Merge pull request #5115 from dotty-staging/tailrec-use-labeled-blocks

Use `Labeled` blocks in `TailRec`, instead of label-defs.

Author: sjrd

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

@@ -130,6 +130,9 @@ object tpd extends Trees.Instance[Type] with TypedTreeInfo {
   def Return(expr: Tree, from: Tree)(implicit ctx: Context): Return =
     ta.assignType(untpd.Return(expr, from))
 
+  def Return(expr: Tree, from: Symbol)(implicit ctx: Context): Return =
+    Return(expr, Ident(from.termRef))
+
   def WhileDo(cond: Tree, body: Tree)(implicit ctx: Context): WhileDo =
     ta.assignType(untpd.WhileDo(cond, body))
 

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

@@ -286,6 +286,8 @@ object NameKinds {
   val NonLocalReturnKeyName: UniqueNameKind  = new UniqueNameKind("nonLocalReturnKey")
   val WildcardParamName: UniqueNameKind      = new UniqueNameKind("_$")
   val TailLabelName: UniqueNameKind          = new UniqueNameKind("tailLabel")
+  val TailLocalName: UniqueNameKind          = new UniqueNameKind("$tailLocal")
+  val TailTempName: UniqueNameKind           = new UniqueNameKind("$tmp")
   val ExceptionBinderName: UniqueNameKind    = new UniqueNameKind("ex")
   val SkolemName: UniqueNameKind             = new UniqueNameKind("?")
   val LiftedTreeName: UniqueNameKind         = new UniqueNameKind("liftedTree")