full_moon 2.2.0

// actually, it might but only because the last token isn't an eof. parser is going to have to throw out those tokens
// and then read another block and merge them or something? wow that sounds awful because it won't work inside if's. good luck
// maybe keep parsing until there's an `end`???? but then global blocks...aaa

use super::{
    parser_structs::{ParserResult, ParserState},
    punctuated::{Pair, Punctuated},
    span::ContainedSpan,
    Expression, FunctionBody, Parameter,
};

#[cfg(any(feature = "cfxlua", feature = "luau"))]
use ast::Var;

use crate::{
    ast,
    node::Node,
    tokenizer::{Symbol, Token, TokenKind, TokenReference, TokenType},
};

#[cfg(feature = "luau")]
use crate::tokenizer::InterpolatedStringKind;

#[cfg(feature = "luau")]
static PARSE_NAME_ERROR: &str = "%error-id%";

#[cfg(feature = "luau")]
fn error_token() -> TokenReference {
    TokenReference::new(
        Vec::new(),
        Token::new(TokenType::Identifier {
            identifier: PARSE_NAME_ERROR.into(),
        }),
        Vec::new(),
    )
}

pub fn parse_block(state: &mut ParserState) -> ParserResult<ast::Block> {
    let mut stmts = Vec::new();

    loop {
        match parse_stmt(state) {
            ParserResult::Value(StmtVariant::Stmt(stmt)) => {
                let semicolon = state.consume_if(Symbol::Semicolon);
                stmts.push((stmt, semicolon));
            }

            ParserResult::Value(StmtVariant::LastStmt(last_stmt)) => {
                let semicolon = state.consume_if(Symbol::Semicolon);
                let last_stmt = Some((last_stmt, semicolon));
                return ParserResult::Value(ast::Block { stmts, last_stmt });
            }

            ParserResult::NotFound => break,
            ParserResult::LexerMoved => {
                if stmts.is_empty() {
                    return ParserResult::LexerMoved;
                } else {
                    break;
                }
            }
        }
    }

    let last_stmt = match parse_last_stmt(state) {
        ParserResult::Value(stmt) => Some(stmt),
        ParserResult::LexerMoved | ParserResult::NotFound => None,
    };

    ParserResult::Value(ast::Block { stmts, last_stmt })
}

// Blocks in general are not very fallible. This means, for instance, not finishing `function()`
// will result in a completely ignored function body.
// This is an opinionated choice because I believe selene is going to produce terrible outputs if we don't.
fn expect_block_with_end(
    state: &mut ParserState,
    name: &str,
    start_for_errors: &TokenReference,
) -> Result<(ast::Block, TokenReference), ()> {
    let block = match parse_block(state) {
        ParserResult::Value(block) => block,
        ParserResult::NotFound => unreachable!("parse_block should always return a value"),
        ParserResult::LexerMoved => return Err(()),
    };

    let (start, end) = if let Some(last_stmt) = block.last_stmt() {
        let mut tokens = last_stmt.tokens();
        let start = tokens.next().unwrap();
        let end = tokens.next_back().unwrap_or(start);
        (start, end)
    } else if let Some(the_last_of_the_stmts) = block.stmts().last() {
        let mut tokens = the_last_of_the_stmts.tokens();
        let start = tokens.next().unwrap();
        let end = tokens.next_back().unwrap_or(start);
        (start, end)
    } else {
        (start_for_errors, start_for_errors)
    };

    let Some(end_token) = state.require_with_reference_range(
        Symbol::End,
        || format!("expected `end` to close {} block", name),
        start,
        end,
    ) else {
        return Ok((block, TokenReference::basic_symbol("end")));
    };

    Ok((block, end_token))
}

enum StmtVariant {
    Stmt(ast::Stmt),

    // Used for things like Luau's `continue`, but nothing constructs it in Lua 5.1 alone.
    #[allow(unused)]
    LastStmt(ast::LastStmt),
}

#[cfg(any(feature = "luau", feature = "cfxlua"))]
fn parse_compound_assignment(state: &mut ParserState, var: Var) -> ParserResult<StmtVariant> {
    let compound_operator = state.consume().unwrap();

    let ParserResult::Value(expr) = parse_expression(state) else {
        state.token_error(compound_operator, "expected expression to set to");
        return ParserResult::LexerMoved;
    };

    ParserResult::Value(StmtVariant::Stmt(ast::Stmt::CompoundAssignment(
        ast::CompoundAssignment {
            lhs: var,
            compound_operator: ast::CompoundOp::from_token(compound_operator),
            rhs: expr,
        },
    )))
}

fn parse_stmt(state: &mut ParserState) -> ParserResult<StmtVariant> {
    let Ok(current_token) = state.current() else {
        return ParserResult::NotFound;
    };

    match current_token.token_type() {
        TokenType::Symbol {
            symbol: Symbol::Local,
        } => {
            let local_token = state.consume().unwrap();
            let next_token = match state.current() {
                Ok(token) => token,
                Err(()) => return ParserResult::LexerMoved,
            };

            match next_token.token_type() {
                TokenType::Identifier { .. } => ParserResult::Value(StmtVariant::Stmt(
                    ast::Stmt::LocalAssignment(match expect_local_assignment(state, local_token) {
                        Ok(local_assignment) => local_assignment,
                        Err(()) => return ParserResult::LexerMoved,
                    }),
                )),

                TokenType::Symbol {
                    symbol: Symbol::Function,
                } => {
                    let function_token = state.consume().unwrap();

                    let local_function =
                        match expect_local_function_declaration(state, local_token, function_token)
                        {
                            Ok(local_function) => local_function,
                            Err(()) => return ParserResult::LexerMoved,
                        };

                    ParserResult::Value(StmtVariant::Stmt(ast::Stmt::LocalFunction(local_function)))
                }

                _ => {
                    state.token_error(
                        next_token.clone(),
                        "expected either a variable name or `function`",
                    );

                    ParserResult::LexerMoved
                }
            }
        }

        TokenType::Symbol {
            symbol: Symbol::For,
        } => {
            let for_token = state.consume().unwrap();

            ParserResult::Value(StmtVariant::Stmt(match expect_for_stmt(state, for_token) {
                Ok(for_stmt) => for_stmt,
                Err(()) => return ParserResult::LexerMoved,
            }))
        }

        TokenType::Symbol { symbol: Symbol::Do } => {
            let do_token = state.consume().unwrap();
            let (block, end_token) = match expect_block_with_end(state, "do", &do_token) {
                Ok(block) => block,
                Err(()) => return ParserResult::LexerMoved,
            };

            ParserResult::Value(StmtVariant::Stmt(ast::Stmt::Do(ast::Do {
                do_token,
                block,
                end_token,
            })))
        }

        TokenType::Symbol { symbol: Symbol::If } => {
            let if_token = state.consume().unwrap();

            ParserResult::Value(StmtVariant::Stmt(ast::Stmt::If(
                match expect_if_stmt(state, if_token) {
                    Ok(if_stmt) => if_stmt,
                    Err(()) => return ParserResult::LexerMoved,
                },
            )))
        }

        TokenType::Symbol {
            symbol: Symbol::Function,
        } => {
            let function_token = state.consume().unwrap();

            let function_declaration = match expect_function_declaration(state, function_token) {
                Ok(function_declaration) => function_declaration,
                Err(()) => return ParserResult::LexerMoved,
            };

            ParserResult::Value(StmtVariant::Stmt(ast::Stmt::FunctionDeclaration(
                function_declaration,
            )))
        }

        TokenType::Symbol {
            symbol: Symbol::Repeat,
        } => {
            let repeat_token = state.consume().unwrap();

            ParserResult::Value(StmtVariant::Stmt(
                match expect_repeat_stmt(state, repeat_token) {
                    Ok(repeat_stmt) => repeat_stmt,
                    Err(()) => return ParserResult::LexerMoved,
                },
            ))
        }

        TokenType::Symbol {
            symbol: Symbol::While,
        } => {
            let while_token = state.consume().unwrap();

            ParserResult::Value(StmtVariant::Stmt(ast::Stmt::While(
                match expect_while_stmt(state, while_token) {
                    Ok(while_stmt) => while_stmt,
                    Err(()) => return ParserResult::LexerMoved,
                },
            )))
        }

        TokenType::Symbol {
            symbol: Symbol::LeftParen,
        }
        | TokenType::Identifier { .. } => {
            // unwrap() because we're always starting on the right path
            let (prefix, suffixes) = try_parser!(parse_prefix_and_suffixes(state)).unwrap();

            let var = match suffixes.last() {
                Some(ast::Suffix::Call(_)) => {
                    return ParserResult::Value(StmtVariant::Stmt(ast::Stmt::FunctionCall(
                        ast::FunctionCall { prefix, suffixes },
                    )));
                }

                Some(ast::Suffix::Index(_)) => {
                    ast::Var::Expression(Box::new(ast::VarExpression { prefix, suffixes }))
                }

                #[cfg(feature = "luau")]
                Some(ast::Suffix::TypeInstantiation(_)) => {
                    ast::Var::Expression(Box::new(ast::VarExpression { prefix, suffixes }))
                }

                None => match prefix {
                    ast::Prefix::Name(name) => ast::Var::Name(name),

                    // I think this only happens in error cases
                    prefix @ ast::Prefix::Expression(_) => {
                        ast::Var::Expression(Box::new(ast::VarExpression { prefix, suffixes }))
                    }
                },
            };

            match state.current() {
                #[cfg(feature = "luau")]
                // Compound Assignment
                Ok(token)
                    if state.lua_version().has_luau()
                        && (token.is_symbol(Symbol::PlusEqual)
                            || token.is_symbol(Symbol::MinusEqual)
                            || token.is_symbol(Symbol::StarEqual)
                            || token.is_symbol(Symbol::SlashEqual)
                            || token.is_symbol(Symbol::DoubleSlashEqual)
                            || token.is_symbol(Symbol::PercentEqual)
                            || token.is_symbol(Symbol::CaretEqual)
                            || token.is_symbol(Symbol::TwoDotsEqual)) =>
                {
                    return parse_compound_assignment(state, var);
                }

                #[cfg(feature = "cfxlua")]
                Ok(token)
                    if state.lua_version().has_cfxlua()
                        && (token.is_symbol(Symbol::PlusEqual)
                            || token.is_symbol(Symbol::MinusEqual)
                            || token.is_symbol(Symbol::StarEqual)
                            || token.is_symbol(Symbol::SlashEqual)
                            || token.is_symbol(Symbol::CaretEqual)
                            || token.is_symbol(Symbol::DoubleLessThanEqual)
                            || token.is_symbol(Symbol::DoubleGreaterThanEqual)
                            || token.is_symbol(Symbol::AmpersandEqual)
                            || token.is_symbol(Symbol::PipeEqual)) =>
                {
                    return parse_compound_assignment(state, var);
                }

                Ok(token) if token.is_symbol(Symbol::Comma) || token.is_symbol(Symbol::Equal) => {}

                Ok(token) => {
                    // Check if the consumed token is a potential context-sensitive keyword
                    #[cfg(feature = "luau")]
                    if state.lua_version().has_luau() {
                        if let ast::Var::Name(token) = var {
                            match token.token_type() {
                                TokenType::Identifier { identifier }
                                    if identifier.as_str() == "export" =>
                                {
                                    let export_token = token;

                                    let type_token = match state.current() {
                                        Ok(token) if matches!(token.token_type(), TokenType::Identifier { identifier } if identifier.as_str() == "type") => {
                                            state.consume().unwrap()
                                        }

                                        Ok(token) => {
                                            state.token_error_ranged(
                                                token.clone(),
                                                "expected `type` after `export`",
                                                &export_token,
                                                &token.clone(),
                                            );

                                            return ParserResult::LexerMoved;
                                        }

                                        Err(()) => return ParserResult::LexerMoved,
                                    };

                                    if let Some(function_token) = state.consume_if(Symbol::Function)
                                    {
                                        return ParserResult::Value(StmtVariant::Stmt(
                                            ast::Stmt::ExportedTypeFunction(
                                                ast::ExportedTypeFunction {
                                                    export_token,
                                                    type_function: match expect_type_function(
                                                        state,
                                                        type_token,
                                                        function_token,
                                                    ) {
                                                        Ok(type_function) => type_function,
                                                        Err(()) => return ParserResult::LexerMoved,
                                                    },
                                                },
                                            ),
                                        ));
                                    }

                                    return ParserResult::Value(StmtVariant::Stmt(
                                        ast::Stmt::ExportedTypeDeclaration(
                                            ast::ExportedTypeDeclaration {
                                                export_token,
                                                type_declaration: match expect_type_declaration(
                                                    state, type_token,
                                                ) {
                                                    Ok(type_declaration) => type_declaration,
                                                    Err(()) => return ParserResult::LexerMoved,
                                                },
                                            },
                                        ),
                                    ));
                                }
                                TokenType::Identifier { identifier }
                                    if identifier.as_str() == "type" =>
                                {
                                    let type_token = token;

                                    if let Some(function_token) = state.consume_if(Symbol::Function)
                                    {
                                        return ParserResult::Value(StmtVariant::Stmt(
                                            ast::Stmt::TypeFunction(
                                                match expect_type_function(
                                                    state,
                                                    type_token,
                                                    function_token,
                                                ) {
                                                    Ok(type_function) => type_function,
                                                    Err(()) => return ParserResult::LexerMoved,
                                                },
                                            ),
                                        ));
                                    }

                                    return ParserResult::Value(StmtVariant::Stmt(
                                        ast::Stmt::TypeDeclaration(
                                            match expect_type_declaration(state, type_token) {
                                                Ok(type_declaration) => type_declaration,
                                                Err(()) => return ParserResult::LexerMoved,
                                            },
                                        ),
                                    ));
                                }
                                TokenType::Identifier { identifier }
                                    if identifier.as_str() == "continue" =>
                                {
                                    let continue_token = token;
                                    return ParserResult::Value(StmtVariant::LastStmt(
                                        ast::LastStmt::Continue(continue_token),
                                    ));
                                }
                                TokenType::Identifier { identifier }
                                    if identifier.as_str() == "const" =>
                                {
                                    let const_token = token;

