'Else' is not required in 'when' if Unit is expected

compiler/testData/codegen/box/when/noElseInRetunedExpression.kt

@@ -0,0 +1,11 @@
+var r = "Fail 0"
+
+fun foo(x: Int) {
+    return when (x) {
+        1 -> { r = "OK" }
+    }
+}
+fun box(): String {
+    foo(1)
+    return r
+}