feat(Types): Improve type spec and ignore signatures that use unknown type

src/core/utils.mjs

@@ -0,0 +1,12 @@
+/* Returns true if set is a subset of the keys of obj */
+export function subsetOfKeys(set, obj) {
+   for (const e of set) {
+      if (!(e in obj)) return false
+   }
+   return true
+}
+
+/* Returns a set of all of the types mentioned in a typed-function signature */
+export function typesOfSignature(signature) {
+   return new Set(signature.split(/[^\w\d]/).filter(s => s.length))
+}