just_engine/parser/

api.rs

use crate::parser::ast::StatementType::BreakStatement;
use crate::parser::ast::{
    AssignmentOperator, AssignmentPropertyData, AstBuilderValidationErrorType, BinaryOperator,
    BlockStatementData, CatchClauseData, ClassBodyData, ClassData, DeclarationType,
    ExpressionOrSpreadElement, ExpressionOrSuper, ExpressionPatternType, ExpressionType,
    ExtendedNumberLiteralType, FormalParameters, ForIteratorData, FunctionBodyData,
    FunctionBodyOrExpression, FunctionData, HasMeta, IdentifierData, JsError, JsErrorType,
    LiteralData, LiteralType, LogicalOperator, MemberExpressionType, Meta, MethodDefinitionData,
    MethodDefinitionKind, NumberLiteralType, PatternOrExpression, PatternType, ProgramData,
    PropertyData, PropertyKind, StatementType, SwitchCaseData, TemplateElementData,
    TemplateLiteralData, UnaryOperator, UpdateOperator, VariableDeclarationData,
    VariableDeclarationKind, VariableDeclarationOrExpression, VariableDeclarationOrPattern,
    VariableDeclaratorData,
};
use crate::parser::static_semantics::Semantics;
use crate::parser::util::TAB_WIDTH;
use pest::iterators::{Pair, Pairs};
use pest::Parser;
use pest_derive::Parser;
use std::borrow::Borrow;
use std::collections::HashMap;
use std::rc::Rc;
use std::time::Instant;

/// JavaScript parser using PEG grammar.
///
/// Parses ES6 JavaScript source code into an ESTree-compliant AST.
/// The parser is built on [Pest](https://pest.rs/) and follows the
/// [ECMAScript 2015 specification](https://262.ecma-international.org/6.0/).
///
/// # Examples
///
/// ```
/// use just::parser::JsParser;
///
/// let code = "var x = 5 + 3;";
/// let ast = JsParser::parse_to_ast_from_str(code).unwrap();
/// assert_eq!(ast.body.len(), 1);
/// ```
#[derive(Parser)]
#[grammar = "parser/js_grammar.pest"] // relative to src
pub struct JsParser;

type JsRuleError = JsError<Rule>;

fn pair_to_string(pair: Pair<Rule>, level: usize) -> Vec<String> {
    let mut tree = vec![];
    let span = pair.as_span();
    let rule_name = format!(
        "{:?} => ({},{}) #{:?}",
        pair.as_rule(),
        span.start(),
        span.end(),
        span.as_str()
    );
    let mut string_pads = String::with_capacity(level * TAB_WIDTH);
    for _ in 1..level * TAB_WIDTH + 1 {
        string_pads.push('_');
    }
    tree.push(format!("{}{}", string_pads, rule_name));
    for child_pair in pair.into_inner() {
        tree.append(pair_to_string(child_pair, level + 1).as_mut());
    }
    tree
}

impl JsParser {
    /// Parse JavaScript source into a debug token tree.
    ///
    /// Returns a formatted string representation of the parse tree,
    /// useful for debugging the parser grammar.
    ///
    /// # Examples
    ///
    /// ```
    /// use just::parser::JsParser;
    ///
    /// let code = "var x = 5;";
    /// let tree = JsParser::parse_to_token_tree(code).unwrap();
    /// assert!(tree.contains("script"));
    /// ```
    pub fn parse_to_token_tree(script: &str) -> Result<String, String> {
        let mut tree = vec![];
        let start = Instant::now();
        let result = Self::parse(Rule::script, script);
        let end = Instant::now();
        let total_time = end.saturating_duration_since(start);
        println!("Actual parse time is {}ms", total_time.as_millis());

        match result {
            Ok(pairs) => {
                for pair in pairs {
                    tree.push(pair_to_string(pair, 0).join("\n"));
                }
            }
            Err(err) => {
                return Err(format!("Parse error due to {:?}", err));
            }
        }
        Ok(tree.join("\n"))
    }

    /// Parse JavaScript source into an AST.
    ///
    /// Takes an `Rc<String>` to allow efficient sharing of the source text
    /// across AST nodes for error reporting and formatting.
    ///
    /// # Examples
    ///
    /// ```
    /// use just::parser::JsParser;
    /// use std::rc::Rc;
    ///
    /// let code = Rc::new("var x = 5 + 3;".to_string());
    /// let ast = JsParser::parse_to_ast(code).unwrap();
    /// assert_eq!(ast.body.len(), 1);
    /// ```
    pub fn parse_to_ast(script: Rc<String>) -> Result<ProgramData, JsRuleError> {
        let result = Self::parse(Rule::script, &script);
        match result {
            Ok(pairs) => build_ast_from_script(pairs, &script),
            Err(err) => {
                return Err(JsRuleError {
                    kind: JsErrorType::ParserValidation(err.clone()),
                    message: format!("Parse error due to \n{}", err),
                });
            }
        }
    }

    /// Parse JavaScript source string into an AST.
    ///
    /// Convenience method that wraps the source in an `Rc<String>`.
    /// This is the most commonly used parsing method.
    ///
    /// # Examples
    ///
    /// ```
    /// use just::parser::JsParser;
    ///
    /// let code = "function add(a, b) { return a + b; }";
    /// let ast = JsParser::parse_to_ast_from_str(code).unwrap();
    /// assert_eq!(ast.body.len(), 1);
    /// ```
    pub fn parse_to_ast_from_str(script: &str) -> Result<ProgramData, JsRuleError> {
        Self::parse_to_ast(Rc::new(script.to_string()))
    }

    /// Parse JavaScript and return a formatted AST string.
    ///
    /// Useful for debugging and visualizing the AST structure.
    ///
    /// # Examples
    ///
    /// ```
    /// use just::parser::JsParser;
    ///
    /// let code = "var x = 5;";
    /// let formatted = JsParser::parse_to_ast_formatted_string(code).unwrap();
    /// assert!(formatted.contains("VariableDeclaration"));
    /// ```
    pub fn parse_to_ast_formatted_string(script: &str) -> Result<String, JsRuleError> {
        let result = Self::parse_to_ast_from_str(script)?;
        Ok(result.to_formatted_string(script))
    }

    /// Parse a numeric literal string.
    ///
    /// Supports decimal, hexadecimal (0x), binary (0b), octal (0o),
    /// floating point, and scientific notation.
    ///
    /// # Arguments
    ///
    /// * `s` - The numeric string to parse
    /// * `is_error_on_empty` - Whether to return an error on empty string
    ///
    /// # Examples
    ///
    /// ```
    /// use just::parser::JsParser;
    ///
    /// let hex = "0xFF".to_string();
    /// let result = JsParser::parse_numeric_string(&hex, true).unwrap();
    /// ```
    pub fn parse_numeric_string(
        s: &String,
        is_error_on_empty: bool,
    ) -> Result<ExtendedNumberLiteralType, JsRuleError> {
        let result = Self::parse(Rule::string_numeric_literal, s);
        Ok(match result {
            Ok(mut pairs) => {
                if let Some(pair) = pairs.next() {
                    match pair.as_rule() {
                        Rule::str_numeric_literal => build_ast_from_str_numeric_literal(pair)?,
                        _ => return Err(get_unexpected_error("parse_numeric_string", &pair)),
                    }
                } else {
                    if is_error_on_empty {
                        return Err(JsRuleError {
                            kind: JsErrorType::ParserGeneralError,
                            message: "Got empty string".to_string(),
                        });
                    } else {
                        ExtendedNumberLiteralType::Std(NumberLiteralType::IntegerLiteral(0))
                    }
                }
            }
            Err(err) => {
                return Err(JsRuleError {
                    kind: JsErrorType::ParserValidation(err.clone()),
                    message: format!("Parse error due to \n{}", err),
                });
            }
        })
    }
}

fn get_unexpected_error(src: &'static str, pair: &Pair<Rule>) -> JsRuleError {
    get_unexpected_error_with_rule(src, &pair.as_rule())
}

fn get_unexpected_error_with_rule(src: &'static str, rule: &Rule) -> JsRuleError {
    let message = format!("Unexpected state reached in the parser at \"{:?}\". This indicates internal logic error in the parser.", rule);
    JsRuleError {
        message,
        kind: JsErrorType::Unexpected(src),
    }
}

fn get_validation_error(
    error: String,
    kind: AstBuilderValidationErrorType,
    pair: &Pair<Rule>,
    script: &Rc<String>,
) -> JsRuleError {
    get_validation_error_with_meta(error, kind, get_meta(pair, script))
}

fn get_validation_error_with_meta(
    error: String,
    kind: AstBuilderValidationErrorType,
    meta: Meta,
) -> JsRuleError {
    let message = format!("Parsing error encountered: {}", error);
    JsRuleError {
        message,
        kind: JsErrorType::AstBuilderValidation(kind, meta),
    }
}

fn get_meta(pair: &Pair<Rule>, script: &Rc<String>) -> Meta {
    Meta {
        start_index: pair.as_span().start(),
        end_index: pair.as_span().end(),
        script: script.clone(),
    }
}

/// Helper to safely get the first inner pair with proper error handling.
/// Use this instead of `.into_inner().next().unwrap()` for safer error propagation.
fn expect_inner<'a>(
    pair: Pair<'a, Rule>,
    context: &str,
    script: &Rc<String>,
) -> Result<Pair<'a, Rule>, JsRuleError> {
    let meta = get_meta(&pair, script);
    pair.into_inner().next().ok_or_else(|| {
        get_validation_error_with_meta(
            format!("Expected inner token in {}", context),
            AstBuilderValidationErrorType::SyntaxError,
            meta,
        )
    })
}

fn build_ast_from_script(
    pairs: Pairs<Rule>,
    script: &Rc<String>,
) -> Result<ProgramData, JsRuleError> {
    let mut instructions = vec![];
    let mut end: usize = 0;
    for pair in pairs {
        let meta = get_meta(&pair, script);
        if meta.end_index > end {
            end = meta.end_index;
        }
        match pair.as_rule() {
            Rule::EOI => { /* Do nothing */ }
            Rule::statement_list => {
                // There should be only one pair and it should be statement_list (except EOI)
                let (sl, sl_s) = build_ast_from_statement_list(pair, script)?;
                if sl_s.contains_unpaired_continue.is_true() {
                    return Err(get_validation_error_with_meta(
                        "Invalid 'continue' statement".to_string(),
                        AstBuilderValidationErrorType::SyntaxError,
                        meta,
                    ));
                }
                if sl_s.contains_unpaired_break.is_true() {
                    return Err(get_validation_error_with_meta(
                        "Invalid 'break' statement".to_string(),
                        AstBuilderValidationErrorType::SyntaxError,
                        meta,
                    ));
                }
                validate_lexically_declared_names_have_no_duplicates_and_also_not_present_in_var_declared_names(&sl_s)?;
                //sl_s.top_level_lexically_declared_names should be lexically_declared_names for this production
                //sl_s.top_level_var_declared_names should be var_declared_names for this production
                instructions = sl;
            }
            _ => return Err(get_unexpected_error("build_ast_from_script", &pair)),
        };
    }
    Ok(ProgramData {
        meta: Meta {
            start_index: 0,
            end_index: end,
            script: script.clone(),
        },
        body: instructions,
    })
}

fn build_ast_from_declaration(
    pair: Pair<Rule>,
    script: &Rc<String>,
) -> Result<(DeclarationType, Semantics), JsRuleError> {
    let inner_pair = expect_inner(pair, "build_ast_from_declaration", script)?;
    Ok(match inner_pair.as_rule() {
        Rule::hoistable_declaration | Rule::hoistable_declaration__yield => {
            let (h, _h_s) = build_ast_from_hoistable_declaration(inner_pair, script)?;
            (h, Semantics::new_empty()) // empty top_level_lexically_declared_names
        }
        Rule::class_declaration | Rule::class_declaration__yield => {
            let (c, c_s) = build_ast_from_class_declaration(inner_pair, script)?;
            let mut s = Semantics::new_empty();
            s.top_level_lexically_declared_names = c_s.bound_names;
            (DeclarationType::ClassDeclaration(c), s)
        }
        Rule::lexical_declaration__in | Rule::lexical_declaration__in_yield => {
            let (ld, ld_s) = build_ast_from_lexical_declaration(inner_pair, script)?;
            let mut s = Semantics::new_empty();
            s.top_level_lexically_declared_names = ld_s.bound_names;
            (DeclarationType::VariableDeclaration(ld), s)
        }
        _ => {
            return Err(get_unexpected_error(
                "build_ast_from_declaration",
                &inner_pair,
            ))
        }
    })
}

fn build_ast_from_lexical_declaration(
    pair: Pair<Rule>,
    script: &Rc<String>,
) -> Result<(VariableDeclarationData, Semantics), JsRuleError> {
    let meta = get_meta(&pair, script);
    let mut s = Semantics::new_empty();
    let mut declarations = vec![];
    let mut inner_iter = pair.into_inner();
    let let_or_const_pair = inner_iter.next().unwrap();
    let is_let = let_or_const_pair.as_str() == "let";
    let binding_list_pair = inner_iter.next().unwrap();
    for lexical_binding_pair in binding_list_pair.into_inner() {
        let lexical_binding_meta = get_meta(&lexical_binding_pair, script);
        let (l, l_s) = build_ast_from_lexical_binding_or_variable_declaration_or_binding_element(
            lexical_binding_pair,
            script,
        )?;
        if !is_let {
            // init is mandatory when it is constant declaration assigning to binding_identifier
            if let PatternType::PatternWhichCanBeExpression(ExpressionPatternType::Identifier(id)) =
                l.id.borrow()
            {
                if l.init.is_none() {
                    return Err(get_validation_error_with_meta(
                        format!(
                            "Initializer not provided for constant declaration: {}",
                            id.name
                        ),
                        AstBuilderValidationErrorType::SyntaxError,
                        lexical_binding_meta,
                    ));
                }
            }
        }
        s.merge(l_s);
        declarations.push(l);
    }
    // Look for duplicates in BoundNames
    let mut found = HashMap::new();
    for n in &s.bound_names {
        if n.name == "let" {
            return Err(get_validation_error_with_meta(
                format!("Illegal name found: {}", n),
                AstBuilderValidationErrorType::SyntaxError,
                n.meta.clone(),
            ));
        } else if found.contains_key(&n.name) {
            return Err(get_validation_error_with_meta(
                format!("Duplicate declaration found: {}", n),
                AstBuilderValidationErrorType::SyntaxError,
                n.meta.clone(),
            ));
        } else {
            found.insert(n.name.clone(), true);
        }
    }
    Ok((
        VariableDeclarationData {
            meta,
            declarations,
            kind: if is_let {
                VariableDeclarationKind::Let
            } else {
                VariableDeclarationKind::Const
            },
        },
        s,
    ))
}

fn build_ast_from_hoistable_declaration(
    pair: Pair<Rule>,
    script: &Rc<String>,
) -> Result<(DeclarationType, Semantics), JsRuleError> {
    let inner_pair = pair.into_inner().next().unwrap();
    Ok(match inner_pair.as_rule() {
        Rule::generator_declaration | Rule::generator_declaration__yield => {
            let (f, s) =
                build_ast_from_generator_declaration_or_generator_expression(inner_pair, script)?;
            (DeclarationType::FunctionOrGeneratorDeclaration(f), s)
        }
        Rule::function_declaration | Rule::function_declaration__yield => {
            let (f, s) =
                build_ast_from_function_declaration_or_function_expression(inner_pair, script)?;
            (DeclarationType::FunctionOrGeneratorDeclaration(f), s)
        }
        _ => {
            return Err(get_unexpected_error(
                "build_ast_from_hoistable_declaration",
                &inner_pair,
            ))
        }
    })
}

fn build_ast_from_generator_declaration_or_generator_expression(
    pair: Pair<Rule>,
    script: &Rc<String>,
) -> Result<(FunctionData, Semantics), JsRuleError> {
    let is_generator_declaration = match pair.as_rule() {
        Rule::generator_declaration | Rule::generator_declaration__yield => true,
        _ => false,
    };
    let meta = get_meta(&pair, script);
    let mut pair_iter = pair.into_inner();
    let first_pair = pair_iter.next().unwrap();
    let (f_name, mut s, formal_parameters_pair) =
        if first_pair.as_rule() == Rule::binding_identifier {
            let (bi, mut bi_s) = get_binding_identifier_data(first_pair, script)?;
            if !is_generator_declaration {
                // In case of generator_expression we ignore the binding_identifier
                bi_s.bound_names = vec![];
            }
            (Some(bi), bi_s, pair_iter.next().unwrap())
        } else {
            (None, Semantics::new_empty(), first_pair)
        };
    let (args, args_s) = build_ast_from_formal_parameters(formal_parameters_pair, script)?;
    if args_s.contains_yield_expression.is_true() {
        return Err(get_validation_error_with_meta(
            "Cannot reference 'yield' in parameters".to_string(),
            AstBuilderValidationErrorType::SyntaxError,
            meta.clone(),
        ));
    }
    if args_s.contains_super_property.is_true() {
        return Err(get_validation_error_with_meta(
            "Cannot invoke 'super'".to_string(),
            AstBuilderValidationErrorType::SyntaxError,
            meta.clone(),
        ));
    }
    // We first have generator_body then function_body__yield in it
    let function_body_pair = pair_iter.next().unwrap().into_inner().next().unwrap();
    let (f_body, f_body_s) = build_ast_from_function_body(function_body_pair, script)?;
    if f_body_s.contains_super_property.is_true() {
        return Err(get_validation_error_with_meta(
            "Cannot invoke 'super'".to_string(),
            AstBuilderValidationErrorType::SyntaxError,
            meta.clone(),
        ));
    }
    if f_body_s.has_direct_super.is_true() {
        return Err(get_validation_error_with_meta(
            "Invalid reference to 'super'".to_string(),
            AstBuilderValidationErrorType::SyntaxError,
            meta.clone(),
        ));
    }
    validate_bound_names_have_no_duplicates_and_also_not_present_in_var_declared_names_or_lexically_declared_names(&args_s.bound_names, &vec![], &f_body_s.lexically_declared_names)?;
    let body = Box::new(f_body);
    s.merge(args_s);
    // .merge(f_body_s); bound_names from f_body_s are not returned
    Ok((
        FunctionData {
            meta,
            id: f_name,
            body,
            params: FormalParameters::new(args),
            generator: true,
        },
        s,
    ))
}

