refactor(AST): use pointers instead of results inside of AST nodes

This commit is contained in:
2026-06-03 18:19:20 +02:00
parent 3006b58212
commit 2cfbc12977
8 changed files with 129 additions and 117 deletions
+3 -3
View File
@@ -108,7 +108,7 @@ public:
* @param body Body of the function.
*/
template <typename T>
function_definition_node(struct location location, T&& name, body_r&& body)
function_definition_node(struct location location, T&& name, body&& body)
: function_declaration_node(location, std::forward<T>(name)), m_body(std::move(body)) {}
public:
/**
@@ -123,7 +123,7 @@ public:
*
* @return Body of the function.
*/
const body_r& body() const { return m_body; }
const body& body() const { return m_body; }
public:
void accept(visitor& visitor) const override;
@@ -131,7 +131,7 @@ public:
protected:
bool equal(const node& rhs) const override;
private:
body_r m_body;
struct body m_body;
};
} // namespace ast
+29 -32
View File
@@ -59,8 +59,6 @@ protected:
* @brief Var read expression AST node.
*/
class var_read_expression_node final : public expression_node {
public:
using name_type = furlang::result<std::string_view, error>; /**< Name type alias. */
public:
/**
* @brief Construct a new var read expression node object from a name handle.
@@ -68,22 +66,23 @@ public:
* @param location Node location.
* @param name Handle to the name.
*/
var_read_expression_node(struct location location, name_type&& name)
: expression_node(location), m_name(std::move(name)) {}
template <typename T>
var_read_expression_node(struct location location, T&& name)
: expression_node(location), m_name(std::forward<T>(name)) {}
/**
* @brief Returns the variable's name.
*
* @return Name of the variable.
*/
const name_type& get_name() const { return m_name; }
const std::string& get_name() const { return m_name; }
/**
* @brief Returns the variable's name.
*
* @return Name of the variable.
*/
name_type&& move_name() { return std::move(m_name); }
std::string&& move_name() { return std::move(m_name); }
public:
/**
* @brief Returns this node's expression type.
@@ -98,7 +97,7 @@ public:
protected:
bool equal(const node& rhs) const override;
private:
name_type m_name;
std::string m_name;
};
/**
@@ -117,8 +116,6 @@ enum class unaryop_expression_node_t {
* @brief Unary operation expression AST node.
*/
class unaryop_expression_node final : public expression_node {
public:
using value_type = std::optional<expression_node_r>; /**< Value type. */
public:
/**
* @brief Construct a new unaryop expression node object from type and expression node handle.
@@ -127,7 +124,7 @@ public:
* @param type Operation type.
* @param node Handle to the inner expression node.
*/
unaryop_expression_node(struct location location, unaryop_expression_node_t type, expression_node_r&& node)
unaryop_expression_node(struct location location, unaryop_expression_node_t type, expression_node_p&& node)
: expression_node(location), m_type(type), m_node(std::move(node)) {}
/**
@@ -135,7 +132,7 @@ public:
*
* @param node New node handle.
*/
void set_node(expression_node_r&& node) { m_node = std::move(node); }
void set_node(expression_node_p&& node) { m_node = std::move(node); }
/**
* @brief Returns the type of this node's operation.
@@ -149,21 +146,21 @@ public:
*
* @return The inner expression.
*/
const value_type& get_node() const { return m_node; }
const expression_node_p& get_node() const { return m_node; }
/**
* @brief Returns this node's inner expression.
*
* @return The inner expression.
*/
value_type& get_node() { return m_node; }
expression_node_p& get_node() { return m_node; }
/**
* @brief Moves this node's inner expression.
*
* @return The moved inner expression.
*/
value_type&& move_node() { return std::move(m_node); }
expression_node_p&& move_node() { return std::move(m_node); }
public:
/**
* @brief Returns this node's expression type.
@@ -179,7 +176,7 @@ protected:
bool equal(const node& rhs) const override;
private:
unaryop_expression_node_t m_type;
value_type m_node; /**< The inner expression. */
expression_node_p m_node; /**< The inner expression. */
};
/**
@@ -216,8 +213,8 @@ public:
*/
binop_expression_node(struct location location,
binop_expression_node_t type,
expression_node_r&& lhs,
expression_node_r&& rhs)
expression_node_p&& lhs,
expression_node_p&& rhs)
: expression_node(location), m_type(type), m_lhs(std::move(lhs)), m_rhs(std::move(rhs)) {}
/**
@@ -232,42 +229,42 @@ public:
*
* @return The left-hand-side expression.
