Add support for the WhileDo loops of dotty.

src/compiler/scala/tools/nsc/backend/jvm/BCodeBodyBuilder.scala

@@ -204,7 +204,7 @@ trait BCodeBodyBuilder extends BCodeSkelBuilder {
 
       val hasElse = !elsep.isEmpty && (elsep match {
         case Literal(value) if value.tag == UnitTag => false
-	case _ => true
+        case _ => true
       })
       val postIf  = if (hasElse) new asm.Label else failure
 
@@ -308,6 +308,9 @@ trait BCodeBodyBuilder extends BCodeSkelBuilder {
           genReturn(r)
           generatedType = expectedType
 
+        case t @ WhileDo(_, _) =>
+          generatedType = genWhileDo(t)
+
         case t @ Try(_, _, _) =>
           generatedType = genLoadTry(t)
 
@@ -599,6 +602,45 @@ trait BCodeBodyBuilder extends BCodeSkelBuilder {
       }
     } // end of genReturn()
 
+    def genWhileDo(tree: WhileDo): BType = tree match{
+      case WhileDo(cond, body) =>
+
+      val isInfinite = cond match {
+        case Literal(value) if value.tag == BooleanTag => value.booleanValue
+        case _ => false
+      }
+
+      val loop = new asm.Label
+      markProgramPoint(loop)
+
+      if (isInfinite) {
+        genLoad(body, UNIT)
+        bc goTo loop
+      } else {
+        val hasBody = cond match {
+          case Literal(value) if value.tag == UnitTag => false
+          case _ => true
+        }
+
+        if (hasBody) {
+          val success = new asm.Label
+          val failure = new asm.Label
+          genCond(cond, success, failure, targetIfNoJump = success)
+          markProgramPoint(success)
+          genLoad(body, UNIT)
+          bc goTo loop
+          markProgramPoint(failure)
+        } else {
+          // this is the shape of do..while loops, so do something smart about them
+          val failure = new asm.Label
+          genCond(cond, loop, failure, targetIfNoJump = failure)
+          markProgramPoint(failure)
+        }
+      }
+
+      UNIT
+    }
+
     def genTypeApply(t: TypeApply): BType = t match {
       case TypeApply(fun@Select(obj, _), targs) =>
 

src/compiler/scala/tools/nsc/backend/jvm/BackendInterface.scala

@@ -33,6 +33,7 @@ abstract class BackendInterface extends BackendInterfaceDefinitions {
   type Throw      >: Null <: Tree
   type Labeled    >: Null <: Tree
   type Return     >: Null <: Tree
+  type WhileDo    >: Null <: Tree
   type Literal    >: Null <: Tree
   type Block      >: Null <: Tree
   type Typed      >: Null <: Tree
@@ -69,6 +70,7 @@ abstract class BackendInterface extends BackendInterfaceDefinitions {
   implicit val ThrowTag: ClassTag[Throw]
   implicit val LabeledTag: ClassTag[Labeled]
   implicit val ReturnTag: ClassTag[Return]
+  implicit val WhileDoTag: ClassTag[WhileDo]
   implicit val LiteralTag: ClassTag[Literal]
   implicit val BlockTag: ClassTag[Block]
   implicit val TypedTag: ClassTag[Typed]
@@ -205,6 +207,7 @@ abstract class BackendInterface extends BackendInterfaceDefinitions {
   val Try: TryDeconstructor
   val Labeled: LabeledDeconstructor
   val Return: ReturnDeconstructor
+  val WhileDo: WhileDoDeconstructor
   val LabelDef: LabelDeconstructor
   val Literal: LiteralDeconstructor
   val Typed: TypedDeconstrutor
@@ -302,6 +305,11 @@ abstract class BackendInterface extends BackendInterfaceDefinitions {
     def _2: Symbol // target label, NoSymbol if return to method
   }
 
+  abstract class WhileDoDeconstructor extends DeconstructorCommon[WhileDo]{
+    def _1: Tree // cond
+    def _2: Tree // body
+  }
+
   abstract class ThrownException {
     def unapply(a: Annotation): Option[Symbol]
   }