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363 lines
12 KiB
Rust
363 lines
12 KiB
Rust
pub(crate) mod tree;
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use crate::error::Error;
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use crate::lex::token;
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use crate::lex::token::Token;
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use crate::lex::Lexer;
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use std::fs;
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use std::io;
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use crate::ast::tree::Operator;
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#[derive(PartialEq)]
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enum Scope {
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File,
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Target,
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DepList,
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SourceList,
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}
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struct Parser {
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lexer: Lexer,
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scope: Vec<Scope>,
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filename: String,
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}
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pub fn parse(filename: String) -> io::Result<Result<tree::Node, Error>> {
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let raw: String = fs::read_to_string(filename.clone())?;
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let mut p = Parser::new(filename, raw);
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Ok(p.parse_file())
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}
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impl Parser {
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pub fn new(filename: String, raw: String) -> Parser {
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let lexer = Lexer::new(filename.clone(), raw);
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Parser {
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lexer,
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scope: Vec::new(),
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filename,
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}
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}
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pub fn parse_file(&mut self) -> Result<tree::Node, Error> {
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let mut nodes = Vec::new();
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self.scope.push(Scope::File);
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while self.lexer.peek().is_some() {
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nodes.push(self.parse_stmt()?);
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}
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self.scope.pop();
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Ok(tree::Node::File {
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name: self.filename.clone(),
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content: nodes,
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})
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}
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fn parse_stmt(&mut self) -> Result<tree::Node, Error> {
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let token = self.lexer.peek_or_err()?;
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match token.kind {
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token::Kind::DependKeyword => self.parse_depend_stmt(),
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token::Kind::SetKeyword => self.parse_set_stmt(),
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token::Kind::SourceKeyword => self.parse_source_stmt(),
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token::Kind::TargetKeyword => self.parse_target_stmt(),
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token::Kind::TypeKeyword => self.parse_type_stmt(),
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token::Kind::Ident => self.parse_expr_stmt(),
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_ => self.syntax_error(format!("Unexpected token {}", token), &token),
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}
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}
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fn parse_target_stmt(&mut self) -> Result<tree::Node, Error> {
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self.assert_scope(Scope::File)?;
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self.assert_scope_not(Scope::Target)?;
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self.scope.push(Scope::Target);
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self.lexer.expect_kind(token::Kind::TargetKeyword)?;
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let name_token = self.lexer.expect_kind(token::Kind::Ident)?;
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self.lexer.expect_kind(token::Kind::OBrace)?;
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let mut children = Vec::new();
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while let Some(result) = self.lexer.peek() {
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match result?.kind {
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token::Kind::CBrace => {
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self.lexer.next();
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break;
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}
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_ => children.push(self.parse_stmt()?),
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}
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}
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self.scope.pop();
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Ok(tree::Node::Target {
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name: Box::new(tree::Node::Ident(name_token.raw)),
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content: children,
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})
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}
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fn parse_depend_stmt(&mut self) -> Result<tree::Node, Error> {
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self.assert_scope(Scope::Target)?;
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self.scope.push(Scope::DepList);
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self.lexer.expect_kind(token::Kind::DependKeyword)?;
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let rvalue = self.parse_expr(&[token::Kind::Semi])?;
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self.scope.pop();
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Ok(tree::Node::DepList(Box::new(rvalue)))
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}
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fn parse_set_stmt(&mut self) -> Result<tree::Node, Error> {
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self.assert_scope(Scope::File)?;
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self.lexer.expect_kind(token::Kind::SetKeyword)?;
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let expr = self.parse_expr(&[token::Kind::Semi])?;
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match expr {
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tree::Node::BinaryExpr { op, lhs, rhs } => {
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if op == Operator::Eq {
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Ok(tree::Node::SetExpr {
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name: lhs,
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val: rhs,
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})
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} else {
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self.syntax_error(format!("Invalid operator"), self.lexer.current().unwrap())
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}
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}
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_ => self.syntax_error(format!("Expected an assignment"), self.lexer.current().unwrap())
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}
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}
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fn parse_type_stmt(&mut self) -> Result<tree::Node, Error> {