                                    let next_token_type = match state.current() {
                                        Ok(next) => next.token_type().clone(),
                                        Err(()) => return ParserResult::LexerMoved,
                                    };

                                    match next_token_type {
                                        TokenType::Identifier { .. } => {
                                            return ParserResult::Value(StmtVariant::Stmt(
                                                ast::Stmt::ConstAssignment(
                                                    match expect_const_assignment(
                                                        state,
                                                        const_token,
                                                    ) {
                                                        Ok(ca) => ca,
                                                        Err(()) => return ParserResult::LexerMoved,
                                                    },
                                                ),
                                            ));
                                        }

                                        TokenType::Symbol {
                                            symbol: Symbol::Function,
                                        } => {
                                            let function_token = state.consume().unwrap();
                                            let const_function =
                                                match expect_const_function_declaration(
                                                    state,
                                                    const_token,
                                                    function_token,
                                                ) {
                                                    Ok(cf) => cf,
                                                    Err(()) => return ParserResult::LexerMoved,
                                                };
                                            return ParserResult::Value(StmtVariant::Stmt(
                                                ast::Stmt::ConstFunction(const_function),
                                            ));
                                        }

                                        _ => {
                                            if let Ok(t) = state.current() {
                                                state.token_error(
                                                    t.clone(),
                                                    "expected a variable name or `function` after `const`",
                                                );
                                            }
                                            return ParserResult::LexerMoved;
                                        }
                                    }
                                }
                                _ => (),
                            }
                        }
                    }

                    state.token_error(
                        token.clone(),
                        "unexpected expression when looking for a statement",
                    );

                    return ParserResult::LexerMoved;
                }

                Err(()) => return ParserResult::LexerMoved,
            };

            let mut var_list = Punctuated::new();
            var_list.push(Pair::End(var));

            loop {
                let next_comma = match state.current() {
                    Ok(token) if token.is_symbol(Symbol::Comma) => state.consume().unwrap(),
                    Ok(_) => break,
                    Err(()) => return ParserResult::LexerMoved,
                };

                let (next_prefix, next_suffixes) = match parse_prefix_and_suffixes(state) {
                    ParserResult::Value((prefix, suffixes)) => (prefix, suffixes),

                    ParserResult::LexerMoved => {
                        break;
                    }

                    ParserResult::NotFound => {
                        state.token_error(next_comma, "expected another variable");
                        break;
                    }
                };

                match next_suffixes.last() {
                    Some(ast::Suffix::Call(call)) => {
                        state.token_error(
                            call.tokens().next_back().unwrap().clone(),
                            "can't assign to the result of a call",
                        );
                        break;
                    }

                    Some(ast::Suffix::Index(_)) => {
                        var_list.push_punctuated(
                            ast::Var::Expression(Box::new(ast::VarExpression {
                                prefix: next_prefix,
                                suffixes: next_suffixes,
                            })),
                            next_comma,
                        );
                    }

                    #[cfg(feature = "luau")]
                    Some(ast::Suffix::TypeInstantiation(_)) => {
                        var_list.push_punctuated(
                            ast::Var::Expression(Box::new(ast::VarExpression {
                                prefix: next_prefix,
                                suffixes: next_suffixes,
                            })),
                            next_comma,
                        );
                    }

                    None => match next_prefix {
                        ast::Prefix::Name(name) => {
                            var_list.push_punctuated(ast::Var::Name(name), next_comma);
                        }

                        prefix @ ast::Prefix::Expression(_) => var_list.push_punctuated(
                            ast::Var::Expression(Box::new(ast::VarExpression {
                                prefix,
                                suffixes: next_suffixes,
                            })),
                            next_comma,
                        ),
                    },
                }
            }

            let Some(equal_token) = state.require(Symbol::Equal, "expected `=` after name") else {
                return ParserResult::LexerMoved;
            };

            let expr_list = match parse_expression_list(state) {
                ParserResult::Value(expr_list) => expr_list,

                ParserResult::NotFound => {
                    state.token_error(equal_token.clone(), "expected values to set to");
                    Punctuated::new()
                }

                ParserResult::LexerMoved => Punctuated::new(),
            };

            ParserResult::Value(StmtVariant::Stmt(ast::Stmt::Assignment(ast::Assignment {
                var_list,
                equal_token,
                expr_list,
            })))
        }

        #[cfg(any(feature = "lua52", feature = "luajit", feature = "cfxlua"))]
        TokenType::Symbol {
            symbol: Symbol::Goto,
        } => {
            debug_assert!(state.lua_version().has_lua52() || state.lua_version().has_luajit());

            let goto_token = state.consume().unwrap();

            match state.current() {
                Ok(token) if matches!(token.token_type(), TokenType::Identifier { .. }) => {
                    let label_name = state.consume().unwrap();
                    ParserResult::Value(StmtVariant::Stmt(ast::Stmt::Goto(ast::Goto {
                        goto_token,
                        label_name,
                    })))
                }

                Ok(token) => {
                    state.token_error_ranged(
                        token.clone(),
                        "expected label name after `goto`",
                        &goto_token,
                        &token.clone(),
                    );

                    ParserResult::LexerMoved
                }

                Err(()) => {
                    state.token_error(goto_token, "expected label name after `goto`");
                    ParserResult::LexerMoved
                }
            }
        }

        #[cfg(any(feature = "lua52", feature = "luajit"))]
        TokenType::Symbol {
            symbol: Symbol::TwoColons,
        } if state.lua_version().has_lua52() || state.lua_version().has_luajit() => {
            let left_colons = state.consume().unwrap();

            let name = match state.current() {
                Ok(token) if matches!(token.token_type(), TokenType::Identifier { .. }) => {
                    state.consume().unwrap()
                }

                Ok(token) => {
                    state.token_error_ranged(
                        token.clone(),
                        "expected label name after `::`",
                        &left_colons,
                        &token.clone(),
                    );

                    return ParserResult::LexerMoved;
                }

                Err(()) => return ParserResult::LexerMoved,
            };

            let right_colons = match state.require(Symbol::TwoColons, "expected `::` after label") {
                Some(token) => token,
                None => TokenReference::symbol("::").unwrap(),
            };

            ParserResult::Value(StmtVariant::Stmt(ast::Stmt::Label(ast::Label {
                left_colons,
                name,
                right_colons,
            })))
        }

        #[cfg(feature = "luau")]
        TokenType::Symbol {
            symbol: Symbol::AtSign,
        } if state.lua_version().has_luau() => {
            let ParserResult::Value(attributes) = parse_attributes(state) else {
                return ParserResult::LexerMoved;
            };

            match state.current() {
                Ok(token) if token.is_symbol(Symbol::Function) => {
                    let function_token = state.consume().unwrap();

                    let function_declaration =
                        match expect_function_declaration(state, function_token) {
                            Ok(function_declaration) => function_declaration,
                            Err(()) => return ParserResult::LexerMoved,
                        };

                    ParserResult::Value(StmtVariant::Stmt(ast::Stmt::FunctionDeclaration(
                        function_declaration.with_attributes(attributes),
                    )))
                }
                Ok(token) if token.is_symbol(Symbol::Local) => {
                    let local_token = state.consume().unwrap();
                    match state.current() {
                        Ok(token) if token.is_symbol(Symbol::Function) => {
                            let function_token = state.consume().unwrap();

                            let local_function = match expect_local_function_declaration(
                                state,
                                local_token,
                                function_token,
                            ) {
                                Ok(local_function) => local_function,
                                Err(()) => return ParserResult::LexerMoved,
                            };

                            ParserResult::Value(StmtVariant::Stmt(ast::Stmt::LocalFunction(
                                local_function.with_attributes(attributes),
                            )))
                        }
                        Ok(token) => {
                            state.token_error(
                                token.clone(),
                                "expected `local function` after attribute",
                            );
                            ParserResult::LexerMoved
                        }
                        Err(()) => ParserResult::LexerMoved,
                    }
                }
                Ok(token) if matches!(token.token_type(), TokenType::Identifier { identifier } if identifier.as_str() == "const") =>
                {
                    let const_token = state.consume().unwrap();
                    match state.current() {
                        Ok(token) if token.is_symbol(Symbol::Function) => {
                            let function_token = state.consume().unwrap();

                            let const_function = match expect_const_function_declaration(
                                state,
                                const_token,
                                function_token,
                            ) {
                                Ok(const_function) => const_function,
                                Err(()) => return ParserResult::LexerMoved,
                            };

                            ParserResult::Value(StmtVariant::Stmt(ast::Stmt::ConstFunction(
                                const_function.with_attributes(attributes),
                            )))
                        }
                        Ok(token) => {
                            state.token_error(
                                token.clone(),
                                "expected `const function` after attribute",
                            );
                            ParserResult::LexerMoved
                        }
                        Err(()) => ParserResult::LexerMoved,
                    }
                }
                Ok(token) => {
                    state.token_error(
                        token.clone(),
                        "expected `function`, `local function`, or `const function` after attribute",
                    );
                    ParserResult::LexerMoved
                }
                Err(()) => ParserResult::LexerMoved,
            }
        }

        _ => ParserResult::NotFound,
    }
}

fn parse_last_stmt(
    state: &mut ParserState,
) -> ParserResult<(ast::LastStmt, Option<TokenReference>)> {
    let last_stmt = match state.current() {
        Ok(token) if token.is_symbol(Symbol::Return) => {
            let return_token = state.consume().unwrap();

            let expr_list = match parse_expression_list(state) {
                ParserResult::Value(expr_list) => expr_list,
                ParserResult::LexerMoved | ParserResult::NotFound => Punctuated::new(),
            };

            ast::LastStmt::Return(ast::Return {
                token: return_token,
                returns: expr_list,
            })
        }

        Ok(token) if token.is_symbol(Symbol::Break) => {
            let break_token = state.consume().unwrap();
            ast::LastStmt::Break(break_token)
        }

        _ => return ParserResult::NotFound,
    };

    let semicolon = state.consume_if(Symbol::Semicolon);

    ParserResult::Value((last_stmt, semicolon))
}

fn expect_function_name(state: &mut ParserState) -> ParserResult<ast::FunctionName> {
    let mut names = Punctuated::new();

    let name = match state.current() {
        Ok(token) if matches!(token.token_type(), TokenType::Identifier { .. }) => {
            state.consume().unwrap()
        }

        Ok(token) => {
            state.token_error(token.clone(), "expected function name");
            return ParserResult::NotFound;
        }

        Err(()) => return ParserResult::NotFound,
    };

    names.push(Pair::End(name));

    loop {
        let middle_token = match state.current() {
            Ok(token) if token.is_symbol(Symbol::Colon) || token.is_symbol(Symbol::Dot) => {
                state.consume().unwrap()
            }
            Ok(_) => break,
            Err(()) => return ParserResult::LexerMoved,
        };

        let name = match state.current() {
            Ok(token) if matches!(token.token_type(), TokenType::Identifier { .. }) => {
                state.consume().unwrap()
            }

            Ok(token) => {
                state.token_error(
                    token.clone(),
                    format!("expected name after `{}`", middle_token.token()),
                );
                return ParserResult::NotFound;
            }

            Err(()) => {
                return ParserResult::LexerMoved;
            }
        };

        if middle_token.is_symbol(Symbol::Dot) {
            names.push_punctuated(name, middle_token);
        } else if middle_token.is_symbol(Symbol::Colon) {
            return ParserResult::Value(ast::FunctionName {
                names,
                colon_name: Some((middle_token, name)),
            });
        } else {
            unreachable!();
        }
    }

    ParserResult::Value(ast::FunctionName {
        names,
        colon_name: None,
    })
}

fn expect_function_declaration(
    state: &mut ParserState,
    function_token: TokenReference,
) -> Result<ast::FunctionDeclaration, ()> {
    let function_name = match expect_function_name(state) {
        ParserResult::Value(name) => name,
        ParserResult::NotFound | ParserResult::LexerMoved => return Err(()),
    };

    let function_body = match parse_function_body(state) {
        ParserResult::Value(body) => body,

        ParserResult::LexerMoved => ast::FunctionBody::new(),

        ParserResult::NotFound => {
            state.token_error(function_token.clone(), "expected a function body");
            ast::FunctionBody::new()
        }
    };

    Ok(ast::FunctionDeclaration {
        #[cfg(feature = "luau")]
        attributes: Vec::new(),
        function_token,
        name: function_name,
        body: function_body,
    })
}

fn expect_local_function_declaration(
    state: &mut ParserState,
    local_token: TokenReference,
    function_token: TokenReference,
) -> Result<ast::LocalFunction, ()> {
    let function_name = match state.current() {
        Ok(token) if token.token_kind() == TokenKind::Identifier => state.consume().unwrap(),

        Ok(token) => {
            state.token_error(token.clone(), "expected a function name");
            return Err(());
        }

        Err(()) => return Err(()),
    };

    let function_body = match parse_function_body(state) {
        ParserResult::Value(function_body) => function_body,
        ParserResult::NotFound => {
            state.token_error(function_token, "expected a function body");
            return Err(());
        }
        ParserResult::LexerMoved => return Err(()),
    };

