Make sure that DropBreaks catch also constant folded statements

Author: natsukagami

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

@@ -27,6 +27,8 @@ object DropBreaks:
     /** The number of other references to associated label */
     var otherRefs: Int = 0
 
+    override def toString() = s"LabelUsage($goto, $enclMeth, returnRefs = $returnRefs, otherRefs = $otherRefs)"
+
   private val LabelUsages = new Property.Key[Map[Symbol, LabelUsage]]
   private val ShadowedLabels = new Property.Key[Set[Symbol]]
 
@@ -70,6 +72,15 @@ class DropBreaks extends MiniPhase:
             && throww.symbol == defn.throwMethod
             && ex.symbol == ex2.symbol && ex.symbol == ex3.symbol =>
           Some((ex.symbol, lbl.symbol))
+        case If(
+          Apply(Select(ex: Ident, isSameLabelAs), (lbl @ Ident(local)) :: Nil),
+          Literal(_), // in the case where the value is constant folded
+          Apply(throww, (ex3: Ident) :: Nil))
+        if isSameLabelAs == nme.isSameLabelAs && local == nme.local
+            && throww.symbol == defn.throwMethod
+            && ex.symbol == ex3.symbol
+            && expr.tpe.isSingleton =>
+          Some((ex.symbol, lbl.symbol))
         case _ =>
           None
     end GuardedThrow