When a specialization of a generic type occurs within the signature of
a generic function, it implies that the generic arguments meet the
requirements of the generic type. For example, in
func printHashes<K, V>(dict : Dictionary<K, V>) {
for (k, v) in dict {
print("\(k.hashValue())\n")
}
}
the presence of Dictionary<K, V> in the signature implies that K and V
meet the requirements on Dictionary's generic parameters, i.e., that K
is Hashable. Thus, infer that K is Hashable in printHashes().
Fixes the easy part of <rdar://problem/14691708>. Same-type and
superclass requirements are more interesting.
<rdar://problem/14691708>
Swift SVN r7574