fn build_ast_from_function_declaration_or_function_expression(
    pair: Pair<Rule>,
    script: &Rc<String>,
) -> Result<(FunctionData, Semantics), JsRuleError> {
    let is_function_declaration = match pair.as_rule() {
        Rule::function_declaration | Rule::function_declaration__yield => true,
        _ => false,
    };
    let meta = get_meta(&pair, script);
    let mut pair_iter = pair.into_inner();
    let first_pair = pair_iter.next().unwrap();
    let (f_name, mut s, formal_parameters_pair) =
        if first_pair.as_rule() == Rule::binding_identifier {
            let (bi, mut bi_s) = get_binding_identifier_data(first_pair, script)?;
            if !is_function_declaration {
                // In case of function_expression we ignore the binding_identifier
                bi_s.bound_names = vec![];
            }
            (Some(bi), bi_s, pair_iter.next().unwrap())
        } else {
            (None, Semantics::new_empty(), first_pair)
        };
    let formal_parameters_meta = get_meta(&formal_parameters_pair, script);
    let (args, args_s) = build_ast_from_formal_parameters(formal_parameters_pair, script)?;
    if args_s.contains_super_call.is_true() || args_s.contains_super_property.is_true() {
        return Err(get_validation_error_with_meta(
            "Cannot invoke 'super'".to_string(),
            AstBuilderValidationErrorType::SyntaxError,
            formal_parameters_meta,
        ));
    }
    let function_body_pair = pair_iter.next().unwrap();
    let function_body_meta = get_meta(&function_body_pair, script);
    let (f_body, f_body_s) = build_ast_from_function_body(function_body_pair, script)?;
    if f_body_s.contains_super_call.is_true() || f_body_s.contains_super_property.is_true() {
        return Err(get_validation_error_with_meta(
            "Cannot invoke 'super'".to_string(),
            AstBuilderValidationErrorType::SyntaxError,
            function_body_meta,
        ));
    }
    validate_bound_names_have_no_duplicates_and_also_not_present_in_var_declared_names_or_lexically_declared_names(&args_s.bound_names, &vec![], &f_body_s.lexically_declared_names,)?;
    let body = Box::new(f_body);
    s.merge(args_s);
    // .merge(f_body_s); bound_names from f_body_s are not returned
    Ok((
        FunctionData {
            meta,
            id: f_name,
            body,
            params: FormalParameters::new(args),
            generator: false,
        },
        s,
    ))
}

fn build_ast_from_formal_parameters(
    pair: Pair<Rule>,
    script: &Rc<String>,
) -> Result<(Vec<PatternType>, Semantics), JsRuleError> {
    let mut args: Vec<PatternType> = vec![];
    let mut s = Semantics::new_empty();
    for param in pair.into_inner() {
        let meta = get_meta(&param, script);
        args.push(match param.as_rule() {
            Rule::function_rest_parameter | Rule::function_rest_parameter__yield => {
                let binding_rest_element = param.into_inner().next().unwrap();
                let binding_identifier_item = binding_rest_element.into_inner().next().unwrap();
                let (binding_identifier, binding_identifier_s) =
                    get_binding_identifier_data(binding_identifier_item, script)?;
                s.merge(binding_identifier_s);
                PatternType::RestElement {
                    meta,
                    argument: Box::new(
                        ExpressionPatternType::Identifier(binding_identifier).convert_to_pattern(),
                    ),
                }
            }
            Rule::formal_parameter | Rule::formal_parameter__yield => {
                // formal_parameter contains binding_element
                let binding_element = param.into_inner().next().unwrap();
                let (pattern, pattern_s) = build_ast_from_binding_element(binding_element, script)?;
                s.merge(pattern_s);
                pattern
            }
            _ => {
                return Err(get_unexpected_error(
                    "build_ast_from_formal_parameters",
                    &param,
                ))
            }
        });
    }
    Ok((args, s))
}

/// Build AST from a single formal parameter (used for setter property_set_parameter_list).
fn build_ast_from_single_formal_parameter(
    pair: Pair<Rule>,
    script: &Rc<String>,
) -> Result<(Vec<PatternType>, Semantics), JsRuleError> {
    let mut args: Vec<PatternType> = vec![];
    let mut s = Semantics::new_empty();

    match pair.as_rule() {
        Rule::formal_parameter | Rule::formal_parameter__yield => {
            // formal_parameter contains binding_element
            let binding_element = pair.into_inner().next().unwrap();
            let (pattern, pattern_s) = build_ast_from_binding_element(binding_element, script)?;
            s.merge(pattern_s);
            args.push(pattern);
        }
        _ => {
            return Err(get_unexpected_error(
                "build_ast_from_single_formal_parameter",
                &pair,
            ))
        }
    }
    Ok((args, s))
}

fn build_ast_from_generator_body(
    pair: Pair<Rule>,
    script: &Rc<String>,
) -> Result<(FunctionBodyData, Semantics), JsRuleError> {
    build_ast_from_function_body(pair.into_inner().next().unwrap(), script)
}

fn build_ast_from_function_body(
    pair: Pair<Rule>,
    script: &Rc<String>,
) -> Result<(FunctionBodyData, Semantics), JsRuleError> {
    let meta = get_meta(&pair, script);
    let statement_list_pair = pair.into_inner().next().unwrap();
    let statement_list_meta = get_meta(&statement_list_pair, script);
    let (statements, statements_s) = build_ast_from_statement_list(statement_list_pair, script)?;
    if statements_s.contains_unpaired_continue.is_true() {
        return Err(get_validation_error_with_meta(
            "Invalid 'continue' statement".to_string(),
            AstBuilderValidationErrorType::SyntaxError,
            statement_list_meta,
        ));
    }
    if statements_s.contains_unpaired_break.is_true() {
        return Err(get_validation_error_with_meta(
            "Invalid 'break' statement".to_string(),
            AstBuilderValidationErrorType::SyntaxError,
            statement_list_meta,
        ));
    }
    validate_lexically_declared_names_have_no_duplicates_and_also_not_present_in_var_declared_names(&statements_s)?;
    let mut s = Semantics::new_empty();
    s.lexically_declared_names = statements_s.top_level_lexically_declared_names;
    s.var_declared_names = statements_s.top_level_var_declared_names;
    Ok((
        FunctionBodyData {
            meta,
            body: statements,
        },
        s,
    ))
}

fn build_ast_from_statement(
    pair: Pair<Rule>,
    script: &Rc<String>,
) -> Result<(StatementType, Semantics), JsRuleError> {
    let inner_pair = pair.into_inner().next().unwrap();
    let meta = get_meta(&inner_pair, script);
    Ok(match inner_pair.as_rule() {
        Rule::debugger_statement => unimplemented!(),
        Rule::continue_statement | Rule::continue_statement__yield => {
            let (c, _) = build_ast_from_continue_statement(inner_pair, script)?;
            (c, Semantics::new_empty())
        }
        Rule::break_statement | Rule::break_statement__yield => {
            (BreakStatement { meta }, Semantics::new_empty())
        }
        Rule::throw_statement | Rule::throw_statement__yield => {
            let (t, _) = build_ast_from_throw_statement(inner_pair, script)?;
            (t, Semantics::new_empty())
        }
        Rule::if_statement
        | Rule::if_statement__yield
        | Rule::if_statement__return
        | Rule::if_statement__yield_return => build_ast_from_if_statement(inner_pair, script)?,
        Rule::with_statement
        | Rule::with_statement__yield
        | Rule::with_statement__return
        | Rule::with_statement__yield_return => unimplemented!(),
        Rule::try_statement
        | Rule::try_statement__yield
        | Rule::try_statement__return
        | Rule::try_statement__yield_return => build_ast_from_try_statement(inner_pair, script)?,
        Rule::variable_statement | Rule::variable_statement__yield => {
            build_ast_from_variable_statement(inner_pair, script)?
        }
        Rule::breakable_statement
        | Rule::breakable_statement__yield
        | Rule::breakable_statement__return
        | Rule::breakable_statement__yield_return => {
            build_ast_from_breakable_statement(inner_pair, script)?
        }
        Rule::block_statement
        | Rule::block_statement__yield
        | Rule::block_statement__return
        | Rule::block_statement__yield_return => {
            let (bsd, bsd_s) =
                build_ast_from_block(inner_pair.into_inner().next().unwrap(), script)?;
            (StatementType::BlockStatement(bsd), bsd_s)
        }
        Rule::expression_statement | Rule::expression_statement__yield => {
            let (exp, _exp_s) =
                build_ast_from_expression(inner_pair.into_inner().next().unwrap(), script)?;
            (
                StatementType::ExpressionStatement {
                    meta,
                    expression: Box::new(exp),
                },
                Semantics::new_empty(),
            )
        }
        Rule::empty_statement => (
            StatementType::EmptyStatement { meta },
            Semantics::new_empty(),
        ),
        Rule::return_statement | Rule::return_statement__yield => {
            let (r, _) = build_ast_from_return_statement(inner_pair, script)?;
            (r, Semantics::new_empty())
        }
        _ => {
            return Err(get_unexpected_error(
                "build_ast_from_statement",
                &inner_pair,
            ))
        }
    })
}

fn build_ast_from_if_statement(
    pair: Pair<Rule>,
    script: &Rc<String>,
) -> Result<(StatementType, Semantics), JsRuleError> {
    let meta = get_meta(&pair, script);
    let mut inner_iter = pair.into_inner();
    let expression_pair = inner_iter.next().unwrap();
    let (expression, _) = build_ast_from_expression(expression_pair, script)?;
    let mut s = Semantics::new_empty();
    let (statement_true, statement_true_s) =
        build_ast_from_statement(inner_iter.next().unwrap(), script)?;
    s.var_declared_names = statement_true_s.var_declared_names;
    let (statement_else, _statement_else_s) = if let Some(statement_else_pair) = inner_iter.next() {
        let (st, mut st_s) = build_ast_from_statement(statement_else_pair, script)?;
        s.var_declared_names.append(&mut st_s.var_declared_names);
        (Some(Box::new(st)), st_s)
    } else {
        (None, Semantics::new_empty())
    };
    Ok((
        StatementType::IfStatement {
            meta,
            test: Box::new(expression),
            consequent: Box::new(statement_true),
            alternate: statement_else,
        },
        s,
    ))
}

fn build_ast_from_throw_statement(
    pair: Pair<Rule>,
    script: &Rc<String>,
) -> Result<(StatementType, Semantics), JsRuleError> {
    let meta = get_meta(&pair, script);
    let inner_pair = pair.into_inner().next().unwrap();
    let (e, e_s) = build_ast_from_expression(inner_pair, script)?;
    Ok((
        StatementType::ThrowStatement {
            meta,
            argument: Box::new(e),
        },
        e_s,
    ))
}

fn build_ast_from_continue_statement(
    pair: Pair<Rule>,
    script: &Rc<String>,
) -> Result<(StatementType, Semantics), JsRuleError> {
    let mut s = Semantics::new_empty();
    s.contains_unpaired_continue.make_true();
    Ok((
        StatementType::ContinueStatement {
            meta: get_meta(&pair, script),
        },
        s,
    ))
}

fn build_ast_from_statement_list(
    pair: Pair<Rule>,
    script: &Rc<String>,
) -> Result<(Vec<StatementType>, Semantics), JsRuleError> {
    let _meta = get_meta(&pair, script);
    let mut declarations = vec![];
    let mut s = Semantics::new_empty();
    for inner_pair in pair.into_inner() {
        declarations.push(match inner_pair.as_rule() {
            Rule::declaration | Rule::declaration__yield => {
                let (d, mut d_s) = build_ast_from_declaration(inner_pair, script)?;
                s.lexically_declared_names.append(&mut d_s.bound_names);
                StatementType::DeclarationStatement(d)
            }
            Rule::statement
            | Rule::statement__yield
            | Rule::statement__return
            | Rule::statement__yield_return => {
                let (st, st_s) = build_ast_from_statement(inner_pair, script)?;
                s.merge(st_s);
                st
            }
            _ => {
                return Err(get_unexpected_error(
                    "build_ast_from_statement_list",
                    &inner_pair,
                ))
            }
        });
    }
    Ok((declarations, s))
}

fn validate_lexically_declared_names_have_no_duplicates_and_also_not_present_in_var_declared_names(
    s: &Semantics,
) -> Result<(), JsRuleError> {
    // Look for duplicates in LexicallyDeclaredNames
    let mut found = HashMap::new();
    for n in &s.lexically_declared_names {
        if found.contains_key(&n.name) || s.var_declared_names.contains(n) {
            return Err(get_validation_error_with_meta(
                format!("Duplicate declaration found: {}", n),
                AstBuilderValidationErrorType::SyntaxError,
                n.meta.clone(),
            ));
        } else {
            found.insert(n.name.clone(), true);
        }
    }
    Ok(())
}

fn validate_bound_names_have_no_duplicates_and_also_not_present_in_var_declared_names_or_lexically_declared_names(
    bound_names: &Vec<IdentifierData>,
    var_declared_names: &Vec<IdentifierData>,
    lexically_declared_names: &Vec<IdentifierData>,
) -> Result<(), JsRuleError> {
    // Look for duplicates in LexicallyDeclaredNames
    let mut found = HashMap::new();
    for n in bound_names {
        if found.contains_key(&n.name)
            || var_declared_names.contains(n)
            || lexically_declared_names.contains(n)
        {
            return Err(get_validation_error_with_meta(
                format!("Duplicate declaration found: {}", n),
                AstBuilderValidationErrorType::SyntaxError,
                n.meta.clone(),
            ));
        } else {
            found.insert(n.name.clone(), true);
        }
    }
    Ok(())
}

fn build_ast_from_block(
    pair: Pair<Rule>,
    script: &Rc<String>,
) -> Result<(BlockStatementData, Semantics), JsRuleError> {
    let meta = get_meta(&pair, script);
    let (declarations, s) = if let Some(inner_pair) = pair.into_inner().next() {
        build_ast_from_statement_list(inner_pair, script)?
    } else {
        (vec![], Semantics::new_empty())
    };
    validate_lexically_declared_names_have_no_duplicates_and_also_not_present_in_var_declared_names(&s)?;
    Ok((
        BlockStatementData {
            meta,
            body: declarations,
        },
        s,
    ))
}

fn build_ast_from_breakable_statement(
    pair: Pair<Rule>,
    script: &Rc<String>,
) -> Result<(StatementType, Semantics), JsRuleError> {
    let inner_pair = pair.into_inner().next().unwrap();
    Ok(
        if inner_pair.as_rule() == Rule::iteration_statement
            || inner_pair.as_rule() == Rule::iteration_statement__yield
            || inner_pair.as_rule() == Rule::iteration_statement__return
            || inner_pair.as_rule() == Rule::iteration_statement__yield_return
        {
            build_ast_from_iteration_statement(inner_pair, script)?
        } else {
            build_ast_from_switch_statement(inner_pair, script)?
        },
    )
}

fn build_ast_from_iteration_statement(
    pair: Pair<Rule>,
    script: &Rc<String>,
) -> Result<(StatementType, Semantics), JsRuleError> {
    let tag = pair.as_str().splitn(2, ' ').next().unwrap();
    Ok(match tag {
        "do" => build_ast_for_breakable_statement_do(pair, script)?,
        "while" => build_ast_for_breakable_statement_while(pair, script)?,
        "for" => build_ast_for_breakable_statement_for(pair, script)?,
        _ => {
            return Err(get_unexpected_error(
                "build_ast_from_iteration_statement",
                &pair,
            ))
        }
    })
}

