fix for KT-237. Unit as value part

idea/testData/codegen/regressions/kt237.jet

@@ -1,20 +1,41 @@
-fun foreach(array: Array<Int>, action: fun(Int): Unit) {
+fun main(args: Array<String>?) {
+    val y: Unit = () //do not compile
+    A<Unit>()        //do not compile
+    C<Unit>(())      //do not compile
+        //do not compile
+    System.out?.println(fff<Unit>(()))  //do not compile
+    System.out?.println(id<Unit>(y))  //do not compile
+    System.out?.println(fff<Unit>(id<Unit>(y)) == id<Unit>(foreach(Array<Int>(0),{(e : Int) : Unit => })))  //do not compile
+}
+class A<T>()
+
+class C<T>(val value: T) {
+    fun foo(): T = value
+}
+
+fun <T> fff(x: T) : T { return x }
+
+fun <T> id(value: T): T = value
+
+fun foreach(array: Array<Int>?, action: fun(Int): Unit) {
     for (el in array) {
        action(el) //exception through compilation (see below)
     }
 }
-/*
+
 fun almostFilter(array: Array<Int>, action: fun(Int): Int) {
     for (el in array) {
        action(el)
     }
 }
-*/
+
 fun box() : String {
     val a = Array<Int> (3)
     a[0] = 0
     a[1] = 1
     a[2] = 2
     foreach(a, { (el : Int) : Unit => System.out?.println(el) })
+    almostFilter(a, { (el : Int) : Int => el })
+    main(null)
     return "OK"
 }