*/
const expression_node_r& lhs() const { return m_lhs; };
const expression_node_p& lhs() const { return m_lhs; };
/**
* @brief Returns this node's left-hand-side expression.
*
* @return The left-hand-side expression.
*/
expression_node_r& lhs() { return m_lhs; };
expression_node_p& lhs() { return m_lhs; };
/**
* @brief Moves this node's left-hand-side expression.
*
* @return The moved left-hand-side expression.
*/
expression_node_r&& move_lhs() { return std::move(m_lhs); };
expression_node_p&& move_lhs() { return std::move(m_lhs); };
/**
* @brief Returns this node's right-hand-side expression.
*
* @return The right-hand-side expression.
*/
const expression_node_r& rhs() const { return m_rhs; };
const expression_node_p& rhs() const { return m_rhs; };
/**
* @brief Returns this node's right-hand-side expression.
*
* @return The right-hand-side expression.
*/
expression_node_r& rhs() { return m_rhs; };
expression_node_p& rhs() { return m_rhs; };
/**
* @brief Moves this node's right-hand-side expression.
*
* @return The moved right-hand-side expression.
*/
expression_node_r&& move_rhs() { return std::move(m_rhs); };
expression_node_p&& move_rhs() { return std::move(m_rhs); };
public:
expression_node_t expression_type() const override { return expression_node_t::Binop; }
public:
@@ -278,8 +275,8 @@ protected:
bool equal(const node& rhs) const override;
private:
binop_expression_node_t m_type;
expression_node_r m_lhs;
expression_node_r m_rhs;
expression_node_p m_lhs;
expression_node_p m_rhs;
};
/**
@@ -294,7 +291,7 @@ public:
* @param lhs Left-hand-side expression handle.
* @param rhs Right-hand-side expression handle.
*/
var_assign_expression_node(struct location location, expression_node_r&& lhs, expression_node_r&& rhs)
var_assign_expression_node(struct location location, expression_node_p&& lhs, expression_node_p&& rhs)
: expression_node(location),
m_compound(binop_expression_node_t::None),
m_lhs(std::move(lhs)),
@@ -310,8 +307,8 @@ public:
*/
var_assign_expression_node(struct location location,
binop_expression_node_t compound,
expression_node_r&& lhs,
expression_node_r&& rhs)
expression_node_p&& lhs,
expression_node_p&& rhs)
: expression_node(location), m_compound(compound), m_lhs(std::move(lhs)), m_rhs(std::move(rhs)) {}
/**
@@ -326,14 +323,14 @@ public:
*
* @return The left-hand-side expression.
*/
const expression_node_r& lhs() const { return m_lhs; }
const expression_node_p& lhs() const { return m_lhs; }
/**
* @brief Returns this node's right-hand-side expression.
*
* @return The right-hand-side expression.
*/
const expression_node_r& rhs() const { return m_rhs; }
const expression_node_p& rhs() const { return m_rhs; }
public:
/**
* @brief Returns this node's expression type.
@@ -349,8 +346,8 @@ protected:
bool equal(const node& rhs) const override;
private:
binop_expression_node_t m_compound;
expression_node_r m_lhs;
expression_node_r m_rhs;
expression_node_p m_lhs;
expression_node_p m_rhs;
};
} // namespace ast
+3 -4
View File
@@ -1,7 +1,6 @@
#ifndef FURC_AST_PROGRAM_HPP
#define FURC_AST_PROGRAM_HPP
#include "furc/ast/declaration.hpp"
#include "furc/ast/node.hpp"
#include <vector>
@@ -29,14 +28,14 @@ public:
*
* @param declaration Declaration to add.
*/
void push(node_r<declaration_node>&& declaration) { m_declarations.push_back(std::move(declaration)); }
void push(declaration_node_p&& declaration) { m_declarations.push_back(std::move(declaration)); }
/**
* @brief Returns a list of declarations of this program.
*
* @return The list of this program's declarations.