fn build_ast_for_breakable_statement_do(
    pair: Pair<Rule>,
    script: &Rc<String>,
) -> Result<(StatementType, Semantics), JsRuleError> {
    let meta = get_meta(&pair, script);
    let mut inner_iter = pair.into_inner();
    let statement_pair = inner_iter.next().unwrap();
    let test_expression_pair = inner_iter.next().unwrap();
    let mut s = Semantics::new_empty();
    let (e, _) = build_ast_from_expression(test_expression_pair, script)?;
    let (st, st_s) = build_ast_from_statement(statement_pair, script)?;
    s.var_declared_names = st_s.var_declared_names;
    Ok((
        StatementType::DoWhileStatement {
            meta,
            test: Box::new(e),
            body: Box::new(st),
        },
        s,
    ))
}

fn build_ast_for_breakable_statement_while(
    pair: Pair<Rule>,
    script: &Rc<String>,
) -> Result<(StatementType, Semantics), JsRuleError> {
    let meta = get_meta(&pair, script);
    let mut inner_iter = pair.into_inner();
    let test_expression_pair = inner_iter.next().unwrap();
    let statement_pair = inner_iter.next().unwrap();
    let mut s = Semantics::new_empty();
    let (e, _) = build_ast_from_expression(test_expression_pair, script)?;
    let (st, st_s) = build_ast_from_statement(statement_pair, script)?;
    s.var_declared_names = st_s.var_declared_names;
    Ok((
        StatementType::WhileStatement {
            meta,
            test: Box::new(e),
            body: Box::new(st),
        },
        s,
    ))
}

fn build_ast_for_breakable_statement_for(
    pair: Pair<Rule>,
    script: &Rc<String>,
) -> Result<(StatementType, Semantics), JsRuleError> {
    let meta = get_meta(&pair, script);
    let mut inner_iter = pair.into_inner();
    let first_pair = inner_iter.next().unwrap();
    let mut s = Semantics::new_empty();
    Ok(match first_pair.as_rule() {
        Rule::left_hand_side_expression
        | Rule::left_hand_side_expression__yield
        | Rule::for_binding
        | Rule::for_binding__yield
        | Rule::for_declaration
        | Rule::for_declaration__yield => {
            /* for-in or for-of */
            let in_of_left = match first_pair.as_rule() {
                Rule::left_hand_side_expression | Rule::left_hand_side_expression__yield => {
                    let (exp, exp_s) =
                        build_ast_from_left_hand_side_expression(first_pair, script)?;
                    let m = Box::new(convert_lhs_expression_to_pattern_for_assignment_operation(
                        exp,
                        Some(&exp_s),
                    )?);
                    VariableDeclarationOrPattern::Pattern(m)
                }
                Rule::for_binding | Rule::for_binding__yield => {
                    let meta = get_meta(&first_pair, script);
                    let meta2 = meta.clone();
                    let (b, mut b_s) = build_ast_from_for_binding(first_pair, script)?;
                    s.var_declared_names.append(&mut b_s.bound_names);

                    VariableDeclarationOrPattern::VariableDeclaration(VariableDeclarationData {
                        meta,
                        declarations: vec![VariableDeclaratorData {
                            meta: meta2,
                            id: Box::new(b),
                            init: None,
                        }],
                        kind: VariableDeclarationKind::Var,
                    })
                }
                Rule::for_declaration | Rule::for_declaration__yield => {
                    let (d, d_s) = build_ast_from_for_declaration(first_pair, script)?;
                    let mut found = HashMap::new();
                    for bn in &d_s.bound_names {
                        if bn.name == "let" {
                            return Err(get_validation_error_with_meta(
                                "Illegal name: let".to_string(),
                                AstBuilderValidationErrorType::SyntaxError,
                                bn.meta.clone(),
                            ));
                        } else if found.contains_key(&bn.name) {
                            return Err(get_validation_error_with_meta(
                                format!("Duplicate declaration present: {}", bn),
                                AstBuilderValidationErrorType::SyntaxError,
                                bn.meta.clone(),
                            ));
                        } else if d_s.var_declared_names.contains(bn) {
                            return Err(get_validation_error_with_meta(
                                format!("Duplicate declaration present: {}", bn),
                                AstBuilderValidationErrorType::SyntaxError,
                                bn.meta.clone(),
                            ));
                        }
                        found.insert(bn.name.clone(), true);
                    }
                    VariableDeclarationOrPattern::VariableDeclaration(d)
                }
                _ => {
                    return Err(get_unexpected_error(
                        "build_ast_for_breakable_statement_for:2",
                        &first_pair,
                    ))
                }
            };
            let second_pair = inner_iter.next().unwrap();
            let ((in_of_right, _in_of_right_s), is_for_of) = match second_pair.as_rule() {
                Rule::assignment_expression__in | Rule::assignment_expression__in_yield => (
                    build_ast_from_assignment_expression(second_pair, script)?,
                    true,
                ),
                _ => (build_ast_from_expression(second_pair, script)?, false),
            };
            let (statement, mut statement_s) =
                build_ast_from_statement(inner_iter.next().unwrap(), script)?;
            let node = ForIteratorData {
                meta,
                left: in_of_left,
                right: Box::new(in_of_right),
                body: Box::new(statement),
            };
            s.var_declared_names
                .append(&mut statement_s.var_declared_names);
            (
                if is_for_of {
                    StatementType::ForOfStatement(node)
                } else {
                    StatementType::ForInStatement(node)
                },
                s,
            )
        }
        _ => {
            /* for(;;) variation */
            let mut lexical_bound_names = HashMap::new();
            let init = match first_pair.as_rule() {
                Rule::lexical_declaration | Rule::lexical_declaration__yield => {
                    //Lexical Declaration rule ends with smart semicolon which is too flexible. We need to ensure it is semi-colon and nothing else.
                    let last_char = first_pair.as_str().trim_end().chars().last().unwrap();
                    if last_char != ';' {
                        return Err(get_validation_error(
                            format!(
                                "Was expecting semi-colon at the end, but got '{}'.",
                                last_char
                            ),
                            AstBuilderValidationErrorType::SyntaxError,
                            &first_pair,
                            script,
                        ));
                    } else {
                        let (d, d_s) = build_ast_from_lexical_declaration(first_pair, script)?;
                        for n in &d_s.bound_names {
                            lexical_bound_names.insert(n.name.clone(), true);
                        }
                        Some(VariableDeclarationOrExpression::VariableDeclaration(d))
                    }
                }
                Rule::variable_declaration_list | Rule::variable_declaration_list__yield => {
                    let meta = get_meta(&first_pair, script);
                    let (declarations, mut declarations_s) =
                        build_ast_from_variable_declaration_list(first_pair, script)?;
                    s.var_declared_names.append(&mut declarations_s.bound_names);

                    if declarations.is_empty() {
                        None
                    } else {
                        Some(VariableDeclarationOrExpression::VariableDeclaration(
                            VariableDeclarationData {
                                meta,
                                declarations,
                                kind: VariableDeclarationKind::Var,
                            },
                        ))
                    }
                }
                Rule::init_expression | Rule::init_expression__yield => {
                    if let Some(inner_pair) = first_pair.into_inner().next() {
                        let (e, _e_s) = build_ast_from_expression(inner_pair, script)?;
                        Some(VariableDeclarationOrExpression::Expression(Box::new(e)))
                    } else {
                        None
                    }
                }
                _ => {
                    return Err(get_unexpected_error(
                        "build_ast_for_breakable_statement_for:2",
                        &first_pair,
                    ))
                }
            };
            let test_pair = inner_iter.next().unwrap();
            let (test, _test_s) = if let Some(test_expression_pair) = test_pair.into_inner().next() {
                let (e, e_s) = build_ast_from_expression(test_expression_pair, script)?;
                (Some(Box::new(e)), e_s)
            } else {
                (None, Semantics::new_empty())
            };
            let update_pair = inner_iter.next().unwrap();
            let (update, _update_s) =
                if let Some(update_expression_pair) = update_pair.into_inner().next() {
                    let (e, e_s) = build_ast_from_expression(update_expression_pair, script)?;
                    (Some(Box::new(e)), e_s)
                } else {
                    (None, Semantics::new_empty())
                };
            let st_pair = inner_iter.next().unwrap();
            let (st, mut st_s) = build_ast_from_statement(st_pair, script)?;
            for n in &st_s.bound_names {
                if lexical_bound_names.contains_key(&n.name) {
                    return Err(get_validation_error_with_meta(
                        format!("Duplicate declaration found: {}", n),
                        AstBuilderValidationErrorType::SyntaxError,
                        n.meta.clone(),
                    ));
                }
            }
            s.var_declared_names.append(&mut st_s.var_declared_names);
            (
                StatementType::ForStatement {
                    meta,
                    init,
                    test,
                    update,
                    body: Box::new(st),
                },
                s,
            )
        }
    })
}

fn build_ast_from_binding_pattern(
    pair: Pair<Rule>,
    script: &Rc<String>,
) -> Result<(PatternType, Semantics), JsRuleError> {
    let meta = get_meta(&pair, script);
    let mut binding_properties = vec![];
    let mut s = Semantics::new_empty();
    let inner_pair = pair.into_inner().next().unwrap();
    Ok(match inner_pair.as_rule() {
        Rule::object_binding_pattern | Rule::object_binding_pattern__yield => {
            let binding_pattern_inner_iter = inner_pair.into_inner();
            for binding_property_pair in binding_pattern_inner_iter {
                let (b, b_s) = build_ast_from_binding_property(binding_property_pair, script)?;
                s.merge(b_s);
                binding_properties.push(b);
            }
            (
                PatternType::ObjectPattern {
                    meta,
                    properties: binding_properties,
                },
                s,
            )
        }
        Rule::array_binding_pattern | Rule::array_binding_pattern__yield => {
            let mut elements: Vec<Option<Box<PatternType>>> = vec![];
            for item_pair in inner_pair.into_inner() {
                match item_pair.as_rule() {
                    Rule::elision => {
                        // Each comma in elision represents a hole
                        for _ in 0..(item_pair.as_str().matches(',').count()) {
                            elements.push(None);
                        }
                    }
                    Rule::binding_element | Rule::binding_element__yield => {
                        let (element, element_s) =
                            build_ast_from_binding_element(item_pair, script)?;
                        s.merge(element_s);
                        elements.push(Some(Box::new(element)));
                    }
                    Rule::binding_rest_element | Rule::binding_rest_element__yield => {
                        let rest_meta = get_meta(&item_pair, script);
                        let binding_id_pair = item_pair.into_inner().next().ok_or_else(|| {
                            get_validation_error_with_meta(
                                "Expected binding identifier in rest element".to_string(),
                                AstBuilderValidationErrorType::SyntaxError,
                                rest_meta.clone(),
                            )
                        })?;
                        let (id, id_s) = get_binding_identifier_data(binding_id_pair, script)?;
                        s.merge(id_s);
                        elements.push(Some(Box::new(PatternType::RestElement {
                            meta: rest_meta,
                            argument: Box::new(
                                ExpressionPatternType::Identifier(id).convert_to_pattern(),
                            ),
                        })));
                    }
                    _ => {
                        return Err(get_unexpected_error(
                            "build_ast_from_binding_pattern:array",
                            &item_pair,
                        ))
                    }
                }
            }
            (PatternType::ArrayPattern { meta, elements }, s)
        }
        _ => {
            return Err(get_unexpected_error(
                "build_ast_from_binding_pattern",
                &inner_pair,
            ))
        }
    })
}

/// Handles binding_element rule: single_name_binding | binding_pattern ~ initializer?
fn build_ast_from_binding_element(
    pair: Pair<Rule>,
    script: &Rc<String>,
) -> Result<(PatternType, Semantics), JsRuleError> {
    let meta = get_meta(&pair, script);
    let mut inner_iter = pair.into_inner();
    let inner_pair = inner_iter.next().ok_or_else(|| {
        get_validation_error_with_meta(
            "Expected binding element content".to_string(),
            AstBuilderValidationErrorType::SyntaxError,
            meta.clone(),
        )
    })?;

    match inner_pair.as_rule() {
        Rule::single_name_binding | Rule::single_name_binding__yield => {
            let (var_decl, s) = build_ast_from_single_name_binding(inner_pair, script)?;
            let VariableDeclaratorData { meta, id, init } = var_decl;
            if let Some(init_expr) = init {
                // Has default value: create AssignmentPattern
                Ok((
                    PatternType::AssignmentPattern {
                        meta,
                        left: id,
                        right: init_expr,
                    },
                    s,
                ))
            } else {
                // No default value: just return the pattern
                Ok((*id, s))
            }
        }
        Rule::binding_pattern | Rule::binding_pattern__yield => {
            let (pattern, s) = build_ast_from_binding_pattern(inner_pair, script)?;
            // Check for optional initializer
            if let Some(init_pair) = inner_iter.next() {
                let init_inner = init_pair.into_inner().next().ok_or_else(|| {
                    get_validation_error_with_meta(
                        "Expected initializer expression".to_string(),
                        AstBuilderValidationErrorType::SyntaxError,
                        meta.clone(),
                    )
                })?;
                let (init_expr, _init_s) =
                    build_ast_from_assignment_expression(init_inner, script)?;
                Ok((
                    PatternType::AssignmentPattern {
                        meta,
                        left: Box::new(pattern),
                        right: Box::new(init_expr),
                    },
                    s,
                ))
            } else {
                Ok((pattern, s))
            }
        }
        _ => Err(get_unexpected_error(
            "build_ast_from_binding_element",
            &inner_pair,
        )),
    }
}

fn build_ast_from_binding_property(
    pair: Pair<Rule>,
    script: &Rc<String>,
) -> Result<(AssignmentPropertyData, Semantics), JsRuleError> {
    let mut inner_iter = pair.into_inner();
    let inner_pair = inner_iter.next().unwrap();
    let meta = get_meta(&inner_pair, script);
    if inner_pair.as_rule() == Rule::single_name_binding
        || inner_pair.as_rule() == Rule::single_name_binding__yield
    {
        let inner_pair_rule = &inner_pair.as_rule();
        let (VariableDeclaratorData { meta, id, init }, s) =
            build_ast_from_single_name_binding(inner_pair, script)?;
        let id = if let PatternType::PatternWhichCanBeExpression(
            ExpressionPatternType::Identifier(id),
        ) = *id
        {
            id
        } else {
            return Err(get_unexpected_error_with_rule(
                "build_ast_from_binding_property:1",
                inner_pair_rule,
            ));
        };
        let meta2 = meta.clone();
        let id2 = id.clone();
        let value = if let Some(init) = init {
            PatternType::AssignmentPattern {
                meta,
                left: Box::new(ExpressionPatternType::Identifier(id).convert_to_pattern()),
                right: init,
            }
        } else {
            ExpressionPatternType::Identifier(id).convert_to_pattern()
        };
        Ok((
            AssignmentPropertyData::new_with_identifier_key(meta2, id2, value, true),
            s,
        ))
    } else if inner_pair.as_rule() == Rule::property_name
        || inner_pair.as_rule() == Rule::property_name__yield
    {
        let (key, _key_s) = build_ast_from_property_name(inner_pair, script)?;
        let (value, value_s) =
            build_ast_from_lexical_binding_or_variable_declaration_or_binding_element(
                inner_iter.next().unwrap(),
                script,
            )?;
        let value_exp = if let Some(init) = value.init {
            PatternType::AssignmentPattern {
                meta: value.meta,
                left: value.id,
                right: init,
            }
        } else {
            *value.id
        };
        // s.merge(value_s); bound_names is read only from value_s (binding_element)
        Ok((
            AssignmentPropertyData::new_with_any_expression_key(meta, key, value_exp, false),
            value_s,
        ))
    } else {
        Err(get_unexpected_error(
            "build_ast_from_binding_property:2",
            &inner_pair,
        ))
    }
}

fn build_ast_from_property_name(
    pair: Pair<Rule>,
    script: &Rc<String>,
) -> Result<(ExpressionType, Semantics), JsRuleError> {
    let inner_pair = pair.into_inner().next().unwrap();
    Ok(if inner_pair.as_rule() == Rule::literal_property_name {
        let pn_pair = inner_pair.into_inner().next().unwrap();
        let s = Semantics::new_empty();
        (
            if pn_pair.as_rule() == Rule::identifier_name {
                let id = get_identifier_data(pn_pair, script);
                ExpressionPatternType::Identifier(id).convert_to_expression()
            } else if pn_pair.as_rule() == Rule::string_literal {
                let d = build_ast_from_string_literal(pn_pair, script)?;
                ExpressionType::Literal(d)
            } else if pn_pair.as_rule() == Rule::numeric_literal {
                let meta = get_meta(&pn_pair, script);
                let d = build_ast_from_numeric_literal(pn_pair)?;
                ExpressionType::Literal(LiteralData {
                    meta,
                    value: LiteralType::NumberLiteral(d),
                })
            } else {
                return Err(get_unexpected_error(
                    "build_ast_from_property_name:1",
                    &pn_pair,
                ));
            },
            s,
        )
    } else if inner_pair.as_rule() == Rule::computed_property_name
        || inner_pair.as_rule() == Rule::computed_property_name__yield
    {
        build_ast_from_assignment_expression(inner_pair.into_inner().next().unwrap(), script)?
    } else {
        return Err(get_unexpected_error(
            "build_ast_from_property_name:2",
            &inner_pair,
        ));
    })
}

