Do not allow inference of type arguments on the rhs if there's no information available

compiler/testData/diagnostics/tests/cast/bare/AsNullableNotEnough.kt

@@ -0,0 +1,8 @@
+trait Tr
+trait G<T>
+
+fun test(tr: Tr) {
+    val v = tr as <!NO_TYPE_ARGUMENTS_ON_RHS!>G?<!>
+    // If v is not nullable, there will be a warning on this line:
+    v!!: G<*>
+}