = dataConCantHappen x
 
-dsExpr (HsGetField x _ _)     = absurd x
-dsExpr (HsProjection x _)     = absurd x
+dsExpr (HsGetField x _ _)     = dataConCantHappen x
+dsExpr (HsProjection x _)     = dataConCantHappen x
 
 dsExpr (HsLit _ lit)
   = do { warnAboutOverflowedLit lit
@@ -736,7 +735,7 @@ Thus, we pass @r@ as the scrutinee expression to @matchWrapper@ above.
 
 -- Template Haskell stuff
 
-dsExpr (HsRnBracketOut _ _ _)  = panic "dsExpr HsRnBracketOut"
+dsExpr (HsRnBracketOut x _ _)  = dataConCantHappen x
 dsExpr (HsTcBracketOut _ hs_wrapper x ps) = dsBracket hs_wrapper x ps
 dsExpr (HsSpliceE _ s)         = pprPanic "dsExpr:splice" (ppr s)
 
@@ -766,13 +765,12 @@ dsExpr (HsBinTick _ ixT ixF e) = do
 -- HsSyn constructs that just shouldn't be here, because
 -- the renamer removed them.  See GHC.Rename.Expr.
 -- Note [Handling overloaded and rebindable constructs]
-dsExpr (HsOverLabel x _) = absurd x
-dsExpr (OpApp x _ _ _)   = absurd x
-dsExpr (SectionL x _ _)  = absurd x
-dsExpr (SectionR x _ _)  = absurd x
-
+dsExpr (HsOverLabel x _) = dataConCantHappen x
+dsExpr (OpApp x _ _ _)   = dataConCantHappen x
+dsExpr (SectionL x _ _)  = dataConCantHappen x
+dsExpr (SectionR x _ _)  = dataConCantHappen x
+dsExpr (HsBracket x _)   = dataConCantHappen x
 -- HsSyn constructs that just shouldn't be here:
-dsExpr (HsBracket   {}) = panic "dsExpr:HsBracket"
 dsExpr (HsDo        {}) = panic "dsExpr:HsDo"
 
 ds_prag_expr :: HsPragE GhcTc -> LHsExpr GhcTc -> DsM CoreExpr
diff --git a/compiler/GHC/HsToCore/ListComp.hs b/compiler/GHC/HsToCore/ListComp.hs
index 0816bf3c1c..ee5edd8ac5 100644
--- a/compiler/GHC/HsToCore/ListComp.hs
+++ b/compiler/GHC/HsToCore/ListComp.hs
@@ -17,7 +17,7 @@ import {-# SOURCE #-} GHC.HsToCore.Expr ( dsExpr, dsLExpr, dsLExprNoLP, dsLocalB
 
 import GHC.Hs
 import GHC.Tc.Errors.Types ( LevityCheckProvenance(..) )
-import GHC.Tc.Utils.Zonk
+import GHC.Hs.Syn.Type
 import GHC.Core
 import GHC.Core.Make
 
diff --git a/compiler/GHC/HsToCore/Match.hs b/compiler/GHC/HsToCore/Match.hs
index 50aaef9b56..6576add1a2 100644
--- a/compiler/GHC/HsToCore/Match.hs
+++ b/compiler/GHC/HsToCore/Match.hs
@@ -29,7 +29,7 @@ import GHC.Types.Basic ( Origin(..), isGenerated, Boxity(..) )
 import GHC.Types.SourceText
 import GHC.Driver.Session
 import GHC.Hs
-import GHC.Tc.Utils.Zonk
+import GHC.Hs.Syn.Type
 import GHC.Tc.Types.Evidence
 import GHC.Tc.Utils.Monad
 import GHC.HsToCore.Pmc
diff --git a/compiler/GHC/HsToCore/Utils.hs b/compiler/GHC/HsToCore/Utils.hs
index 49b21e2111..d5cbed2e36 100644
--- a/compiler/GHC/HsToCore/Utils.hs
+++ b/compiler/GHC/HsToCore/Utils.hs
@@ -51,7 +51,7 @@ import {-# SOURCE #-} GHC.HsToCore.Match ( matchSimply )
 import {-# SOURCE #-} GHC.HsToCore.Expr  ( dsLExpr, dsSyntaxExpr )
 
 import GHC.Hs
-import GHC.Tc.Utils.Zonk
+import GHC.Hs.Syn.Type
 import GHC.Tc.Utils.TcType( tcSplitTyConApp )
 import GHC.Core
 import GHC.HsToCore.Monad