Struct flexi_parse::ParseBuffer
source · pub struct ParseBuffer<'a> { /* private fields */ }Expand description
A cursor position within a token stream.
Implementations§
source§impl<'a> ParseBuffer<'a>
impl<'a> ParseBuffer<'a>
sourcepub fn parse<T: Parse>(&self) -> Result<T>
pub fn parse<T: Parse>(&self) -> Result<T>
Attempts to parse self into the given syntax tree node, using T’s
default parsing implementation.
Examples found in repository?
examples/calc.rs (line 48)
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fn term(input: ParseStream<'_>) -> Result<Expr> {
let mut expr = factor(input)?;
loop {
if input.peek(Punct!["+"]) {
expr = Expr::Add(Box::new(expr), input.parse()?, Box::new(factor(input)?));
} else if input.peek(Punct!["-"]) {
expr = Expr::Sub(Box::new(expr), input.parse()?, Box::new(factor(input)?));
} else {
break;
}
}
Ok(expr)
}
fn factor(input: ParseStream<'_>) -> Result<Expr> {
let mut expr: Expr = unary(input)?;
loop {
if input.peek(Punct!["*"]) {
expr = Expr::Mul(Box::new(expr), input.parse()?, Box::new(unary(input)?));
} else if input.peek(Punct!["/"]) {
expr = Expr::Div(Box::new(expr), input.parse()?, Box::new(unary(input)?));
} else if input.peek(Punct!["%"]) {
expr = Expr::Mod(Box::new(expr), input.parse()?, Box::new(unary(input)?));
} else {
break;
}
}
Ok(expr)
}
fn unary(input: ParseStream<'_>) -> Result<Expr> {
if input.peek(Punct!["-"]) {
Ok(Expr::Neg(input.parse()?, Box::new(unary(input)?)))
} else {
primary(input)
}
}
fn primary(input: ParseStream<'_>) -> Result<Expr> {
let lookahead = input.lookahead();
if lookahead.peek(token::LitFloat) {
Ok(Expr::Num(input.parse::<token::LitFloat>()?.value()))
} else if lookahead.peek(token::LitInt) {
Ok(Expr::Num(input.parse::<token::LitInt>()?.value() as f64))
} else if lookahead.peek(token::LeftParen) {
let group: Group<Parentheses> = input.parse()?;
parse(group.into_token_stream())
} else {
Err(lookahead.error())
}
}More examples
examples/lox/main.rs (line 193)
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fn assignment(input: ParseStream<'_>) -> Result<Self> {
let expr = Expr::or(input)?;
if input.peek(Punct!["="]) {
let equals: Punct!["="] = input.parse()?;
let value = Box::new(Expr::assignment(input)?);
if let Expr::Variable { name, .. } = expr {
return Ok(Expr::Assign {
name,
value,
distance: Cell::new(None),
});
} else if let Expr::Get { object, name } = expr {
return Ok(Expr::Set {
object,
name,
value,
});
}
input.add_error(input.new_error(
"Invalid assignment target".to_string(),
&equals,
error_codes::INVALID_ASSIGN,
))
}
Ok(expr)
}
fn or(input: ParseStream<'_>) -> Result<Self> {
let mut expr = Expr::and(input)?;
while input.peek(kw::keyword_or) {
expr = Expr::Logical(Box::new(Logical::Or(
expr,
input.parse()?,
Expr::and(input)?,
)));
}
Ok(expr)
}
fn and(input: ParseStream<'_>) -> Result<Self> {
let mut expr = Expr::equality(input)?;
while input.peek(kw::keyword_and) {
expr = Expr::Logical(Box::new(Logical::And(
expr,
input.parse()?,
Expr::equality(input)?,
)));
}
Ok(expr)
}
fn equality(input: ParseStream<'_>) -> Result<Self> {
let mut expr = Expr::comparison(input)?;
loop {
if input.peek(Punct!["=="]) {
expr = Expr::binary(Binary::Equal(
expr,
input.parse()?,
Expr::comparison(input)?,
));
} else if input.peek(Punct!["!="]) {
expr = Expr::binary(Binary::NotEqual(
expr,
input.parse()?,
Expr::comparison(input)?,
));
} else {
break Ok(expr);
}
}
}
fn comparison(input: ParseStream<'_>) -> Result<Self> {
let mut expr = Expr::term(input)?;
loop {
if input.peek(Punct![">"]) {
expr = Expr::binary(Binary::Greater(expr, input.parse()?, Expr::term(input)?));
} else if input.peek(Punct![">="]) {
expr = Expr::binary(Binary::GreaterEqual(
expr,
input.parse()?,
Expr::term(input)?,
));
} else if input.peek(Punct!["<"]) {
expr = Expr::binary(Binary::Less(expr, input.parse()?, Expr::term(input)?));
} else if input.peek(Punct!["<="]) {
expr = Expr::binary(Binary::LessEqual(expr, input.parse()?, Expr::term(input)?));
} else {
break Ok(expr);
}
}
}
fn term(input: ParseStream<'_>) -> Result<Self> {
let mut expr = Expr::factor(input)?;
loop {
if input.peek(Punct!["+"]) {
expr = Expr::binary(Binary::Add(expr, input.parse()?, Expr::factor(input)?));
} else if input.peek(Punct!["-"]) {
expr = Expr::binary(Binary::Sub(expr, input.parse()?, Expr::factor(input)?));
} else {
break Ok(expr);
}
}
}
fn factor(input: ParseStream<'_>) -> Result<Self> {
let mut expr = Expr::unary(input)?;
loop {
if input.peek(Punct!["*"]) {
expr = Expr::binary(Binary::Mul(expr, input.parse()?, Expr::unary(input)?));
} else if input.peek(Punct!["/"]) {
expr = Expr::binary(Binary::Div(expr, input.parse()?, Expr::unary(input)?));
} else {
break Ok(expr);
}
}
}
fn unary(input: ParseStream<'_>) -> Result<Self> {
if input.peek(Punct!["-"]) {
Ok(Expr::Unary(Box::new(Unary::Neg(
input.parse()?,
Expr::unary(input)?,
))))
} else if input.peek(Punct!["!"]) {
Ok(Expr::Unary(Box::new(Unary::Not(
input.parse()?,
Expr::unary(input)?,
))))
} else {
Expr::call(input)
}
}
fn call(input: ParseStream<'_>) -> Result<Self> {
let mut expr = Expr::primary(input)?;
loop {
if input.peek(Punct!["("]) {
expr = Expr::finish_call(input, expr)?;
} else if input.peek(Punct!["."]) {
let _: Punct!["."] = input.parse()?;
let name: Ident = input.parse()?;
expr = Expr::Get {
object: Box::new(expr),
name,
};
} else {
break Ok(expr);
}
}
}
fn finish_call(input: ParseStream<'_>, callee: Expr) -> Result<Self> {
let mut contents: Group<Parentheses> = input.parse()?;
contents.remove_whitespace();
let paren = contents.delimiters();
let arguments: Punctuated<Expr, Punct![","]> =
Punctuated::parse_separated_trailing.parse(contents.into_token_stream())?;
let arguments: Vec<_> = arguments.into_iter().collect();
if arguments.len() >= 255 {
input.add_error(input.new_error(
"Can't have more than 254 arguments".to_string(),
paren.0.clone(),
error_codes::TOO_MANY_ARGS,
));
}
Ok(Expr::Call {
callee: Box::new(callee),
paren,
arguments,
})
}
fn primary(input: ParseStream<'_>) -> Result<Self> {
let lookahead = input.lookahead();
if lookahead.peek(kw::keyword_false) {
Ok(Expr::Literal(Literal::False(input.parse()?)))