*/
const std::vector<node_r<declaration_node>>& declarations() const { return m_declarations; }
const std::vector<declaration_node_p>& declarations() const { return m_declarations; }
public:
void accept(visitor& visitor) const override;
@@ -44,7 +43,7 @@ public:
protected:
bool equal(const node& rhs) const override;
private:
std::vector<node_r<declaration_node>> m_declarations;
std::vector<declaration_node_p> m_declarations;
};
} // namespace ast
+15 -15
View File
@@ -46,7 +46,7 @@ protected:
*/
class return_statement_node final : public statement_node, public abstract_node {
public:
using value_type = std::optional<expression_node_r>; /**< Value type. */
using value_type = std::optional<expression_node_p>; /**< Value type. */
public:
/**
* @brief Construct a new return statement AST node.
@@ -60,7 +60,7 @@ public:
* @param location Node location.
* @param value Return value handle.
*/
return_statement_node(struct location location, expression_node_r&& value)
return_statement_node(struct location location, expression_node_p&& value)
: abstract_node(location), m_value(std::move(value)) {}
public:
/**
@@ -98,7 +98,7 @@ public:
* @param cond Condition expression handle.
* @param then Then statement handle.
*/
if_statement_node(struct location location, expression_node_r&& cond, statement_node_r&& then)
if_statement_node(struct location location, expression_node_p&& cond, statement_node_p&& then)
: abstract_node(location), m_cond(std::move(cond)), m_then(std::move(then)) {}
/**
@@ -110,9 +110,9 @@ public:
* @param elze Else statement handle.
*/
if_statement_node(struct location location,
expression_node_r&& cond,
statement_node_r&& then,
statement_node_r&& elze)
expression_node_p&& cond,
statement_node_p&& then,
statement_node_p&& elze)
: abstract_node(location), m_cond(std::move(cond)), m_then(std::move(then)), m_else(std::move(elze)) {}
public:
/**
@@ -120,21 +120,21 @@ public:
*
* @return The condition expression handle.
*/
expression_node_r cond() const { return m_cond; }
expression_node_p cond() const { return m_cond; }
/**
* @brief Returns this node's then statement handle.
*
* @return The then statement handle.
*/
const statement_node_r& then() const { return m_then; }
const statement_node_p& then() const { return m_then; }
/**
* @brief Returns this node's else statement handle.
*
* @return The else statement handle.
*/
const std::optional<statement_node_r>& elze() const { return m_else; }
const std::optional<statement_node_p>& elze() const { return m_else; }
public:
/**
* @brief Returns this node's statement type.
@@ -149,9 +149,9 @@ public:
protected:
bool equal(const node& rhs) const override;
private:
expression_node_r m_cond; /**< The condition expression handle */
statement_node_r m_then; /**< The then statement handle */
std::optional<statement_node_r> m_else; /**< The else statement handle */
expression_node_p m_cond; /**< The condition expression handle */
statement_node_p m_then; /**< The then statement handle */
std::optional<statement_node_p> m_else; /**< The else statement handle */
};
/**
@@ -165,7 +165,7 @@ public:
* @param location Node location.
* @param body Body handle.
*/
compound_statement_node(struct location location, body_r&& body)
compound_statement_node(struct location location, body&& body)
: abstract_node(location), m_body(std::move(body)) {}
public:
/**
@@ -173,7 +173,7 @@ public:
*
* @return The body handle.
*/
const body_r& body() const { return m_body; }
const body& body() const { return m_body; }
public:
/**
* @brief Returns this node's statement type.
