Unit obtained through a generic substitution should not be mapped to VOID

compiler/testData/codegen/boxAgainstJava/platformTypes/GenericUnit.java

@@ -0,0 +1,11 @@
+public class GenericUnit {
+    public static class Key<T> {}
+
+    public static <T> T getNull(Key<T> key) {
+        return null;
+    }
+
+    public static <T> T get(Key<T> key, T t) {
+        return t;
+    }
+}

compiler/testData/codegen/boxAgainstJava/platformTypes/GenericUnit.kt

@@ -0,0 +1,17 @@
+import GenericUnit.*
+
+val key = Key<Unit>()
+
+fun box(): String {
+    val n1 = getNull(key)
+    if (n1 != null) return "Fail 1: $n1"
+
+    val n2 = get(key, null)
+    if (n2 != null) return "Fail 2: $n2"
+
+    val n3 = get(key, Unit)
+    if (n3 == null) return "Fail 3.0: $n3"
+    if (n3 != Unit) return "Fail 3.1: $n3"
+
+    return "OK"
+}