} else if lookahead.peek(kw::keyword_true) {
Ok(Expr::Literal(Literal::True(input.parse()?)))
} else if lookahead.peek(kw::keyword_nil) {
Ok(Expr::Literal(Literal::Nil(input.parse()?)))
} else if lookahead.peek(LitFloat) {
Ok(Expr::Literal(Literal::Float(input.parse()?)))
} else if lookahead.peek(LitInt) {
Ok(Expr::Literal(Literal::Int(input.parse()?)))
} else if lookahead.peek(LitStr) {
Ok(Expr::Literal(Literal::String(input.parse()?)))
} else if input.peek(kw::keyword_super) {
Ok(Expr::Super {
keyword: input.parse()?,
distance: Cell::new(None),
dot: input.parse()?,
method: input.parse()?,
})
} else if input.peek(kw::keyword_this) {
Ok(Expr::This {
keyword: input.parse()?,
distance: Cell::new(None),
})
} else if lookahead.peek(Ident) {
Ok(Expr::Variable {
name: kw::ident(input)?,
distance: Cell::new(None),
})
} else if lookahead.peek(Punct!["("]) {
let group: Group<Parentheses> = input.parse()?;
Ok(Expr::Group(Box::new(parse(group.into_token_stream())?)))
} else {
Err(lookahead.error())
}
}
}
impl Parse for Expr {
fn parse(input: ParseStream<'_>) -> Result<Self> {
Expr::assignment(input)
}
}
#[derive(Debug, Clone, PartialEq)]
struct Function {
name: Ident,
params: Vec<Ident>,
body: Vec<Stmt>,
}
impl Parse for Function {
fn parse(input: ParseStream<'_>) -> Result<Self> {
let name: Ident = input.parse()?;
let mut contents: Group<Parentheses> = input.parse()?;
contents.remove_whitespace();
let Parentheses(span) = contents.delimiters();
let tokens = contents.into_token_stream();
let params: Vec<Ident> = if tokens.is_empty() {
vec![]
} else {
let params: Punctuated<Ident, Punct![","]> =
Punctuated::parse_separated.parse(tokens)?;
params.into_iter().collect()
};
if params.len() >= 255 {
input.add_error(input.new_error(
"Can't have more than 254 parameters".to_string(),
span,
error_codes::TOO_MANY_ARGS,
));
}
let mut contents: Group<Braces> = input.parse()?;
contents.remove_whitespace();
let body = block.parse(contents.into_token_stream())?;
Ok(Function { name, params, body })
}
}
#[derive(Debug, Clone, PartialEq)]
enum Stmt {
Block(Vec<Stmt>),
Class {
name: Ident,
superclass: Option<Ident>,
superclass_distance: Cell<Option<usize>>,
methods: Vec<Function>,
},
Expr(Expr),
Function(Function),
If {
condition: Expr,
then_branch: Box<Stmt>,
else_branch: Option<Box<Stmt>>,
},
Print(Expr),
Return {
keyword: kw::keyword_return,
value: Option<Expr>,
},
Variable {
name: Ident,
initialiser: Option<Expr>,
},
While {
condition: Expr,
body: Box<Stmt>,
},
}
fn block(input: ParseStream<'_>) -> Result<Vec<Stmt>> {
let mut statements = vec![];
while !input.is_empty() {
statements.push(Stmt::declaration(input)?);
}
Ok(statements)
}
impl Stmt {
fn declaration(input: ParseStream<'_>) -> Result<Self> {
if input.peek(kw::keyword_class) {
Stmt::class_declaration(input)
} else if input.peek(kw::keyword_fun) {
let _: kw::keyword_fun = input.parse()?;
Ok(Stmt::Function(Function::parse(input)?))
} else if input.peek(kw::keyword_var) {
Stmt::var_declaration(input)
} else {
Stmt::statement(input)
}
}
fn class_declaration(input: ParseStream<'_>) -> Result<Self> {
let _: kw::keyword_class = input.parse()?;
let name: Ident = input.parse()?;
let superclass = if input.peek(Punct!["<"]) {
let _: Punct!["<"] = input.parse()?;
Some(input.parse()?)
} else {
None
};
let mut contents: Group<Braces> = input.parse()?;
contents.remove_whitespace();
let methods = parse_repeated.parse(contents.into_token_stream())?;
Ok(Stmt::Class {
name,
superclass,
superclass_distance: Cell::new(None),
methods,
})
}
fn var_declaration(input: ParseStream<'_>) -> Result<Self> {
let _: kw::keyword_var = input.parse()?;
let name = kw::ident(input)?;
let initialiser = if input.peek(Punct!["="]) {
let _: Punct!["="] = input.parse()?;
Some(input.parse()?)
} else {
None
};
let _: Punct![";"] = input.parse()?;
Ok(Stmt::Variable { name, initialiser })
}
fn statement(input: ParseStream<'_>) -> Result<Self> {
if input.peek(kw::keyword_if) {
Stmt::if_statement(input)
} else if input.peek(kw::keyword_for) {
Stmt::for_statement(input)
} else if input.peek(kw::keyword_print) {
Stmt::print_statement(input)
} else if input.peek(kw::keyword_return) {
Stmt::return_statement(input)
} else if input.peek(kw::keyword_while) {
Stmt::while_statement(input)
} else if input.peek(Punct!["{"]) {
let mut group: Group<Braces> = input.parse()?;
group.remove_whitespace();
Ok(Stmt::Block(block.parse(group.into_token_stream())?))
