//
// The second field identifies the type's parent node in the tree, or
// is null or omitted for a root node. A type is considered to alias
-// all of its decendents and all of its ancestors in the tree.
+// all of its decendents and all of its ancestors in the tree. Also,
+// a type is considered to alias all types in other trees, so that
+// bitcode produced from multiple front-ends is handled conservatively.
//
// If the third field is present, it's an integer which if equal to 1
// indicates that the type is "constant" (meaning pointsToConstantMemory