feat(furc/parser): add return statement

furc/include/furc/front/ast.hpp

@@ -53,6 +53,7 @@ public:
 
         Compound,
         If,
+        Return,
     };
 public:
     category_e category() const override { return ast_node_cat::Statement; }
@@ -76,6 +77,12 @@ struct if_stmt_node final : public stmt_node {
     stmt_node* elseBranch = nullptr;
 };
 
+struct return_stmt_node final : public stmt_node {
+    stmt_type_e stmt_type() const override { return Return; }
+
+    expr_node* value = nullptr;
+};
+
 class decl_node : public stmt_node {
 public:
     enum decl_type_e {

furc/src/front/parser.cpp

@@ -24,6 +24,15 @@ ast parser::parse() {
 stmt_node* parser::parse_stmt() {
     switch (m_lexer.peek_token().type) {
     case token::LBrace: return m_arena->allocate<comp_stmt_node>(parse_comp());
+    case token::Return: {
+        m_lexer.next_token();
+        return_stmt_node node;
+        if (m_lexer.peek_token().type != token::Semicolon) {
+            node.value = parse_expr();
+        }
+        eat_token(token::Semicolon);
+        return m_arena->allocate<return_stmt_node>(std::move(node));
+    }
     case token::If: {
         m_lexer.next_token();
         eat_token(token::LParen);