} else {
Stmt::expression_statement(input)
}
}
fn for_statement(input: ParseStream<'_>) -> Result<Self> {
struct ForInner(Option<Stmt>, Expr, Option<Expr>);
impl Parse for ForInner {
fn parse(input: ParseStream<'_>) -> Result<Self> {
let initialiser = if input.peek(Punct![";"]) {
let _: Punct![";"] = input.parse()?;
None
} else if input.peek(kw::keyword_var) {
Some(Stmt::var_declaration(input)?)
} else {
Some(Stmt::expression_statement(input)?)
};
let condition = if input.peek(Punct![";"]) {
Expr::Literal(Literal::True(kw::keyword_true::new(input)))
} else {
Expr::parse(input)?
};
let _: Punct![";"] = input.parse()?;
let increment = if input.is_empty() {
None
} else {
Some(Expr::parse(input)?)
};
Ok(ForInner(initialiser, condition, increment))
}
}
let _: kw::keyword_for = input.parse()?;
let mut inner: Group<Parentheses> = input.parse()?;
inner.remove_whitespace();
let ForInner(initialiser, condition, increment) = parse(inner.into_token_stream())?;
let mut body = Stmt::statement(input)?;
if let Some(increment) = increment {
body = Stmt::Block(vec![body, Stmt::Expr(increment)]);
}
body = Stmt::While {
condition,
body: Box::new(body),
};
if let Some(initialiser) = initialiser {
body = Stmt::Block(vec![initialiser, body]);
}
Ok(body)
}
fn if_statement(input: ParseStream<'_>) -> Result<Self> {
let _: kw::keyword_if = input.parse()?;
let condition: Group<Parentheses> = input.parse()?;
let condition = parse(condition.into_token_stream())?;
let then_branch = Box::new(Stmt::statement(input)?);
let else_branch = if input.peek(kw::keyword_else) {
Some(Box::new(Stmt::statement(input)?))
} else {
None
};
Ok(Stmt::If {
condition,
then_branch,
else_branch,
})
}
fn print_statement(input: ParseStream<'_>) -> Result<Self> {
let _: kw::keyword_print = input.parse()?;
let value = input.parse()?;
let _: Punct![";"] = input.parse()?;
Ok(Self::Print(value))
}
fn return_statement(input: ParseStream<'_>) -> Result<Self> {
let keyword: kw::keyword_return = input.parse()?;
let value = if input.peek(Punct![";"]) {
None
} else {
Some(input.parse()?)
};
let _: Punct![";"] = input.parse()?;
Ok(Stmt::Return { keyword, value })
}
fn while_statement(input: ParseStream<'_>) -> Result<Self> {
let _: kw::keyword_while = input.parse()?;
let condition: Group<Parentheses> = input.parse()?;
let condition = parse(condition.into_token_stream())?;
let body = Box::new(Stmt::statement(input)?);
Ok(Stmt::While { condition, body })
}
fn expression_statement(input: ParseStream<'_>) -> Result<Self> {
let expr = input.parse()?;
let _: Punct![";"] = input.parse()?;
Ok(Self::Expr(expr))
}
}
impl Parse for Stmt {
fn parse(input: ParseStream<'_>) -> Result<Self> {
Stmt::declaration(input)
}
}
struct Ast(Vec<Stmt>);
impl Ast {
fn synchronise(input: ParseStream<'_>) {
input.synchronise(|input| {
use kw::*;
input.peek(Punct![";"])
|| peek2_any!(
input,
keyword_class,
keyword_for,
keyword_fun,
keyword_if,
keyword_print,
keyword_return,
keyword_var,
keyword_while
)
});
}
}
impl Parse for Ast {
fn parse(input: ParseStream<'_>) -> Result<Self> {
let mut stmts = vec![];
while !input.is_empty() {
match input.parse() {
Ok(stmt) => stmts.push(stmt),
Err(err) => {
Ast::synchronise(input);
input.add_error(err);
}
}
}
if let Some(error) = input.get_error() {
Err(error)
} else {
Ok(Ast(stmts))
}
}sourcepub fn parse_with<T, F: FnOnce(ParseStream<'_>) -> Result<T>>(
&self,
function: F
) -> Result<T>
pub fn parse_with<T, F: FnOnce(ParseStream<'_>) -> Result<T>>( &self, function: F ) -> Result<T>
Attempts to parse self into the given syntax tree node, using
function.
sourcepub fn is_empty(&self) -> bool
pub fn is_empty(&self) -> bool
Returns true if this stream has been exhausted.
Examples found in repository?
examples/lox/main.rs (line 491)
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fn block(input: ParseStream<'_>) -> Result<Vec<Stmt>> {
let mut statements = vec![];
while !input.is_empty() {
statements.push(Stmt::declaration(input)?);
}
Ok(statements)
}
impl Stmt {
fn declaration(input: ParseStream<'_>) -> Result<Self> {
if input.peek(kw::keyword_class) {
Stmt::class_declaration(input)
} else if input.peek(kw::keyword_fun) {
let _: kw::keyword_fun = input.parse()?;
Ok(Stmt::Function(Function::parse(input)?))
} else if input.peek(kw::keyword_var) {
Stmt::var_declaration(input)
} else {
Stmt::statement(input)
}
}
fn class_declaration(input: ParseStream<'_>) -> Result<Self> {
let _: kw::keyword_class = input.parse()?;
let name: Ident = input.parse()?;
let superclass = if input.peek(Punct!["<"]) {
let _: Punct!["<"] = input.parse()?;
Some(input.parse()?)
} else {
None
};
let mut contents: Group<Braces> = input.parse()?;
contents.remove_whitespace();
let methods = parse_repeated.parse(contents.into_token_stream())?;
Ok(Stmt::Class {
name,
superclass,
superclass_distance: Cell::new(None),
methods,
})
}
fn var_declaration(input: ParseStream<'_>) -> Result<Self> {
let _: kw::keyword_var = input.parse()?;
let name = kw::ident(input)?;
let initialiser = if input.peek(Punct!["="]) {
let _: Punct!["="] = input.parse()?;
Some(input.parse()?)
} else {
None
};
let _: Punct![";"] = input.parse()?;
Ok(Stmt::Variable { name, initialiser })
}
fn statement(input: ParseStream<'_>) -> Result<Self> {
if input.peek(kw::keyword_if) {
Stmt::if_statement(input)
} else if input.peek(kw::keyword_for) {
Stmt::for_statement(input)
} else if input.peek(kw::keyword_print) {
Stmt::print_statement(input)
} else if input.peek(kw::keyword_return) {
Stmt::return_statement(input)
} else if input.peek(kw::keyword_while) {
Stmt::while_statement(input)
} else if input.peek(Punct!["{"]) {
let mut group: Group<Braces> = input.parse()?;
group.remove_whitespace();
Ok(Stmt::Block(block.parse(group.into_token_stream())?))