@@ -188,7 +188,7 @@ public:
protected:
bool equal(const node& rhs) const override;
private:
body_r m_body; /**< The body handle. */
struct body m_body; /**< The body handle. */
};
} // namespace ast
+1 -1
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@@ -62,7 +62,7 @@ private:
ast::expression_node_r parse_expression_primary();
ast::expression_node_r parse_expression_unary(std::uint32_t precedence);
ast::expression_node_r parse_expression_rhs(ast::expression_node_r&& init, std::uint32_t precedence);
ast::expression_node_r parse_expression_rhs(ast::expression_node_p&& init, std::uint32_t precedence);
ast::body_r parse_body();
private:
+5 -13
View File
@@ -21,8 +21,7 @@ void var_read_expression_node::accept(visitor& visitor) const {
}
std::ostream& var_read_expression_node::print(std::ostream& os) const {
if (m_name.has_error()) return os << m_name.error();
return os << *m_name;
return os << m_name;
}
bool var_read_expression_node::equal(const node& rhsNode) const {
@@ -47,7 +46,7 @@ void unaryop_expression_node::accept(visitor& visitor) const {
}
std::ostream& unaryop_expression_node::print(std::ostream& os) const {
if (!m_node.has_value()) return os;
if (m_node == nullptr) return os;
switch (m_type) {
case unaryop_expression_node_t::Positive:
case unaryop_expression_node_t::Negative:
@@ -132,12 +131,9 @@ void function_definition_node::accept(visitor& visitor) const {
std::ostream& function_definition_node::print(std::ostream& os) const {
function_declaration_node::print(os);
os << ":\n";
if (m_body.has_value()) {
for (const auto& entry : m_body->statements)
for (const auto& entry : m_body.statements)
os << entry << '\n';
return os << m_body->end << ": " << p_name << " end";
}
return os << m_body.error();
return os << m_body.end << ": " << p_name << " end";
}
bool function_definition_node::equal(const node& rhs) const {
@@ -192,11 +188,7 @@ bool compound_statement_node::equal(const node& rhs) const {
void program_node::accept(visitor& visitor) const {
for (const auto& decl : m_declarations) {
if (decl.has_error()) {
visitor.visit_error(decl.error());
} else {
decl.value()->accept(visitor);
}
decl->accept(visitor);
}
}
+16 -27
View File
@@ -6,7 +6,6 @@
#include "furc/ast/statement.hpp" // IWYU pragma: keep
#include <cassert>
#include <iostream>
namespace furc::front {
@@ -18,28 +17,18 @@ void ir_generator::visit(const ast::function_definition_node& funcDef) {
m_currentFunction = std::make_unique<furlang::ir::function>(std::string(funcDef.name()));
push_block();
if (funcDef.body().has_error()) {
std::cerr << funcDef.body().error() << '\n';
return;
}
for (const auto& stmt : funcDef.body()->statements) {
for (const auto& stmt : funcDef.body().statements) {
stmt.value()->accept(*this);
}
m_currentBlock->emplace<ir::return_instruction>();
m_module.push(std::move(m_currentFunction));
}
void ir_generator::visit(const ast::return_statement_node& returnStmt) {
if (!returnStmt.value().has_value()) return;
auto value = returnStmt.value().value();
if (value.has_error()) {
std::cerr << value.error() << '\n';
return;
}
if (value.has_value()) {
value.value()->accept(*this);
if (returnStmt.value().has_value()) {
returnStmt.value().value()->accept(*this);
push<ir::return_instruction>(ir::operand::new_reg(m_registerCounter - 1));
} else {
push<ir::return_instruction>();
@@ -47,19 +36,19 @@ void ir_generator::visit(const ast::return_statement_node& returnStmt) {
}
void ir_generator::visit(const ast::if_statement_node& node) {
node.cond().value()->accept(*this);
node.cond()->accept(*this);
ir_register cond = m_registerCounter - 1;
push<ir::branch_cond_instruction>(ir::operand::new_reg(cond),
m_currentFunction->blocks().size(),
m_currentFunction->blocks().size() + 1);
push_block(); // then block
node.then().value()->accept(*this);
node.then()->accept(*this);
if (node.elze().has_value()) {
m_currentBlock->emplace<ir::branch_instruction>(m_currentFunction->blocks().size() + 1);
push_block(); // else block
node.elze().value().value()->accept(*this);
node.elze().value()->accept(*this);
}
m_currentBlock->emplace<ir::branch_instruction>(m_currentFunction->blocks().size());
@@ -67,7 +56,7 @@ void ir_generator::visit(const ast::if_statement_node& node) {
}
