Incorrect list type inference

[brynrhodes]

define "Flatten Lists and Elements":
  flatten { { 1, 2, 3 }, 2, 3, 4 }

This test works fine if list promotion is allowed, but if list promotion is disallowed (which is the default for quality improvement artifacts), the list type of the expression should be List, but it incorrectly allows the Any to be downcast to an Integer because Any is "compatible" with any other type. Once a list element type has been inferred as Any, it needs to remain there. Further, because the signature of Flatten requires List<List>, the resolution fails for List and the operator cannot be resolved. This is inconsistent with the intent of allowing flatten to work with Lists of mixed elements of Lists and Singletons.