feat(furc/ast): add visitor pattern for AST

furc/include/furc/front/ast.hpp

@@ -8,6 +8,50 @@
 
 namespace furc {
 
+struct comp_stmt_node;
+struct if_stmt_node;
+struct while_stmt_node;
+struct return_stmt_node;
+struct var_decl_node;
+struct func_decl_node;
+struct var_read_expr_node;
+struct func_call_expr_node;
+struct group_expr_node;
+struct binary_op_expr_node;
+struct unary_op_expr_node;
+struct if_expr_node;
+struct int_lit_node;
+struct char_lit_node;
+
+struct ast_visitor {
+    ast_visitor()          = default;
+    virtual ~ast_visitor() = default;
+
+    ast_visitor(ast_visitor&&) noexcept            = default;
+    ast_visitor& operator=(ast_visitor&&) noexcept = default;
+
+    ast_visitor(const ast_visitor&)            = default;
+    ast_visitor& operator=(const ast_visitor&) = default;
+
+    virtual void visit_comp_stmt_node(const comp_stmt_node& node) {}
+    virtual void visit_if_stmt_node(const if_stmt_node& node) {}
+    virtual void visit_while_stmt_node(const while_stmt_node& node) {}
+    virtual void visit_return_stmt_node(const return_stmt_node& node) {}
+
+    virtual void visit_var_decl_node(const var_decl_node& node) {}
+    virtual void visit_func_decl_node(const func_decl_node& node) {}
+
+    virtual void visit_var_read_expr_node(const var_read_expr_node& node) {}
+    virtual void visit_func_call_expr_node(const func_call_expr_node& node) {}
+    virtual void visit_group_expr_node(const group_expr_node& node) {}
+    virtual void visit_binary_op_expr_node(const binary_op_expr_node& node) {}
+    virtual void visit_unary_op_expr_node(const unary_op_expr_node& node) {}
+    virtual void visit_if_expr_node(const if_expr_node& node) {}
+
+    virtual void visit_int_lit_node(const int_lit_node& node) {}
+    virtual void visit_char_lit_node(const char_lit_node& node) {}
+};
+
 struct ast_type {
     enum type_e {
         Void = 0,
@@ -41,6 +85,8 @@ public:
     ast_node& operator=(const ast_node&) = delete;
 public:
     virtual category_e category() const = 0;
+
+    virtual void accept(ast_visitor& visitor) const = 0;
 };
 
 using ast_node_cat = ast_node::category_e;
@@ -65,6 +111,8 @@ public:
 struct comp_stmt_node final : public stmt_node {
     stmt_type_e stmt_type() const override { return Compound; }
 
+    void accept(ast_visitor& visitor) const override { visitor.visit_comp_stmt_node(*this); }
+
     std::vector<stmt_node*> stmts;
 };
 
@@ -73,6 +121,8 @@ class expr_node;
 struct if_stmt_node final : public stmt_node {
     stmt_type_e stmt_type() const override { return If; }
 
+    void accept(ast_visitor& visitor) const override { visitor.visit_if_stmt_node(*this); }
+
     expr_node* cond       = nullptr;
     stmt_node* thenBranch = nullptr;
     stmt_node* elseBranch = nullptr;
@@ -81,6 +131,8 @@ struct if_stmt_node final : public stmt_node {
 struct while_stmt_node final : public stmt_node {
     stmt_type_e stmt_type() const override { return While; }
 
+    void accept(ast_visitor& visitor) const override { visitor.visit_while_stmt_node(*this); }
+
     expr_node* cond = nullptr;
     stmt_node* body = nullptr;
 };
@@ -88,6 +140,8 @@ struct while_stmt_node final : public stmt_node {
 struct return_stmt_node final : public stmt_node {
     stmt_type_e stmt_type() const override { return Return; }
 
+    void accept(ast_visitor& visitor) const override { visitor.visit_return_stmt_node(*this); }
+
     expr_node* value = nullptr;
 };
 
@@ -108,6 +162,8 @@ public:
 struct var_decl_node final : public decl_node {
     decl_type_e decl_type() const override { return Variable; }
 
+    void accept(ast_visitor& visitor) const override { visitor.visit_var_decl_node(*this); }
+
     std::string name;
     ast_type    type;
     expr_node*  init = nullptr;
@@ -116,6 +172,8 @@ struct var_decl_node final : public decl_node {
 struct func_decl_node final : public decl_node {
     decl_type_e decl_type() const override { return Function; }
 
+    void accept(ast_visitor& visitor) const override { visitor.visit_func_decl_node(*this); }
+
     struct def_s {
         comp_stmt_node          body;
         std::vector<expr_node*> preConds;
@@ -151,6 +209,8 @@ public:
 struct var_read_expr_node final : public expr_node {
     expr_type_e expr_type() const override { return VarRead; }
 
+    void accept(ast_visitor& visitor) const override { visitor.visit_var_read_expr_node(*this); }
+
     std::string name;
 
     var_read_expr_node(std::string&& name)
@@ -160,6 +220,8 @@ struct var_read_expr_node final : public expr_node {
 struct func_call_expr_node final : public expr_node {
     expr_type_e expr_type() const override { return FunctionCall; }
 
+    void accept(ast_visitor& visitor) const override { visitor.visit_func_call_expr_node(*this); }
+
     expr_node*              lhs = nullptr;
     std::vector<expr_node*> args;
 };
@@ -167,6 +229,8 @@ struct func_call_expr_node final : public expr_node {
 struct group_expr_node final : public expr_node {
     expr_type_e expr_type() const override { return Group; }
 
+    void accept(ast_visitor& visitor) const override { visitor.visit_group_expr_node(*this); }
+
     expr_node* inner = nullptr;
 };
 
@@ -196,6 +260,8 @@ struct binary_op_expr_node final : public expr_node {
 
     expr_type_e expr_type() const override { return BinaryOp; }
 
+    void accept(ast_visitor& visitor) const override { visitor.visit_binary_op_expr_node(*this); }
+
     expr_node*     lhs  = nullptr;
     expr_node*     rhs  = nullptr;
     binary_op_type type = Add;
@@ -219,6 +285,8 @@ struct unary_op_expr_node final : public expr_node {
 
     expr_type_e expr_type() const override { return UnaryOp; }
 
+    void accept(ast_visitor& visitor) const override { visitor.visit_unary_op_expr_node(*this); }
+
     expr_node*    lhs  = nullptr;
     unary_op_type type = Positive;
 };
@@ -226,6 +294,8 @@ struct unary_op_expr_node final : public expr_node {
 struct if_expr_node final : public expr_node {
     expr_type_e expr_type() const override { return If; }
 
+    void accept(ast_visitor& visitor) const override { visitor.visit_if_expr_node(*this); }
+
     expr_node* cond     = nullptr;
     expr_node* thenExpr = nullptr;
     expr_node* elseExpr = nullptr;
@@ -251,6 +321,8 @@ struct int_lit_node final : public lit_node {
 
     lit_type_e lit_type() const override { return Integer; }
 
+    void accept(ast_visitor& visitor) const override { visitor.visit_int_lit_node(*this); }
+
     std::uint64_t value;
 };
 
@@ -260,6 +332,8 @@ struct char_lit_node final : public lit_node {
 
     lit_type_e lit_type() const override { return Char; }
 
+    void accept(ast_visitor& visitor) const override { visitor.visit_char_lit_node(*this); }
+
     char value;
 };