} else {
Stmt::expression_statement(input)
}
}
fn for_statement(input: ParseStream<'_>) -> Result<Self> {
struct ForInner(Option<Stmt>, Expr, Option<Expr>);
impl Parse for ForInner {
fn parse(input: ParseStream<'_>) -> Result<Self> {
let initialiser = if input.peek(Punct![";"]) {
let _: Punct![";"] = input.parse()?;
None
} else if input.peek(kw::keyword_var) {
Some(Stmt::var_declaration(input)?)
} else {
Some(Stmt::expression_statement(input)?)
};
let condition = if input.peek(Punct![";"]) {
Expr::Literal(Literal::True(kw::keyword_true::new(input)))
} else {
Expr::parse(input)?
};
let _: Punct![";"] = input.parse()?;
let increment = if input.is_empty() {
None
} else {
Some(Expr::parse(input)?)
};
Ok(ForInner(initialiser, condition, increment))
}
}
let _: kw::keyword_for = input.parse()?;
let mut inner: Group<Parentheses> = input.parse()?;
inner.remove_whitespace();
let ForInner(initialiser, condition, increment) = parse(inner.into_token_stream())?;
let mut body = Stmt::statement(input)?;
if let Some(increment) = increment {
body = Stmt::Block(vec![body, Stmt::Expr(increment)]);
}
body = Stmt::While {
condition,
body: Box::new(body),
};
if let Some(initialiser) = initialiser {
body = Stmt::Block(vec![initialiser, body]);
}
Ok(body)
}
fn if_statement(input: ParseStream<'_>) -> Result<Self> {
let _: kw::keyword_if = input.parse()?;
let condition: Group<Parentheses> = input.parse()?;
let condition = parse(condition.into_token_stream())?;
let then_branch = Box::new(Stmt::statement(input)?);
let else_branch = if input.peek(kw::keyword_else) {
Some(Box::new(Stmt::statement(input)?))
} else {
None
};
Ok(Stmt::If {
condition,
then_branch,
else_branch,
})
}
fn print_statement(input: ParseStream<'_>) -> Result<Self> {
let _: kw::keyword_print = input.parse()?;
let value = input.parse()?;
let _: Punct![";"] = input.parse()?;
Ok(Self::Print(value))
}
fn return_statement(input: ParseStream<'_>) -> Result<Self> {
let keyword: kw::keyword_return = input.parse()?;
let value = if input.peek(Punct![";"]) {
None
} else {
Some(input.parse()?)
};
let _: Punct![";"] = input.parse()?;
Ok(Stmt::Return { keyword, value })
}
fn while_statement(input: ParseStream<'_>) -> Result<Self> {
let _: kw::keyword_while = input.parse()?;
let condition: Group<Parentheses> = input.parse()?;
let condition = parse(condition.into_token_stream())?;
let body = Box::new(Stmt::statement(input)?);
Ok(Stmt::While { condition, body })
}
fn expression_statement(input: ParseStream<'_>) -> Result<Self> {
let expr = input.parse()?;
let _: Punct![";"] = input.parse()?;
Ok(Self::Expr(expr))
}
}
impl Parse for Stmt {
fn parse(input: ParseStream<'_>) -> Result<Self> {
Stmt::declaration(input)
}
}
struct Ast(Vec<Stmt>);
impl Ast {
fn synchronise(input: ParseStream<'_>) {
input.synchronise(|input| {
use kw::*;
input.peek(Punct![";"])
|| peek2_any!(
input,
keyword_class,
keyword_for,
keyword_fun,
keyword_if,
keyword_print,
keyword_return,
keyword_var,
keyword_while
)
});
}
}
impl Parse for Ast {
fn parse(input: ParseStream<'_>) -> Result<Self> {
let mut stmts = vec![];
while !input.is_empty() {
match input.parse() {
Ok(stmt) => stmts.push(stmt),
Err(err) => {
Ast::synchronise(input);
input.add_error(err);
}
}
}
if let Some(error) = input.get_error() {
Err(error)
} else {
Ok(Ast(stmts))
}
}sourcepub fn new_error<T: Into<Span>>(
&self,
message: String,
location: T,
code: u16
) -> Error
pub fn new_error<T: Into<Span>>( &self, message: String, location: T, code: u16 ) -> Error
Creates a new error at the given location with the given message and code.
Examples found in repository?
