Add var read expression

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

furc/src/ast.cpp

@@ -34,6 +34,16 @@ bool expression_node::equal(const node& rhs) const {
     return expression_type() == reinterpret_cast<const expression_node&>(rhs).expression_type();
 }
 
+std::ostream& var_read_expression_node::print(std::ostream& os) const {
+    if (m_name.present()) return os << *m_name;
+    return os << m_name.error();
+}
+
+bool var_read_expression_node::equal(const node& rhsNode) const {
+    const auto& rhs = reinterpret_cast<const var_read_expression_node&>(rhsNode);
+    return expression_node::equal(rhsNode) && m_name == rhs.m_name;
+}
+
 std::ostream& operator<<(std::ostream& os, unaryop_expression_node_t type) {
     switch (type) {
     case unaryop_expression_node_t::Positive: return os << "+";

furc/src/front/parser.cpp

@@ -146,6 +146,12 @@ ast::literal_node_h parser::parse_literal() {
 ast::expression_node_h parser::parse_expression_primary() {
     const auto& tok = peek_token();
     switch (tok->type) {
+    case token_t::Identifier: {
+        auto tok = next_token();
+        return ast::var_read_expression_node_h{ tok.location(),
+            m_arena,
+            handle<std::string_view>{ tok.location(), (*tok)->string } };
+    }
     case token_t::Lparen: {
         auto tok  = next_token();
         auto node = parse_expression();

furc/src/main.cpp

@@ -5,7 +5,7 @@
 #include <iostream>
 
 int main(void) {
-    furc::front::parser parser("<TEMP>", "func main() {\n    return (6 - -7) * 9++;\n}");
+    furc::front::parser parser("<TEMP>", "func main() {\n    return (x - -y) * z++;\n}");
     std::cout << parser.parse() << '\n';
 
     return 0;