    Ok(ast::LocalFunction {
        #[cfg(feature = "luau")]
        attributes: Vec::new(),
        local_token,
        function_token,
        name: function_name,
        body: function_body,
    })
}

fn expect_for_stmt(state: &mut ParserState, for_token: TokenReference) -> Result<ast::Stmt, ()> {
    let name_list = match parse_name_list(state) {
        ParserResult::Value(name_list) => name_list,
        ParserResult::NotFound => {
            state.token_error(for_token, "expected name after `for`");
            return Err(());
        }
        ParserResult::LexerMoved => return Err(()),
    };

    let current_token = match state.current() {
        Ok(token) => token,
        Err(()) => return Err(()),
    };

    debug_assert!(!name_list.is_empty());

    if name_list.len() == 1 && current_token.is_symbol(Symbol::Equal) {
        return Ok(ast::Stmt::NumericFor(expect_numeric_for_stmt(
            state,
            for_token,
            name_list.into_iter().next().unwrap(),
        )?));
    }

    let in_token = match current_token {
        token if token.is_symbol(Symbol::In) => state.consume().unwrap(),
        token => {
            state.token_error(token.clone(), "expected `in` after name list");
            return Err(());
        }
    };

    let expressions = match parse_expression_list(state) {
        ParserResult::Value(expressions) => expressions,
        ParserResult::NotFound => {
            state.token_error(in_token, "expected expressions after `in`");
            return Err(());
        }
        ParserResult::LexerMoved => return Err(()),
    };

    let Some(do_token) = state.require(Symbol::Do, "expected `do` after expression list") else {
        return Ok(ast::Stmt::GenericFor(ast::GenericFor {
            for_token,
            names: name_list
                .clone()
                .into_pairs()
                .map(|pair| pair.map(|name| name.name))
                .collect(),
            #[cfg(feature = "luau")]
            type_specifiers: name_list
                .into_iter()
                .map(|name| name.type_specifier)
                .collect(),
            in_token,
            expr_list: expressions,
            do_token: TokenReference::basic_symbol("do"),
            block: ast::Block::new(),
            end_token: TokenReference::basic_symbol("end"),
        }));
    };

    let (block, end) = match expect_block_with_end(state, "for loop", &do_token) {
        Ok(block) => block,
        Err(()) => (ast::Block::new(), TokenReference::basic_symbol("end")),
    };

    Ok(ast::Stmt::GenericFor(ast::GenericFor {
        for_token,
        names: name_list
            .clone()
            .into_pairs()
            .map(|pair| pair.map(|name| name.name))
            .collect(),
        #[cfg(feature = "luau")]
        type_specifiers: name_list
            .into_iter()
            .map(|name| name.type_specifier)
            .collect(),
        in_token,
        expr_list: expressions,
        do_token,
        block,
        end_token: end,
    }))
}

fn expect_numeric_for_stmt(
    state: &mut ParserState,
    for_token: TokenReference,
    index_variable: Name,
) -> Result<ast::NumericFor, ()> {
    let equal_token = state.consume().unwrap();
    debug_assert!(equal_token.is_symbol(Symbol::Equal));

    let start = match parse_expression(state) {
        ParserResult::Value(start) => start,
        ParserResult::NotFound => {
            state.token_error(equal_token, "expected start expression after `=`");
            return Err(());
        }
        ParserResult::LexerMoved => return Err(()),
    };

    let Some(start_end_comma) = state.require(Symbol::Comma, "expected `,` after start expression")
    else {
        return Err(());
    };

    let end = match parse_expression(state) {
        ParserResult::Value(end) => end,
        ParserResult::NotFound => {
            state.token_error(start_end_comma, "expected end expression after `,`");
            return Err(());
        }
        ParserResult::LexerMoved => return Err(()),
    };

    // rewrite todo: this can recover into a numeric for loop with no step (or simulate the do..end)
    let (end_step_comma, step) = match state.consume_if(Symbol::Comma) {
        Some(end_step_comma) => match parse_expression(state) {
            ParserResult::Value(step) => (Some(end_step_comma), Some(step)),
            ParserResult::NotFound => {
                state.token_error(start_end_comma, "expected step expression after `,`");
                return Err(());
            }
            ParserResult::LexerMoved => return Err(()),
        },

        None => (None, None),
    };

    let Some(do_token) = state.require(Symbol::Do, "expected `do` after step expression") else {
        return Err(());
    };

    let (block, end_token) = match expect_block_with_end(state, "numeric for loop", &do_token) {
        Ok(block) => block,
        Err(()) => (ast::Block::new(), TokenReference::basic_symbol("end")),
    };

    Ok(ast::NumericFor {
        for_token,
        index_variable: index_variable.name,
        #[cfg(feature = "luau")]
        type_specifier: index_variable.type_specifier,
        equal_token,
        start,
        start_end_comma,
        end,
        end_step_comma,
        step,
        do_token,
        block,
        end_token,
    })
}

fn expect_if_stmt(state: &mut ParserState, if_token: TokenReference) -> Result<ast::If, ()> {
    let condition = match parse_expression(state) {
        ParserResult::Value(condition) => condition,
        ParserResult::NotFound => {
            state.token_error(if_token, "expected condition after `if`");
            return Err(());
        }
        ParserResult::LexerMoved => return Err(()),
    };

    let Some(then_token) = state.require(Symbol::Then, "expected `then` after condition") else {
        return Err(());
    };

    let then_block = match parse_block(state) {
        ParserResult::Value(block) => block,
        ParserResult::NotFound => {
            state.token_error(then_token, "expected block after `then`");
            return Ok(ast::If::new(condition));
        }
        ParserResult::LexerMoved => {
            return Ok(ast::If::new(condition));
        }
    };

    let mut else_if = Vec::new();

    let else_if_optional = |else_if: Vec<ast::ElseIf>| {
        if else_if.is_empty() {
            None
        } else {
            Some(else_if)
        }
    };

    let unfinished_if =
        |condition, else_if| Ok(ast::If::new(condition).with_else_if(else_if_optional(else_if)));

    loop {
        let else_if_token = match state.current() {
            Ok(else_if_token) if else_if_token.is_symbol(Symbol::ElseIf) => {
                state.consume().unwrap()
            }

            Ok(_) => break,

            Err(()) => {
                return unfinished_if(condition, else_if);
            }
        };

        let condition = match parse_expression(state) {
            ParserResult::Value(condition) => condition,
            ParserResult::NotFound => {
                state.token_error(else_if_token, "expected condition after `elseif`");
                return unfinished_if(condition, else_if);
            }
            ParserResult::LexerMoved => {
                return unfinished_if(condition, else_if);
            }
        };

        let Some(then_token) = state.require(Symbol::Then, "expected `then` after condition")
        else {
            return unfinished_if(condition, else_if);
        };

        let then_block = match parse_block(state) {
            ParserResult::Value(block) => block,
            ParserResult::NotFound => {
                state.token_error(then_token, "expected block after `then`");
                return unfinished_if(condition, else_if);
            }
            ParserResult::LexerMoved => {
                return unfinished_if(condition, else_if);
            }
        };

        else_if.push(ast::ElseIf {
            else_if_token,
            condition,
            then_token,
            block: then_block,
        });
    }

    let (else_block, else_token) = match state.consume_if(Symbol::Else) {
        Some(else_token) => match parse_block(state) {
            ParserResult::Value(block) => (Some(block), Some(else_token)),
            ParserResult::NotFound => {
                state.token_error(else_token.clone(), "expected block after `else`");
                (Some(ast::Block::new()), Some(else_token))
            }
            ParserResult::LexerMoved => (Some(ast::Block::new()), Some(else_token)),
        },

        None => (None, None),
    };

    let end_token = match state.current() {
        Ok(token) if token.is_symbol(Symbol::End) => state.consume().unwrap(),
        Ok(token) => {
            state.token_error(token.clone(), "expected `end` to conclude `if`");
            TokenReference::basic_symbol("end")
        }

        Err(()) => TokenReference::basic_symbol("end"),
    };

    Ok(ast::If {
        if_token,
        condition,
        then_token,
        block: then_block,
        else_if: else_if_optional(else_if),
        else_token,
        r#else: else_block,
        end_token,
    })
}

fn expect_local_assignment(
    state: &mut ParserState,
    local_token: TokenReference,
) -> Result<ast::LocalAssignment, ()> {
    let names = match one_or_more(state, parse_name_with_attributes, Symbol::Comma) {
        ParserResult::Value(names) => names,
        ParserResult::NotFound => {
            unreachable!("expect_local_assignment called without upcoming identifier");
        }
        ParserResult::LexerMoved => return Err(()),
    };

    let mut name_list = Punctuated::new();

    #[cfg(feature = "luau")]
    let mut type_specifiers = Vec::new();
    #[cfg(any(feature = "lua54", feature = "cfxlua"))]
    let mut attributes = Vec::new();

    for name in names.into_pairs() {
        let (name, punctuation) = name.into_tuple();

        #[cfg(any(feature = "lua54", feature = "cfxlua"))]
        attributes.push(name.attribute);

        #[cfg(feature = "luau")]
        type_specifiers.push(name.type_specifier);

        name_list.push(match punctuation {
            Some(punctuation) => Pair::Punctuated(name.name, punctuation),
            None => Pair::End(name.name),
        });
    }

    let mut local_assignment = ast::LocalAssignment {
        local_token,
        name_list,
        #[cfg(feature = "luau")]
        type_specifiers,
        equal_token: None,
        expr_list: Punctuated::new(),
        #[cfg(feature = "lua54")]
        attributes,
    };

    #[cfg(not(feature = "cfxlua"))]
    let symbols = [Symbol::Equal];

    #[cfg(feature = "cfxlua")]
    let symbols = [Symbol::Equal, Symbol::In];

    local_assignment.equal_token = match state.consume_if_symbols(&symbols) {
        Some(equal_token) => Some(equal_token),
        None => return Ok(local_assignment),
    };

    match parse_expression_list(state) {
        ParserResult::Value(expr_list) => local_assignment.expr_list = expr_list,

        ParserResult::NotFound => {
            state.token_error(
                local_assignment.equal_token.clone().unwrap(),
                "expected an expression",
            );
        }

        ParserResult::LexerMoved => {}
    };

    Ok(local_assignment)
}

#[cfg(feature = "luau")]
fn expect_const_assignment(
    state: &mut ParserState,
    const_token: TokenReference,
) -> Result<ast::ConstAssignment, ()> {
    let names = match one_or_more(state, parse_name_with_type_specifiers, Symbol::Comma) {
        ParserResult::Value(names) => names,
        ParserResult::NotFound => {
            unreachable!("expect_const_assignment called without upcoming identifier");
        }
        ParserResult::LexerMoved => return Err(()),
    };

    let mut name_list = Punctuated::new();
    let mut type_specifiers = Vec::new();

    for name in names.into_pairs() {
        let (name, punctuation) = name.into_tuple();
        type_specifiers.push(name.type_specifier);
        name_list.push(match punctuation {
            Some(punctuation) => Pair::Punctuated(name.name, punctuation),
            None => Pair::End(name.name),
        });
    }

    let mut const_assignment = ast::ConstAssignment {
        const_token,
        name_list,
        type_specifiers,
        equal_token: None,
        expr_list: Punctuated::new(),
    };

    const_assignment.equal_token = match state.consume_if_symbols(&[Symbol::Equal]) {
        Some(equal_token) => Some(equal_token),
        None => {
            // const declarations must be initialized
            let last_name = const_assignment.name_list.last().unwrap().value().clone();
            state.token_error_ranged(
                const_assignment.const_token.clone(),
                "const declaration must have an assignment",
                &const_assignment.const_token,
                &last_name,
            );
            return Ok(const_assignment);
        }
    };

    match parse_expression_list(state) {
        ParserResult::Value(expr_list) => {
            const_assignment.expr_list = expr_list;

            let name_count = const_assignment.name_list.len();
            let expr_count = const_assignment.expr_list.len();

            let last_can_expand = const_assignment
                .expr_list
                .last()
                .map(|expr| match expr.value() {
                    ast::Expression::FunctionCall(_) => true,
                    ast::Expression::Symbol(t) => t.is_symbol(Symbol::Ellipsis),
                    _ => false,
                })
                .unwrap_or(false);

            if !last_can_expand && name_count != expr_count {
                state.token_error(
                    const_assignment.const_token.clone(),
                    format!(
                        "const declaration has {} name{} but {} value{}",
                        name_count,
                        if name_count == 1 { "" } else { "s" },
                        expr_count,
                        if expr_count == 1 { "" } else { "s" },
                    ),
                );
            }
        }

        ParserResult::NotFound => {
            state.token_error(
                const_assignment.equal_token.clone().unwrap(),
                "expected an expression",
            );
        }

        ParserResult::LexerMoved => {}
    };

    Ok(const_assignment)
}

#[cfg(feature = "luau")]
fn expect_const_function_declaration(
    state: &mut ParserState,
    const_token: TokenReference,
    function_token: TokenReference,
) -> Result<ast::ConstFunction, ()> {
    let function_name = match state.current() {
        Ok(token) if token.token_kind() == TokenKind::Identifier => state.consume().unwrap(),

        Ok(token) => {
            state.token_error(token.clone(), "expected a function name");
            return Err(());
        }

        Err(()) => return Err(()),
    };

    let function_body = match parse_function_body(state) {
        ParserResult::Value(function_body) => function_body,
        ParserResult::NotFound => {
            state.token_error(function_token, "expected a function body");
            return Err(());
        }
        ParserResult::LexerMoved => return Err(()),
    };

    Ok(ast::ConstFunction {
        attributes: Vec::new(),
        const_token,
        function_token,
        name: function_name,
        body: function_body,
    })
}

fn expect_expression_key(
    state: &mut ParserState,
    left_bracket: TokenReference,
) -> Result<ast::Field, ()> {
    let expression = match parse_expression(state) {
        ParserResult::Value(expression) => expression,

        ParserResult::NotFound => {
            state.token_error(left_bracket, "expected an expression after `[`");

            return Err(());
        }

        ParserResult::LexerMoved => {
            return Err(());
        }
    };

    let Some(right_bracket) = state.require_with_reference_range_callback(
        Symbol::RightBracket,
        "expected `]` after expression",
        || {
            (
                left_bracket.clone(),
                expression.tokens().next_back().unwrap().clone(),
            )
        },
    ) else {
        return Err(());
    };

    // rewrite todo: we can realistically construct a field in error recovery
    // rewrite todo: this should also be range
    let Some(equal_token) = state.require_with_reference_range(
        Symbol::Equal,
        "expected `=` after expression",
        &left_bracket,
        &right_bracket,
    ) else {
        return Err(());
    };

    let value = match parse_expression(state) {
        ParserResult::Value(expression) => expression,

        ParserResult::NotFound => {
            state.token_error(equal_token, "expected an expression after `=`");

            return Err(());
        }

        ParserResult::LexerMoved => {
            return Err(());
        }
    };