examples/lox/main.rs (lines 210-214)
189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 393 394 395 396 397 398 399 400 401 402 403 404 405 406 407 408 409 410 411 412 413 414 415 416 417 418 419 420 421 422 423 424 425 426 427 428 429 430 431 432 433 434 435 436 437 438 439 440 441 442 443 444 445 446 447 448 449 450 451 452 453 454
fn assignment(input: ParseStream<'_>) -> Result<Self> {
let expr = Expr::or(input)?;
if input.peek(Punct!["="]) {
let equals: Punct!["="] = input.parse()?;
let value = Box::new(Expr::assignment(input)?);
if let Expr::Variable { name, .. } = expr {
return Ok(Expr::Assign {
name,
value,
distance: Cell::new(None),
});
} else if let Expr::Get { object, name } = expr {
return Ok(Expr::Set {
object,
name,
value,
});
}
input.add_error(input.new_error(
"Invalid assignment target".to_string(),
&equals,
error_codes::INVALID_ASSIGN,
))
}
Ok(expr)
}
fn or(input: ParseStream<'_>) -> Result<Self> {
let mut expr = Expr::and(input)?;
while input.peek(kw::keyword_or) {
expr = Expr::Logical(Box::new(Logical::Or(
expr,
input.parse()?,
Expr::and(input)?,
)));
}
Ok(expr)
}
fn and(input: ParseStream<'_>) -> Result<Self> {
let mut expr = Expr::equality(input)?;
while input.peek(kw::keyword_and) {
expr = Expr::Logical(Box::new(Logical::And(
expr,
input.parse()?,
Expr::equality(input)?,
)));
}
Ok(expr)
}
fn equality(input: ParseStream<'_>) -> Result<Self> {
let mut expr = Expr::comparison(input)?;
loop {
if input.peek(Punct!["=="]) {
expr = Expr::binary(Binary::Equal(
expr,
input.parse()?,
Expr::comparison(input)?,
));
} else if input.peek(Punct!["!="]) {
expr = Expr::binary(Binary::NotEqual(
expr,
input.parse()?,
Expr::comparison(input)?,
));
} else {
break Ok(expr);
}
}
}
fn comparison(input: ParseStream<'_>) -> Result<Self> {
let mut expr = Expr::term(input)?;
loop {
if input.peek(Punct![">"]) {
expr = Expr::binary(Binary::Greater(expr, input.parse()?, Expr::term(input)?));
} else if input.peek(Punct![">="]) {
expr = Expr::binary(Binary::GreaterEqual(
expr,
input.parse()?,
Expr::term(input)?,
));
} else if input.peek(Punct!["<"]) {
expr = Expr::binary(Binary::Less(expr, input.parse()?, Expr::term(input)?));
} else if input.peek(Punct!["<="]) {
expr = Expr::binary(Binary::LessEqual(expr, input.parse()?, Expr::term(input)?));
} else {
break Ok(expr);
}
}
}
fn term(input: ParseStream<'_>) -> Result<Self> {
let mut expr = Expr::factor(input)?;
loop {
if input.peek(Punct!["+"]) {
expr = Expr::binary(Binary::Add(expr, input.parse()?, Expr::factor(input)?));
} else if input.peek(Punct!["-"]) {
expr = Expr::binary(Binary::Sub(expr, input.parse()?, Expr::factor(input)?));
} else {
break Ok(expr);
}
}
}
fn factor(input: ParseStream<'_>) -> Result<Self> {
let mut expr = Expr::unary(input)?;
loop {
if input.peek(Punct!["*"]) {
expr = Expr::binary(Binary::Mul(expr, input.parse()?, Expr::unary(input)?));
} else if input.peek(Punct!["/"]) {
expr = Expr::binary(Binary::Div(expr, input.parse()?, Expr::unary(input)?));
} else {
break Ok(expr);
}
}
}
fn unary(input: ParseStream<'_>) -> Result<Self> {
if input.peek(Punct!["-"]) {
Ok(Expr::Unary(Box::new(Unary::Neg(
input.parse()?,
Expr::unary(input)?,
))))
} else if input.peek(Punct!["!"]) {
Ok(Expr::Unary(Box::new(Unary::Not(
input.parse()?,
Expr::unary(input)?,
))))
} else {
Expr::call(input)
}
}
fn call(input: ParseStream<'_>) -> Result<Self> {
let mut expr = Expr::primary(input)?;
loop {
if input.peek(Punct!["("]) {
expr = Expr::finish_call(input, expr)?;
} else if input.peek(Punct!["."]) {
let _: Punct!["."] = input.parse()?;
let name: Ident = input.parse()?;
expr = Expr::Get {
object: Box::new(expr),
name,
};
} else {
break Ok(expr);
}
}
}
fn finish_call(input: ParseStream<'_>, callee: Expr) -> Result<Self> {
let mut contents: Group<Parentheses> = input.parse()?;
contents.remove_whitespace();
let paren = contents.delimiters();
let arguments: Punctuated<Expr, Punct![","]> =
Punctuated::parse_separated_trailing.parse(contents.into_token_stream())?;
let arguments: Vec<_> = arguments.into_iter().collect();
if arguments.len() >= 255 {
input.add_error(input.new_error(
"Can't have more than 254 arguments".to_string(),
paren.0.clone(),
error_codes::TOO_MANY_ARGS,
));
}
Ok(Expr::Call {
callee: Box::new(callee),
paren,
arguments,
})
}
fn primary(input: ParseStream<'_>) -> Result<Self> {
let lookahead = input.lookahead();
if lookahead.peek(kw::keyword_false) {
Ok(Expr::Literal(Literal::False(input.parse()?)))
} else if lookahead.peek(kw::keyword_true) {
Ok(Expr::Literal(Literal::True(input.parse()?)))
} else if lookahead.peek(kw::keyword_nil) {
Ok(Expr::Literal(Literal::Nil(input.parse()?)))
} else if lookahead.peek(LitFloat) {
Ok(Expr::Literal(Literal::Float(input.parse()?)))
} else if lookahead.peek(LitInt) {
Ok(Expr::Literal(Literal::Int(input.parse()?)))
} else if lookahead.peek(LitStr) {
Ok(Expr::Literal(Literal::String(input.parse()?)))
} else if input.peek(kw::keyword_super) {
Ok(Expr::Super {
keyword: input.parse()?,
distance: Cell::new(None),
dot: input.parse()?,
method: input.parse()?,
})
} else if input.peek(kw::keyword_this) {
Ok(Expr::This {
keyword: input.parse()?,
distance: Cell::new(None),
})
} else if lookahead.peek(Ident) {
Ok(Expr::Variable {
name: kw::ident(input)?,
distance: Cell::new(None),
})
} else if lookahead.peek(Punct!["("]) {
let group: Group<Parentheses> = input.parse()?;
Ok(Expr::Group(Box::new(parse(group.into_token_stream())?)))
} else {
Err(lookahead.error())
}
}
}
impl Parse for Expr {
fn parse(input: ParseStream<'_>) -> Result<Self> {
Expr::assignment(input)
}
}
#[derive(Debug, Clone, PartialEq)]
struct Function {
name: Ident,
params: Vec<Ident>,
body: Vec<Stmt>,
}
impl Parse for Function {
fn parse(input: ParseStream<'_>) -> Result<Self> {
let name: Ident = input.parse()?;
let mut contents: Group<Parentheses> = input.parse()?;
contents.remove_whitespace();
let Parentheses(span) = contents.delimiters();
let tokens = contents.into_token_stream();
let params: Vec<Ident> = if tokens.is_empty() {
vec![]
} else {
let params: Punctuated<Ident, Punct![","]> =
Punctuated::parse_separated.parse(tokens)?;
params.into_iter().collect()
};
if params.len() >= 255 {
input.add_error(input.new_error(
"Can't have more than 254 parameters".to_string(),
span,
error_codes::TOO_MANY_ARGS,
));
}
let mut contents: Group<Braces> = input.parse()?;
contents.remove_whitespace();
let body = block.parse(contents.into_token_stream())?;
Ok(Function { name, params, body })
}sourcepub fn add_error(&self, error: Error)
pub fn add_error(&self, error: Error)
Adds a new error to this buffer’s storage.