fn build_ast_from_for_binding(
    pair: Pair<Rule>,
    script: &Rc<String>,
) -> Result<(PatternType, Semantics), JsRuleError> {
    let inner_pair = pair.into_inner().next().unwrap();
    Ok(match inner_pair.as_rule() {
        Rule::binding_identifier | Rule::binding_identifier__yield => {
            let (bi, bi_s) = get_binding_identifier_data(inner_pair, script)?;
            (
                ExpressionPatternType::Identifier(bi).convert_to_pattern(),
                bi_s,
            )
        }
        Rule::binding_pattern | Rule::binding_pattern__yield => {
            build_ast_from_binding_pattern(inner_pair, script)?
        }
        _ => {
            return Err(get_unexpected_error(
                "build_ast_from_for_binding",
                &inner_pair,
            ))
        }
    })
}

fn build_ast_from_for_declaration(
    pair: Pair<Rule>,
    script: &Rc<String>,
) -> Result<(VariableDeclarationData, Semantics), JsRuleError> {
    let meta = get_meta(&pair, script);
    let mut inner_iter = pair.into_inner();
    let let_or_const_pair = inner_iter.next().unwrap();
    let for_binding_pair = inner_iter.next().unwrap();
    let meta2 = meta.clone();
    let (b, b_s) = build_ast_from_for_binding(for_binding_pair, script)?;
    Ok((
        VariableDeclarationData {
            meta,
            declarations: vec![VariableDeclaratorData {
                meta: meta2,
                id: Box::new(b),
                init: None,
            }],
            kind: get_let_or_const(let_or_const_pair)?,
        },
        b_s,
    ))
}

fn get_let_or_const(let_or_const_pair: Pair<Rule>) -> Result<VariableDeclarationKind, JsRuleError> {
    Ok(match let_or_const_pair.as_str() {
        "let" => VariableDeclarationKind::Let,
        "const" => VariableDeclarationKind::Const,
        _ => return Err(get_unexpected_error("get_let_or_const", &let_or_const_pair)),
    })
}

fn build_ast_from_switch_statement(
    pair: Pair<Rule>,
    script: &Rc<String>,
) -> Result<(StatementType, Semantics), JsRuleError> {
    let meta = get_meta(&pair, script);
    let mut inner_iter = pair.into_inner();
    let condition_pair = inner_iter.next().unwrap();
    let (condition, _condition_s) = build_ast_from_expression(condition_pair, script)?;
    let case_block_pair = inner_iter.next().unwrap();
    let mut cases = vec![];
    let mut s = Semantics::new_empty();
    for case_clause_pair in case_block_pair.into_inner() {
        match case_clause_pair.as_rule() {
            Rule::case_clause
            | Rule::case_clause__yield
            | Rule::case_clause__return
            | Rule::case_clause__yield_return => {
                let (c, c_s) = build_ast_from_case_clause(case_clause_pair, script)?;
                cases.push(c);
                s.merge(c_s);
            }
            Rule::default_clause
            | Rule::default_clause__yield
            | Rule::default_clause__return
            | Rule::default_clause__yield_return => {
                let (c, c_s) = build_ast_from_default_clause(case_clause_pair, script)?;
                cases.push(c);
                s.merge(c_s);
            }
            _ => {
                return Err(get_unexpected_error(
                    "build_ast_from_switch_statement",
                    &case_clause_pair,
                ))
            }
        }
    }

    Ok((
        StatementType::SwitchStatement {
            meta,
            discriminant: Box::new(condition),
            cases,
        },
        s,
    ))
}

fn build_ast_from_case_clause(
    pair: Pair<Rule>,
    script: &Rc<String>,
) -> Result<(SwitchCaseData, Semantics), JsRuleError> {
    let meta = get_meta(&pair, script);
    let mut inner_iter = pair.into_inner();
    let test_pair = inner_iter.next().unwrap();
    let (test_exp, _test_exp_s) = build_ast_from_expression(test_pair, script)?;
    let (statements, statements_s) = if let Some(statement_pair) = inner_iter.next() {
        build_ast_from_statement_list(statement_pair, script)?
    } else {
        (vec![], Semantics::new_empty())
    };
    // Resetting this flag, since if there is a 'break' here then it applies to this 'case' clause.
    // statements_s.contains_unpaired_break.make_false();
    validate_lexically_declared_names_have_no_duplicates_and_also_not_present_in_var_declared_names(&statements_s)?;
    let mut s = Semantics::new_empty();
    s.var_declared_names = statements_s.var_declared_names;
    Ok((
        SwitchCaseData {
            meta,
            test: Some(Box::new(test_exp)),
            consequent: statements,
        },
        s,
    ))
}

fn build_ast_from_default_clause(
    pair: Pair<Rule>,
    script: &Rc<String>,
) -> Result<(SwitchCaseData, Semantics), JsRuleError> {
    let meta = get_meta(&pair, script);
    let mut inner_iter = pair.into_inner();
    let (statements, statements_s) = if let Some(statement_pair) = inner_iter.next() {
        build_ast_from_statement_list(statement_pair, script)?
    } else {
        (vec![], Semantics::new_empty())
    };
    // Resetting this flag, since if there is a 'break' here then it applies to this 'case' clause.
    // statements_s.contains_unpaired_break.make_false();
    validate_lexically_declared_names_have_no_duplicates_and_also_not_present_in_var_declared_names(&statements_s)?;
    let mut s = Semantics::new_empty();
    s.var_declared_names = statements_s.var_declared_names;
    Ok((
        SwitchCaseData {
            meta,
            test: None,
            consequent: statements,
        },
        s,
    ))
}

fn build_ast_from_return_statement(
    pair: Pair<Rule>,
    script: &Rc<String>,
) -> Result<(StatementType, Semantics), JsRuleError> {
    let meta = get_meta(&pair, script);
    let inner_pair = pair.into_inner().next().unwrap();
    let (argument, s) = if inner_pair.as_rule() == Rule::expression__in {
        let (e, e_s) = build_ast_from_expression(inner_pair, script)?;
        (Some(Box::new(e)), e_s)
    } else if inner_pair.as_rule() == Rule::smart_semicolon {
        (None, Semantics::new_empty())
    } else {
        return Err(get_unexpected_error(
            "build_ast_from_return_statement",
            &inner_pair,
        ));
    };
    Ok((StatementType::ReturnStatement { meta, argument }, s))
}

fn build_ast_from_try_statement(
    pair: Pair<Rule>,
    script: &Rc<String>,
) -> Result<(StatementType, Semantics), JsRuleError> {
    let meta = get_meta(&pair, script);
    let mut inner_iter = pair.into_inner();
    let block_pair = inner_iter.next().unwrap();
    let mut s = Semantics::new_empty();
    let (block, mut block_s) = build_ast_from_block(block_pair, script)?;
    let next_pair = inner_iter.next().unwrap();
    let (handler, mut handler_s, next_pair_option) = match next_pair.as_rule() {
        Rule::catch | Rule::catch__yield | Rule::catch__return | Rule::catch__yield_return => {
            let meta = get_meta(&next_pair, script);
            let mut catch_inner_iter = next_pair.into_inner();
            let catch_parameter_pair = catch_inner_iter.next().unwrap();
            let catch_parameter_inner_pair = catch_parameter_pair.into_inner().next().unwrap();
            let (catch_param, catch_param_s) = match catch_parameter_inner_pair.as_rule() {
                Rule::binding_identifier | Rule::binding_identifier__yield => {
                    let (bi, bi_s) =
                        get_binding_identifier_data(catch_parameter_inner_pair, script)?;
                    (
                        ExpressionPatternType::Identifier(bi).convert_to_pattern(),
                        bi_s,
                    )
                }
                Rule::binding_pattern | Rule::binding_pattern__yield => {
                    build_ast_from_binding_pattern(catch_parameter_inner_pair, script)?
                }
                _ => {
                    return Err(get_unexpected_error(
                        "build_ast_from_try_statement",
                        &catch_parameter_inner_pair,
                    ))
                }
            };
            let block_pair = catch_inner_iter.next().unwrap();
            let (block, block_s) = build_ast_from_block(block_pair, script)?;
            validate_bound_names_have_no_duplicates_and_also_not_present_in_var_declared_names_or_lexically_declared_names(&catch_param_s.bound_names, &block_s.var_declared_names,&block_s.lexically_declared_names)?;
            let mut s = Semantics::new_empty();
            s.var_declared_names = block_s.var_declared_names;
            (
                Some(CatchClauseData {
                    meta,
                    param: Box::new(catch_param),
                    body: block,
                }),
                s,
                inner_iter.next(),
            )
        }
        _ => (None, Semantics::new_empty(), Some(next_pair)),
    };
    let (finalizer, mut finalizer_s) = if let Some(finally_pair) = next_pair_option {
        let finally_block_pair = finally_pair.into_inner().next().unwrap();
        let (b, b_s) = build_ast_from_block(finally_block_pair, script)?;
        (Some(b), b_s)
    } else {
        (None, Semantics::new_empty())
    };
    s.var_declared_names.append(&mut block_s.var_declared_names);
    s.var_declared_names
        .append(&mut handler_s.var_declared_names);
    s.var_declared_names
        .append(&mut finalizer_s.var_declared_names);
    Ok((
        StatementType::TryStatement {
            meta,
            block,
            handler,
            finalizer,
        },
        s,
    ))
}

fn build_ast_from_variable_statement(
    pair: Pair<Rule>,
    script: &Rc<String>,
) -> Result<(StatementType, Semantics), JsRuleError> {
    let meta = get_meta(&pair, script);
    let (dl, dl_s) =
        build_ast_from_variable_declaration_list(pair.into_inner().next().unwrap(), script)?;
    let mut s = Semantics::new_empty();
    s.var_declared_names = dl_s.bound_names;
    Ok((
        StatementType::DeclarationStatement(DeclarationType::VariableDeclaration(
            VariableDeclarationData {
                meta,
                declarations: dl,
                kind: VariableDeclarationKind::Var,
            },
        )),
        s,
    ))
}

fn build_ast_from_variable_declaration_list(
    pair: Pair<Rule>,
    script: &Rc<String>,
) -> Result<(Vec<VariableDeclaratorData>, Semantics), JsRuleError> {
    let mut declarations = vec![];
    let mut s = Semantics::new_empty();
    for var_pair in pair.into_inner() {
        if var_pair.as_rule() == Rule::variable_declaration
            || var_pair.as_rule() == Rule::variable_declaration__in
        {
            let (d, d_s) =
                build_ast_from_lexical_binding_or_variable_declaration_or_binding_element(
                    var_pair, script,
                )?;
            s.merge(d_s);
            declarations.push(d)
        } else {
            return Err(get_unexpected_error(
                "build_ast_from_variable_declaration_list",
                &var_pair,
            ));
        }
    }
    Ok((declarations, s))
}

fn build_ast_from_lexical_binding_or_variable_declaration_or_binding_element(
    pair: Pair<Rule>,
    script: &Rc<String>,
) -> Result<(VariableDeclaratorData, Semantics), JsRuleError> {
    let meta = get_meta(&pair, script);
    let mut inner_iter = pair.into_inner();
    let inner_pair = inner_iter.next().unwrap();
    Ok(
        if inner_pair.as_rule() == Rule::binding_identifier
            || inner_pair.as_rule() == Rule::binding_identifier__yield
        {
            let (bi, bi_s) = get_binding_identifier_data(inner_pair, script)?;
            let id = Box::new(ExpressionPatternType::Identifier(bi).convert_to_pattern());
            (
                if let Some(initializer) = inner_iter.next() {
                    let (a, _a_s) = build_ast_from_assignment_expression(
                        initializer.into_inner().next().unwrap(),
                        script,
                    )?;
                    // bi_s.merge(a_s); bound_names is required only from bi_s
                    VariableDeclaratorData {
                        meta,
                        id,
                        init: Some(Box::new(a)),
                    }
                } else {
                    VariableDeclaratorData {
                        meta,
                        id,
                        init: None,
                    }
                },
                bi_s,
            )
        } else if inner_pair.as_rule() == Rule::binding_pattern
            || inner_pair.as_rule() == Rule::binding_pattern__yield
        {
            let (b, b_s) = build_ast_from_binding_pattern(inner_pair, script)?;
            let id = Box::new(b);
            let init = if let Some(initializer) = inner_iter.next() {
                let (a, _a_s) = build_ast_from_assignment_expression(
                    initializer.into_inner().next().unwrap(),
                    script,
                )?;
                // b_s.merge(a_s);  bound_names is required only from b_s
                Some(Box::new(a))
            } else {
                None
            };
            (VariableDeclaratorData { meta, id, init }, b_s)
        } else if inner_pair.as_rule() == Rule::single_name_binding
            || inner_pair.as_rule() == Rule::single_name_binding__yield
        {
            build_ast_from_single_name_binding(inner_pair, script)?
        } else {
            return Err(get_unexpected_error(
                "build_ast_from_lexical_binding_or_variable_declaration",
                &inner_pair,
            ));
        },
    )
}

fn build_ast_from_single_name_binding(
    pair: Pair<Rule>,
    script: &Rc<String>,
) -> Result<(VariableDeclaratorData, Semantics), JsRuleError> {
    let meta = get_meta(&pair, script);
    let mut inner_iter = pair.into_inner();
    let (b, s) = get_binding_identifier_data(inner_iter.next().unwrap(), script)?;
    let id = Box::new(ExpressionPatternType::Identifier(b).convert_to_pattern());
    Ok(if let Some(initializer) = inner_iter.next() {
        let (a, _a_s) = build_ast_from_assignment_expression(initializer, script)?;
        // s.merge(a_s); bound_names from s is only used
        (
            VariableDeclaratorData {
                meta,
                id,
                init: Some(Box::new(a)),
            },
            s,
        )
    } else {
        (
            VariableDeclaratorData {
                meta,
                id,
                init: None,
            },
            s,
        )
    })
}

fn build_ast_from_assignment_expression(
    pair: Pair<Rule>,
    script: &Rc<String>,
) -> Result<(ExpressionType, Semantics), JsRuleError> {
    let meta = get_meta(&pair, script);
    let mut inner_pair_iter = pair.into_inner();
    let inner_pair = inner_pair_iter.next().unwrap();
    Ok(match inner_pair.as_rule() {
        Rule::arrow_function
        | Rule::arrow_function__in
        | Rule::arrow_function__yield
        | Rule::arrow_function__in_yield => build_ast_from_arrow_function(inner_pair, script)?,
        Rule::left_hand_side_expression | Rule::left_hand_side_expression__yield => {
            let lhs_pair = inner_pair;
            let lhs_meta = get_meta(&lhs_pair, script);
            let (lhs, mut s) = build_ast_from_left_hand_side_expression(lhs_pair, script)?;
            let mut next_pair = inner_pair_iter.next().unwrap();
            let (left, operator) = if next_pair.as_rule() == Rule::assignment_operator {
                if s.is_valid_simple_assignment_target.is_false() {
                    return Err(get_validation_error_with_meta(
                        "L.H.S. needs to be a simple expression".to_string(),
                        AstBuilderValidationErrorType::ReferenceError,
                        lhs_meta,
                    ));
                }
                let op_str = next_pair.as_str();
                next_pair = inner_pair_iter.next().unwrap();
                (
                    PatternOrExpression::Expression(Box::new(lhs)),
                    match op_str {
                        "*=" => AssignmentOperator::MultiplyEquals,
                        "/=" => AssignmentOperator::DivideEquals,
                        "%=" => AssignmentOperator::ModuloEquals,
                        "+=" => AssignmentOperator::AddEquals,
                        "-=" => AssignmentOperator::SubtractEquals,
                        "<<=" => AssignmentOperator::BitwiseLeftShiftEquals,
                        ">>=" => AssignmentOperator::BitwiseRightShiftEquals,
                        ">>>=" => AssignmentOperator::BitwiseUnsignedRightShiftEquals,
                        "&=" => AssignmentOperator::BitwiseAndEquals,
                        "^=" => AssignmentOperator::BitwiseXorEquals,
                        "|=" => AssignmentOperator::BitwiseOrEquals,
                        _ => {
                            return Err(get_unexpected_error(
                                "build_ast_from_assignment_expression:1",
                                &next_pair,
                            ))
                        }
                    },
                )
            } else {
                // For simple `=` assignment, check if LHS needs pattern conversion
                // Member expressions and identifiers stay as expressions
                // Array/object literals become destructuring patterns
                let left = match &lhs {
                    ExpressionType::MemberExpression(_) => {
                        // Member expression stays as expression (e.g., obj.prop = value)
                        PatternOrExpression::Expression(Box::new(lhs))
                    }
                    ExpressionType::ExpressionWhichCanBePattern(ExpressionPatternType::Identifier(_)) => {
                        // Simple identifier stays as expression (e.g., x = value)
                        PatternOrExpression::Expression(Box::new(lhs))
                    }
                    _ => {
                        // Array/object literals need pattern conversion for destructuring
                        PatternOrExpression::Pattern(Box::new(
                            convert_lhs_expression_to_pattern_for_assignment_operation(lhs, Some(&s))?,
                        ))
                    }
                };
                (left, AssignmentOperator::Equals)
            };
            // next_pair is now assignment_expression
            let (assignment_exp, assignment_exp_s) =
                build_ast_from_assignment_expression(next_pair, script)?;
            s.merge(assignment_exp_s);
            (
                ExpressionType::AssignmentExpression {
                    meta,
                    left,
                    operator,
                    right: Box::new(assignment_exp),
                },
                s,
            )
        }
        Rule::yield_expression | Rule::yield_expression__in => {
            match inner_pair.into_inner().next() {
                Some(inner_pair) => {
                    let (assign_rule_pair, delegate) = if inner_pair.as_rule()
                        == Rule::star_assignment_expression__yield
                        || inner_pair.as_rule() == Rule::star_assignment_expression__in_yield
                    {
                        (inner_pair.into_inner().next().unwrap(), true)
                    } else {
                        (inner_pair, false)
                    };
                    let (assignment_exp, assignment_exp_s) =
                        build_ast_from_assignment_expression(assign_rule_pair, script)?;
                    (
                        ExpressionType::YieldExpression {
                            meta,
                            delegate,
                            argument: Some(Box::new(assignment_exp)),
                        },
                        assignment_exp_s,
                    )
                }
                None => (
                    ExpressionType::YieldExpression {
                        meta,
                        delegate: false,
                        argument: None,
                    },
                    Semantics::new_empty(),
                ),
            }
        }
        Rule::conditional_expression
        | Rule::conditional_expression__in
        | Rule::conditional_expression__yield
        | Rule::conditional_expression__in_yield => {
            build_ast_from_conditional_expression(inner_pair, script)?
        }
        _ => {
            return Err(get_unexpected_error(
                "build_ast_from_assignment_expression:2",
                &inner_pair,
            ))
        }
    })
}