    Ok(ast::Field::ExpressionKey {
        brackets: ContainedSpan::new(left_bracket, right_bracket),
        key: expression,
        equal: equal_token,
        value,
    })
}

fn force_table_constructor(
    state: &mut ParserState,
    left_brace: TokenReference,
) -> ast::TableConstructor {
    let mut fields = Punctuated::new();

    let unfinished_table =
        |left_brace: TokenReference, fields: Punctuated<ast::Field>| ast::TableConstructor {
            braces: ContainedSpan::new(left_brace, TokenReference::basic_symbol("}")),
            fields,
        };

    loop {
        let Ok(current_token) = state.current() else {
            return unfinished_table(left_brace, fields);
        };

        let field = match current_token.token_type() {
            TokenType::Symbol {
                symbol: Symbol::RightBrace,
            } => {
                return ast::TableConstructor {
                    braces: ContainedSpan::new(left_brace, state.consume().unwrap()),
                    fields,
                };
            }

            TokenType::Symbol {
                symbol: Symbol::LeftBracket,
            } => {
                let left_bracket = state.consume().unwrap();

                match expect_expression_key(state, left_bracket) {
                    Ok(field) => field,
                    Err(()) => {
                        return unfinished_table(left_brace, fields);
                    }
                }
            }

            TokenType::Identifier { .. } if matches!(state.peek(), Ok(peek_token) if peek_token.is_symbol(Symbol::Equal)) =>
            {
                let key = state.consume().unwrap();

                let equal_token = state.consume().unwrap();

                let value = match parse_expression(state) {
                    ParserResult::Value(expression) => expression,

                    ParserResult::NotFound => {
                        state.token_error(equal_token, "expected an expression after `=`");

                        return unfinished_table(left_brace, fields);
                    }

                    ParserResult::LexerMoved => {
                        return unfinished_table(left_brace, fields);
                    }
                };

                ast::Field::NameKey {
                    key,
                    equal: equal_token,
                    value,
                }
            }

            // used for assignments like this { .a }, its equivalent to { a=true }
            #[cfg(feature = "cfxlua")]
            TokenType::Symbol {
                symbol: Symbol::Dot,
            } => {
                let dot = state.consume().unwrap();

                let key = match state.current() {
                    Ok(token) if token.token_kind() == TokenKind::Identifier => {
                        state.consume().unwrap()
                    }
                    Ok(token) => {
                        state.token_error(token.clone(), "expected identifier after `.`");
                        return unfinished_table(left_brace, fields);
                    }
                    Err(()) => {
                        return unfinished_table(left_brace, fields);
                    }
                };

                ast::Field::SetConstructor { dot, name: key }
            }

            _ => {
                let value = match parse_expression(state) {
                    ParserResult::Value(expression) => expression,

                    ParserResult::NotFound => {
                        state.token_error(
                            match fields.last() {
                                Some(Pair::End(field)) => {
                                    field.tokens().next_back().unwrap().clone()
                                }
                                Some(Pair::Punctuated(field, _)) => {
                                    field.tokens().next_back().unwrap().clone()
                                }
                                None => left_brace.clone(),
                            },
                            "expected a field",
                        );

                        return unfinished_table(left_brace, fields);
                    }

                    ParserResult::LexerMoved => {
                        return unfinished_table(left_brace, fields);
                    }
                };

                ast::Field::NoKey(value)
            }
        };

        match state.current() {
            Ok(token) => {
                if token.is_symbol(Symbol::Comma) || token.is_symbol(Symbol::Semicolon) {
                    fields.push(Pair::Punctuated(field, state.consume().unwrap()))
                } else {
                    fields.push(Pair::End(field));
                    break;
                }
            }

            Err(()) => {
                fields.push(Pair::End(field));
                break;
            }
        };
    }

    let right_brace = match state.require(Symbol::RightBrace, "expected `}` after last field") {
        Some(right_brace) => right_brace,
        None => TokenReference::basic_symbol("}"),
    };

    ast::TableConstructor {
        braces: ContainedSpan::new(left_brace, right_brace),
        fields,
    }
}

fn expect_repeat_stmt(
    state: &mut ParserState,
    repeat_token: TokenReference,
) -> Result<ast::Stmt, ()> {
    let block = match parse_block(state) {
        ParserResult::Value(block) => block,

        ParserResult::NotFound => {
            state.token_error(repeat_token, "expected a block after `repeat`");

            return Err(());
        }

        ParserResult::LexerMoved => {
            return Err(());
        }
    };

    let Some(until_token) = state.require(Symbol::Until, "expected `until` after block") else {
        return Ok(ast::Stmt::Do(ast::Do::new().with_block(block)));
    };

    let condition = match parse_expression(state) {
        ParserResult::Value(expression) => expression,

        ParserResult::NotFound => {
            state.token_error(until_token, "expected a condition after `until`");
            return Ok(ast::Stmt::Do(ast::Do::new().with_block(block)));
        }

        ParserResult::LexerMoved => {
            return Ok(ast::Stmt::Do(ast::Do::new().with_block(block)));
        }
    };

    Ok(ast::Stmt::Repeat(ast::Repeat {
        repeat_token,
        block,
        until: condition,
        until_token,
    }))
}

fn expect_while_stmt(
    state: &mut ParserState,
    while_token: TokenReference,
) -> Result<ast::While, ()> {
    let condition = match parse_expression(state) {
        ParserResult::Value(expression) => expression,

        ParserResult::NotFound => {
            state.token_error(while_token, "expected a condition after `while`");

            return Err(());
        }

        ParserResult::LexerMoved => {
            return Err(());
        }
    };

    let Some(do_token) = state.require(Symbol::Do, "expected `do` after condition") else {
        return Ok(ast::While::new(condition));
    };

    let (block, end_token) = match expect_block_with_end(state, "while loop", &do_token) {
        Ok((block, end_token)) => (block, end_token),

        Err(()) => {
            return Ok(ast::While::new(condition));
        }
    };

    Ok(ast::While {
        while_token,
        condition,
        do_token,
        block,
        end_token,
    })
}

#[cfg(feature = "luau")]
fn expect_type_declaration(
    state: &mut ParserState,
    type_token: TokenReference,
) -> Result<ast::TypeDeclaration, ()> {
    let base = match state.current()? {
        token if token.token_kind() == TokenKind::Identifier => state.consume().unwrap(),
        token => {
            state.token_error(token.clone(), "expected type name");
            // rewrite todo (in future if needed): maybe we can add an error name here to continue parsing?
            return Err(());
        }
    };

    let generics = match parse_generic_type_list(state, TypeListStyle::WithDefaults) {
        ParserResult::Value(generics) => Some(generics),
        ParserResult::NotFound => None,
        _ => return Err(()),
    };

    let equal_token = state
        .require(Symbol::Equal, "expected `=` after type name")
        .unwrap_or_else(|| TokenReference::basic_symbol("="));

    let ParserResult::Value(declare_as) = parse_type(state) else {
        return Err(());
    };

    Ok(ast::TypeDeclaration {
        type_token,
        base,
        generics,
        equal_token,
        declare_as,
    })
}

#[cfg(feature = "luau")]
fn expect_type_function(
    state: &mut ParserState,
    type_token: TokenReference,
    function_token: TokenReference,
) -> Result<ast::TypeFunction, ()> {
    let function_name = match state.current() {
        Ok(token) if token.token_kind() == TokenKind::Identifier => state.consume().unwrap(),

        Ok(token) => {
            state.token_error(token.clone(), "expected a type function name");
            return Err(());
        }

        Err(()) => return Err(()),
    };

    let function_body = match parse_function_body(state) {
        ParserResult::Value(body) => body,
        ParserResult::LexerMoved => return Err(()),
        ParserResult::NotFound => {
            state.token_error(function_token, "expected a type function body");
            return Err(());
        }
    };

    Ok(ast::TypeFunction {
        type_token,
        function_token,
        function_name,
        function_body,
    })
}

fn parse_prefix(state: &mut ParserState) -> ParserResult<ast::Prefix> {
    let current_token = match state.current() {
        Ok(token) => token,
        Err(()) => return ParserResult::NotFound,
    };

    match current_token.token_type() {
        TokenType::Symbol {
            symbol: Symbol::LeftParen,
        } => {
            let left_parenthesis = state.consume().unwrap();

            let expression = Box::new(match try_parser!(parse_expression(state)) {
                Some(expression) => expression,

                None => {
                    state.token_error(left_parenthesis, "expected an expression after `(`");
                    return ParserResult::LexerMoved;
                }
            });

            let Some(right_parenthesis) =
                state.require(Symbol::RightParen, "expected `)` after expression")
            else {
                return ParserResult::Value(ast::Prefix::Expression(Box::new(
                    ast::Expression::Parentheses {
                        contained: ContainedSpan::new(
                            left_parenthesis,
                            TokenReference::basic_symbol(")"),
                        ),
                        expression,
                    },
                )));
            };

            ParserResult::Value(ast::Prefix::Expression(Box::new(
                ast::Expression::Parentheses {
                    contained: ContainedSpan::new(left_parenthesis, right_parenthesis),
                    expression,
                },
            )))
        }

        TokenType::Identifier { .. } => {
            ParserResult::Value(ast::Prefix::Name(state.consume().unwrap()))
        }

        _ => ParserResult::NotFound,
    }
}

fn parse_arguments(state: &mut ParserState) -> ParserResult<ast::FunctionArgs> {
    let current = match state.current() {
        Ok(token) => token,
        Err(()) => return ParserResult::NotFound,
    };

    match current.token_type() {
        TokenType::Symbol {
            symbol: Symbol::LeftParen,
        } => {
            let left_parenthesis = state.consume().unwrap();
            let arguments = try_parser!(parse_expression_list(state)).unwrap_or_default();
            let right_parenthesis = match state.require_with_reference_token(
                Symbol::RightParen,
                "expected `)` to close function call",
                &left_parenthesis,
            ) {
                Some(token) => token,

                None => TokenReference::basic_symbol(")"),
            };

            ParserResult::Value(ast::FunctionArgs::Parentheses {
                parentheses: ContainedSpan::new(left_parenthesis, right_parenthesis),
                arguments,
            })
        }

        TokenType::Symbol {
            symbol: Symbol::LeftBrace,
        } => {
            let left_brace = state.consume().unwrap();

            ParserResult::Value(ast::FunctionArgs::TableConstructor(
                force_table_constructor(state, left_brace),
            ))
        }

        TokenType::StringLiteral { .. } => {
            ParserResult::Value(ast::FunctionArgs::String(state.consume().unwrap()))
        }

        _ => ParserResult::NotFound,
    }
}

fn parse_suffix(state: &mut ParserState) -> ParserResult<ast::Suffix> {
    let Ok(current) = state.current() else {
        return ParserResult::NotFound;
    };

    match current.token_type() {
        #[cfg(feature = "cfxlua")]
        TokenType::Symbol {
            symbol: Symbol::QuestionMarkDot,
        } => {
            let safe_navigation = state.consume().unwrap();
            let name = match state.current() {
                Ok(token) if token.token_kind() == TokenKind::Identifier => {
                    state.consume().unwrap()
                }

                Ok(_) => {
                    state.token_error(safe_navigation, "expected identifier after `?.`");
                    return ParserResult::LexerMoved;
                }

                Err(()) => return ParserResult::LexerMoved,
            };

            ParserResult::Value(ast::Suffix::Index(ast::Index::Dot {
                dot: safe_navigation,
                name,
            }))
        }

        TokenType::Symbol {
            symbol: Symbol::Dot,
        } => {
            let dot = state.consume().unwrap();
            let name = match state.current() {
                Ok(token) if token.token_kind() == TokenKind::Identifier => {
                    state.consume().unwrap()
                }

                Ok(_) => {
                    state.token_error(dot, "expected identifier after `.`");
                    return ParserResult::LexerMoved;
                }

                Err(()) => return ParserResult::LexerMoved,
            };

            ParserResult::Value(ast::Suffix::Index(ast::Index::Dot { dot, name }))
        }

        TokenType::Symbol {
            symbol: Symbol::LeftBracket,
        } => {
            let left_bracket = state.consume().unwrap();

            let expression = match parse_expression(state) {
                ParserResult::Value(expression) => expression,
                ParserResult::LexerMoved => return ParserResult::LexerMoved,
                ParserResult::NotFound => {
                    state.token_error(left_bracket, "expected expression after `[`");
                    return ParserResult::LexerMoved;
                }
            };

            let right_bracket = match state.require_with_reference_range(
                Symbol::RightBracket,
                "expected `]` to close index expression",
                &left_bracket,
                expression.tokens().next_back().unwrap(),
            ) {
                Some(right_bracket) => right_bracket,

                None => TokenReference::basic_symbol("]"),
            };

            ParserResult::Value(ast::Suffix::Index(ast::Index::Brackets {
                brackets: ContainedSpan::new(left_bracket, right_bracket),
                expression,
            }))
        }

        TokenType::Symbol {
            symbol: Symbol::LeftParen | Symbol::LeftBrace,
        }
        | TokenType::StringLiteral { .. } => {
            let arguments = try_parser!(parse_arguments(state)).unwrap();
            ParserResult::Value(ast::Suffix::Call(ast::Call::AnonymousCall(arguments)))
        }

        #[cfg(feature = "luau")]
        TokenType::Symbol {
            symbol: Symbol::LessThan,
        } if state.lua_version().has_luau()
            && matches!(
                state.peek().map(|peek| peek.token_type()),
                Ok(TokenType::Symbol {
                    symbol: Symbol::LessThan
                })
            ) =>
        {
            let outer_0 = state.consume().unwrap();
            match expect_type_instantiation(state, outer_0) {
                Ok(type_instantiation) => {
                    ParserResult::Value(ast::Suffix::TypeInstantiation(type_instantiation))
                }

                Err(_) => ParserResult::LexerMoved,
            }
        }

        TokenType::Symbol {
            symbol: Symbol::Colon,
        } => {
            let colon_token = state.consume().unwrap();

            let name = match state.current() {
                Ok(token) if token.token_kind() == TokenKind::Identifier => {
                    state.consume().unwrap()
                }

                Ok(_) => {
                    state.token_error(colon_token, "expected identifier after `:`");
                    return ParserResult::LexerMoved;
                }

                Err(()) => return ParserResult::LexerMoved,
            };