Examples found in repository?
examples/lox/main.rs (lines 210-214)
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fn assignment(input: ParseStream<'_>) -> Result<Self> {
let expr = Expr::or(input)?;
if input.peek(Punct!["="]) {
let equals: Punct!["="] = input.parse()?;
let value = Box::new(Expr::assignment(input)?);
if let Expr::Variable { name, .. } = expr {
return Ok(Expr::Assign {
name,
value,
distance: Cell::new(None),
});
} else if let Expr::Get { object, name } = expr {
return Ok(Expr::Set {
object,
name,
value,
});
}
input.add_error(input.new_error(
"Invalid assignment target".to_string(),
&equals,
error_codes::INVALID_ASSIGN,
))
}
Ok(expr)
}
fn or(input: ParseStream<'_>) -> Result<Self> {
let mut expr = Expr::and(input)?;
while input.peek(kw::keyword_or) {
expr = Expr::Logical(Box::new(Logical::Or(
expr,
input.parse()?,
Expr::and(input)?,
)));
}
Ok(expr)
}
fn and(input: ParseStream<'_>) -> Result<Self> {
let mut expr = Expr::equality(input)?;
while input.peek(kw::keyword_and) {
expr = Expr::Logical(Box::new(Logical::And(
expr,
input.parse()?,
Expr::equality(input)?,
)));
}
Ok(expr)
}
fn equality(input: ParseStream<'_>) -> Result<Self> {
let mut expr = Expr::comparison(input)?;
loop {
if input.peek(Punct!["=="]) {
expr = Expr::binary(Binary::Equal(
expr,
input.parse()?,
Expr::comparison(input)?,
));
} else if input.peek(Punct!["!="]) {
expr = Expr::binary(Binary::NotEqual(
expr,
input.parse()?,
Expr::comparison(input)?,
));
} else {
break Ok(expr);
}
}
}
fn comparison(input: ParseStream<'_>) -> Result<Self> {
let mut expr = Expr::term(input)?;
loop {
if input.peek(Punct![">"]) {
expr = Expr::binary(Binary::Greater(expr, input.parse()?, Expr::term(input)?));
} else if input.peek(Punct![">="]) {
expr = Expr::binary(Binary::GreaterEqual(
expr,
input.parse()?,
Expr::term(input)?,
));
} else if input.peek(Punct!["<"]) {
expr = Expr::binary(Binary::Less(expr, input.parse()?, Expr::term(input)?));
} else if input.peek(Punct!["<="]) {
expr = Expr::binary(Binary::LessEqual(expr, input.parse()?, Expr::term(input)?));
} else {
break Ok(expr);
}
}
}
fn term(input: ParseStream<'_>) -> Result<Self> {
let mut expr = Expr::factor(input)?;
loop {
if input.peek(Punct!["+"]) {
expr = Expr::binary(Binary::Add(expr, input.parse()?, Expr::factor(input)?));
} else if input.peek(Punct!["-"]) {
expr = Expr::binary(Binary::Sub(expr, input.parse()?, Expr::factor(input)?));
} else {
break Ok(expr);
}
}
}
fn factor(input: ParseStream<'_>) -> Result<Self> {
let mut expr = Expr::unary(input)?;
loop {
if input.peek(Punct!["*"]) {
expr = Expr::binary(Binary::Mul(expr, input.parse()?, Expr::unary(input)?));
} else if input.peek(Punct!["/"]) {
expr = Expr::binary(Binary::Div(expr, input.parse()?, Expr::unary(input)?));
} else {
break Ok(expr);
}
}
}
fn unary(input: ParseStream<'_>) -> Result<Self> {
if input.peek(Punct!["-"]) {
Ok(Expr::Unary(Box::new(Unary::Neg(
input.parse()?,
Expr::unary(input)?,
))))
} else if input.peek(Punct!["!"]) {
Ok(Expr::Unary(Box::new(Unary::Not(
input.parse()?,
Expr::unary(input)?,
))))
} else {
Expr::call(input)
}
}
fn call(input: ParseStream<'_>) -> Result<Self> {
let mut expr = Expr::primary(input)?;
loop {
if input.peek(Punct!["("]) {
expr = Expr::finish_call(input, expr)?;
} else if input.peek(Punct!["."]) {
let _: Punct!["."] = input.parse()?;
let name: Ident = input.parse()?;
expr = Expr::Get {
object: Box::new(expr),
name,
};
} else {
break Ok(expr);
}
}
}
fn finish_call(input: ParseStream<'_>, callee: Expr) -> Result<Self> {
let mut contents: Group<Parentheses> = input.parse()?;
contents.remove_whitespace();
let paren = contents.delimiters();
let arguments: Punctuated<Expr, Punct![","]> =
Punctuated::parse_separated_trailing.parse(contents.into_token_stream())?;
let arguments: Vec<_> = arguments.into_iter().collect();
if arguments.len() >= 255 {
input.add_error(input.new_error(
"Can't have more than 254 arguments".to_string(),
paren.0.clone(),
error_codes::TOO_MANY_ARGS,
));
}
Ok(Expr::Call {
callee: Box::new(callee),
paren,
arguments,
})
}
fn primary(input: ParseStream<'_>) -> Result<Self> {
let lookahead = input.lookahead();
if lookahead.peek(kw::keyword_false) {
Ok(Expr::Literal(Literal::False(input.parse()?)))
} else if lookahead.peek(kw::keyword_true) {
Ok(Expr::Literal(Literal::True(input.parse()?)))
} else if lookahead.peek(kw::keyword_nil) {
Ok(Expr::Literal(Literal::Nil(input.parse()?)))
} else if lookahead.peek(LitFloat) {
Ok(Expr::Literal(Literal::Float(input.parse()?)))
} else if lookahead.peek(LitInt) {
Ok(Expr::Literal(Literal::Int(input.parse()?)))
} else if lookahead.peek(LitStr) {
Ok(Expr::Literal(Literal::String(input.parse()?)))
} else if input.peek(kw::keyword_super) {
Ok(Expr::Super {
keyword: input.parse()?,
distance: Cell::new(None),
dot: input.parse()?,
method: input.parse()?,
})
} else if input.peek(kw::keyword_this) {
Ok(Expr::This {
keyword: input.parse()?,
distance: Cell::new(None),
})
} else if lookahead.peek(Ident) {
Ok(Expr::Variable {
name: kw::ident(input)?,
distance: Cell::new(None),
})
} else if lookahead.peek(Punct!["("]) {
let group: Group<Parentheses> = input.parse()?;
Ok(Expr::Group(Box::new(parse(group.into_token_stream())?)))