fn convert_lhs_expression_to_pattern_for_assignment_operation(
    lhs_exp: ExpressionType,
    s: Option<&Semantics>,
) -> Result<PatternType, JsRuleError> {
    match lhs_exp {
        ExpressionType::ExpressionWhichCanBePattern(p) => Ok(p.convert_to_pattern()),
        ExpressionType::MemberExpression(member_expr) => {
            // MemberExpression is a valid assignment target (e.g., obj.prop = value)
            // but it doesn't convert directly to a pattern in the destructuring sense.
            // Return an error as member expressions can't be destructured.
            Err(get_validation_error_with_meta(
                "Member expression cannot be used as destructuring pattern".to_string(),
                AstBuilderValidationErrorType::ReferenceError,
                member_expr.get_meta().clone(),
            ))
        }
        ExpressionType::ArrayExpression {
            meta,
            elements: o_elements,
        } => {
            // We need to convert this to ObjectPattern
            let mut elements = vec![];
            for p in o_elements {
                elements.push(if let Some(es) = p {
                    Some(Box::new(match es {
                        ExpressionOrSpreadElement::Expression(e) => {
                            convert_lhs_expression_to_pattern_for_assignment_operation(
                                *e,
                                None,
                            )?
                        }
                        ExpressionOrSpreadElement::SpreadElement(s) => {
                            let s = convert_lhs_expression_to_pattern_for_assignment_operation(
                                *s,
                                None,
                            )?;
                            PatternType::RestElement {
                                meta: s.get_meta().clone(),
                                argument: Box::new(s),
                            }
                        }
                    }))
                } else {
                    None
                });
            }
            Ok(PatternType::ArrayPattern { meta, elements })
        }
        ExpressionType::ObjectExpression {
            meta,
            properties: o_props,
        } => {
            // We need to convert this to ObjectPattern
            let mut properties = vec![];
            for p in o_props {
                if p.method {
                    return Err(get_validation_error_with_meta(
                        "Invalid object pattern. Cannot have methods.".to_string(),
                        AstBuilderValidationErrorType::SyntaxError,
                        p.meta,
                    ));
                } else {
                    properties.push(AssignmentPropertyData::new_with_any_expression_key(
                        p.meta,
                        *p.key,
                        convert_lhs_expression_to_pattern_for_assignment_operation(
                            *p.value,
                            None,
                        )?,
                        p.shorthand,
                    ));
                }
            }
            Ok(PatternType::ObjectPattern { meta, properties })
        }
        ExpressionType::Literal(LiteralData { meta, .. })
        | ExpressionType::ThisExpression { meta }
        | ExpressionType::FunctionOrGeneratorExpression(FunctionData { meta, .. })
        | ExpressionType::UnaryExpression { meta, .. }
        | ExpressionType::UpdateExpression { meta, .. }
        | ExpressionType::BinaryExpression { meta, .. }
        | ExpressionType::AssignmentExpression { meta, .. }
        | ExpressionType::LogicalExpression { meta, .. }
        | ExpressionType::ConditionalExpression { meta, .. }
        | ExpressionType::CallExpression { meta, .. }
        | ExpressionType::NewExpression { meta, .. }
        | ExpressionType::SequenceExpression { meta, .. }
        | ExpressionType::ArrowFunctionExpression { meta, .. }
        | ExpressionType::YieldExpression { meta, .. }
        | ExpressionType::TemplateLiteral(TemplateLiteralData { meta, .. })
        | ExpressionType::TaggedTemplateExpression { meta, .. }
        | ExpressionType::ClassExpression(ClassData { meta, .. })
        | ExpressionType::MetaProperty { meta, .. } => {
            if s.is_some() && s.unwrap().is_valid_simple_assignment_target.is_true() {
                Err(JsRuleError{ kind: JsErrorType::Unexpected("Unexpected error reached in convert_lhs_expression_to_pattern"), message: "Did not expect a simple assignment target here. It then needs to be converted to pattern".to_string() })
            } else {
                Err( get_validation_error_with_meta("Parsing error encountered: L.H.S. needs to be a simple expression or object/array literal".to_string(),AstBuilderValidationErrorType::ReferenceError, meta ) )
            }
        }
    }
}

fn build_ast_from_arrow_function(
    pair: Pair<Rule>,
    script: &Rc<String>,
) -> Result<(ExpressionType, Semantics), JsRuleError> {
    let meta = get_meta(&pair, script);
    let mut inner_iter = pair.into_inner();
    let arrow_parameters_pair = inner_iter.next().unwrap();
    let inner_arrow_parameters_pair = arrow_parameters_pair.into_inner().next().unwrap();
    let (params, params_s) = match inner_arrow_parameters_pair.as_rule() {
        Rule::binding_identifier | Rule::binding_identifier__yield => {
            let (b, b_s) = get_binding_identifier_data(inner_arrow_parameters_pair, script)?;
            (
                vec![
                    ExpressionPatternType::Identifier(b).convert_to_pattern()
                ],
                b_s,
            )
        }
        Rule::formal_parameters | Rule::formal_parameters__yield => {
            let (f, f_s) = build_ast_from_formal_parameters(inner_arrow_parameters_pair, script)?;
            (f, f_s)
        }
        _ => {
            return Err(get_unexpected_error(
                "build_ast_from_arrow_function:1",
                &inner_arrow_parameters_pair,
            ));
        }
    };
    let concise_body_pair = inner_iter.next().unwrap();
    let inner_concise_body_pair = concise_body_pair.into_inner().next().unwrap();
    let (body, body_s) = match inner_concise_body_pair.as_rule() {
        Rule::function_body => {
            let (f, f_s) = build_ast_from_function_body(inner_concise_body_pair, script)?;
            (Box::new(FunctionBodyOrExpression::FunctionBody(f)), f_s)
        }
        Rule::assignment_expression | Rule::assignment_expression__in => {
            let (a, _a_s) = build_ast_from_assignment_expression(inner_concise_body_pair, script)?;
            (
                Box::new(FunctionBodyOrExpression::Expression(a)),
                Semantics::new_empty(),
            )
        }
        _ => {
            return Err(get_unexpected_error(
                "build_ast_from_arrow_function:2",
                &inner_concise_body_pair,
            ));
        }
    };
    if body_s.contains_yield_expression.is_true() || params_s.contains_yield_expression.is_true() {
        Err(get_validation_error_with_meta(
            "'yield' is not allowed in arrow function".to_string(),
            AstBuilderValidationErrorType::SyntaxError,
            body.get_meta().clone(),
        ))
    } else {
        validate_bound_names_have_no_duplicates_and_also_not_present_in_var_declared_names_or_lexically_declared_names(&params_s.bound_names,&vec![], &body_s.lexically_declared_names)?;

        // let mut s = Semantics::new_empty();
        // s.merge(params_s).merge(body_s);
        // params_s produces bound_names and body_s produces var_declared_names & lexically_declared_names
        Ok((
            ExpressionType::ArrowFunctionExpression { meta, params, body },
            Semantics::new_empty(),
        ))
    }
}

fn build_ast_from_left_hand_side_expression(
    pair: Pair<Rule>,
    script: &Rc<String>,
) -> Result<(ExpressionType, Semantics), JsRuleError> {
    let inner_pair: Pair<Rule> = pair.into_inner().next().unwrap();
    Ok(match inner_pair.as_rule() {
        Rule::call_expression | Rule::call_expression__yield => {
            build_ast_from_call_expression(inner_pair, script)?
        }
        Rule::new_expression | Rule::new_expression__yield => {
            build_ast_from_new_expression(inner_pair, script)?
        }
        _ => {
            return Err(get_unexpected_error(
                "build_ast_from_left_hand_side_expression",
                &inner_pair,
            ))
        }
    })
}

fn build_ast_from_new_expression(
    pair: Pair<Rule>,
    script: &Rc<String>,
) -> Result<(ExpressionType, Semantics), JsRuleError> {
    let inner_pair = pair.into_inner().next().unwrap();
    Ok(
        if inner_pair.as_rule() == Rule::member_expression
            || inner_pair.as_rule() == Rule::member_expression__yield
        {
            build_ast_from_member_expression(inner_pair, script)?
        } else {
            let ne_meta = get_meta(&inner_pair, script);
            let (n, n_s) = build_ast_from_new_expression(inner_pair, script)?;
            (
                ExpressionType::NewExpression {
                    meta: ne_meta,
                    callee: Box::new(n),
                    arguments: vec![],
                },
                n_s,
            )
        },
    )
}

fn build_ast_from_conditional_expression(
    pair: Pair<Rule>,
    script: &Rc<String>,
) -> Result<(ExpressionType, Semantics), JsRuleError> {
    let meta = get_meta(&pair, script);
    let mut pair_iter = pair.into_inner();
    let logical_or_pair = pair_iter.next().unwrap();
    let (or_node, mut s) = build_ast_from_logical_or_expression(logical_or_pair, script)?;
    if let Some(inner_pair) = pair_iter.next() {
        let (truthy, truthy_s) = build_ast_from_assignment_expression(inner_pair, script)?;
        let (falsy, falsy_s) =
            build_ast_from_assignment_expression(pair_iter.next().unwrap(), script)?;
        s.merge(truthy_s).merge(falsy_s);
        Ok((
            ExpressionType::ConditionalExpression {
                meta,
                test: Box::new(or_node),
                consequent: Box::new(truthy),
                alternate: Box::new(falsy),
            },
            s,
        ))
    } else {
        Ok((or_node, s))
    }
}

fn get_ast_for_logical_expression(
    left: Option<ExpressionType>,
    right: ExpressionType,
    operator: LogicalOperator,
    script: &Rc<String>,
) -> ExpressionType {
    if let Some(actual_left) = left {
        ExpressionType::LogicalExpression {
            meta: Meta {
                start_index: actual_left.get_meta().start_index,
                end_index: right.get_meta().end_index,
                script: script.clone(),
            },
            operator,
            left: Box::new(actual_left),
            right: Box::new(right),
        }
    } else {
        right
    }
}

fn get_ast_for_binary_expression(
    left: Option<ExpressionType>,
    right: ExpressionType,
    operator: Option<BinaryOperator>,
    script: &Rc<String>,
) -> ExpressionType {
    if let Some(actual_left) = left {
        ExpressionType::BinaryExpression {
            meta: Meta {
                start_index: actual_left.get_meta().start_index,
                end_index: right.get_meta().end_index,
                script: script.clone(),
            },
            operator: operator.unwrap(),
            left: Box::new(actual_left),
            right: Box::new(right),
        }
    } else {
        right
    }
}

fn build_ast_from_logical_or_expression(
    pair: Pair<Rule>,
    script: &Rc<String>,
) -> Result<(ExpressionType, Semantics), JsRuleError> {
    let mut left = None;
    let mut s = Semantics::new_empty();
    for inner_pair in pair.into_inner() {
        let (right, right_s) = build_ast_from_logical_and_expression(inner_pair, script)?;
        s.merge(right_s);
        left = Some(get_ast_for_logical_expression(
            left,
            right,
            LogicalOperator::Or,
            script,
        ));
    }
    Ok((left.unwrap(), s))
}

fn build_ast_from_logical_and_expression(
    pair: Pair<Rule>,
    script: &Rc<String>,
) -> Result<(ExpressionType, Semantics), JsRuleError> {
    let mut left = None;
    let mut s = Semantics::new_empty();
    for inner_pair in pair.into_inner() {
        let (right, right_s) = build_ast_from_bitwise_or_expression(inner_pair, script)?;
        s.merge(right_s);
        left = Some(get_ast_for_logical_expression(
            left,
            right,
            LogicalOperator::And,
            script,
        ));
    }
    Ok((left.unwrap(), s))
}

fn build_ast_from_bitwise_or_expression(
    pair: Pair<Rule>,
    script: &Rc<String>,
) -> Result<(ExpressionType, Semantics), JsRuleError> {
    let mut left = None;
    let mut s = Semantics::new_empty();
    for inner_pair in pair.into_inner() {
        let (right, right_s) = build_ast_from_bitwise_xor_expression(inner_pair, script)?;
        s.merge(right_s);
        left = Some(get_ast_for_binary_expression(
            left,
            right,
            Some(BinaryOperator::BitwiseOr),
            script,
        ))
    }
    Ok((left.unwrap(), s))
}

fn build_ast_from_bitwise_xor_expression(
    pair: Pair<Rule>,
    script: &Rc<String>,
) -> Result<(ExpressionType, Semantics), JsRuleError> {
    let mut left = None;
    let mut s = Semantics::new_empty();
    for inner_pair in pair.into_inner() {
        let (right, right_s) = build_ast_from_bitwise_and_expression(inner_pair, script)?;
        s.merge(right_s);
        left = Some(get_ast_for_binary_expression(
            left,
            right,
            Some(BinaryOperator::BitwiseXor),
            script,
        ))
    }
    Ok((left.unwrap(), s))
}

fn build_ast_from_bitwise_and_expression(
    pair: Pair<Rule>,
    script: &Rc<String>,
) -> Result<(ExpressionType, Semantics), JsRuleError> {
    let mut left = None;
    let mut s = Semantics::new_empty();
    for inner_pair in pair.into_inner() {
        let (right, right_s) = build_ast_from_equality_expression(inner_pair, script)?;
        s.merge(right_s);
        left = Some(get_ast_for_binary_expression(
            left,
            right,
            Some(BinaryOperator::BitwiseAnd),
            script,
        ))
    }
    Ok((left.unwrap(), s))
}

fn build_ast_from_equality_expression(
    pair: Pair<Rule>,
    script: &Rc<String>,
) -> Result<(ExpressionType, Semantics), JsRuleError> {
    if cfg!(debug_assertions) {
        if pair.as_rule() != Rule::equality_expression
            && pair.as_rule() != Rule::equality_expression__in
            && pair.as_rule() != Rule::equality_expression__yield
            && pair.as_rule() != Rule::equality_expression__in_yield
        {
            return Err(get_unexpected_error(
                "build_ast_from_equality_expression:0",
                &pair,
            ));
        }
    }
    let mut left = None;
    let mut s = Semantics::new_empty();
    let mut pair_iter = pair.into_inner();
    loop {
        if let Some(mut inner_pair) = pair_iter.next() {
            let mut operator = None;
            if inner_pair.as_rule() == Rule::equality_operator {
                operator = Some(match inner_pair.as_str() {
                    "===" => BinaryOperator::StrictlyEqual,
                    "!==" => BinaryOperator::StrictlyUnequal,
                    "==" => BinaryOperator::LooselyEqual,
                    "!=" => BinaryOperator::LooselyUnequal,
                    _ => {
                        return Err(get_unexpected_error(
                            "build_ast_from_equality_expression",
                            &inner_pair,
                        ))
                    }
                });
                inner_pair = pair_iter.next().unwrap();
            }
            let (right, right_s) = build_ast_from_relational_expression(inner_pair, script)?;
            s.merge(right_s);
            left = Some(get_ast_for_binary_expression(left, right, operator, script));
        } else {
            break;
        }
    }
    Ok((left.unwrap(), s))
}

