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//! Expression parsing for the Pascal parser
use crate::ast::{Expr, Literal};use crate::parser::{ParseResult, Parser};
use crate::tokens::Token;
use crate::utils::ast_helpers::*;
use crate::ParseError;
impl<'a> Parser<'a> {
/// Parse expression
pub fn parse_expression(&mut self) -> ParseResult<Option<Expr>> {
self.parse_binary_op(0)
}
/// Parse binary operations with precedence
pub fn parse_binary_op(&mut self, precedence: u8) -> ParseResult<Option<Expr>> {
let mut left = self.parse_unary_op()?;
while let Some(token) = self.peek() {
let (op, prec) = self.get_binary_op_info(token);
if let Some(op_str) = op {
if prec < precedence {
break;
}
// Clone the operator string before advancing
let op_string = op_str.to_string();
self.advance();
let right = self.parse_binary_op(prec + 1)?;
left = Some(binop(
left.ok_or(ParseError::UnexpectedToken(
"expected left operand".to_string(),
))?,
&op_string,
right.ok_or(ParseError::UnexpectedToken(
"expected right operand".to_string(),
))?,
));
} else {
break;
}
}
Ok(left)
}
/// Get binary operator info (operator string and precedence)
fn get_binary_op_info(&self, token: &Token) -> (Option<&str>, u8) {
match token {
Token::Or => (Some("or"), 1),
Token::Xor => (Some("xor"), 2),
Token::And => (Some("and"), 3),
Token::Equal => (Some("="), 4),
Token::NotEqual => (Some("<>"), 4),
Token::LessThan => (Some("<"), 4),
Token::GreaterThan => (Some(">"), 4),
Token::LessEqual => (Some("<="), 4),
Token::GreaterEqual => (Some(">="), 4),
Token::In => (Some("in"), 4),
Token::Plus => (Some("+"), 5),
Token::Minus => (Some("-"), 5),
Token::Star => (Some("*"), 6),
Token::Slash => (Some("/"), 6),
Token::Divide => (Some("div"), 6),
Token::Mod => (Some("mod"), 6),
Token::Shl => (Some("shl"), 6),
Token::Shr => (Some("shr"), 6),
_ => (None, 0),
}
}
/// Parse unary operations
pub fn parse_unary_op(&mut self) -> ParseResult<Option<Expr>> {
let op = match self.peek() {
Some(Token::Not) => Some("not"),
Some(Token::Minus) => Some("-"),
Some(Token::Plus) => Some("+"),
Some(Token::AddressOf) => Some("@"),
_ => None,
};
if let Some(op_str) = op {
self.advance();
let operand = self.parse_unary_op()?;
Ok(Some(unop(
op_str,
operand.ok_or(ParseError::UnexpectedToken("expected operand".to_string()))?,
)))
} else {
self.parse_primary()
}
}
/// Parse primary expression
pub fn parse_primary(&mut self) -> ParseResult<Option<Expr>> {
Ok(match self.peek() {
Some(Token::Identifier(name)) => {
let name = name.clone();
self.advance();
let mut result = if self.check(Token::LeftParen) {
// Function call
self.advance();
let args = self.parse_argument_list()?;
call(&name, args)
} else {
var(&name)
};
// Handle dot-notation and bracket indexing
loop {
if self.check(Token::Dot) {
self.advance();
if let Some(Token::Identifier(member)) = self.peek() {
let member = member.clone();
self.advance();
let base_name = match &result {
Expr::Variable(n) => n.clone(),
_ => "self".to_string(),
};
let dotted = format!("{}.{}", base_name, member);
if self.check(Token::LeftParen) {
self.advance();
let args = self.parse_argument_list()?;
result = Expr::FunctionCall {
name: dotted,
arguments: args,
};
} else {
result = var(&dotted);
}
} else {
break;
}
} else if self.check(Token::LeftBracket) {
// Array/string indexing: arr[i] or s[i]
self.advance();
let index = self.parse_expression()?;
self.consume_or_skip(Token::RightBracket, &[Token::Semicolon, Token::End]);
if let Some(idx_expr) = index {
// Encode as FunctionCall "__index__(arr, i)"
result = Expr::FunctionCall {
name: "__index__".to_string(),
arguments: vec![result, idx_expr],
};
}
} else if self.check(Token::Caret) {
// Pointer dereference: p^
self.advance();
result = Expr::Dereference { expression: Box::new(result) };
} else {
break;
}
}
Some(result)
}
Some(Token::IntegerLiteral(_))
| Some(Token::RealLiteral(_))
| Some(Token::StringLiteral(_))
| Some(Token::PascalStringLiteral(_))
| Some(Token::CharLiteral(_))
| Some(Token::True)
| Some(Token::False) => {
if let Some(lit) = self.parse_literal()? {
Some(Expr::Literal(lit))
} else {
None
}
}
Some(Token::LeftParen) => {
self.advance();
let expr = self.parse_expression()?;
self.consume_or_skip(
Token::RightParen,
&[Token::Semicolon, Token::End, Token::Comma],
);
expr
}
Some(Token::Function) | Some(Token::Procedure) => self.parse_lambda_expression()?,
Some(Token::LeftBracket) => {
// Set literal: [a, b, c]
self.advance();
let mut elements = vec![];
if !self.check(Token::RightBracket) {
loop {
if let Some(elem) = self.parse_expression()? {
elements.push(elem);
}
match self.peek() {
Some(Token::Comma) => {
self.advance();
continue;
}
Some(Token::RightBracket) => break,
_ => break,
}
}
}
self.consume_or_skip(Token::RightBracket, &[Token::Semicolon, Token::End]);
Some(Expr::Set { elements })
}
_ => None,
})
}
/// Parse argument list: (arg1, arg2, ...)
