Add ast::node and handle<T*, Error> comparison

And parser test for literals fingerscrossed
This commit is good, innit? But there will also be second one, and dessert

Signed-off-by: CHatingPython <chatingpython@gmail.com>

furc/src/front/parser.cpp

@@ -28,7 +28,7 @@ parser::parser(std::string_view filename)
 ast::node_handle<ast::program_node> parser::parse() & {
     auto program = m_arena.allocate_shared<ast::program_node>();
 
-    while (!m_lexer.empty()) {
+    while (peek_token()->type != token_t::None && !m_lexer.empty()) {
         program->push(std::move(parse_declaration()));
     }