            #[cfg(feature = "luau")]
            let type_instantiation = if state.lua_version().has_luau() {
                if let Ok(token) = state.current() {
                    if matches!(
                        token.token_type(),
                        TokenType::Symbol {
                            symbol: Symbol::LessThan
                        }
                    ) {
                        let outer_0 = state.consume().unwrap();
                        match expect_type_instantiation(state, outer_0) {
                            Ok(instantiation) => Some(instantiation),
                            Err(()) => return ParserResult::LexerMoved,
                        }
                    } else {
                        None
                    }
                } else {
                    None
                }
            } else {
                None
            };

            let args = match parse_arguments(state) {
                ParserResult::Value(args) => args,
                ParserResult::LexerMoved => ast::FunctionArgs::empty(),
                ParserResult::NotFound => {
                    state.token_error(name.clone(), "expected arguments after `:`");
                    ast::FunctionArgs::empty()
                }
            };

            ParserResult::Value(ast::Suffix::Call(ast::Call::MethodCall(ast::MethodCall {
                colon_token,
                name,
                args,

                #[cfg(feature = "luau")]
                type_instantiation,
            })))
        }

        _ => ParserResult::NotFound,
    }
}

fn parse_prefix_and_suffixes(
    state: &mut ParserState,
) -> ParserResult<(ast::Prefix, Vec<ast::Suffix>)> {
    let prefix = match parse_prefix(state) {
        ParserResult::Value(prefix) => prefix,
        ParserResult::LexerMoved => return ParserResult::LexerMoved,
        ParserResult::NotFound => return ParserResult::NotFound,
    };

    let mut suffixes = Vec::new();

    loop {
        match parse_suffix(state) {
            ParserResult::Value(suffix) => {
                suffixes.push(suffix);
            }

            ParserResult::LexerMoved => {
                break;
            }

            ParserResult::NotFound => {
                break;
            }
        };
    }

    ParserResult::Value((prefix, suffixes))
}

fn parse_expression(state: &mut ParserState) -> ParserResult<Expression> {
    let primary_expression = match parse_primary_expression(state) {
        ParserResult::Value(expression) => expression,
        ParserResult::NotFound => return ParserResult::NotFound,
        ParserResult::LexerMoved => return ParserResult::LexerMoved,
    };

    parse_expression_with_precedence(state, primary_expression, 0)
}

fn parse_primary_expression(state: &mut ParserState) -> ParserResult<Expression> {
    let current_token = match state.current() {
        Ok(token) => token,
        Err(()) => return ParserResult::NotFound,
    };

    let expression = match current_token.token_type() {
        #[cfg(feature = "luau")]
        TokenType::Symbol {
            symbol: Symbol::AtSign,
        } => {
            let ParserResult::Value(attributes) = parse_attributes(state) else {
                return ParserResult::LexerMoved;
            };

            match state.current() {
                Ok(token) if token.is_symbol(Symbol::Function) => {
                    let function_token = state.consume().unwrap();
                    let function_body = match parse_function_body(state) {
                        ParserResult::Value(body) => body,
                        ParserResult::LexerMoved => return ParserResult::LexerMoved,
                        ParserResult::NotFound => {
                            state.token_error(function_token, "expected a function body");
                            return ParserResult::LexerMoved;
                        }
                    };

                    ParserResult::Value(Expression::Function(Box::new(ast::AnonymousFunction {
                        #[cfg(feature = "luau")]
                        attributes,
                        function_token,
                        body: function_body,
                    })))
                }
                Ok(token) => {
                    state.token_error(token.clone(), "expected `function` after attributes");
                    return ParserResult::LexerMoved;
                }
                Err(()) => return ParserResult::LexerMoved,
            }
        }

        TokenType::Symbol {
            symbol: Symbol::Function,
        } => {
            let function_token = state.consume().unwrap();
            let function_body = match parse_function_body(state) {
                ParserResult::Value(body) => body,
                ParserResult::LexerMoved => return ParserResult::LexerMoved,
                ParserResult::NotFound => {
                    state.token_error(function_token, "expected a function body");
                    return ParserResult::LexerMoved;
                }
            };

            ParserResult::Value(Expression::Function(Box::new(ast::AnonymousFunction {
                #[cfg(feature = "luau")]
                attributes: Vec::new(),
                function_token,
                body: function_body,
            })))
        }

        TokenType::Symbol {
            symbol: Symbol::True | Symbol::False | Symbol::Nil | Symbol::Ellipsis,
        } => ParserResult::Value(Expression::Symbol(state.consume().unwrap())),

        TokenType::StringLiteral { .. } => {
            let string_token = state.consume().unwrap();
            ParserResult::Value(Expression::String(string_token))
        }

        TokenType::Number { .. } => {
            let number_token = state.consume().unwrap();
            ParserResult::Value(Expression::Number(number_token))
        }

        TokenType::Identifier { .. }
        | TokenType::Symbol {
            symbol: Symbol::LeftParen,
        } => {
            let (prefix, suffixes) = match parse_prefix_and_suffixes(state) {
                ParserResult::Value(value) => value,
                ParserResult::LexerMoved => return ParserResult::LexerMoved,
                ParserResult::NotFound => {
                    unreachable!("identifier found but parse_prefix_and_suffixes didn't even move");
                }
            };

            if suffixes.is_empty() {
                match prefix {
                    ast::Prefix::Expression(expression) => ParserResult::Value(*expression),
                    ast::Prefix::Name(name) => {
                        ParserResult::Value(Expression::Var(ast::Var::Name(name)))
                    }
                }
            } else if matches!(suffixes.last().unwrap(), ast::Suffix::Call(_)) {
                ParserResult::Value(Expression::FunctionCall(ast::FunctionCall {
                    prefix,
                    suffixes,
                }))
            } else {
                ParserResult::Value(Expression::Var(ast::Var::Expression(Box::new(
                    ast::VarExpression { prefix, suffixes },
                ))))
            }
        }

        #[cfg(feature = "lua53")]
        TokenType::Symbol {
            symbol: Symbol::Minus | Symbol::Not | Symbol::Hash | Symbol::Tilde,
        } => {
            let unary_operator_token = state.consume().unwrap();
            parse_unary_expression(state, unary_operator_token)
        }

        #[cfg(not(feature = "lua53"))]
        TokenType::Symbol {
            symbol: Symbol::Minus | Symbol::Not | Symbol::Hash,
        } => {
            let unary_operator_token = state.consume().unwrap();
            parse_unary_expression(state, unary_operator_token)
        }

        TokenType::Symbol {
            symbol: Symbol::LeftBrace,
        } => {
            let left_brace = state.consume().unwrap();
            ParserResult::Value(ast::Expression::TableConstructor(force_table_constructor(
                state, left_brace,
            )))
        }

        #[cfg(feature = "luau")]
        TokenType::Symbol { symbol: Symbol::If } if state.lua_version().has_luau() => {
            let if_token = state.consume().unwrap();
            match expect_if_else_expression(state, if_token) {
                Ok(if_expression) => {
                    ParserResult::Value(ast::Expression::IfExpression(if_expression))
                }
                Err(_) => ParserResult::LexerMoved,
            }
        }

        #[cfg(feature = "luau")]
        TokenType::InterpolatedString { kind, .. } if state.lua_version().has_luau() => {
            let kind = *kind;
            let interpolated_string_begin = state.consume().unwrap();

            match kind {
                InterpolatedStringKind::Simple => ParserResult::Value(
                    ast::Expression::InterpolatedString(ast::InterpolatedString {
                        segments: Vec::new(),
                        last_string: interpolated_string_begin,
                    }),
                ),

                InterpolatedStringKind::Begin => {
                    ParserResult::Value(ast::Expression::InterpolatedString(
                        expect_interpolated_string(state, interpolated_string_begin),
                    ))
                }

                _ => ParserResult::NotFound,
            }
        }

        _ => ParserResult::NotFound,
    };

    match expression {
        #[cfg(feature = "luau")]
        ParserResult::Value(expression) if state.lua_version().has_luau() => {
            if let Some(assertion_op) = state.consume_if(Symbol::TwoColons) {
                let ParserResult::Value(cast_to) = parse_type(state) else {
                    return ParserResult::LexerMoved;
                };

                ParserResult::Value(ast::Expression::TypeAssertion {
                    expression: Box::new(expression),
                    type_assertion: ast::TypeAssertion {
                        assertion_op,
                        cast_to,
                    },
                })
            } else {
                ParserResult::Value(expression)
            }
        }
        _ => expression,
    }
}

// rewrite todo: i think this should be iterative instead of recursive
fn parse_expression_with_precedence(
    state: &mut ParserState,
    mut lhs: Expression,
    precedence: u8,
) -> ParserResult<Expression> {
    loop {
        let Some(bin_op_precedence) = ast::BinOp::precedence_of_token(match state.current() {
            Ok(token) => token,
            Err(()) => return ParserResult::Value(lhs),
        }) else {
            return ParserResult::Value(lhs);
        };

        if bin_op_precedence < precedence {
            return ParserResult::Value(lhs);
        }

        let bin_op = ast::BinOp::consume(state).unwrap();

        let mut rhs = match parse_primary_expression(state) {
            ParserResult::Value(expression) => expression,
            ParserResult::NotFound => {
                state.token_error(
                    bin_op.token().clone(),
                    "expected expression after binary operator",
                );
                return ParserResult::Value(lhs);
            }
            ParserResult::LexerMoved => return ParserResult::LexerMoved,
        };

        while let Ok(next_bin_op_token) = state.current() {
            let Some(next_bin_op_precedence) = ast::BinOp::precedence_of_token(next_bin_op_token)
            else {
                break;
            };

            let precedence_to_search;

            if next_bin_op_precedence > bin_op_precedence {
                precedence_to_search = bin_op_precedence + 1;
            } else if ast::BinOp::is_right_associative_token(next_bin_op_token)
                && next_bin_op_precedence == bin_op_precedence
            {
                precedence_to_search = bin_op_precedence;
            } else {
                break;
            }

            rhs = match parse_expression_with_precedence(state, rhs, precedence_to_search) {
                ParserResult::Value(expression) => expression,
                ParserResult::NotFound => {
                    state.token_error(
                        bin_op.token().clone(),
                        "expected expression after binary operator",
                    );
                    return ParserResult::Value(lhs);
                }
                ParserResult::LexerMoved => return ParserResult::Value(lhs),
            };
        }

        lhs = Expression::BinaryOperator {
            lhs: Box::new(lhs),
            binop: bin_op,
            rhs: Box::new(rhs),
        };
    }
}

fn parse_unary_expression(
    state: &mut ParserState,
    unary_operator_token: ast::TokenReference,
) -> ParserResult<ast::Expression> {
    let unary_operator = match unary_operator_token.token_type() {
        TokenType::Symbol { symbol } => match symbol {
            Symbol::Minus => ast::UnOp::Minus(unary_operator_token),
            Symbol::Not => ast::UnOp::Not(unary_operator_token),
            Symbol::Hash => ast::UnOp::Hash(unary_operator_token),
            #[cfg(feature = "lua53")]
            Symbol::Tilde if state.lua_version().has_lua53() => {
                ast::UnOp::Tilde(unary_operator_token)
            }
            _ => unreachable!(),
        },

        _ => unreachable!(),
    };

    let primary_expression = match parse_primary_expression(state) {
        ParserResult::Value(expression) => expression,
        ParserResult::NotFound => {
            state.token_error(
                unary_operator.token().clone(),
                format!(
                    "expected an expression after {}",
                    unary_operator.token().token()
                ),
            );
            return ParserResult::NotFound;
        }
        ParserResult::LexerMoved => return ParserResult::LexerMoved,
    };

    let expression = match parse_expression_with_precedence(
        state,
        primary_expression,
        ast::UnOp::precedence(),
    ) {
        ParserResult::Value(expression) => expression,
        ParserResult::LexerMoved => return ParserResult::LexerMoved,
        ParserResult::NotFound => {
            state.token_error(
                unary_operator.token().clone(),
                format!(
                    "expected an expression after {}",
                    unary_operator.token().token()
                ),
            );
            return ParserResult::LexerMoved;
        }
    };

    ParserResult::Value(Expression::UnaryOperator {
        unop: unary_operator,
        expression: Box::new(expression),
    })
}

fn parse_function_body(state: &mut ParserState) -> ParserResult<FunctionBody> {
    const NO_TRAILING_COMMAS_ERROR: &str = "trailing commas in arguments are not allowed";

    #[cfg(feature = "luau")]
    let generics = match parse_generic_type_list(state, TypeListStyle::Plain) {
        ParserResult::Value(generic_declaration) => Some(generic_declaration),
        ParserResult::NotFound => None,
        ParserResult::LexerMoved => return ParserResult::LexerMoved,
    };

    let Some(left_parenthesis) = state.consume_if(Symbol::LeftParen) else {
        return ParserResult::NotFound;
    };

    let mut parameters = Punctuated::new();
    #[cfg(feature = "luau")]
    let mut type_specifiers = Vec::new();
    let right_parenthesis;

    let unfinished_function_body =
        |left_parenthesis: TokenReference, mut parameters: Punctuated<Parameter>| {
            if matches!(parameters.last(), Some(Pair::Punctuated(..))) {
                let last_parameter = parameters.pop().unwrap();
                parameters.push(Pair::End(last_parameter.into_value()));
            }

            // rewrite todo: we should appropriately recover the parsed generics/type_specifiers here
            // but it becomes messy with cfg feature toggles and moves.
            ParserResult::Value(FunctionBody {
                #[cfg(feature = "luau")]
                generics: None, // rewrite todo: fix
                parameters_parentheses: ContainedSpan::new(
                    left_parenthesis,
                    TokenReference::basic_symbol(")"),
                ),
                parameters,
                #[cfg(feature = "luau")]
                type_specifiers: Vec::new(), // rewrite todo: fix
                #[cfg(feature = "luau")]
                return_type: None,
                block: ast::Block::new(),
                end_token: TokenReference::basic_symbol("end"),
            })
        };

    loop {
        match state.current() {
            Ok(token) if token.is_symbol(Symbol::RightParen) => {
                right_parenthesis = state.consume().unwrap();
                break;
            }

