Add flags to SyntheticValDef

Author: som-snytt

compiler/src/dotty/tools/dotc/ast/tpd.scala

@@ -206,8 +206,8 @@ object tpd extends Trees.Instance[Type] with TypedTreeInfo {
   def ValDef(sym: TermSymbol, rhs: LazyTree = EmptyTree)(using Context): ValDef =
     ta.assignType(untpd.ValDef(sym.name, TypeTree(sym.info), rhs), sym)
 
-  def SyntheticValDef(name: TermName, rhs: Tree)(using Context): ValDef =
-    ValDef(newSymbol(ctx.owner, name, Synthetic, rhs.tpe.widen, coord = rhs.span), rhs)
+  def SyntheticValDef(name: TermName, rhs: Tree, flags: FlagSet = EmptyFlags)(using Context): ValDef =
+    ValDef(newSymbol(ctx.owner, name, Synthetic | flags, rhs.tpe.widen, coord = rhs.span), rhs)
 
   def DefDef(sym: TermSymbol, paramss: List[List[Symbol]],
              resultType: Type, rhs: Tree)(using Context): DefDef =

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

@@ -159,9 +159,7 @@ class CapturedVars extends MiniPhase with IdentityDenotTransformer:
       case TypeApply(Select(qual@Select(_, nme.elem), nme.asInstanceOf_), _) =>
         recur(qual)
       case Select(_, nme.elem) if refInfo.boxedRefClasses.contains(lhs.symbol.maybeOwner) =>
-        val tempDef = transformFollowing {
-          ValDef(newSymbol(ctx.owner, TempResultName.fresh(), Mutable | Synthetic, tree.rhs.tpe.widen, coord = tree.rhs.span), tree.rhs)
-        }
+        val tempDef = transformFollowing(SyntheticValDef(TempResultName.fresh(), tree.rhs, flags = Mutable))
         val update  = cpy.Assign(tree)(lhs, ref(tempDef.symbol))
         def reset   = cpy.Assign(tree)(ref(tempDef.symbol), nullLiteral.cast(tempDef.symbol.info))
         val res     = if refInfo.objectRefClasses(lhs.symbol.maybeOwner) && !absolved then reset else unitLiteral