fn build_ast_from_relational_expression(
    pair: Pair<Rule>,
    script: &Rc<String>,
) -> Result<(ExpressionType, Semantics), JsRuleError> {
    if cfg!(debug_assertions) {
        if pair.as_rule() != Rule::relational_expression
            && pair.as_rule() != Rule::relational_expression__in
            && pair.as_rule() != Rule::relational_expression__yield
            && pair.as_rule() != Rule::relational_expression__in_yield
        {
            return Err(get_unexpected_error(
                "build_ast_from_relational_expression:0",
                &pair,
            ));
        }
    }
    let mut left = None;
    let mut s = Semantics::new_empty();
    let mut pair_iter = pair.into_inner();
    loop {
        if let Some(mut inner_pair) = pair_iter.next() {
            let mut operator = None;
            if inner_pair.as_rule() == Rule::relational_operator
                || inner_pair.as_rule() == Rule::relational_operator__in
            {
                operator = Some(match inner_pair.as_str() {
                    "<=" => BinaryOperator::LessThanEqual,
                    ">=" => BinaryOperator::GreaterThanEqual,
                    "<" => BinaryOperator::LessThan,
                    ">" => BinaryOperator::GreaterThan,
                    "instanceof" => BinaryOperator::InstanceOf,
                    "in" => BinaryOperator::In,
                    _ => {
                        return Err(get_unexpected_error(
                            "build_ast_from_relational_expression",
                            &inner_pair,
                        ))
                    }
                });
                inner_pair = pair_iter.next().unwrap();
            }
            let (right, right_s) = build_ast_from_shift_expression(inner_pair, script)?;
            s.merge(right_s);
            left = Some(get_ast_for_binary_expression(left, right, operator, script));
        } else {
            break;
        }
    }
    Ok((left.unwrap(), s))
}

fn build_ast_from_shift_expression(
    pair: Pair<Rule>,
    script: &Rc<String>,
) -> Result<(ExpressionType, Semantics), JsRuleError> {
    if cfg!(debug_assertions) {
        if pair.as_rule() != Rule::shift_expression
            && pair.as_rule() != Rule::shift_expression__yield
        {
            return Err(get_unexpected_error(
                "build_ast_from_shift_expression:0",
                &pair,
            ));
        }
    }
    let mut left = None;
    let mut s = Semantics::new_empty();
    let mut pair_iter = pair.into_inner();
    loop {
        if let Some(mut inner_pair) = pair_iter.next() {
            let mut operator = None;
            if inner_pair.as_rule() == Rule::shift_operator {
                operator = Some(match inner_pair.as_str() {
                    "<<" => BinaryOperator::BitwiseLeftShift,
                    ">>>" => BinaryOperator::BitwiseUnsignedRightShift,
                    ">>" => BinaryOperator::BitwiseRightShift,
                    _ => {
                        return Err(get_unexpected_error(
                            "build_ast_from_shift_expression",
                            &inner_pair,
                        ))
                    }
                });
                inner_pair = pair_iter.next().unwrap();
            }
            let (right, right_s) = build_ast_from_additive_expression(inner_pair, script)?;
            s.merge(right_s);
            left = Some(get_ast_for_binary_expression(left, right, operator, script));
        } else {
            break;
        }
    }
    Ok((left.unwrap(), s))
}

fn build_ast_from_additive_expression(
    pair: Pair<Rule>,
    script: &Rc<String>,
) -> Result<(ExpressionType, Semantics), JsRuleError> {
    let mut left = None;
    let mut s = Semantics::new_empty();
    let mut pair_iter = pair.into_inner();
    loop {
        if let Some(mut inner_pair) = pair_iter.next() {
            let mut operator = None;
            if inner_pair.as_rule() == Rule::additive_operator {
                operator = Some(match inner_pair.as_str() {
                    "+" => BinaryOperator::Add,
                    "-" => BinaryOperator::Subtract,
                    _ => {
                        return Err(get_unexpected_error(
                            "build_ast_from_additive_expression",
                            &inner_pair,
                        ))
                    }
                });
                inner_pair = pair_iter.next().unwrap();
            }
            let (right, right_s) = build_ast_from_multiplicative_expression(inner_pair, script)?;
            s.merge(right_s);
            left = Some(get_ast_for_binary_expression(left, right, operator, script));
        } else {
            break;
        }
    }
    Ok((left.unwrap(), s))
}

fn build_ast_from_multiplicative_expression(
    pair: Pair<Rule>,
    script: &Rc<String>,
) -> Result<(ExpressionType, Semantics), JsRuleError> {
    let mut left = None;
    let mut s = Semantics::new_empty();
    let mut pair_iter = pair.into_inner();
    loop {
        if let Some(mut inner_pair) = pair_iter.next() {
            let mut operator = None;
            if inner_pair.as_rule() == Rule::multiplicative_operator {
                operator = Some(match inner_pair.as_str() {
                    "*" => BinaryOperator::Multiply,
                    "/" => BinaryOperator::Divide,
                    "%" => BinaryOperator::Modulo,
                    _ => {
                        return Err(get_unexpected_error(
                            "build_ast_from_multiplicative_expression",
                            &inner_pair,
                        ))
                    }
                });
                inner_pair = pair_iter.next().unwrap();
            }
            let (right, right_s) = build_ast_from_unary_expression(inner_pair, script)?;
            s.merge(right_s);
            left = Some(get_ast_for_binary_expression(left, right, operator, script));
        } else {
            break;
        }
    }
    Ok((left.unwrap(), s))
}

fn build_ast_from_unary_expression(
    pair: Pair<Rule>,
    script: &Rc<String>,
) -> Result<(ExpressionType, Semantics), JsRuleError> {
    let meta = get_meta(&pair, script);
    let mut pair_iter = pair.into_inner();
    let first_pair = pair_iter.next().unwrap();

    Ok(
        if first_pair.as_rule() == Rule::postfix_expression
            || first_pair.as_rule() == Rule::postfix_expression__yield
        {
            build_ast_from_postfix_expression(first_pair, script)?
        } else {
            // first_pair is unary_operator - get the operator string directly
            let operator_str = first_pair.as_str();
            match operator_str {
                "++" | "--" => {
                    let u_pair = pair_iter.next().unwrap();
                    let u_pair_meta = get_meta(&u_pair, script);
                    let (u, u_s) = build_ast_from_unary_expression(u_pair, script)?;
                    if u_s.is_valid_simple_assignment_target.is_false() {
                        return Err(get_validation_error_with_meta(
                            "Invalid expression for prefix operator".to_string(),
                            AstBuilderValidationErrorType::ReferenceError,
                            u_pair_meta,
                        ));
                    } else {
                        (
                            ExpressionType::UpdateExpression {
                                meta,
                                operator: match operator_str {
                                    "++" => UpdateOperator::PlusPlus,
                                    "--" => UpdateOperator::MinusMinus,
                                    _ => unreachable!(),
                                },
                                argument: Box::new(u),
                                prefix: true,
                            },
                            u_s,
                        )
                    }
                }
                _ => {
                    let (u, u_s) =
                        build_ast_from_unary_expression(pair_iter.next().unwrap(), script)?;
                    (
                        ExpressionType::UnaryExpression {
                            meta,
                            operator: match operator_str {
                                "delete" => {
                                    if let ExpressionType::ExpressionWhichCanBePattern(
                                        ExpressionPatternType::Identifier(id),
                                    ) = &u
                                    {
                                        return Err(get_validation_error_with_meta(
                                            format!(
                                                "Cannot delete identifier reference: {}",
                                                id.name
                                            ),
                                            AstBuilderValidationErrorType::SyntaxError,
                                            id.meta.clone(),
                                        ));
                                    }
                                    UnaryOperator::Delete
                                }
                                "void" => UnaryOperator::Void,
                                "typeof" => UnaryOperator::TypeOf,
                                "+" => UnaryOperator::Plus,
                                "-" => UnaryOperator::Minus,
                                "~" => UnaryOperator::BitwiseNot,
                                "!" => UnaryOperator::LogicalNot,
                                _ => {
                                    return Err(get_unexpected_error(
                                        "build_ast_from_unary_expression:2",
                                        &first_pair,
                                    ))
                                }
                            },
                            argument: Box::new(u),
                        },
                        u_s,
                    )
                }
            }
        },
    )
}

fn build_ast_from_postfix_expression(
    pair: Pair<Rule>,
    script: &Rc<String>,
) -> Result<(ExpressionType, Semantics), JsRuleError> {
    let meta = get_meta(&pair, script);
    let mut pair_iter = pair.into_inner();
    let lhs_pair = pair_iter.next().unwrap();
    let (lhs, lhs_s) = build_ast_from_left_hand_side_expression(lhs_pair, script)?;
    if lhs_s.is_valid_simple_assignment_target.is_false() {
        Err(get_validation_error_with_meta(
            "Invalid expression for postfix operator".to_string(),
            AstBuilderValidationErrorType::ReferenceError,
            lhs.get_meta().clone(),
        ))
    } else {
        Ok((
            if let Some(op_pair) = pair_iter.next() {
                ExpressionType::UpdateExpression {
                    meta,
                    operator: match op_pair.as_str() {
                        "++" => UpdateOperator::PlusPlus,
                        "--" => UpdateOperator::MinusMinus,
                        _ => {
                            return Err(get_unexpected_error(
                                "build_ast_from_postfix_expression",
                                &op_pair,
                            ))
                        }
                    },
                    argument: Box::new(lhs),
                    prefix: false,
                }
            } else {
                lhs
            },
            lhs_s,
        ))
    }
}

fn build_ast_from_call_expression(
    pair: Pair<Rule>,
    script: &Rc<String>,
) -> Result<(ExpressionType, Semantics), JsRuleError> {
    let mut pair_iter = pair.into_inner();
    let pair = pair_iter.next().unwrap();
    let meta = get_meta(&pair, script);
    let (mut obj, mut s) =
        if pair.as_rule() == Rule::super_call || pair.as_rule() == Rule::super_call__yield {
            let (a, a_s) = build_ast_from_arguments(pair.into_inner().next().unwrap(), script)?;
            (
                ExpressionType::CallExpression {
                    meta,
                    callee: ExpressionOrSuper::Super,
                    arguments: a,
                },
                a_s,
            )
        } else {
            let arguments_pair = pair_iter.next().unwrap();
            let (m, mut s) = build_ast_from_member_expression(pair, script)?;
            let (a, a_s) = build_ast_from_arguments(arguments_pair, script)?;
            s.merge(a_s);
            (
                ExpressionType::CallExpression {
                    meta,
                    callee: ExpressionOrSuper::Expression(Box::new(m)),
                    arguments: a,
                },
                s,
            )
        };
    for pair in pair_iter {
        let second_meta = get_meta(&pair, script);
        let meta = Meta {
            start_index: obj.get_meta().start_index,
            end_index: second_meta.end_index,
            script: script.clone(),
        };
        obj = match pair.as_rule() {
            Rule::expression__in_yield | Rule::expression__in => {
                let (e, e_s) = build_ast_from_expression(pair, script)?;
                s.merge(e_s);
                ExpressionType::MemberExpression(
                    MemberExpressionType::ComputedMemberExpression {
                        meta,
                        object: ExpressionOrSuper::Expression(Box::new(obj)),
                        property: Box::new(e),
                    },
                )
            }
            Rule::identifier_name => ExpressionType::MemberExpression(
                MemberExpressionType::SimpleMemberExpression {
                    meta,
                    object: ExpressionOrSuper::Expression(Box::new(obj)),
                    property: get_identifier_data(pair, script),
                },
            ),
            //Tagged template literal
            Rule::template_literal | Rule::template_literal__yield => {
                let (template, t_s) = build_ast_from_template_literal(pair, script)?;
                s.merge(t_s);
                let quasi = if let ExpressionType::TemplateLiteral(data) = template {
                    data
                } else {
                    return Err(get_validation_error_with_meta(
                        "Expected template literal".to_string(),
                        AstBuilderValidationErrorType::SyntaxError,
                        meta.clone(),
                    ));
                };
                ExpressionType::TaggedTemplateExpression {
                    meta,
                    tag: Box::new(obj),
                    quasi,
                }
            }
            Rule::arguments | Rule::arguments__yield => {
                let (a, a_s) = build_ast_from_arguments(pair, script)?;
                s.merge(a_s);
                ExpressionType::CallExpression {
                    meta,
                    callee: ExpressionOrSuper::Expression(Box::new(obj)),
                    arguments: a,
                }
            }
            _ => {
                return Err(get_unexpected_error(
                    "build_ast_from_call_expression",
                    &pair,
                ))
            }
        };
    }
    Ok((obj, s))
}

fn get_binding_identifier_data(
    pair: Pair<Rule>,
    script: &Rc<String>,
) -> Result<(IdentifierData, Semantics), JsRuleError> {
    let mut id = get_identifier_data(pair, script);
    if id.name == "arguments" || id.name == "eval" || id.name == "yield" {
        Err(get_validation_error_with_meta(
            format!("Invalid binding identifier: {}", id.name),
            AstBuilderValidationErrorType::SyntaxError,
            id.meta,
        ))
    } else {
        id.is_binding_identifier = true;
        let mut s = Semantics::new_empty();
        s.bound_names.push(id.clone());
        Ok((id, s))
    }
}

fn get_identifier_data(pair: Pair<Rule>, script: &Rc<String>) -> IdentifierData {
    IdentifierData {
        meta: get_meta(&pair, script),
        name: pair.as_str().trim().to_string(),
        is_binding_identifier: false,
    }
}

fn build_ast_from_expression(
    pair: Pair<Rule>,
    script: &Rc<String>,
) -> Result<(ExpressionType, Semantics), JsRuleError> {
    let meta = get_meta(&pair, script);
    let mut node_children: Vec<Box<ExpressionType>> = vec![];
    let mut s = Semantics::new_empty();
    for inner_pair in pair.into_inner() {
        let (a, a_s) = build_ast_from_assignment_expression(inner_pair, script)?;
        s.merge(a_s);
        node_children.push(Box::new(a));
    }
    Ok((
        ExpressionType::SequenceExpression {
            meta,
            expressions: node_children,
        },
        s,
    ))
}

fn build_ast_from_arguments(
    pair: Pair<Rule>,
    script: &Rc<String>,
) -> Result<(Vec<ExpressionOrSpreadElement>, Semantics), JsRuleError> {
    let mut arguments = vec![];
    let mut s = Semantics::new_empty();
    if let Some(argument_list_pair) = pair.into_inner().next() {
        for inner_pair in argument_list_pair.into_inner() {
            arguments.push(
                if inner_pair.as_rule() == Rule::rest_assignment_expression__in
                    || inner_pair.as_rule() == Rule::rest_assignment_expression__in_yield
                {
                    let (a, a_s) = build_ast_from_assignment_expression(
                        inner_pair.into_inner().next().unwrap(),
                        script,
                    )?;
                    s.merge(a_s);
                    ExpressionOrSpreadElement::SpreadElement(Box::new(a))
                } else {
                    let (a, a_s) = build_ast_from_assignment_expression(inner_pair, script)?;
                    s.merge(a_s);
                    ExpressionOrSpreadElement::Expression(Box::new(a))
                },
            );
        }
    }
    Ok((arguments, s))
}