            Ok(token) if token.is_symbol(Symbol::Ellipsis) => {
                let ellipsis = state.consume().unwrap();
                parameters.push(Pair::End(ast::Parameter::Ellipsis(ellipsis)));

                #[cfg(feature = "luau")]
                if state.lua_version().has_luau() {
                    let type_specifier = if let Some(colon) = state.consume_if(Symbol::Colon) {
                        // varargs can also be annotated using generic packs: T...
                        let type_info = if matches!(state.current(), Ok(token) if token.token_kind() == TokenKind::Identifier)
                            && matches!(state.peek(), Ok(token) if token.is_symbol(Symbol::Ellipsis))
                        {
                            let name = match parse_name(state) {
                                ParserResult::Value(name) => name.name,
                                _ => unreachable!(),
                            };

                            let Some(ellipsis) =
                                state.require(Symbol::Ellipsis, "expected `...` after type name")
                            else {
                                unreachable!()
                            };

                            ast::TypeInfo::GenericPack { name, ellipsis }
                        } else {
                            match parse_type(state) {
                                ParserResult::Value(type_info) => type_info,
                                _ => return unfinished_function_body(left_parenthesis, parameters),
                            }
                        };

                        Some(ast::TypeSpecifier {
                            punctuation: colon,
                            type_info,
                        })
                    } else {
                        None
                    };
                    type_specifiers.push(type_specifier);
                }

                right_parenthesis = match state.require(Symbol::RightParen, "expected a `)`") {
                    Some(right_parenthesis) => right_parenthesis,
                    None => return unfinished_function_body(left_parenthesis, parameters),
                };

                break;
            }

            Ok(TokenReference {
                token:
                    Token {
                        token_type: TokenType::Identifier { .. },
                        ..
                    },
                ..
            }) => {
                let name_parameter = match parse_name_with_type_specifiers(state) {
                    ParserResult::Value(name) => {
                        #[cfg(feature = "luau")]
                        type_specifiers.push(name.type_specifier);
                        ast::Parameter::Name(name.name)
                    }
                    _ => unreachable!(),
                };

                let Some(comma) = state.consume_if(Symbol::Comma) else {
                    parameters.push(Pair::End(name_parameter));

                    match state.require(Symbol::RightParen, "expected a `)`") {
                        Some(new_right_parenthesis) => {
                            right_parenthesis = new_right_parenthesis;
                            break;
                        }

                        None => return unfinished_function_body(left_parenthesis, parameters),
                    };
                };

                parameters.push(Pair::Punctuated(name_parameter, comma));
            }

            Ok(token) => {
                state.token_error(token.clone(), "expected a parameter name or `)`");

                return unfinished_function_body(left_parenthesis, parameters);
            }

            Err(()) => {
                return unfinished_function_body(left_parenthesis, parameters);
            }
        }
    }

    if matches!(parameters.last(), Some(Pair::Punctuated(..))) {
        let last_parameter = parameters.pop().unwrap();

        state.token_error(
            last_parameter.punctuation().unwrap().clone(),
            NO_TRAILING_COMMAS_ERROR,
        );

        parameters.push(Pair::End(last_parameter.into_value()));
    }

    #[cfg(feature = "luau")]
    let return_type = if state.lua_version().has_luau() {
        if let Some(punctuation) = state.consume_if(Symbol::Colon) {
            match parse_return_type(state) {
                ParserResult::Value(type_info) => Some(ast::TypeSpecifier {
                    punctuation,
                    type_info,
                }),
                _ => return ParserResult::LexerMoved,
            }
        } else if let Some(punctuation) = state.consume_if(Symbol::ThinArrow) {
            state.token_error(
                punctuation.clone(),
                "function return type annotations should use `:` instead of `->`",
            );
            match parse_return_type(state) {
                ParserResult::Value(type_info) => Some(ast::TypeSpecifier {
                    punctuation,
                    type_info,
                }),
                _ => return ParserResult::LexerMoved,
            }
        } else {
            None
        }
    } else {
        None
    };

    let (block, end) = match expect_block_with_end(state, "function body", &right_parenthesis) {
        Ok((block, end)) => (block, end),
        Err(()) => return ParserResult::LexerMoved,
    };

    ParserResult::Value(FunctionBody {
        #[cfg(feature = "luau")]
        generics,
        parameters_parentheses: ContainedSpan::new(left_parenthesis, right_parenthesis),
        parameters,
        #[cfg(feature = "luau")]
        type_specifiers,
        #[cfg(feature = "luau")]
        return_type,
        block,
        end_token: end,
    })
}

#[cfg(feature = "luau")]
fn expect_if_else_expression(
    state: &mut ParserState,
    if_token: TokenReference,
) -> Result<ast::IfExpression, ()> {
    let ParserResult::Value(condition) = parse_expression(state) else {
        return Err(());
    };

    let Some(then_token) = state.require(Symbol::Then, "expected `then` after condition") else {
        return Err(());
    };

    let ParserResult::Value(if_expression) = parse_expression(state) else {
        return Err(());
    };

    let mut else_if_expressions = Vec::new();
    while let Some(else_if_token) = state.consume_if(Symbol::ElseIf) {
        let ParserResult::Value(condition) = parse_expression(state) else {
            return Err(());
        };

        let Some(then_token) = state.require(Symbol::Then, "expected `then` after condition")
        else {
            return Err(());
        };
        let ParserResult::Value(expression) = parse_expression(state) else {
            return Err(());
        };
        else_if_expressions.push(ast::ElseIfExpression {
            else_if_token,
            condition,
            then_token,
            expression,
        })
    }

    let Some(else_token) = state.require(
        Symbol::Else,
        "expected `else` when parsing if then else expression",
    ) else {
        return Err(());
    };

    let ParserResult::Value(else_expression) = parse_expression(state) else {
        return Err(());
    };

    Ok(ast::IfExpression {
        if_token,
        condition: Box::new(condition),
        then_token,
        if_expression: Box::new(if_expression),
        else_if_expressions: if else_if_expressions.is_empty() {
            None
        } else {
            Some(else_if_expressions)
        },
        else_token,
        else_expression: Box::new(else_expression),
    })
}

#[cfg(feature = "luau")]
fn expect_interpolated_string(
    state: &mut ParserState,
    mut current: TokenReference,
) -> ast::InterpolatedString {
    use crate::ShortString;

    use super::luau::InterpolatedStringSegment;

    let mut segments = Vec::new();
    let first_string = current.clone();

    loop {
        let has_double_brace = if current.trailing_trivia.is_empty() {
            if let Some(double_brace) = state.consume_if(Symbol::LeftBrace) {
                state.token_error(
                    double_brace,
                    "unexpected double brace, try \\{ if you meant to escape",
                );

                true
            } else {
                false
            }
        } else {
            false
        };

        let expression = match parse_expression(state) {
            ParserResult::Value(expression) => expression,
            ParserResult::NotFound => {
                state.token_error(current, "expected expression after `{`");
                break;
            }
            ParserResult::LexerMoved => break,
        };

        segments.push(InterpolatedStringSegment {
            expression,
            literal: current,
        });

        // If incorrectly using `x = {{y}}`, provide a better error message by ignoring the right brace
        if has_double_brace {
            state.consume_if(Symbol::RightBrace);
        }

        let Ok(next) = state.current() else {
            break;
        };

        if matches!(
            next.token_type(),
            TokenType::InterpolatedString {
                kind: InterpolatedStringKind::End,
                ..
            }
        ) {
            return ast::InterpolatedString {
                segments,
                last_string: state.consume().unwrap(),
            };
        }

        // `hello {"world" "wait"}`
        if next.token_kind() != TokenKind::InterpolatedString {
            state.token_error(
                next.clone(),
                "interpolated string parameter can only contain an expression",
            );
            break;
        }

        current = match state.consume() {
            ParserResult::Value(token) => token,
            ParserResult::NotFound | ParserResult::LexerMoved => break,
        }
    }

    ast::InterpolatedString {
        last_string: if segments.is_empty() {
            first_string
        } else {
            TokenReference::new(
                Vec::new(),
                Token::new(TokenType::InterpolatedString {
                    literal: ShortString::default(),
                    kind: InterpolatedStringKind::End,
                }),
                Vec::new(),
            )
        },

        segments,
    }
}

#[cfg(feature = "luau")]
fn parse_type(state: &mut ParserState) -> ParserResult<ast::TypeInfo> {
    let Ok(current_token) = state.current() else {
        return ParserResult::NotFound;
    };

    if let TokenType::Symbol {
        symbol: Symbol::Pipe | Symbol::Ampersand,
    } = current_token.token_type()
    {
        parse_type_suffix(state, None)
    } else {
        let ParserResult::Value(simple_type) = parse_simple_type(state, SimpleTypeStyle::Default)
        else {
            return ParserResult::LexerMoved;
        };

        parse_type_suffix(state, Some(simple_type))
    }
}

#[cfg(feature = "luau")]
fn parse_type_or_pack(state: &mut ParserState) -> ParserResult<ast::TypeInfo> {
    if matches!(
        state.current(),
        Ok(token) if matches!(
            token.token_type(),
            TokenType::Symbol { symbol: Symbol::Pipe | Symbol::Ampersand }
        )
    ) {
        return parse_type_suffix(state, None);
    }

    let ParserResult::Value(simple_type) = parse_simple_type(state, SimpleTypeStyle::AllowPack)
    else {
        return ParserResult::LexerMoved;
    };

    // type packs cannot have suffixes
    match simple_type {
        ast::TypeInfo::Tuple { ref types, .. } if types.len() != 1 => {
            ParserResult::Value(simple_type)
        }
        ast::TypeInfo::VariadicPack { .. } | ast::TypeInfo::GenericPack { .. } => unreachable!(),
        _ => parse_type_suffix(state, Some(simple_type)),
    }
}

#[cfg(feature = "luau")]
fn parse_type_pack(state: &mut ParserState) -> ParserResult<ast::TypeInfo> {
    let Ok(current_token) = state.current() else {
        return ParserResult::NotFound;
    };

    if current_token.is_symbol(Symbol::Ellipsis) {
        let ellipsis = state.consume().unwrap();
        let ParserResult::Value(type_info) = parse_type(state) else {
            return ParserResult::LexerMoved;
        };

        ParserResult::Value(ast::TypeInfo::Variadic {
            ellipsis,
            type_info: Box::new(type_info),
        })
    } else if current_token.token_kind() == TokenKind::Identifier
        && matches!(state.peek(), Ok(token) if token.is_symbol(Symbol::Ellipsis))
    {
        let name = match parse_name(state) {
            ParserResult::Value(name) => name.name,
            _ => unreachable!(),
        };

        let Some(ellipsis) = state.require(Symbol::Ellipsis, "expected `...` after type name")
        else {
            unreachable!()
        };

        ParserResult::Value(ast::TypeInfo::GenericPack { name, ellipsis })
    } else {
        // rewrite todo: should we be returning this? or should this be unreachable
        ParserResult::NotFound
    }
}

#[cfg(feature = "luau")]
#[derive(PartialEq, Eq)]
enum SimpleTypeStyle {
    Default,
    AllowPack,
}

#[cfg(feature = "luau")]
fn parse_simple_type(
    state: &mut ParserState,
    style: SimpleTypeStyle,
) -> ParserResult<ast::TypeInfo> {
    let Ok(current_token) = state.current() else {
        return ParserResult::NotFound;
    };

    match current_token.token_type() {
        TokenType::Symbol {
            symbol: Symbol::Nil,
        } => {
            let nil_token = state.consume().unwrap();
            ParserResult::Value(ast::TypeInfo::Basic(nil_token))
        }
        TokenType::Symbol {
            symbol: Symbol::True,
        }
        | TokenType::Symbol {
            symbol: Symbol::False,
        } => {
            let token = state.consume().unwrap();
            ParserResult::Value(ast::TypeInfo::Boolean(token))
        }
        TokenType::StringLiteral { .. } => {
            let token = state.consume().unwrap();
            ParserResult::Value(ast::TypeInfo::String(token))
        }
        // Interpolated strings cannot be used as types
        TokenType::InterpolatedString { .. } => {
            let token = state.consume().unwrap();
            state.token_error(
                token,
                "interpolated string literals cannot be used as types",
            );
            ParserResult::LexerMoved
        }
        TokenType::Identifier { .. } => {
            let name = state.consume().unwrap();

            if name.token.to_string() == "typeof" {
                let left_parenthesis =
                    match state.require(Symbol::LeftParen, "expected `(` after `typeof`") {
                        Some(token) => token,
                        None => TokenReference::basic_symbol("("),
                    };

                let ParserResult::Value(expression) = parse_expression(state) else {
                    return ParserResult::LexerMoved;
                };

                let right_parenthesis = match state.require_with_reference_token(
                    Symbol::RightParen,
                    "expected `)` to close typeof call",
                    &left_parenthesis,
                ) {
                    Some(token) => token,
                    None => TokenReference::basic_symbol(")"),
                };

                ParserResult::Value(ast::TypeInfo::Typeof {
                    typeof_token: name,
                    parentheses: ContainedSpan::new(left_parenthesis, right_parenthesis),
                    inner: Box::new(expression),
                })
            } else {
                match state.current() {
                    Ok(token) if token.is_symbol(Symbol::Dot) => {
                        let punctuation = state.consume().unwrap();

                        let type_base = match parse_name(state) {
                            ParserResult::Value(name) => name.name,
                            ParserResult::NotFound => {
                                state.token_error(
                                    state.current().unwrap().clone(),
                                    "expected identifier after `.`",
                                );
                                return ParserResult::LexerMoved;
                            }
                            ParserResult::LexerMoved => return ParserResult::LexerMoved,
                        };

                        let type_info = if let Some(left_arrow) = state.consume_if(Symbol::LessThan)
                        {
                            let Ok(generics) = expect_generic_type_params(state, left_arrow) else {
                                return ParserResult::LexerMoved;
                            };
                            ast::IndexedTypeInfo::Generic {
                                base: type_base,
                                arrows: generics.arrows,
                                generics: generics.generics,
                            }
                        } else {
                            ast::IndexedTypeInfo::Basic(type_base)
                        };

