- Incorrect type checking when &[] and [] return optional values.

- Failed to find subscript overloading on optional values.
- Added `&[]` overload to HashMap.

lib/std/collections/hashmap.c3

@@ -182,6 +182,24 @@ fn Value*? HashMap.get_ref(&map, Key key)
 	return NOT_FOUND?;
 }
 
+fn Value* HashMap.get_or_create_ref(&map, Key key) @operator(&[])
+{
+	uint hash = rehash(key.hash());
+	if (map.count)
+	{
+		for (Entry *e = map.table[index_for(hash, map.table.len)]; e != null; e = e.next)
+		{
+			if (e.hash == hash && equals(key, e.key)) return &e.value;
+		}
+	}
+	map.set(key, {});
+	for (Entry *e = map.table[index_for(hash, map.table.len)]; e != null; e = e.next)
+    {
+    	if (e.hash == hash && equals(key, e.key)) return &e.value;
+    }
+	unreachable();
+}
+
 fn Entry*? HashMap.get_entry(&map, Key key)
 {
 	if (!map.count) return NOT_FOUND?;