KT-12873: add temporary variables generated by delegation expression to class initializer. Fix #KT-12873

js/js.translator/testData/delegation/cases/complexDelegation.kt

@@ -0,0 +1,29 @@
+package foo
+
+interface C {
+    fun f(): String
+}
+
+class B(val value: String) : C {
+    override fun f() = value
+}
+
+val b: Any = B("O")
+
+val x = B("failure1")
+val y = B("K")
+val z = B("failure2")
+
+fun selector() = 2
+
+class A : C by (b as C)
+
+class D : C by when (selector()) {
+    1 -> x
+    2 -> y
+    else -> z
+}
+
+fun box(): String {
+    return A().f() + D().f()
+}