} else {
Err(lookahead.error())
}
}
}
impl Parse for Expr {
fn parse(input: ParseStream<'_>) -> Result<Self> {
Expr::assignment(input)
}
}
#[derive(Debug, Clone, PartialEq)]
struct Function {
name: Ident,
params: Vec<Ident>,
body: Vec<Stmt>,
}
impl Parse for Function {
fn parse(input: ParseStream<'_>) -> Result<Self> {
let name: Ident = input.parse()?;
let mut contents: Group<Parentheses> = input.parse()?;
contents.remove_whitespace();
let Parentheses(span) = contents.delimiters();
let tokens = contents.into_token_stream();
let params: Vec<Ident> = if tokens.is_empty() {
vec![]
} else {
let params: Punctuated<Ident, Punct![","]> =
Punctuated::parse_separated.parse(tokens)?;
params.into_iter().collect()
};
if params.len() >= 255 {
input.add_error(input.new_error(
"Can't have more than 254 parameters".to_string(),
span,
error_codes::TOO_MANY_ARGS,
));
}
let mut contents: Group<Braces> = input.parse()?;
contents.remove_whitespace();
let body = block.parse(contents.into_token_stream())?;
Ok(Function { name, params, body })
}
}
#[derive(Debug, Clone, PartialEq)]
enum Stmt {
Block(Vec<Stmt>),
Class {
name: Ident,
superclass: Option<Ident>,
superclass_distance: Cell<Option<usize>>,
methods: Vec<Function>,
},
Expr(Expr),
Function(Function),
If {
condition: Expr,
then_branch: Box<Stmt>,
else_branch: Option<Box<Stmt>>,
},
Print(Expr),
Return {
keyword: kw::keyword_return,
value: Option<Expr>,
},
Variable {
name: Ident,
initialiser: Option<Expr>,
},
While {
condition: Expr,
body: Box<Stmt>,
},
}
fn block(input: ParseStream<'_>) -> Result<Vec<Stmt>> {
let mut statements = vec![];
while !input.is_empty() {
statements.push(Stmt::declaration(input)?);
}
Ok(statements)
}
impl Stmt {
fn declaration(input: ParseStream<'_>) -> Result<Self> {
if input.peek(kw::keyword_class) {
Stmt::class_declaration(input)
} else if input.peek(kw::keyword_fun) {
let _: kw::keyword_fun = input.parse()?;
Ok(Stmt::Function(Function::parse(input)?))
} else if input.peek(kw::keyword_var) {
Stmt::var_declaration(input)
} else {
Stmt::statement(input)
}
}
fn class_declaration(input: ParseStream<'_>) -> Result<Self> {
let _: kw::keyword_class = input.parse()?;
let name: Ident = input.parse()?;
let superclass = if input.peek(Punct!["<"]) {
let _: Punct!["<"] = input.parse()?;
Some(input.parse()?)
} else {
None
};
let mut contents: Group<Braces> = input.parse()?;
contents.remove_whitespace();
let methods = parse_repeated.parse(contents.into_token_stream())?;
Ok(Stmt::Class {
name,
superclass,
superclass_distance: Cell::new(None),
methods,
})
}
fn var_declaration(input: ParseStream<'_>) -> Result<Self> {
let _: kw::keyword_var = input.parse()?;
let name = kw::ident(input)?;
let initialiser = if input.peek(Punct!["="]) {
let _: Punct!["="] = input.parse()?;
Some(input.parse()?)
} else {
None
};
let _: Punct![";"] = input.parse()?;
Ok(Stmt::Variable { name, initialiser })
}
fn statement(input: ParseStream<'_>) -> Result<Self> {
if input.peek(kw::keyword_if) {
Stmt::if_statement(input)
} else if input.peek(kw::keyword_for) {
Stmt::for_statement(input)
} else if input.peek(kw::keyword_print) {
Stmt::print_statement(input)
} else if input.peek(kw::keyword_return) {
Stmt::return_statement(input)
} else if input.peek(kw::keyword_while) {
Stmt::while_statement(input)
} else if input.peek(Punct!["{"]) {
let mut group: Group<Braces> = input.parse()?;
group.remove_whitespace();
Ok(Stmt::Block(block.parse(group.into_token_stream())?))
} else {
Stmt::expression_statement(input)
}
}
fn for_statement(input: ParseStream<'_>) -> Result<Self> {
struct ForInner(Option<Stmt>, Expr, Option<Expr>);
impl Parse for ForInner {
fn parse(input: ParseStream<'_>) -> Result<Self> {
let initialiser = if input.peek(Punct![";"]) {
let _: Punct![";"] = input.parse()?;
None
} else if input.peek(kw::keyword_var) {
Some(Stmt::var_declaration(input)?)
} else {
Some(Stmt::expression_statement(input)?)
};
let condition = if input.peek(Punct![";"]) {
Expr::Literal(Literal::True(kw::keyword_true::new(input)))
} else {
Expr::parse(input)?
};
let _: Punct![";"] = input.parse()?;
let increment = if input.is_empty() {
None
} else {
Some(Expr::parse(input)?)
};
Ok(ForInner(initialiser, condition, increment))
}
}
let _: kw::keyword_for = input.parse()?;
let mut inner: Group<Parentheses> = input.parse()?;
inner.remove_whitespace();
let ForInner(initialiser, condition, increment) = parse(inner.into_token_stream())?;
let mut body = Stmt::statement(input)?;
if let Some(increment) = increment {
body = Stmt::Block(vec![body, Stmt::Expr(increment)]);
}
body = Stmt::While {
condition,
body: Box::new(body),
};
if let Some(initialiser) = initialiser {
body = Stmt::Block(vec![initialiser, body]);
}
Ok(body)
}
fn if_statement(input: ParseStream<'_>) -> Result<Self> {
let _: kw::keyword_if = input.parse()?;
let condition: Group<Parentheses> = input.parse()?;
let condition = parse(condition.into_token_stream())?;
let then_branch = Box::new(Stmt::statement(input)?);
let else_branch = if input.peek(kw::keyword_else) {
Some(Box::new(Stmt::statement(input)?))
} else {
None
};
Ok(Stmt::If {
condition,
then_branch,
else_branch,
})
}
fn print_statement(input: ParseStream<'_>) -> Result<Self> {
let _: kw::keyword_print = input.parse()?;
let value = input.parse()?;
let _: Punct![";"] = input.parse()?;
Ok(Self::Print(value))
}
fn return_statement(input: ParseStream<'_>) -> Result<Self> {
let keyword: kw::keyword_return = input.parse()?;
let value = if input.peek(Punct![";"]) {
None
} else {
Some(input.parse()?)
