Add AST visitor

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

furc/include/furc/ast/declaration.hpp

@@ -36,6 +36,8 @@ public:
 
     front::token name() const { return m_name; }
 public:
+    void accept(visitor& visitor) const override;
+
     std::ostream& print(std::ostream& os) const override;
 protected:
     bool equal(const node& rhs) const override;
@@ -65,6 +67,8 @@ public:
 
     const function_body_h& body() const { return m_body; }
 public:
+    void accept(visitor& visitor) const override;
+
     std::ostream& print(std::ostream& os) const override;
 protected:
     bool equal(const node& rhs) const override;

furc/include/furc/ast/expression.hpp

@@ -36,6 +36,8 @@ public:
     handle<std::string_view>&&      move_name() { return std::move(m_name); }
 public:
     expression_node_t expression_type() const override { return expression_node_t::VarRead; }
+public:
+    void accept(visitor& visitor) const override;
 
     std::ostream& print(std::ostream& os) const override;
 protected:
@@ -66,6 +68,8 @@ public:
     expression_node_h&&       move_node() { return std::move(m_node); }
 public:
     expression_node_t expression_type() const override { return expression_node_t::Unaryop; }
+public:
+    void accept(visitor& visitor) const override;
 
     std::ostream& print(std::ostream& os) const override;
 protected:
@@ -105,6 +109,8 @@ public:
     expression_node_h&&      move_rhs() { return std::move(m_rhs); };
 public:
     expression_node_t expression_type() const override { return expression_node_t::Binop; }
+public:
+    void accept(visitor& visitor) const override;
 
     std::ostream& print(std::ostream& os) const override;
 protected:
@@ -128,6 +134,8 @@ public:
     const expression_node_h& rhs() const { return m_rhs; }
 public:
     expression_node_t expression_type() const override { return expression_node_t::VarAssign; }
+public:
+    void accept(visitor& visitor) const override;
 
     std::ostream& print(std::ostream& os) const override;
 protected:

furc/include/furc/ast/fwd.hpp

@@ -10,8 +10,8 @@ namespace ast {
 
 class node;
 
-template <typename T, typename Error = std::string>
-using node_handle = handle<T*, Error>;
+template <typename T>
+using node_handle = handle<T*, std::string>;
 
 class literal_node;
 using literal_node_h = node_handle<literal_node>;

furc/include/furc/ast/literal.hpp

@@ -33,6 +33,8 @@ public:
 
     const handle<std::string_view>& value() const { return m_value; }
 public:
+    void accept(visitor& visitor) const override;
+
     std::ostream& print(std::ostream& os) const override;
 protected:
     bool equal(const node& rhs) const override;
@@ -51,6 +53,8 @@ public:
 
     bool operator==(front::integer_token integer) const { return m_value == integer; }
 public:
+    void accept(visitor& visitor) const override;
+
     std::ostream& print(std::ostream& os) const override;
 protected:
     bool equal(const node& rhs) const override;

furc/include/furc/ast/node.hpp

@@ -2,6 +2,7 @@
 #define FURC_AST_NODE_HPP
 
 #include "furc/ast/fwd.hpp"
+#include "furc/ast/visitor.hpp"
 
 namespace furc {
 namespace ast {
@@ -39,6 +40,8 @@ public:
     bool operator==(const node& rhs) const { return category() == rhs.category() && equal(rhs); }
     bool operator!=(const node& rhs) const { return !this->operator==(rhs); }
 public:
+    virtual void accept(visitor& visitor) const = 0;
+
     virtual std::ostream& print(std::ostream& os) const = 0;
 
     friend std::ostream& operator<<(std::ostream& os, const node& node) { return node.print(os); }

furc/include/furc/ast/program.hpp

@@ -19,6 +19,8 @@ public:
 
     const std::vector<node_handle<declaration_node>>& declarations() const { return m_declarations; }
 public:
+    void accept(visitor& visitor) const override;
+
     std::ostream& print(std::ostream& os) const override;
 protected:
     bool equal(const node& rhs) const override;

furc/include/furc/ast/statement.hpp

@@ -31,6 +31,8 @@ public:
     node_handle<expression_node> value() const { return m_value; }
 public:
     statement_node_t statement_type() const override { return statement_node_t::Return; }
+public:
+    void accept(visitor& visitor) const override;
 
     std::ostream& print(std::ostream& os) const override;
 protected:

furc/include/furc/ast/visitor.hpp

@@ -0,0 +1,34 @@
+#ifndef FURC_AST_VISITOR_HPP
+#define FURC_AST_VISITOR_HPP
+
+#include "furc/ast/fwd.hpp"
+
+namespace furc {
+namespace ast {
+
+class visitor {
+public:
+    virtual ~visitor() = default;
+
+    visitor(visitor&&)                 = default;
+    visitor& operator=(visitor&&)      = default;
+    visitor(const visitor&)            = default;
+    visitor& operator=(const visitor&) = default;
+public:
+    virtual void visit_string_literal_node(const string_literal_node&) {}
+    virtual void visit_integer_literal_node(const integer_literal_node&) {}
+    virtual void visit_var_read_expression_node(const var_read_expression_node&) {}
+    virtual void visit_unaryop_expression_node(const unaryop_expression_node&) {}
+    virtual void visit_binop_expression_node(const binop_expression_node&) {}
+    virtual void visit_var_assign_expression_node(const var_assign_expression_node&) {}
+    virtual void visit_function_declaration_node(const function_declaration_node&) {}
+    virtual void visit_function_definition_node(const function_definition_node&) {}
+    virtual void visit_return_statement_node(const return_statement_node&) {}
+
+    virtual void visit_error(const node_handle<node>& handle) {}
+};
+
+} // namespace ast
+} // namespace furc
+
+#endif // FURC_AST_VISITOR_HPP