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self.assert_scope(Scope::Target)?;
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self.lexer.expect_kind(token::Kind::TypeKeyword)?;
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let expr = self.parse_expr(&[token::Kind::Semi])?;
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Ok(tree::Node::TypeExpr(Box::new(expr)))
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}
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fn parse_source_stmt(&mut self) -> Result<tree::Node, Error> {
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self.assert_scope(Scope::Target)?;
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self.lexer.expect_kind(token::Kind::SourceKeyword)?;
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self.scope.push(Scope::SourceList);
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let source = self.parse_expr(&[token::Kind::Semi])?;
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self.scope.pop();
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Ok(tree::Node::SourceList(Box::new(source)))
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}
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fn parse_expr_stmt(&mut self) -> Result<tree::Node, Error> {
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self.parse_expr(&[token::Kind::Semi])
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}
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fn parse_expr(&mut self, terminators: &[token::Kind]) -> Result<tree::Node, Error> {
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self.assert_scope(Scope::File)?;
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let expr = if let Some(result) = self.lexer.peek() {
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let token = result?;
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if !token.kind.is_start_of_expr() {
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self.syntax_error(String::from("Expected an expression"), &token)
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} else {
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self.parse_assignment_expr_or_higher(terminators)
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}
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} else {
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self.syntax_error(
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String::from("Unexpected EOF"),
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&self.lexer.current().unwrap(),
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)
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};
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expr
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}
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fn parse_assignment_expr_or_higher(&mut self, terminators: &[token::Kind]) -> Result<tree::Node, Error> {
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let lhs = self.parse_primary_expr()?;
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if let Some(Ok(token)) = self.lexer.peek() {
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if token.kind.is_assignment_op() {
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let op_token = self.lexer.require_next()?;
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let op = Operator::from_token(&op_token)?;
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let rhs = self.parse_binary_expr_or_higher(terminators)?;
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return Ok(tree::Node::BinaryExpr {
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op,
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lhs: Box::new(lhs),
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rhs: Box::new(rhs),
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});
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} else {
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self.lexer.expect_kinds(terminators)?;
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}
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}
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Ok(lhs)
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}
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/// Binary expressions are generally left associative.
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/// However, things get a little more tricky when taking the fact that there
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/// are 9 different levels of precedence into account.
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fn parse_binary_expr_or_higher(&mut self, terminators: &[token::Kind]) -> Result<tree::Node, Error> {
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let mut expr = self.parse_unary_expr_or_higher()?;
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while let Some(Ok(token)) = self.lexer.peek() {
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if terminators.contains(&token.kind) {
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self.lexer.next();
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break;
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}
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let op = Operator::from_token(&token)?;
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self.lexer.next();
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let precedence = token.kind.binary_op_precedence().unwrap();
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expr = tree::Node::BinaryExpr {
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op,
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lhs: Box::new(expr),
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rhs: Box::new(self.parse_partial_binary_expr(precedence, terminators)?),
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};
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}
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Ok(expr)
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}
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fn parse_partial_binary_expr(&mut self, precedence: u32, terminators: &[token::Kind]) -> Result<tree::Node, Error> {
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let mut lhs = self.parse_unary_expr_or_higher()?;
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while let Some(Ok(token)) = self.lexer.peek() {
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if let Some(new_precedence) = token.kind.binary_op_precedence() {
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if new_precedence > precedence {
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let op = Operator::from_token(&token)?;
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self.lexer.next();
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lhs = tree::Node::BinaryExpr {
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op,
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lhs: Box::new(lhs),
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rhs: Box::new(self.parse_partial_binary_expr(new_precedence, terminators)?),
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};
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} else {
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break;
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}
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} else {
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break;
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}
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}
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Ok(lhs)
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}
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fn parse_unary_expr_or_higher(&mut self) -> Result<tree::Node, Error> {
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if let Some(result) = self.lexer.peek() {
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let token = result?;
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if token.kind == token::Kind::Bang || token.kind == token::Kind::Minus {
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self.lexer.next(); // consume unary operator token
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let op = Operator::from_token(&token)?;
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let expr = self.parse_primary_expr()?;
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return Ok(tree::Node::UnaryExpr {
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op,
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node: Box::new(expr),
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});
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}