fn build_ast_from_member_expression(
    pair: Pair<Rule>,
    script: &Rc<String>,
) -> Result<(ExpressionType, Semantics), JsRuleError> {
    let meta = get_meta(&pair, script);
    let mut pair_iter = pair.into_inner();
    let pair_1 = pair_iter.next().unwrap();
    Ok(
        if pair_1.as_rule() == Rule::new_member_expression
            || pair_1.as_rule() == Rule::new_member_expression__yield
        {
            let member_expression_pair = pair_1.into_inner().next().unwrap();
            let arguments_pair = pair_iter.next().unwrap();
            let (m, mut s) = build_ast_from_member_expression(member_expression_pair, script)?;
            let (a, a_s) = build_ast_from_arguments(arguments_pair, script)?;
            s.merge(a_s);
            (
                ExpressionType::NewExpression {
                    meta,
                    callee: Box::new(m),
                    arguments: a,
                },
                s,
            )
        } else {
            let mut s = Semantics::new_empty();
            let mut obj: ExpressionType = match pair_1.as_rule() {
                Rule::super_property | Rule::super_property__yield => {
                    let super_pair = pair_1.into_inner().next().unwrap();
                    if super_pair.as_rule() == Rule::identifier_name {
                        ExpressionType::MemberExpression(
                            MemberExpressionType::SimpleMemberExpression {
                                meta,
                                object: ExpressionOrSuper::Super,
                                property: get_identifier_data(super_pair, script),
                            },
                        )
                    } else {
                        let (e, e_s) = build_ast_from_expression(super_pair, script)?;
                        s.merge(e_s);
                        ExpressionType::MemberExpression(
                            MemberExpressionType::ComputedMemberExpression {
                                meta,
                                object: ExpressionOrSuper::Super,
                                property: Box::new(e),
                            },
                        )
                    }
                }
                Rule::meta_property => {
                    let start = meta.start_index;
                    let end = meta.end_index;
                    ExpressionType::MetaProperty {
                        meta,
                        meta_object: IdentifierData {
                            meta: Meta {
                                start_index: start,
                                end_index: start + 3,
                                script: script.clone(),
                            },
                            name: "new".to_string(),
                            is_binding_identifier: false,
                        },
                        property: IdentifierData {
                            meta: Meta {
                                start_index: start + 4,
                                end_index: end,
                                script: script.clone(),
                            },
                            name: "target".to_string(),
                            is_binding_identifier: false,
                        },
                    }
                }
                Rule::primary_expression | Rule::primary_expression__yield => {
                    let (p, p_s) = build_ast_from_primary_expression(pair_1, script)?;
                    s.merge(p_s);
                    p
                }
                _ => {
                    return Err(get_unexpected_error(
                        "build_ast_from_member_expression:1",
                        &pair_1,
                    ))
                }
            };
            for pair in pair_iter {
                let second_meta = get_meta(&pair, script);
                let meta = Meta {
                    start_index: obj.get_meta().start_index,
                    end_index: second_meta.end_index,
                    script: script.clone(),
                };
                obj = match pair.as_rule() {
                    Rule::expression__in_yield | Rule::expression__in => {
                        let (st, st_s) = build_ast_from_expression(pair, script)?;
                        s.merge(st_s);
                        ExpressionType::MemberExpression(
                            MemberExpressionType::ComputedMemberExpression {
                                meta,
                                object: ExpressionOrSuper::Expression(Box::new(obj)),
                                property: Box::new(st),
                            },
                        )
                    }
                    Rule::identifier_name => ExpressionType::MemberExpression(
                        MemberExpressionType::SimpleMemberExpression {
                            meta,
                            object: ExpressionOrSuper::Expression(Box::new(obj)),
                            property: get_identifier_data(pair, script),
                        },
                    ),
                    Rule::template_literal | Rule::template_literal__yield => {
                        let (template, t_s) = build_ast_from_template_literal(pair, script)?;
                        s.merge(t_s);
                        let quasi = if let ExpressionType::TemplateLiteral(data) = template {
                            data
                        } else {
                            return Err(get_validation_error_with_meta(
                                "Expected template literal".to_string(),
                                AstBuilderValidationErrorType::SyntaxError,
                                meta.clone(),
                            ));
                        };
                        ExpressionType::TaggedTemplateExpression {
                            meta,
                            tag: Box::new(obj),
                            quasi,
                        }
                    }
                    _ => {
                        return Err(get_unexpected_error(
                            "build_ast_from_member_expression:2",
                            &pair,
                        ))
                    }
                };
            }
            (obj, s)
        },
    )
}

fn build_ast_from_primary_expression(
    pair: Pair<Rule>,
    script: &Rc<String>,
) -> Result<(ExpressionType, Semantics), JsRuleError> {
    let inner_pair = pair.into_inner().next().unwrap();
    let meta = get_meta(&inner_pair, script);
    Ok(match inner_pair.as_rule() {
        Rule::identifier_reference | Rule::identifier_reference__yield => {
            let (i, i_s) = build_ast_from_identifier_reference(inner_pair, script)?;
            (i, i_s)
        }
        Rule::literal => (
            ExpressionType::Literal(build_ast_from_literal(inner_pair, script)?),
            Semantics::new_empty(),
        ),
        Rule::this_exp => (
            ExpressionType::ThisExpression { meta },
            Semantics::new_empty(),
        ),
        Rule::array_literal | Rule::array_literal__yield => {
            let (a, a_s) = build_ast_from_array_literal(inner_pair, script)?;
            (a, a_s)
        }
        Rule::object_literal | Rule::object_literal__yield => {
            build_ast_from_object_literal(inner_pair, script)?
        } /* is_valid_simple_assignment_target&is_function_definition&is_identifier_ref=false */
        Rule::generator_expression => {
            let (f, f_s) =
                build_ast_from_generator_declaration_or_generator_expression(inner_pair, script)?;
            (ExpressionType::FunctionOrGeneratorExpression(f), f_s)
        } /* is_valid_simple_assignment_target&is_identifier_ref=false */
        Rule::function_expression => {
            let (f, f_s) =
                build_ast_from_function_declaration_or_function_expression(inner_pair, script)?;
            (ExpressionType::FunctionOrGeneratorExpression(f), f_s)
        }
        Rule::class_expression | Rule::class_expression__yield => {
            let (c, c_s) = build_ast_from_class_expression(inner_pair, script)?;
            (ExpressionType::ClassExpression(c), c_s)
        } /* is_valid_simple_assignment_target&is_identifier_ref=false */
        Rule::regular_expression_literal => unimplemented!(), /* is_valid_simple_assignment_target&is_function_definition&is_identifier_ref=false */
        Rule::template_literal | Rule::template_literal__yield => {
            build_ast_from_template_literal(inner_pair, script)?
        } /* is_valid_simple_assignment_target&is_function_definition&is_identifier_ref=false */
        Rule::cover_parenthesized_expression_and_arrow_parameter_list
        | Rule::cover_parenthesized_expression_and_arrow_parameter_list__yield => {
            build_ast_from_cover_parenthesized_expression_and_arrow_parameter_list(
                inner_pair, script,
            )?
        }
        _ => {
            return Err(get_unexpected_error(
                "build_ast_from_primary_expression",
                &inner_pair,
            ))
        }
    })
}

fn build_ast_from_cover_parenthesized_expression_and_arrow_parameter_list(
    pair: Pair<Rule>,
    script: &Rc<String>,
) -> Result<(ExpressionType, Semantics), JsRuleError> {
    let inner_pair = expect_inner(pair, "build_ast_from_cover_parenthesized_expression_and_arrow_parameter_list", script)?;
    build_ast_from_expression(inner_pair, script)
}

fn build_ast_from_literal(
    pair: Pair<Rule>,
    script: &Rc<String>,
) -> Result<LiteralData, JsRuleError> {
    let inner_pair = expect_inner(pair, "build_ast_from_literal", script)?;
    let meta = get_meta(&inner_pair, script);
    Ok(match inner_pair.as_rule() {
        Rule::null_literal => LiteralData {
            meta,
            value: LiteralType::NullLiteral,
        },
        Rule::numeric_literal => LiteralData {
            meta,
            value: LiteralType::NumberLiteral(build_ast_from_numeric_literal(inner_pair)?),
        },
        Rule::string_literal => build_ast_from_string_literal(inner_pair, script)?,
        Rule::boolean_literal => {
            let bool = inner_pair.as_str();
            LiteralData {
                meta,
                value: LiteralType::BooleanLiteral(bool == "true"),
            }
        }
        _ => return Err(get_unexpected_error("build_ast_from_literal", &inner_pair)),
    })
}

fn build_ast_from_string_literal(
    pair: Pair<Rule>,
    script: &Rc<String>,
) -> Result<LiteralData, JsRuleError> {
    let meta = get_meta(&pair, script);
    let s = pair.as_str();
    Ok(LiteralData {
        meta,
        value: LiteralType::StringLiteral(String::from(&s[1..s.len() - 1])),
    })
}

/// Builds AST from a template literal.
/// Template literals can be:
///   - no_substitution_template: `hello world`
///   - template with substitutions: `hello ${name}!`
fn build_ast_from_template_literal(
    pair: Pair<Rule>,
    script: &Rc<String>,
) -> Result<(ExpressionType, Semantics), JsRuleError> {
    let meta = get_meta(&pair, script);
    let mut quasis: Vec<TemplateElementData> = vec![];
    let mut expressions: Vec<Box<ExpressionType>> = vec![];
    let mut s = Semantics::new_empty();

    for inner_pair in pair.into_inner() {
        match inner_pair.as_rule() {
            Rule::no_substitution_template => {
                // Simple template with no interpolations: `hello`
                let raw_str = inner_pair.as_str();
                // Remove the backticks
                let content = &raw_str[1..raw_str.len() - 1];
                let quasi_meta = get_meta(&inner_pair, script);
                quasis.push(TemplateElementData {
                    meta: quasi_meta,
                    tail: true,
                    cooked_value: process_template_escapes(content),
                    raw_value: content.to_string(),
                });
            }
            Rule::template_head => {
                // Head of template with substitutions: `hello ${
                let raw_str = inner_pair.as_str();
                // Remove ` from start and ${ from end
                let content = &raw_str[1..raw_str.len() - 2];
                let quasi_meta = get_meta(&inner_pair, script);
                quasis.push(TemplateElementData {
                    meta: quasi_meta,
                    tail: false,
                    cooked_value: process_template_escapes(content),
                    raw_value: content.to_string(),
                });
            }
            Rule::template_middle => {
                // Middle part between substitutions: }...${
                let raw_str = inner_pair.as_str();
                // Remove } from start and ${ from end
                let content = &raw_str[1..raw_str.len() - 2];
                let quasi_meta = get_meta(&inner_pair, script);
                quasis.push(TemplateElementData {
                    meta: quasi_meta,
                    tail: false,
                    cooked_value: process_template_escapes(content),
                    raw_value: content.to_string(),
                });
            }
            Rule::template_tail => {
                // End of template with substitutions: }...`
                let raw_str = inner_pair.as_str();
                // Remove } from start and ` from end
                let content = &raw_str[1..raw_str.len() - 1];
                let quasi_meta = get_meta(&inner_pair, script);
                quasis.push(TemplateElementData {
                    meta: quasi_meta,
                    tail: true,
                    cooked_value: process_template_escapes(content),
                    raw_value: content.to_string(),
                });
            }
            Rule::expression__in | Rule::expression__in_yield => {
                let (expr, expr_s) = build_ast_from_expression(inner_pair, script)?;
                s.merge(expr_s);
                expressions.push(Box::new(expr));
            }
            _ => {
                return Err(get_unexpected_error(
                    "build_ast_from_template_literal",
                    &inner_pair,
                ))
            }
        }
    }

    Ok((
        ExpressionType::TemplateLiteral(TemplateLiteralData {
            meta,
            quasis,
            expressions,
        }),
        s,
    ))
}

/// Process escape sequences in template literal content.
fn process_template_escapes(s: &str) -> String {
    let mut result = String::with_capacity(s.len());
    let mut chars = s.chars().peekable();

    while let Some(c) = chars.next() {
        if c == '\\' {
            match chars.next() {
                Some('n') => result.push('\n'),
                Some('r') => result.push('\r'),
                Some('t') => result.push('\t'),
                Some('\\') => result.push('\\'),
                Some('`') => result.push('`'),
                Some('$') => result.push('$'),
                Some('0') => result.push('\0'),
                Some('\'') => result.push('\''),
                Some('"') => result.push('"'),
                Some('x') => {
                    // Hex escape: \xHH
                    let mut hex = String::new();
                    for _ in 0..2 {
                        if let Some(&c) = chars.peek() {
                            if c.is_ascii_hexdigit() {
                                hex.push(chars.next().unwrap());
                            }
                        }
                    }
                    if hex.len() == 2 {
                        if let Ok(val) = u8::from_str_radix(&hex, 16) {
                            result.push(val as char);
                        }
                    }
                }
                Some('u') => {
                    // Unicode escape: \uHHHH or \u{H...}
                    if chars.peek() == Some(&'{') {
                        chars.next(); // consume '{'
                        let mut hex = String::new();
                        while let Some(&c) = chars.peek() {
                            if c == '}' {
                                chars.next();
                                break;
                            }
                            if c.is_ascii_hexdigit() {
                                hex.push(chars.next().unwrap());
                            } else {
                                break;
                            }
                        }
                        if let Ok(val) = u32::from_str_radix(&hex, 16) {
                            if let Some(ch) = char::from_u32(val) {
                                result.push(ch);
                            }
                        }
                    } else {
                        let mut hex = String::new();
                        for _ in 0..4 {
                            if let Some(&c) = chars.peek() {
                                if c.is_ascii_hexdigit() {
                                    hex.push(chars.next().unwrap());
                                }
                            }
                        }
                        if hex.len() == 4 {
                            if let Ok(val) = u16::from_str_radix(&hex, 16) {
                                result.push(char::from_u32(val as u32).unwrap_or('\u{FFFD}'));
                            }
                        }
                    }
                }
                Some(other) => {
                    // Unknown escape, just include the character
                    result.push(other);
                }
                None => {
                    // Trailing backslash
                    result.push('\\');
                }
            }
        } else {
            result.push(c);
        }
    }

    result
}

fn build_ast_from_str_numeric_literal(
    pair: Pair<Rule>,
) -> Result<ExtendedNumberLiteralType, JsRuleError> {
    let inner_pair = pair.into_inner().next().unwrap();
    Ok(match inner_pair.as_rule() {
        Rule::binary_integer_literal => {
            ExtendedNumberLiteralType::Std(get_ast_for_binary_integer_literal(inner_pair))
        }
        Rule::octal_integer_literal => {
            ExtendedNumberLiteralType::Std(get_ast_for_octal_integer_literal(inner_pair))
        }
        Rule::hex_integer_literal => {
            ExtendedNumberLiteralType::Std(get_ast_for_hex_integer_literal(inner_pair))
        }
        Rule::str_decimal_literal => build_ast_str_decimal_literal(inner_pair)?,
        _ => {
            return Err(get_unexpected_error(
                "build_ast_from_str_numeric_literal",
                &inner_pair,
            ))
        }
    })
}

fn build_ast_str_decimal_literal(
    pair: Pair<Rule>,
) -> Result<ExtendedNumberLiteralType, JsRuleError> {
    let mut pair_iter = pair.into_inner();
    let mut inner_pair = pair_iter.next().unwrap();
    let is_negative = if inner_pair.as_rule() == Rule::str_negative_op {
        inner_pair = pair_iter.next().unwrap();
        true
    } else {
        false
    };
    build_ast_str_unsigned_decimal_literal(inner_pair, is_negative)
}

fn build_ast_str_unsigned_decimal_literal(
    pair: Pair<Rule>,
    is_negative: bool,
) -> Result<ExtendedNumberLiteralType, JsRuleError> {
    let mut num: f64 = 0.0;
    let mut is_float = false;
    for decimal_pair in pair.into_inner() {
        num = match decimal_pair.as_rule() {
            Rule::str_decimal_literal_infinity => {
                return Ok(if is_negative {
                    ExtendedNumberLiteralType::NegativeInfinity
                } else {
                    ExtendedNumberLiteralType::Infinity
                });
            }
            Rule::decimal_digits_integer_part => parse_decimal_integer_literal(decimal_pair),
            Rule::decimal_digits => {
                is_float = true;
                num + parse_decimal_digits(decimal_pair)
            }
            Rule::exponent_part => num * parse_exponent_part(decimal_pair),
            _ => {
                return Err(get_unexpected_error(
                    "build_ast_str_unsigned_decimal_literal",
                    &decimal_pair,
                ))
            }
        }
    }
    if is_negative {
        num *= -1.0;
    }
    Ok(if !is_float {
        ExtendedNumberLiteralType::Std(NumberLiteralType::IntegerLiteral(num as i64))
    } else {
        ExtendedNumberLiteralType::Std(NumberLiteralType::FloatLiteral(num))
    })
}

fn get_ast_for_binary_integer_literal(pair: Pair<Rule>) -> NumberLiteralType {
    NumberLiteralType::IntegerLiteral(isize::from_str_radix(&pair.as_str()[2..], 2).unwrap() as i64)
}

fn get_ast_for_octal_integer_literal(pair: Pair<Rule>) -> NumberLiteralType {
    NumberLiteralType::IntegerLiteral(isize::from_str_radix(&pair.as_str()[2..], 8).unwrap() as i64)
}

fn get_ast_for_hex_integer_literal(pair: Pair<Rule>) -> NumberLiteralType {
    NumberLiteralType::IntegerLiteral(isize::from_str_radix(&pair.as_str()[2..], 16).unwrap() as i64)
}

fn parse_decimal_integer_literal(decimal_pair: Pair<Rule>) -> f64 {
    isize::from_str_radix(decimal_pair.as_str(), 10).unwrap() as f64
}

fn parse_decimal_digits(decimal_pair: Pair<Rule>) -> f64 {
    let d = decimal_pair.as_str();
    isize::from_str_radix(d, 10).unwrap() as f64 / 10_f64.powf(d.len() as f64)
}

fn parse_exponent_part(decimal_pair: Pair<Rule>) -> f64 {
    10_f64.powf(isize::from_str_radix(&decimal_pair.as_str()[1..], 10).unwrap() as f64)
}

fn build_ast_decimal_literal(pair: Pair<Rule>) -> Result<NumberLiteralType, JsRuleError> {
    let mut num: f64 = 0.0;
    let mut is_float = false;
    for decimal_pair in pair.into_inner() {
        num = match decimal_pair.as_rule() {
            Rule::decimal_integer_literal => parse_decimal_integer_literal(decimal_pair),
            Rule::decimal_digits => {
                is_float = true;
                num + parse_decimal_digits(decimal_pair)
            }
            Rule::exponent_part => num * parse_exponent_part(decimal_pair),
            _ => {
                return Err(get_unexpected_error(
                    "build_ast_decimal_literal",
                    &decimal_pair,
                ))
            }
        }
    }
    Ok(if !is_float {
        NumberLiteralType::IntegerLiteral(num as i64)
    } else {
        NumberLiteralType::FloatLiteral(num)
    })
}