void ir_generator::visit(const ast::compound_statement_node& node) {
for (const auto& stmt : node.body()->statements) {
for (const auto& stmt : node.body().statements) {
stmt.value()->accept(*this);
}
}
@@ -83,7 +72,7 @@ void ir_generator::visit(const ast::integer_literal_node& node) {
}
void ir_generator::visit(const ast::var_read_expression_node& node) {
if (auto it = m_variables.find(*node.get_name()); it != m_variables.end()) {
if (auto it = m_variables.find(node.get_name()); it != m_variables.end()) {
push<furlang::ir::assign_instruction>(ir::operand::new_reg(it->second),
ir::operand::new_reg(m_registerCounter++));
} else {
@@ -114,9 +103,9 @@ static inline furlang::ir::binary_op_instruction_t binary_op_instruction_t(ast::
}
void ir_generator::visit(const ast::binop_expression_node& node) {
node.lhs().value()->accept(*this);
node.lhs()->accept(*this);
ir_register lhs = m_registerCounter - 1;
node.rhs().value()->accept(*this);
node.rhs()->accept(*this);
ir_register rhs = m_registerCounter - 1;
ir_register dst = m_registerCounter++;
push<furlang::ir::binary_op_instruction>(binary_op_instruction_t(node.type()),
@@ -126,16 +115,16 @@ void ir_generator::visit(const ast::binop_expression_node& node) {
}
void ir_generator::visit(const ast::var_assign_expression_node& node) {
node.rhs().value()->accept(*this);
node.rhs()->accept(*this);
ir_register rhs = m_registerCounter - 1;
assert(node.lhs().value()->expression_type() == ast::expression_node_t::VarRead);
auto lhs = std::dynamic_pointer_cast<ast::var_read_expression_node>(node.lhs().value());
assert(node.lhs()->expression_type() == ast::expression_node_t::VarRead);
auto lhs = std::dynamic_pointer_cast<ast::var_read_expression_node>(node.lhs());
ir_register reg = 0;
if (auto it = m_variables.find(*lhs->get_name()); it != m_variables.end()) {
if (auto it = m_variables.find(lhs->get_name()); it != m_variables.end()) {
reg = it->second;
} else {
m_variables[*lhs->get_name()] = reg = m_registerCounter++;
m_variables[lhs->get_name()] = reg = m_registerCounter++;
}
auto compound = node.compound();
+55 -20
View File
@@ -34,10 +34,15 @@ ast::program_node_r parser::parse() & {
auto program = m_arena.allocate_shared<ast::program_node>(location{ m_filename });
while (peek_token().has_value()) {
program->push(std::move(parse_declaration()));
auto decl = parse_declaration();
if (decl.has_error()) {
program = nullptr;
} else if (program != nullptr) {
program->push(std::move(decl.value()));
}
}
return std::move(program);
return program != nullptr ? std::move(program) : ast::program_node_r(ast::error{ location{ m_filename } });
}
ast::declaration_node_r parser::parse_declaration() {
@@ -63,7 +68,7 @@ ast::declaration_node_r parser::parse_declaration() {
if (body.has_error()) return ast::declaration_node_r(ast::error{ body.error().location });
return m_arena.allocate_shared<ast::function_definition_node>(first->location,
name->value.string,
std::move(body));
std::move(body.value()));
}
case token_t::Semicolon: {
m_peekBuffer.clear();
@@ -109,7 +114,7 @@ ast::statement_node_r parser::parse_statement() {
auto value = parse_expression();
auto err = eat_token(token_t::Semicolon);
if (err.has_error()) return ast::statement_node_r(ast::error{ err.error().location });
return m_arena.allocate_shared<ast::return_statement_node>(location, std::move(value));
return m_arena.allocate_shared<ast::return_statement_node>(location, std::move(value.value()));
}
case keyword_token::If: {
auto tok = next_token();
@@ -128,20 +133,28 @@ ast::statement_node_r parser::parse_statement() {
peek_token()->value.keyword == keyword_token::Else) {
next_token();
auto elseBody = parse_statement();
if (elseBody.has_error()) return ast::statement_node_r(ast::error{ elseBody.error().location });
return m_arena.allocate_shared<ast::if_statement_node>(location,
std::move(cond),
std::move(then),
std::move(parse_statement()));
std::move(cond.value()),
std::move(then.value()),
std::move(elseBody.value()));
}
return m_arena.allocate_shared<ast::if_statement_node>(location, std::move(cond), std::move(then));
return m_arena.allocate_shared<ast::if_statement_node>(location,
std::move(cond.value()),
std::move(then.value()));
}
case keyword_token::None:
case keyword_token::Func:
