Allow return in tailrec position

Author: mbovel

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

@@ -456,7 +456,7 @@ class TailRec extends MiniPhase {
 
         case Return(expr, from) =>
           val fromSym = from.symbol
-          val inTailPosition = fromSym.is(Label) && tailPositionLabeledSyms.contains(fromSym)
+          val inTailPosition = !fromSym.is(Label) || tailPositionLabeledSyms.contains(fromSym)
           cpy.Return(tree)(transform(expr, inTailPosition), from)
 
         case _ =>

tests/run/tailrec-return.check

@@ -0,0 +1,2 @@
+6
+false

tests/run/tailrec-return.scala

@@ -0,0 +1,16 @@
+object Test:
+
+  @annotation.tailrec
+  def sum(n: Int, acc: Int = 0): Int =
+    if n != 0 then return sum(n - 1, acc + n)
+    acc
+
+  @annotation.tailrec
+  def isEven(n: Int): Boolean =
+    if n != 0 && n != 1 then return isEven(n - 2)
+    if n == 1 then return false
+    true
+
+  def main(args: Array[String]): Unit =
+    println(sum(3))
+    println(isEven(5))