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}
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self.parse_primary_expr()
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}
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fn parse_primary_expr(&mut self) -> Result<tree::Node, Error> {
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let token = self.lexer.require_next()?;
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match token.kind {
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token::Kind::OParen => {
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let expr = self.parse_binary_expr_or_higher(&[token::Kind::CParen])?;
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self.parse_primary_expr_rest(expr)
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},
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token::Kind::Ident => {
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let ident = tree::Node::Ident(String::from(token.raw));
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self.parse_primary_expr_rest(ident)
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}
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token::Kind::IntLiteral => {
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let raw = token.raw;
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let num = match raw.chars().nth(1) {
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Some('x') => i128::from_str_radix(&raw[2..], 16).unwrap(),
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Some('o') => i128::from_str_radix(&raw[2..], 8).unwrap(),
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Some('b') => i128::from_str_radix(&raw[2..], 2).unwrap(),
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_ => raw.parse().unwrap(),
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};
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Ok(tree::Node::Int(num))
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}
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token::Kind::StringLiteral => Ok(tree::Node::String(token.raw)),
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token::Kind::OBracket => self.parse_array(),
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_ => self.syntax_error(format!("Unexpected token {}", token.kind), &token),
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}
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}
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fn parse_primary_expr_rest(&mut self, start: tree::Node) -> Result<tree::Node, Error> {
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if let Some(Ok(token)) = self.lexer.peek() {
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match token.kind {
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token::Kind::OParen => {
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// function call
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self.lexer.next();
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let params = self.parse_param_list()?;
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Ok(tree::Node::CallExpr {
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func: Box::new(start),
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params,
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})
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}
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token::Kind::OBracket => {
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// array index
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self.lexer.next();
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let index = self.parse_expr(&[token::Kind::CBracket])?;
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Ok(tree::Node::ArrayExpr {
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array: Box::new(start),
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index: Box::new(index),
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})
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}
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_ => Ok(start),
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}
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} else {
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Ok(start)
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}
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}
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fn parse_array(&mut self) -> Result<tree::Node, Error> {
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let mut elements = Vec::new();
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while let Some(result) = self.lexer.peek() {
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if result?.kind == token::Kind::CBracket {
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self.lexer.next();
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break;
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} else {
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elements.push(self.parse_expr(&[token::Kind::Comma, token::Kind::CBracket])?);
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}
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}
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Ok(tree::Node::Array(elements))
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}
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fn parse_param_list(&mut self) -> Result<Vec<tree::Node>, Error> {
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let mut params = Vec::new();
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while let Some(result) = self.lexer.peek() {
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match result?.kind {
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token::Kind::CParen => {
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self.lexer.next();
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break;
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},
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_ => {
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params.push(self.parse_expr(&[token::Kind::Comma, token::Kind::CParen])?);
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if self.lexer.current().unwrap().kind == token::Kind::CParen {
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break;
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}
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},
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}
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}
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Ok(params)
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}
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fn assert_scope(&self, scope: Scope) -> Result<(), Error> {
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if self.scope.contains(&scope) {
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Ok(())
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} else {
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let token = self.lexer.current().unwrap();
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self.syntax_error(
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format!("Token {} cannot be used in this context", token),
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token,
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)
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}
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}
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fn assert_scope_not(&self, scope: Scope) -> Result<(), Error> {
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if self.scope.contains(&scope) {
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let token = self.lexer.current().unwrap();
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self.syntax_error(
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format!("Token {} cannot be used in this context", token),
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token,
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)
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} else {
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Ok(())
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}
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}
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fn syntax_error<T>(&self, msg: String, token: &Token) -> Result<T, Error> {
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Err(Error::syntax_error(token.pos.clone(), msg))
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}
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}
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