fn build_ast_from_numeric_literal(pair: Pair<Rule>) -> Result<NumberLiteralType, JsRuleError> {
    let inner_pair = pair.into_inner().next().unwrap();
    Ok(match inner_pair.as_rule() {
        Rule::binary_integer_literal => get_ast_for_binary_integer_literal(inner_pair),
        Rule::octal_integer_literal => get_ast_for_octal_integer_literal(inner_pair),
        Rule::hex_integer_literal => get_ast_for_hex_integer_literal(inner_pair),
        Rule::decimal_literal => build_ast_decimal_literal(inner_pair)?,
        _ => {
            return Err(get_unexpected_error(
                "build_ast_from_numeric_literal",
                &inner_pair,
            ))
        }
    })
}

fn build_ast_from_array_literal(
    pair: Pair<Rule>,
    script: &Rc<String>,
) -> Result<(ExpressionType, Semantics), JsRuleError> {
    let meta = get_meta(&pair, script);
    let mut arguments = vec![];
    let mut s = Semantics::new_empty();
    for inner_pair in pair.into_inner() {
        match inner_pair.as_rule() {
            Rule::elision => {
                for _ in 0..(inner_pair.as_str().matches(',').count()) {
                    arguments.push(None);
                }
            }
            Rule::assignment_expression__in | Rule::assignment_expression__in_yield => {
                let (a, a_s) = build_ast_from_assignment_expression(inner_pair, script)?;
                s.merge(a_s);
                arguments.push(Some(ExpressionOrSpreadElement::Expression(Box::new(a))));
            }
            Rule::spread_element | Rule::spread_element__yield => {
                let spread_inner = expect_inner(inner_pair, "spread_element", script)?;
                let (a, a_s) = build_ast_from_assignment_expression(spread_inner, script)?;
                s.merge(a_s);
                arguments.push(Some(ExpressionOrSpreadElement::SpreadElement(Box::new(a))));
            }
            _ => {
                return Err(get_unexpected_error(
                    "build_ast_from_array_literal",
                    &inner_pair,
                ))
            }
        }
    }
    Ok((
        ExpressionType::ArrayExpression {
            meta,
            elements: arguments,
        },
        s,
    ))
}

fn build_ast_from_object_literal(
    pair: Pair<Rule>,
    script: &Rc<String>,
) -> Result<(ExpressionType, Semantics), JsRuleError> {
    let meta = get_meta(&pair, script);
    let mut s = Semantics::new_empty();
    let mut properties = vec![];
    for property_pair in pair.into_inner() {
        let (p, p_s) = build_ast_from_property_definition(property_pair, script)?;
        s.merge(p_s);
        properties.push(p);
    }
    Ok((ExpressionType::ObjectExpression { meta, properties }, s))
}

fn build_ast_from_property_definition(
    pair: Pair<Rule>,
    script: &Rc<String>,
) -> Result<(PropertyData<Box<ExpressionType>>, Semantics), JsRuleError> {
    let meta = get_meta(&pair, script);
    let mut s = Semantics::new_empty();
    let mut inner_pair_iter = pair.into_inner();
    let inner_pair = inner_pair_iter.next().unwrap();
    let p = match inner_pair.as_rule() {
        Rule::property_name | Rule::property_name__yield => {
            let (p, p_s) = build_ast_from_property_name(inner_pair, script)?;
            let (a, a_s) =
                build_ast_from_assignment_expression(inner_pair_iter.next().unwrap(), script)?;
            s.merge(p_s).merge(a_s);
            PropertyData::new_with_any_expression_key(
                meta,
                p,
                Box::new(a),
                PropertyKind::Init,
                false,
                false,
            )
        }
        Rule::cover_initialized_name | Rule::cover_initialized_name__yield => {
            let error = format!("Initialization is only possible for object destruction pattern not in object literal: {}", inner_pair.as_str());
            return Err(get_validation_error(
                error,
                AstBuilderValidationErrorType::SyntaxError,
                &inner_pair,
                &script,
            ));
        }
        Rule::method_definition | Rule::method_definition__yield => {
            let meta = get_meta(&inner_pair, script);
            let (m, m_s) = build_ast_from_method_definition(inner_pair, script)?;
            if m_s.has_direct_super.is_true() {
                return Err(get_validation_error_with_meta(
                    "Invalid reference to super".to_string(),
                    AstBuilderValidationErrorType::SyntaxError,
                    meta,
                ));
            }
            s.merge(m_s);
            m
        }
        Rule::identifier_reference | Rule::identifier_reference__yield => {
            let id = get_identifier_data(inner_pair, script);
            let id2 = id.clone();
            PropertyData::new_with_identifier_key(
                meta,
                id,
                Box::new(ExpressionPatternType::Identifier(id2).convert_to_expression()),
                PropertyKind::Init,
                false,
                true,
            )
        }
        _ => {
            return Err(get_unexpected_error(
                "build_ast_from_property_definition",
                &inner_pair,
            ))
        }
    };
    Ok((p, s))
}

fn build_ast_from_method_definition(
    pair: Pair<Rule>,
    script: &Rc<String>,
) -> Result<(PropertyData<Box<ExpressionType>>, Semantics), JsRuleError> {
    let meta = get_meta(&pair, script);
    let mut s = Semantics::new_empty();
    let mut inner_iter = pair.into_inner();
    let inner_pair = inner_iter.next().unwrap();
    let m = match inner_pair.as_rule() {
        Rule::property_name | Rule::property_name__yield => {
            let (p, p_s) = build_ast_from_property_name(inner_pair, script)?;
            let (fp, fp_s) = build_ast_from_formal_parameters(inner_iter.next().unwrap(), script)?;
            let (fb, fb_s) = build_ast_from_function_body(inner_iter.next().unwrap(), script)?;
            validate_bound_names_have_no_duplicates_and_also_not_present_in_var_declared_names_or_lexically_declared_names(&fp_s.bound_names,&vec![],&fb_s.lexically_declared_names)?;
            s.merge(p_s).merge(fp_s).merge(fb_s);
            let meta2 = meta.clone();
            PropertyData::new_with_any_expression_key(
                meta,
                p,
                Box::new(ExpressionType::FunctionOrGeneratorExpression(
                    FunctionData {
                        meta: meta2,
                        id: None,
                        params: FormalParameters::new(fp),
                        body: Box::new(fb),
                        generator: false,
                    },
                )),
                PropertyKind::Init,
                true,
                false,
            )
        }
        Rule::generator_method | Rule::generator_method__yield => {
            let mut inner_inner_iter = inner_pair.into_inner();
            let (p, p_s) = build_ast_from_property_name(inner_inner_iter.next().unwrap(), script)?;
            let (fp, fp_s) =
                build_ast_from_formal_parameters(inner_inner_iter.next().unwrap(), script)?;
            let (fb, fb_s) =
                build_ast_from_generator_body(inner_inner_iter.next().unwrap(), script)?;
            if fb_s.has_direct_super.is_true() {
                return Err(get_validation_error_with_meta(
                    "Invalid reference to 'super'".to_string(),
                    AstBuilderValidationErrorType::SyntaxError,
                    meta.clone(),
                ));
            }
            validate_bound_names_have_no_duplicates_and_also_not_present_in_var_declared_names_or_lexically_declared_names(&fp_s.bound_names,&vec![],&fb_s.lexically_declared_names)?;
            s.merge(p_s).merge(fp_s).merge(fb_s);
            let meta2 = meta.clone();
            PropertyData::new_with_any_expression_key(
                meta,
                p,
                Box::new(ExpressionType::FunctionOrGeneratorExpression(
                    FunctionData {
                        meta: meta2,
                        id: None,
                        params: FormalParameters::new(fp),
                        body: Box::new(fb),
                        generator: true,
                    },
                )),
                PropertyKind::Init,
                true,
                false,
            )
        }
        Rule::getter => {
            let (p, p_s) = build_ast_from_property_name(inner_iter.next().unwrap(), script)?;
            let (fb, fb_s) = build_ast_from_function_body(inner_iter.next().unwrap(), script)?;
            s.merge(p_s).merge(fb_s);
            let meta2 = meta.clone();
            PropertyData::new_with_any_expression_key(
                meta,
                p,
                Box::new(ExpressionType::FunctionOrGeneratorExpression(
                    FunctionData {
                        meta: meta2,
                        id: None,
                        params: FormalParameters::new(vec![]),
                        body: Box::new(fb),
                        generator: false,
                    },
                )),
                PropertyKind::Get,
                false,
                false,
            )
        }
        Rule::setter => {
            let (p, p_s) = build_ast_from_property_name(inner_iter.next().unwrap(), script)?;
            // Setters use property_set_parameter_list which is a single formal_parameter (silent rule)
            let (fp, fp_s) = build_ast_from_single_formal_parameter(inner_iter.next().unwrap(), script)?;
            let (fb, fb_s) = build_ast_from_function_body(inner_iter.next().unwrap(), script)?;
            validate_bound_names_have_no_duplicates_and_also_not_present_in_var_declared_names_or_lexically_declared_names(&fp_s.bound_names,&vec![],&fb_s.lexically_declared_names)?;
            s.merge(p_s).merge(fp_s).merge(fb_s);
            let meta2 = meta.clone();
            PropertyData::new_with_any_expression_key(
                meta,
                p,
                Box::new(ExpressionType::FunctionOrGeneratorExpression(
                    FunctionData {
                        meta: meta2,
                        id: None,
                        params: FormalParameters::new(fp),
                        body: Box::new(fb),
                        generator: false,
                    },
                )),
                PropertyKind::Set,
                false,
                false,
            )
        }
        _ => {
            return Err(get_unexpected_error(
                "build_ast_from_method_definition",
                &inner_pair,
            ))
        }
    };
    Ok((m, s))
}

fn build_ast_from_identifier_reference(
    pair: Pair<Rule>,
    script: &Rc<String>,
) -> Result<(ExpressionType, Semantics), JsRuleError> {
    let id = pair.as_str();
    if id == "yield" {
        Err(get_validation_error(
            format!("Invalid identifier reference: {}", id),
            AstBuilderValidationErrorType::SyntaxError,
            &pair,
            &script,
        ))
    } else {
        let s = Semantics::new_empty();
        Ok((
            ExpressionPatternType::Identifier(get_identifier_data(pair, script))
                .convert_to_expression(),
            s,
        ))
    }
}

/// Builds AST from a class declaration.
/// Grammar: "class" ~ binding_identifier ~ class_tail
fn build_ast_from_class_declaration(
    pair: Pair<Rule>,
    script: &Rc<String>,
) -> Result<(ClassData, Semantics), JsRuleError> {
    let meta = get_meta(&pair, script);
    let mut pair_iter = pair.into_inner();
    let mut s = Semantics::new_empty();

    // binding_identifier is required for class declarations
    let id_pair = pair_iter.next().ok_or_else(|| {
        get_validation_error_with_meta(
            "Expected class name".to_string(),
            AstBuilderValidationErrorType::SyntaxError,
            meta.clone(),
        )
    })?;
    let (id, id_s) = get_binding_identifier_data(id_pair, script)?;
    s.merge(id_s);

    // Parse class_tail
    let class_tail_pair = pair_iter.next().ok_or_else(|| {
        get_validation_error_with_meta(
            "Expected class body".to_string(),
            AstBuilderValidationErrorType::SyntaxError,
            meta.clone(),
        )
    })?;
    let (super_class, body, tail_s) = build_ast_from_class_tail(class_tail_pair, script)?;
    s.merge(tail_s);

    Ok((
        ClassData {
            meta,
            id: Some(id),
            super_class,
            body,
        },
        s,
    ))
}

/// Builds AST from a class expression.
/// Grammar: "class" ~ binding_identifier? ~ class_tail
fn build_ast_from_class_expression(
    pair: Pair<Rule>,
    script: &Rc<String>,
) -> Result<(ClassData, Semantics), JsRuleError> {
    let meta = get_meta(&pair, script);
    let mut pair_iter = pair.into_inner();
    let mut s = Semantics::new_empty();

    // Check if there's an optional binding_identifier
    let first_pair = pair_iter.next();
    let (id, class_tail_pair) = if let Some(fp) = first_pair {
        if fp.as_rule() == Rule::binding_identifier || fp.as_rule() == Rule::binding_identifier__yield
        {
            let (id, _id_s) = get_binding_identifier_data(fp, script)?;
            // For class expressions, we don't include the name in bound_names
            let tail = pair_iter.next().ok_or_else(|| {
                get_validation_error_with_meta(
                    "Expected class body".to_string(),
                    AstBuilderValidationErrorType::SyntaxError,
                    meta.clone(),
                )
            })?;
            (Some(id), tail)
        } else {
            // It's the class_tail
            (None, fp)
        }
    } else {
        return Err(get_validation_error_with_meta(
            "Expected class body".to_string(),
            AstBuilderValidationErrorType::SyntaxError,
            meta.clone(),
        ));
    };

    let (super_class, body, tail_s) = build_ast_from_class_tail(class_tail_pair, script)?;
    s.merge(tail_s);

    Ok((
        ClassData {
            meta,
            id,
            super_class,
            body,
        },
        s,
    ))
}

/// Builds AST from class_tail.
/// Grammar: class_heritage? ~ "{" ~ class_body? ~ "}"
fn build_ast_from_class_tail(
    pair: Pair<Rule>,
    script: &Rc<String>,
) -> Result<(Option<Box<ExpressionType>>, ClassBodyData, Semantics), JsRuleError> {
    let meta = get_meta(&pair, script);
    let mut s = Semantics::new_empty();
    let mut super_class = None;
    let mut methods: Vec<MethodDefinitionData> = vec![];

    for inner_pair in pair.into_inner() {
        match inner_pair.as_rule() {
            Rule::class_heritage | Rule::class_heritage__yield => {
                // class_heritage = "extends" ~ left_hand_side_expression
                let lhs_pair = inner_pair.into_inner().next().ok_or_else(|| {
                    get_validation_error_with_meta(
                        "Expected superclass expression".to_string(),
                        AstBuilderValidationErrorType::SyntaxError,
                        meta.clone(),
                    )
                })?;
                let (expr, expr_s) = build_ast_from_left_hand_side_expression(lhs_pair, script)?;
                s.merge(expr_s);
                super_class = Some(Box::new(expr));
            }
            Rule::class_body | Rule::class_body__yield => {
                // class_body = class_element_list
                for element_pair in inner_pair.into_inner() {
                    if let Some(method) =
                        build_ast_from_class_element(element_pair, script, &mut s)?
                    {
                        methods.push(method);
                    }
                }
            }
            _ => {
                return Err(get_unexpected_error("build_ast_from_class_tail", &inner_pair))
            }
        }
    }

    Ok((
        super_class,
        ClassBodyData { meta, body: methods },
        s,
    ))
}

/// Builds AST from a class_element.
/// Grammar: method_definition | "static" ~ method_definition | ";"
fn build_ast_from_class_element(
    pair: Pair<Rule>,
    script: &Rc<String>,
    s: &mut Semantics,
) -> Result<Option<MethodDefinitionData>, JsRuleError> {
    let meta = get_meta(&pair, script);
    let mut inner_iter = pair.into_inner();

    // Check if empty (semicolon-only element)
    let first_pair = match inner_iter.next() {
        Some(p) => p,
        None => return Ok(None), // Empty class element (;)
    };

    let (is_static, method_pair) = if first_pair.as_rule() == Rule::class_static {
        let mp = inner_iter.next().ok_or_else(|| {
            get_validation_error_with_meta(
                "Expected method definition after 'static'".to_string(),
                AstBuilderValidationErrorType::SyntaxError,
                meta.clone(),
            )
        })?;
        (true, mp)
    } else {
        (false, first_pair)
    };

    // Parse the method definition
    let (prop_data, method_s) = build_ast_from_method_definition(method_pair, script)?;
    s.merge(method_s);

    // Convert PropertyData to MethodDefinitionData
    let PropertyData {
        meta: prop_meta,
        key,
        value,
        kind,
        method: _,
        shorthand: _,
        computed,
    } = prop_data;

    // Extract FunctionData from the value expression
    let func_data = match *value {
        ExpressionType::FunctionOrGeneratorExpression(f) => f,
        _ => {
            return Err(get_validation_error_with_meta(
                "Expected function in method definition".to_string(),
                AstBuilderValidationErrorType::SyntaxError,
                prop_meta.clone(),
            ));
        }
    };

    // Determine method kind
    let method_kind = match kind {
        PropertyKind::Init => {
            // Check if it's a constructor
            if let ExpressionType::ExpressionWhichCanBePattern(ExpressionPatternType::Identifier(
                ref id,
            )) = *key
            {
                if id.name == "constructor" && !is_static {
                    MethodDefinitionKind::Constructor
                } else {
                    MethodDefinitionKind::Method
                }
            } else {
                MethodDefinitionKind::Method
            }
        }
        PropertyKind::Get => MethodDefinitionKind::Get,
        PropertyKind::Set => MethodDefinitionKind::Set,
    };

    Ok(Some(MethodDefinitionData {
        meta: prop_meta,
        key,
        value: func_data,
        kind: method_kind,
        computed,
        static_flag: is_static,
    }))
}