pub fn parse_argument_list(&mut self) -> ParseResult<Vec<Expr>> {
let mut args = Vec::new();
if !self.check(Token::RightParen) {
loop {
if let Some(arg) = self.parse_expression()? {
args.push(arg);
}
match self.peek() {
Some(Token::Comma) => {
self.advance();
continue;
}
Some(Token::RightParen) => break,
_ => break,
}
}
}
self.consume_or_skip(Token::RightParen, &[Token::Semicolon, Token::End]);
Ok(args)
}
/// Parse an anonymous function / lambda expression.
///
/// Syntax: `function(params): type begin ... end` or `procedure(params) begin ... end`
pub fn parse_lambda_expression(&mut self) -> ParseResult<Option<Expr>> {
let is_function = self.check(Token::Function);
self.advance(); // function | procedure
let mut params: Vec<crate::ast::Parameter> = Vec::new();
if self.check(Token::LeftParen) {
self.advance();
if !self.check(Token::RightParen) {
loop {
// collect names
let mut names: Vec<String> = Vec::new();
loop {
if let Some(Token::Identifier(name)) = self.peek() {
names.push(name.clone());
self.advance();
}
if self.check(Token::Comma) {
self.advance();
} else {
break;
}
}
self.consume_or_skip(Token::Colon, &[Token::Semicolon, Token::RightParen]);
let ptype = self.parse_type().unwrap_or(crate::ast::Type::Simple(
crate::ast::SimpleType::Integer,
));
for n in names {
params.push(crate::ast::Parameter {
name: n,
param_type: ptype.clone(),
is_var: false,
is_const: false,
is_out: false,
default_value: None,
});
}
if self.check(Token::Semicolon) {
self.advance();
continue;
}
break;
}
}
self.consume_or_skip(Token::RightParen, &[Token::Colon, Token::Begin]);
}
let return_type = if is_function {
self.consume_or_skip(Token::Colon, &[Token::Begin]);
Some(self.parse_type()?)
} else {
None
};
let body = if self.check(Token::Begin) {
let stmts = self.parse_compound_statement()?;
crate::ast::Block {
consts: vec![],
types: vec![],
vars: vec![],
procedures: vec![],
functions: vec![],
classes: vec![],
statements: stmts,
}
} else {
crate::ast::Block::empty()
};
Ok(Some(Expr::Lambda {
params,
body: Box::new(body),
return_type,
captures: true,
}))
}
/// Parse a literal value
pub fn parse_literal(&mut self) -> ParseResult<Option<Literal>> {
Ok(match self.peek() {
Some(Token::IntegerLiteral(n)) => {
let lit = Some(Literal::Integer(*n));
self.advance();
lit
}
Some(Token::RealLiteral(r)) => {
let lit = Some(Literal::Real(*r));
self.advance();
lit
}
Some(Token::StringLiteral(s)) => {
let lit = Some(Literal::String(s.clone()));
self.advance();
lit
}
Some(Token::PascalStringLiteral(s)) => {
let s = s.clone();
self.advance();
if s.len() == 1 {
Some(Literal::Char(s.chars().next().unwrap()))
} else {
Some(Literal::String(s))
}
}
Some(Token::CharLiteral(c)) => {
let lit = Some(Literal::Char(*c));
self.advance();
lit
}
Some(Token::True) => {
self.advance();
Some(Literal::Boolean(true))
}
Some(Token::False) => {
self.advance();
Some(Literal::Boolean(false))
}
_ => None,
})
}
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn test_parse_simple_expression() {
let source = "42";
let mut parser = Parser::new(source);
let expr = parser.parse_expression();
assert!(expr.is_ok());
}
#[test]
fn test_parse_binary_op() {
let source = "1 + 2 * 3";
let mut parser = Parser::new(source);
let expr = parser.parse_expression();
assert!(expr.is_ok());
}
#[test]
fn test_parse_function_call() {
let source = "foo(1, 2, 3)";
let mut parser = Parser::new(source);
let expr = parser.parse_expression();
assert!(expr.is_ok());
}
}