default: break;
}
}
case token_t::LBrace: return m_arena.allocate_shared<ast::compound_statement_node>(location, parse_body());
case token_t::LBrace: {
auto body = parse_body();
if (body.has_error()) return ast::statement_node_r(ast::error{ body.error().location });
return m_arena.allocate_shared<ast::compound_statement_node>(location, std::move(body.value()));
}
default: break;
}
@@ -159,7 +172,11 @@ ast::statement_node_r parser::parse_statement() {
}
ast::expression_node_r parser::parse_expression(std::uint32_t precedence) {
return parse_expression_rhs(parse_expression_unary(precedence), precedence);
auto expr = parse_expression_unary(precedence);
if (expr.has_error()) {
return ast::expression_node_r(ast::error{ expr.error().location });
}
return parse_expression_rhs(std::move(expr.value()), precedence);
}
ast::expression_node_r parser::parse_expression_primary() {
@@ -214,12 +231,16 @@ ast::expression_node_r parser::parse_expression_unary(std::uint32_t precedence)
if (current.precedence >= precedence) break;
auto token = next_token();
ast::expression_node_r expression;
ast::expression_node_p expression;
auto nextIt = s_prefixes.find(peek_token()->type);
if (nextIt != s_prefixes.end()) {
auto next = nextIt->second;
expression = parse_expression_unary(current.precedence + 1);
auto expr = parse_expression_unary(current.precedence + 1);
if (expr.has_error()) {
return ast::expression_node_r(ast::error{ expr.error().location });
}
expression = std::move(std::move(expr.value()));
}
result =
@@ -227,7 +248,13 @@ ast::expression_node_r parser::parse_expression_unary(std::uint32_t precedence)
}
if (result == nullptr) return parse_expression_primary();
if (result->get_node().has_value()) result->set_node(parse_expression_primary());
if (result->get_node() == nullptr) {
auto expr = parse_expression_primary();
if (expr.has_error()) {
return ast::expression_node_r(ast::error{ expr.error().location });
}
result->set_node(std::move(std::move(expr.value())));
}
return result;
}
@@ -282,7 +309,7 @@ struct rhsop_info {
}
};
ast::expression_node_r parser::parse_expression_rhs(ast::expression_node_r&& init, std::uint32_t precedence) {
ast::expression_node_r parser::parse_expression_rhs(ast::expression_node_p&& init, std::uint32_t precedence) {
static std::unordered_map<token_t, rhsop_info> s_rhsops = {
{ token_t::Plus, rhsop_info::create(ast::binop_expression_node_t::Add, 5, associativity::Left) },
{ token_t::Minus, rhsop_info::create(ast::binop_expression_node_t::Sub, 5, associativity::Left) },
@@ -306,7 +333,7 @@ ast::expression_node_r parser::parse_expression_rhs(ast::expression_node_r&& ini
{ token_t::GreaterEq, rhsop_info::create(ast::binop_expression_node_t::GreaterEqual, 9, associativity::Left) },
};
ast::expression_node_r lhs = std::move(init);
ast::expression_node_p lhs = std::move(init);
while (peek_token().has_value()) {
auto it = s_rhsops.find(peek_token()->type);
if (it == s_rhsops.end()) return lhs;
@@ -315,20 +342,28 @@ ast::expression_node_r parser::parse_expression_rhs(ast::expression_node_r&& ini
if (current.precedence >= precedence) return lhs;
auto opToken = next_token();
ast::expression_node_r rhs;
ast::expression_node_p rhs;
if (current.type != rhsop_info_t::Unaryop) {
rhs = parse_expression_unary(current.precedence + 1); // unary prefix is always right-associative
auto expr = parse_expression_unary(current.precedence + 1); // unary prefix is always right-associative
if (expr.has_error()) {
return ast::expression_node_r(ast::error{ expr.error().location });
}
rhs = std::move(expr.value());
}
auto nextIt = s_rhsops.find(peek_token()->type);
if (nextIt != s_rhsops.end()) {
rhsop_info next = nextIt->second;
if (current.type != rhsop_info_t::Unaryop) {
rhs = std::move(parse_expression_rhs(std::move(rhs),
auto expr = std::move(parse_expression_rhs(std::move(rhs),
current.precedence + static_cast<std::uint32_t>(current.associativity == associativity::Right)));
if (expr.has_error()) {
return ast::expression_node_r(ast::error{ expr.error().location });
}
if (current.type != rhsop_info_t::Unaryop) {
rhs = std::move(expr.value());
} else {
lhs = std::move(parse_expression_rhs(std::move(lhs), current.precedence));
lhs = std::move(expr.value());
}
}