Move quoted null and () encoding to internal

These are opimizations for `'{}`/`'{()}` and `'{null}` which should not be used directly

Author: nicolasstucki

compiler/src/dotty/tools/dotc/core/Definitions.scala

@@ -685,8 +685,6 @@ class Definitions {
 
   @tu lazy val QuotedExprClass: ClassSymbol = requiredClass("scala.quoted.Expr")
   @tu lazy val QuotedExprModule: Symbol = QuotedExprClass.companionModule
-    @tu lazy val QuotedExprModule_nullExpr: Symbol = QuotedExprModule.requiredMethod(nme.nullExpr)
-    @tu lazy val QuotedExprModule_unitExpr: Symbol = QuotedExprModule.requiredMethod(nme.unitExpr)
 
   @tu lazy val QuoteContextClass: ClassSymbol = requiredClass("scala.quoted.QuoteContext")
 
@@ -716,6 +714,8 @@ class Definitions {
 
   @tu lazy val InternalQuotedExprModule: Symbol = requiredModule("scala.internal.quoted.Expr")
     @tu lazy val InternalQuotedExpr_unapply: Symbol = InternalQuotedExprModule.requiredMethod(nme.unapply)
+    @tu lazy val InternalQuotedExpr_nullExpr: Symbol = InternalQuotedExprModule.requiredMethod(nme.nullExpr)
+    @tu lazy val InternalQuotedExpr_unitExpr: Symbol = InternalQuotedExprModule.requiredMethod(nme.unitExpr)
 
   @tu lazy val InternalQuotedTypeModule: Symbol = requiredModule("scala.internal.quoted.Type")
     @tu lazy val InternalQuotedType_unapply: Symbol = InternalQuotedTypeModule.requiredMethod(nme.unapply)

compiler/src/dotty/tools/dotc/transform/ReifyQuotes.scala

@@ -150,8 +150,8 @@ class ReifyQuotes extends MacroTransform {
         def liftedValue(lifter: Symbol) =
           ref(lifter).appliedToType(originalTp).select(nme.toExpr).appliedTo(lit)
         lit.const.tag match {
-          case Constants.NullTag => ref(defn.QuotedExprModule_nullExpr)
-          case Constants.UnitTag => ref(defn.QuotedExprModule_unitExpr)
+          case Constants.NullTag => ref(defn.InternalQuotedExpr_nullExpr)
+          case Constants.UnitTag => ref(defn.InternalQuotedExpr_unitExpr)
           case Constants.BooleanTag => liftedValue(defn.LiftableModule_BooleanIsLiftable)
           case Constants.ByteTag => liftedValue(defn.LiftableModule_ByteIsLiftable)
           case Constants.ShortTag => liftedValue(defn.LiftableModule_ShortIsLiftable)

library/src-bootstrapped/scala/quoted/Expr.scala

@@ -79,18 +79,6 @@ object Expr {
       case Some(expr1) => expr1.seal.asInstanceOf[Expr[T]]
       case _ => expr
 
-  /** Returns a null expresssion equivalent to `'{null}` */
-  def nullExpr: QuoteContext ?=> Expr[Null] = qctx ?=> {
-    import qctx.tasty._
-    Literal(Constant(null)).seal.asInstanceOf[Expr[Null]]
-  }
-
-  /** Returns a unit expresssion equivalent to `'{}` or `'{()}` */
-  def unitExpr: QuoteContext ?=> Expr[Unit] = qctx ?=> {
-    import qctx.tasty._
-    Literal(Constant(())).seal.asInstanceOf[Expr[Unit]]
-  }
-
   /** Returns an expression containing a block with the given statements and ending with the expresion
    *  Given list of statements `s1 :: s2 :: ... :: Nil` and an expression `e` the resulting expression
    *  will be equivalent to `'{ $s1; $s2; ...; $e }`.

library/src/scala/internal/quoted/Expr.scala

@@ -55,4 +55,17 @@ object Expr {
     new Matcher.QuoteMatcher[qctx.type].termMatch(scrutineeExpr.unseal, patternExpr.unseal, hasTypeSplices).asInstanceOf[Option[Tup]]
   }
 
+
+  /** Returns a null expresssion equivalent to `'{null}` */
+  def nullExpr: QuoteContext ?=> quoted.Expr[Null] = qctx ?=> {
+    import qctx.tasty._
+    Literal(Constant(null)).seal.asInstanceOf[quoted.Expr[Null]]
+  }
+
+  /** Returns a unit expresssion equivalent to `'{}` or `'{()}` */
+  def unitExpr: QuoteContext ?=> quoted.Expr[Unit] = qctx ?=> {
+    import qctx.tasty._
+    Literal(Constant(())).seal.asInstanceOf[quoted.Expr[Unit]]
+  }
+
 }

staging/src/scala/quoted/staging/staging.scala

@@ -37,7 +37,7 @@ package object staging:
     var result: T = noResult.asInstanceOf[T]
     def dummyRun(using QuoteContext): Expr[Unit] = {
       result = thunk
-      Expr.unitExpr
+      '{}
     }
     toolbox.run(dummyRun(using _))
     assert(result != noResult) // toolbox.run should have thrown an exception