                        ParserResult::Value(ast::TypeInfo::Module {
                            module: name,
                            punctuation,
                            type_info: Box::new(type_info),
                        })
                    }
                    Ok(token) if token.is_symbol(Symbol::LessThan) => {
                        let left_arrow = state.consume().unwrap();
                        let Ok(generics) = expect_generic_type_params(state, left_arrow) else {
                            return ParserResult::LexerMoved;
                        };
                        ParserResult::Value(ast::TypeInfo::Generic {
                            base: name,
                            arrows: generics.arrows,
                            generics: generics.generics,
                        })
                    }
                    _ => ParserResult::Value(ast::TypeInfo::Basic(name)),
                }
            }
        }
        TokenType::Symbol {
            symbol: Symbol::LeftBrace,
        } => {
            let left_brace = state.consume().unwrap();

            match expect_type_table(state, left_brace) {
                Ok(table) => ParserResult::Value(table),
                Err(_) => ParserResult::LexerMoved,
            }
        }
        TokenType::Symbol {
            symbol: Symbol::LeftParen,
        }
        | TokenType::Symbol {
            symbol: Symbol::LessThan,
        } => match expect_function_type(state, style) {
            Ok(type_info) => ParserResult::Value(type_info),
            Err(_) => ParserResult::LexerMoved,
        },
        _ => ParserResult::NotFound,
    }
}

#[cfg(feature = "luau")]
fn parse_type_suffix(
    state: &mut ParserState,
    simple_type: Option<ast::TypeInfo>,
) -> ParserResult<ast::TypeInfo> {
    let mut is_union = false;
    let mut is_intersection = false;

    let mut types = Punctuated::new();

    let leading = if simple_type.is_some() {
        None
    } else {
        let Ok(current_token) = state.current() else {
            unreachable!("parse_type_suffix called with no simple_type and no current token")
        };

        match current_token.token_type() {
            TokenType::Symbol {
                symbol: Symbol::Pipe,
            } => is_union = true,

            TokenType::Symbol {
                symbol: Symbol::Ampersand,
            } => is_intersection = true,

            _ => unreachable!("parse_type_suffix called with no simple_type and no `|` or `&`"),
        }

        Some(state.consume().unwrap())
    };

    let mut current_type = simple_type;

    loop {
        let type_info = if current_type.is_some() {
            current_type.take().unwrap()
        } else {
            let ParserResult::Value(type_info) = parse_simple_type(state, SimpleTypeStyle::Default)
            else {
                return ParserResult::LexerMoved;
            };

            type_info
        };

        let Ok(current_token) = state.current() else {
            types.push(Pair::End(type_info));
            break;
        };

        match current_token.token_type() {
            TokenType::Symbol {
                symbol: Symbol::QuestionMark,
            } => {
                if is_intersection {
                    state.token_error(
                        current_token.clone(),
                        "cannot mix union and intersection types",
                    );
                    return ParserResult::LexerMoved;
                }

                let question_mark = state.consume().unwrap();

                current_type = Some(ast::TypeInfo::Optional {
                    base: Box::new(type_info),
                    question_mark,
                });

                is_union = true;
            }

            TokenType::Symbol {
                symbol: Symbol::Pipe,
            } => {
                if is_intersection {
                    state.token_error(
                        current_token.clone(),
                        "cannot mix union and intersection types",
                    );
                    return ParserResult::LexerMoved;
                }

                let pipe = state.consume().unwrap();
                types.push(Pair::new(type_info, Some(pipe)));
                is_union = true;
            }

            TokenType::Symbol {
                symbol: Symbol::Ampersand,
            } => {
                if is_union {
                    state.token_error(
                        current_token.clone(),
                        "cannot mix union and intersection types",
                    );
                    return ParserResult::LexerMoved;
                }

                let ampersand = state.consume().unwrap();
                types.push(Pair::new(type_info, Some(ampersand)));
                is_intersection = true;
            }

            _ if types.is_empty() && leading.is_none() => return ParserResult::Value(type_info),

            _ => {
                types.push(Pair::End(type_info));
                break;
            }
        }
    }

    match (is_union, is_intersection) {
        (true, false) => {
            ParserResult::Value(ast::TypeInfo::Union(ast::TypeUnion::new(leading, types)))
        }

        (false, true) => ParserResult::Value(ast::TypeInfo::Intersection(
            ast::TypeIntersection::new(leading, types),
        )),

        _ => unreachable!(),
    }
}

#[cfg(feature = "luau")]
fn expect_type_table(
    state: &mut ParserState,
    left_brace: TokenReference,
) -> Result<ast::TypeInfo, ()> {
    let mut fields = Punctuated::new();

    let mut has_indexer = false;
    let mut array_type = None;

    loop {
        let access = if matches!(state.current(), Ok(token) if token.token_kind() == TokenKind::Identifier && matches!(token.token().to_string().as_str(), "read" | "write"))
            && !matches!(state.peek(), Ok(token) if token.is_symbol(Symbol::Colon))
        {
            Some(state.consume().unwrap())
        } else {
            None
        };

        let current_token = state.current()?;

        let field = if current_token.is_symbol(Symbol::RightBrace) {
            debug_assert!(
                array_type.is_none(),
                "consuming right brace in loop but have seen array type"
            );
            let braces = ContainedSpan::new(left_brace, state.consume().unwrap());
            return Ok(ast::TypeInfo::Table { braces, fields });
        } else if current_token.is_symbol(Symbol::LeftBracket)
            && matches!(state.peek(), Ok(token) if token.token_kind() == TokenKind::StringLiteral)
        {
            let left_brace = state.consume().unwrap();
            let property = state.consume().unwrap();
            let Some(right_brace) = state.require(
                Symbol::RightBracket,
                "expected `]` to close `[` for type table field",
            ) else {
                return Err(());
            };
            let Some(colon) = state.require(Symbol::Colon, "expected `:` after type field key")
            else {
                return Err(());
            };

            let value = match parse_type(state) {
                ParserResult::Value(value) => value,
                ParserResult::LexerMoved | ParserResult::NotFound => {
                    state.token_error(
                        state.current().unwrap().clone(),
                        "expected type after type field key",
                    );
                    return Err(());
                }
            };

            ast::TypeField {
                access,
                key: ast::TypeFieldKey::IndexSignature {
                    brackets: ContainedSpan::new(left_brace, right_brace),
                    inner: ast::TypeInfo::String(property),
                },
                colon,
                value,
            }
        } else if current_token.is_symbol(Symbol::LeftBracket) {
            let left_brace = state.consume().unwrap();
            let key = match parse_type(state) {
                ParserResult::Value(value) => value,
                ParserResult::NotFound => {
                    state.token_error(
                        state.current().unwrap().clone(),
                        "expected type for type field key",
                    );
                    return Err(());
                }
                ParserResult::LexerMoved => return Err(()),
            };
            let Some(right_brace) = state.require(
                Symbol::RightBracket,
                "expected `]` to close `[` for type table field",
            ) else {
                return Err(());
            };
            let Some(colon) = state.require(Symbol::Colon, "expected `:` after type field key")
            else {
                return Err(());
            };

            let value = match parse_type(state) {
                ParserResult::Value(value) => value,
                ParserResult::NotFound => {
                    state.token_error(
                        state.current().unwrap().clone(),
                        "expected type after type field key",
                    );
                    return Err(());
                }
                ParserResult::LexerMoved => return Err(()),
            };

            if has_indexer {
                state.token_error_ranged(
                    left_brace.clone(),
                    "cannot have more than one table indexer",
                    &left_brace,
                    value.tokens().next_back().unwrap(),
                );
            }
            has_indexer = true;

            ast::TypeField {
                access,
                key: ast::TypeFieldKey::IndexSignature {
                    brackets: ContainedSpan::new(left_brace, right_brace),
                    inner: key,
                },
                colon,
                value,
            }
        } else if fields.is_empty()
            && !has_indexer
            && !(current_token.token_kind() == TokenKind::Identifier
                && matches!(state.peek(), Ok(token) if token.is_symbol(Symbol::Colon)))
        {
            array_type = Some((
                access,
                match parse_type(state) {
                    ParserResult::Value(value) => value,
                    ParserResult::NotFound => {
                        state.token_error(
                            state.current().unwrap().clone(),
                            "expected type for table array",
                        );
                        return Err(());
                    }
                    ParserResult::LexerMoved => return Err(()),
                },
            ));
            break;
        } else {
            match parse_name(state) {
                ParserResult::Value(name) => {
                    let Some(colon) =
                        state.require(Symbol::Colon, "expected `:` after type field key")
                    else {
                        return Err(());
                    };
                    let value = match parse_type(state) {
                        ParserResult::Value(value) => value,
                        ParserResult::NotFound => {
                            state.token_error(
                                state.current().unwrap().clone(),
                                "expected type after type field key",
                            );
                            return Err(());
                        }
                        ParserResult::LexerMoved => return Err(()),
                    };

                    ast::TypeField {
                        access,
                        key: ast::TypeFieldKey::Name(name.name),
                        colon,
                        value,
                    }
                }
                ParserResult::NotFound => break,
                ParserResult::LexerMoved => return Err(()),
            }
        };

        match state.current() {
            Ok(token) => {
                if token.is_symbol(Symbol::Comma) || token.is_symbol(Symbol::Semicolon) {
                    fields.push(Pair::Punctuated(field, state.consume().unwrap()))
                } else {
                    fields.push(Pair::End(field));
                    break;
                }
            }

            Err(()) => {
                fields.push(Pair::End(field));
                break;
            }
        };
    }

    let right_brace = state
        .require(Symbol::RightBrace, "expected `}` to close type table")
        .unwrap_or_else(|| TokenReference::basic_symbol("}"));

    let braces = ContainedSpan::new(left_brace, right_brace);

    if let Some((access, type_info)) = array_type {
        Ok(ast::TypeInfo::Array {
            braces,
            access,
            type_info: Box::new(type_info),
        })
    } else {
        Ok(ast::TypeInfo::Table { braces, fields })
    }
}

#[cfg(feature = "luau")]
fn expect_function_type(
    state: &mut ParserState,
    style: SimpleTypeStyle,
) -> Result<ast::TypeInfo, ()> {
    let mut force_function_type =
        matches!(state.current(), Ok(token) if token.is_symbol(Symbol::LessThan));

    let generics = match parse_generic_type_list(state, TypeListStyle::Plain) {
        ParserResult::Value(generics) => Some(generics),
        ParserResult::NotFound => None,
        ParserResult::LexerMoved => return Err(()),
    };

    let mut arguments = Punctuated::new();

    let Some(left_paren) = state.require(Symbol::LeftParen, "expected `(`") else {
        return Err(());
    };

    while !matches!(state.current(), Ok(token) if token.is_symbol(Symbol::RightParen)) {
        // vararg annotation
        match parse_type_pack(state) {
            ParserResult::Value(type_info) => {
                arguments.push(Pair::End(ast::TypeArgument {
                    name: None,
                    type_info,
                }));
                break;
            }
            ParserResult::LexerMoved => return Err(()),
            ParserResult::NotFound => (),
        }

        let Ok(current_token) = state.current() else {
            return Err(());
        };

        let name = if current_token.token_kind() == TokenKind::Identifier
            && matches!(state.peek(), Ok(token) if token.is_symbol(Symbol::Colon))
        {
            Some((state.consume().unwrap(), state.consume().unwrap()))
        } else {
            None
        };

        let ParserResult::Value(type_info) = parse_type(state) else {
            return Err(());
        };

        let type_argument = ast::TypeArgument { name, type_info };

        if !matches!(state.current(), Ok(token) if token.is_symbol(Symbol::Comma)) {
            arguments.push(Pair::End(type_argument));
            break;
        }

        let punctuation = state.consume().unwrap();
        arguments.push(Pair::Punctuated(type_argument, punctuation));

        if matches!(state.current(), Ok(token) if token.is_symbol(Symbol::RightParen)) {
            state.token_error(
                state.current().unwrap().clone(),
                "expected type after `,` but got `)` instead",
            );
            break;
        }
    }

    let Some(right_paren) = state.require(Symbol::RightParen, "expected `)` to close `(`") else {
        return Err(());
    };

    let parentheses = ContainedSpan::new(left_paren, right_paren);

    if arguments
        .iter()
        .any(|arg: &ast::TypeArgument| arg.name().is_some())
    {
        force_function_type = true;
    }

    if !force_function_type
        && !matches!(state.current(), Ok(token) if token.is_symbol(Symbol::ThinArrow))
    {
        // Simple type wrapped in parentheses (not allowed to be a vararg type), or an allowed type pack
        if (arguments.len() == 1
            && !matches!(
                arguments.iter().next().unwrap().type_info,
                ast::TypeInfo::Variadic { .. }
            ))
            || style == SimpleTypeStyle::AllowPack
        {
            return Ok(ast::TypeInfo::Tuple {
                parentheses,
                types: arguments
                    .into_pairs()
                    .map(|pair| pair.map(|argument| argument.type_info))
                    .collect(),
            });
        }
    }

    let Some(arrow) = state.require(
        Symbol::ThinArrow,
        "expected `->` after `()` for function type",
    ) else {
        // rewrite todo: luau recovers from this, using an AstTypeError return type
        return Err(());
    };

    let return_type = match parse_return_type(state) {
        ParserResult::Value(return_type) => return_type,
        ParserResult::LexerMoved | ParserResult::NotFound => return Err(()),
    };

    Ok(ast::TypeInfo::Callback {
        generics,
        parentheses,
        arguments,
        arrow,
        return_type: Box::new(return_type),
    })
}

#[cfg(feature = "luau")]
fn expect_type_specifier(
    state: &mut ParserState,
    punctuation: TokenReference,
) -> Result<ast::TypeSpecifier, ()> {
    let ParserResult::Value(type_info) = parse_type(state) else {
        state.token_error(punctuation, "expected type info after `:`");
        return Err(());
    };

    Ok(ast::TypeSpecifier {
        punctuation,
        type_info,
    })
}

#[cfg(feature = "luau")]
fn parse_return_type(state: &mut ParserState) -> ParserResult<ast::TypeInfo> {
    // rewrite todo: should this be gated behind a check?
    match parse_type_pack(state) {
        ParserResult::Value(type_info) => ParserResult::Value(type_info),
        ParserResult::NotFound => parse_type_or_pack(state),
        ParserResult::LexerMoved => ParserResult::LexerMoved,
    }
}

#[cfg(feature = "luau")]
#[derive(PartialEq, Eq)]
enum TypeListStyle {
    Plain,
    WithDefaults,
}

#[cfg(feature = "luau")]
fn parse_generic_type_list(
    state: &mut ParserState,
    style: TypeListStyle,
) -> ParserResult<ast::GenericDeclaration> {
    if !state.lua_version().has_luau() {
        return ParserResult::NotFound;
    }

    let Some(left_angle_bracket) = state.consume_if(Symbol::LessThan) else {
        return ParserResult::NotFound;
    };

    let mut generics = Punctuated::new();

    let mut seen_pack = false;
    let mut seen_default = false;

    loop {
        let name = match state.current() {
            Ok(token) if token.token_kind() == TokenKind::Identifier => state.consume().unwrap(),

            Ok(token) => {
                state.token_error(token.clone(), "expected a generic type name");
                error_token()
            }

            Err(()) => return ParserResult::LexerMoved,
        };

        let Ok(current_token) = state.current() else {
            return ParserResult::NotFound;
        };

        let (parameter, default) = if seen_pack || current_token.is_symbol(Symbol::Ellipsis) {
            seen_pack = true;

            let ellipsis = match state.consume_if(Symbol::Ellipsis) {
                Some(token) => token,
                None => {
                    state.token_error(name.clone(), "generic types come before generic type packs");
                    TokenReference::basic_symbol("...")
                }
            };

            let default = if style == TypeListStyle::WithDefaults
                && matches!(state.current(), Ok(token) if token.is_symbol(Symbol::Equal))
            {
                seen_default = true;
                let equal_token = state.consume().unwrap();

                // rewrite todo: behind check? is this backtracking?
                let default_type = match parse_type_pack(state) {
                    ParserResult::Value(type_info) => type_info,
                    ParserResult::NotFound => match parse_type_or_pack(state) {
                        ParserResult::Value(type_info)
                            if matches!(type_info, ast::TypeInfo::Tuple { .. }) =>
                        {
                            type_info
                        }
                        ParserResult::Value(type_info) => {
                            state.token_error_ranged(
                                equal_token.clone(),
                                "expected type pack after `=` but got type instead",
                                type_info.tokens().next().unwrap(),
                                type_info.tokens().next_back().unwrap(),
                            );
                            type_info
                        }
                        _ => return ParserResult::LexerMoved,
                    },
                    ParserResult::LexerMoved => return ParserResult::LexerMoved,
                };

                Some((equal_token, default_type))
            } else {
                if seen_default {
                    state.token_error(
                        state.current().unwrap().clone(),
                        "expected default type after type name",
                    )
                }

                None
            };

            (
                ast::GenericParameterInfo::Variadic { name, ellipsis },
                default,
            )
        } else {
            let default = if style == TypeListStyle::WithDefaults
                && matches!(state.current(), Ok(token) if token.is_symbol(Symbol::Equal))
            {
                seen_default = true;
                let equal_token = state.consume().unwrap();
                let default_type = match parse_type(state) {
                    ParserResult::Value(default_type) => default_type,
                    _ => return ParserResult::LexerMoved,
                };

                Some((equal_token, default_type))
            } else {
                if seen_default {
                    state.token_error(
                        state.current().unwrap().clone(),
                        "expected default type after type name",
                    )
                }

                None
            };

            (ast::GenericParameterInfo::Name(name), default)
        };

        match state.current() {
            Ok(token) if token.is_symbol(Symbol::Comma) => {
                let punctuation = state.consume().unwrap();
                generics.push(Pair::Punctuated(
                    ast::GenericDeclarationParameter { parameter, default },
                    punctuation,
                ));

                if let Ok(token) = state.current() {
                    if token.is_symbol(Symbol::GreaterThan) {
                        state.token_error(
                            token.clone(),
                            "expected type after `,` but got `>` instead",
                        );
                    }
                }
            }
            Ok(_) => {
                generics.push(Pair::End(ast::GenericDeclarationParameter {
                    parameter,
                    default,
                }));
                break;
            }
            Err(()) => return ParserResult::LexerMoved,
        };
    }

    let right_angle_bracket = state
        .require(Symbol::GreaterThan, "expected `>` to close generic list")
        .unwrap_or_else(|| TokenReference::basic_symbol(">"));

    ParserResult::Value(ast::GenericDeclaration {
        arrows: ContainedSpan::new(left_angle_bracket, right_angle_bracket),
        generics,
    })
}

#[cfg(feature = "luau")]
struct GenericTypeParams {
    arrows: ContainedSpan,
    generics: Punctuated<ast::TypeInfo>,
}

#[cfg(feature = "luau")]
fn expect_generic_type_params(
    state: &mut ParserState,
    left_arrow: TokenReference,
) -> Result<GenericTypeParams, ()> {
    let mut generics = Punctuated::new();

    loop {
        if state.current()?.is_symbol(Symbol::GreaterThan) {
            break;
        }

        let type_info = match parse_type_pack(state) {
            ParserResult::Value(type_info) => type_info,
            ParserResult::NotFound => match parse_type_or_pack(state) {
                ParserResult::Value(type_info) => type_info,
                _ => return Err(()),
            },
            ParserResult::LexerMoved => return Err(()),
        };

        if let Some(punctuation) = state.consume_if(Symbol::Comma) {
            generics.push(Pair::Punctuated(type_info, punctuation));
            if state.current()?.is_symbol(Symbol::GreaterThan) {
                state.token_error(
                    state.current()?.clone(),
                    "expected type after ',' but got '>' instead",
                );
                break;
            }
        } else {
            generics.push(Pair::End(type_info));
            break;
        }
    }

    let Some(right_arrow) = state.require(
        Symbol::GreaterThan,
        "expected '>' to close generic type parameter list",
    ) else {
        return Err(());
    };

    Ok(GenericTypeParams {
        arrows: ContainedSpan::new(left_arrow, right_arrow),
        generics,
    })
}

#[cfg(feature = "luau")]
fn parse_attributes(state: &mut ParserState) -> ParserResult<Vec<ast::LuauAttribute>> {
    debug_assert!(state
        .current()
        .is_ok_and(|token| token.is_symbol(Symbol::AtSign)));

    let mut attributes = Vec::new();

    while let Some(at_sign) = state.consume_if(Symbol::AtSign) {
        let name = match parse_name(state) {
            ParserResult::Value(name) => name.name,
            ParserResult::NotFound => {
                state.token_error(
                    state.current().unwrap().clone(),
                    "expected identifier after `@`",
                );
                return ParserResult::LexerMoved;
            }
            ParserResult::LexerMoved => return ParserResult::LexerMoved,
        };

        attributes.push(ast::LuauAttribute { at_sign, name });
    }

    ParserResult::Value(attributes)
}

#[derive(Clone)]
struct Name {
    name: TokenReference,
    #[cfg(any(feature = "lua54", feature = "cfxlua"))]
    attribute: Option<super::lua54::Attribute>,
    #[cfg(feature = "luau")]
    type_specifier: Option<ast::TypeSpecifier>,
}

#[cfg(feature = "luau")]
fn parse_name(state: &mut ParserState) -> ParserResult<Name> {
    let Ok(current_token) = state.current() else {
        return ParserResult::NotFound;
    };

    match current_token.token_type() {
        TokenType::Identifier { .. } => {
            let name_token = state.consume().unwrap();
            ParserResult::Value(force_name(state, name_token))
        }

        _ => ParserResult::NotFound,
    }
}

fn parse_name_with_attributes(state: &mut ParserState) -> ParserResult<Name> {
    let Ok(current_token) = state.current() else {
        return ParserResult::NotFound;
    };

    match current_token.token_type() {
        TokenType::Identifier { .. } => {
            let name_token = state.consume().unwrap();
            ParserResult::Value(force_name_with_attributes(state, name_token))
        }

        _ => ParserResult::NotFound,
    }
}

fn parse_name_with_type_specifiers(state: &mut ParserState) -> ParserResult<Name> {
    let Ok(current_token) = state.current() else {
        return ParserResult::NotFound;
    };

    match current_token.token_type() {
        TokenType::Identifier { .. } => {
            let name_token = state.consume().unwrap();
            ParserResult::Value(force_name_with_type_specifiers(state, name_token))
        }

        _ => ParserResult::NotFound,
    }
}

fn force_name(_state: &mut ParserState, name: TokenReference) -> Name {
    Name {
        name,
        #[cfg(feature = "lua54")]
        attribute: None,
        #[cfg(feature = "luau")]
        type_specifier: None,
    }
}

#[cfg(any(feature = "lua54", feature = "cfxlua"))]
fn force_name_with_attributes(state: &mut ParserState, name: TokenReference) -> Name {
    // NOTE: whenever attributes can be parsed, type specifiers are possible
    // so we should fall back to parsing type specifiers if an attribute is not found.
    // NOTE: we do not attempt to parse both type specifiers and attributes at the same time
    if !state.lua_version().has_lua54() && !state.lua_version().has_cfxlua() {
        return force_name_with_type_specifiers(state, name);
    }

    #[cfg(any(feature = "lua54", feature = "cfxlua"))]
    if let Some(left_angle_bracket) = state.consume_if(Symbol::LessThan) {
        const ERROR_INVALID_ATTRIBUTE: &str = "expected identifier after `<` for attribute";

        let attribute_name = match state.current() {
            Ok(token) if matches!(token.token_type(), TokenType::Identifier { .. }) => {
                state.consume().unwrap()
            }

            Ok(token) => {
                state.token_error_ranged(
                    token.clone(),
                    ERROR_INVALID_ATTRIBUTE,
                    &left_angle_bracket,
                    &token.clone(),
                );

                return Name {
                    name,
                    attribute: None,
                    #[cfg(feature = "luau")]
                    type_specifier: None,
                };
            }

            Err(()) => {
                state.token_error(left_angle_bracket, ERROR_INVALID_ATTRIBUTE);

                return Name {
                    name,
                    attribute: None,
                    #[cfg(feature = "luau")]
                    type_specifier: None,
                };
            }
        };

        let Some(right_angle_bracket) =
            state.require(Symbol::GreaterThan, "expected `>` to close attribute")
        else {
            return Name {
                name,
                attribute: Some(super::lua54::Attribute {
                    brackets: ContainedSpan::new(
                        left_angle_bracket,
                        TokenReference::basic_symbol(">"),
                    ),
                    name: attribute_name,
                }),
                #[cfg(feature = "luau")]
                type_specifier: None,
            };
        };

        return Name {
            name,
            attribute: Some(super::lua54::Attribute {
                brackets: ContainedSpan::new(left_angle_bracket, right_angle_bracket),
                name: attribute_name,
            }),
            #[cfg(feature = "luau")]
            type_specifier: None,
        };
    }

    force_name_with_type_specifiers(state, name)
}

#[cfg(feature = "luau")]
fn force_name_with_type_specifiers(state: &mut ParserState, name: TokenReference) -> Name {
    if !state.lua_version().has_luau() {
        return force_name(state, name);
    }

    if let Some(punctuation) = state.consume_if(Symbol::Colon) {
        let Ok(type_specifier) = expect_type_specifier(state, punctuation) else {
            return Name {
                name,
                #[cfg(feature = "lua54")]
                attribute: None,
                type_specifier: None,
            };
        };

        Name {
            name,
            #[cfg(feature = "lua54")]
            attribute: None,
            type_specifier: Some(type_specifier),
        }
    } else {
        force_name(state, name)
    }
}

#[cfg(not(feature = "luau"))]
fn force_name_with_type_specifiers(state: &mut ParserState, name: TokenReference) -> Name {
    force_name(state, name)
}

#[cfg(not(feature = "lua54"))]
fn force_name_with_attributes(state: &mut ParserState, name: TokenReference) -> Name {
    force_name_with_type_specifiers(state, name)
}

#[cfg(feature = "luau")]
fn expect_type_instantiation(
    state: &mut ParserState,
    outer_0: TokenReference,
) -> Result<super::luau::TypeInstantiation, ()> {
    let Some(inner_0) = state.require(
        Symbol::LessThan,
        "expected second `<` in type instantiation",
    ) else {
        return Err(());
    };

    let types = expect_generic_type_params(state, inner_0)?;

    let Some(outer_1) = state.require(
        Symbol::GreaterThan,
        "expected second `>` in type instantiation",
    ) else {
        return Err(());
    };

    Ok(super::luau::TypeInstantiation {
        outer_arrows: ContainedSpan::new(outer_0, outer_1),
        inner_arrows: types.arrows,
        types: types.generics,
    })
}

fn one_or_more<T, F: Fn(&mut ParserState) -> ParserResult<T>>(
    state: &mut ParserState,
    parser: F,
    delimiter: Symbol,
) -> ParserResult<Punctuated<T>> {
    let mut values = Punctuated::new();

    loop {
        let value = match parser(state) {
            ParserResult::Value(value) => value,
            ParserResult::NotFound | ParserResult::LexerMoved => break,
        };

        match state.consume_if(delimiter) {
            Some(delimiter) => {
                values.push(Pair::Punctuated(value, delimiter));
            }

            None => {
                values.push(Pair::End(value));
                break;
            }
        }
    }

    if values.is_empty() {
        return ParserResult::NotFound;
    }

    if let Some(Pair::Punctuated(..)) = values.last() {
        let last_value = values.pop().unwrap();

        state.token_error(
            last_value.punctuation().unwrap().clone(),
            "trailing commas are not allowed",
        );

        values.push(Pair::End(last_value.into_value()));
    }

    ParserResult::Value(values)
}

fn parse_name_list(state: &mut ParserState) -> ParserResult<Punctuated<Name>> {
    one_or_more(state, parse_name_with_type_specifiers, Symbol::Comma)
}

fn parse_expression_list(state: &mut ParserState) -> ParserResult<Punctuated<Expression>> {
    one_or_more(state, parse_expression, Symbol::Comma)
}