};
let _: Punct![";"] = input.parse()?;
Ok(Stmt::Return { keyword, value })
}
fn while_statement(input: ParseStream<'_>) -> Result<Self> {
let _: kw::keyword_while = input.parse()?;
let condition: Group<Parentheses> = input.parse()?;
let condition = parse(condition.into_token_stream())?;
let body = Box::new(Stmt::statement(input)?);
Ok(Stmt::While { condition, body })
}
fn expression_statement(input: ParseStream<'_>) -> Result<Self> {
let expr = input.parse()?;
let _: Punct![";"] = input.parse()?;
Ok(Self::Expr(expr))
}
}
impl Parse for Stmt {
fn parse(input: ParseStream<'_>) -> Result<Self> {
Stmt::declaration(input)
}
}
struct Ast(Vec<Stmt>);
impl Ast {
fn synchronise(input: ParseStream<'_>) {
input.synchronise(|input| {
use kw::*;
input.peek(Punct![";"])
|| peek2_any!(
input,
keyword_class,
keyword_for,
keyword_fun,
keyword_if,
keyword_print,
keyword_return,
keyword_var,
keyword_while
)
});
}
}
impl Parse for Ast {
fn parse(input: ParseStream<'_>) -> Result<Self> {
let mut stmts = vec![];
while !input.is_empty() {
match input.parse() {
Ok(stmt) => stmts.push(stmt),
Err(err) => {
Ast::synchronise(input);
input.add_error(err);
}
}
}
if let Some(error) = input.get_error() {
Err(error)
} else {
Ok(Ast(stmts))
}
}sourcepub fn get_error(&self) -> Option<Error>
pub fn get_error(&self) -> Option<Error>
Returns an error consisting of all errors from
ParseBuffer::add_error, if it has been called.
Examples found in repository?
examples/lox/main.rs (line 721)
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fn parse(input: ParseStream<'_>) -> Result<Self> {
let mut stmts = vec![];
while !input.is_empty() {
match input.parse() {
Ok(stmt) => stmts.push(stmt),
Err(err) => {
Ast::synchronise(input);
input.add_error(err);
}
}
}
if let Some(error) = input.get_error() {
Err(error)
} else {
Ok(Ast(stmts))
}
}sourcepub fn synchronise<F: FnMut(ParseStream<'_>) -> bool>(&self, function: F)
pub fn synchronise<F: FnMut(ParseStream<'_>) -> bool>(&self, function: F)
Repeatedly skips tokens until function returns true or self is
empty.
Examples found in repository?
examples/lox/main.rs (lines 689-703)
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fn synchronise(input: ParseStream<'_>) {
input.synchronise(|input| {
use kw::*;
input.peek(Punct![";"])
|| peek2_any!(
input,
keyword_class,
keyword_for,
keyword_fun,
keyword_if,
keyword_print,
keyword_return,
keyword_var,
keyword_while
)
});
}sourcepub fn peek<T: Peek>(&self, token: T) -> bool
pub fn peek<T: Peek>(&self, token: T) -> bool
Returns true if the next token is an instance of T.
Examples found in repository?
examples/calc.rs (line 47)
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fn term(input: ParseStream<'_>) -> Result<Expr> {
let mut expr = factor(input)?;
loop {
if input.peek(Punct!["+"]) {
expr = Expr::Add(Box::new(expr), input.parse()?, Box::new(factor(input)?));
} else if input.peek(Punct!["-"]) {
expr = Expr::Sub(Box::new(expr), input.parse()?, Box::new(factor(input)?));
} else {
break;
}
}
Ok(expr)
}
fn factor(input: ParseStream<'_>) -> Result<Expr> {
let mut expr: Expr = unary(input)?;
loop {
if input.peek(Punct!["*"]) {
expr = Expr::Mul(Box::new(expr), input.parse()?, Box::new(unary(input)?));
} else if input.peek(Punct!["/"]) {
expr = Expr::Div(Box::new(expr), input.parse()?, Box::new(unary(input)?));
} else if input.peek(Punct!["%"]) {
expr = Expr::Mod(Box::new(expr), input.parse()?, Box::new(unary(input)?));
} else {
break;
}
}
Ok(expr)
}
fn unary(input: ParseStream<'_>) -> Result<Expr> {
if input.peek(Punct!["-"]) {
Ok(Expr::Neg(input.parse()?, Box::new(unary(input)?)))
} else {
primary(input)
}
}More examples
examples/lox/main.rs (line 192)
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fn assignment(input: ParseStream<'_>) -> Result<Self> {
let expr = Expr::or(input)?;
if input.peek(Punct!["="]) {
let equals: Punct!["="] = input.parse()?;
let value = Box::new(Expr::assignment(input)?);
if let Expr::Variable { name, .. } = expr {
return Ok(Expr::Assign {
name,
value,
distance: Cell::new(None),
});
} else if let Expr::Get { object, name } = expr {
return Ok(Expr::Set {
object,
name,
value,
});
}
input.add_error(input.new_error(
"Invalid assignment target".to_string(),
&equals,
error_codes::INVALID_ASSIGN,
))
}
Ok(expr)
}
fn or(input: ParseStream<'_>) -> Result<Self> {
let mut expr = Expr::and(input)?;
while input.peek(kw::keyword_or) {
expr = Expr::Logical(Box::new(Logical::Or(
expr,
input.parse()?,
Expr::and(input)?,
)));
}
Ok(expr)
}
fn and(input: ParseStream<'_>) -> Result<Self> {
let mut expr = Expr::equality(input)?;
while input.peek(kw::keyword_and) {
expr = Expr::Logical(Box::new(Logical::And(
expr,
input.parse()?,
Expr::equality(input)?,
)));
}
Ok(expr)
}
fn equality(input: ParseStream<'_>) -> Result<Self> {
let mut expr = Expr::comparison(input)?;
loop {
if input.peek(Punct!["=="]) {
expr = Expr::binary(Binary::Equal(
expr,
input.parse()?,
Expr::comparison(input)?,
));
} else if input.peek(Punct!["!="]) {
expr = Expr::binary(Binary::NotEqual(
expr,
input.parse()?,
Expr::comparison(input)?,
));
} else {
break Ok(expr);
}
}
}
fn comparison(input: ParseStream<'_>) -> Result<Self> {
let mut expr = Expr::term(input)?;
loop {
if input.peek(Punct![">"]) {
expr = Expr::binary(Binary::Greater(expr, input.parse()?, Expr::term(input)?));
} else if input.peek(Punct![">="]) {
expr = Expr::binary(Binary::GreaterEqual(
expr,
input.parse()?,
Expr::term(input)?,
));
} else if input.peek(Punct!["<"]) {
expr = Expr::binary(Binary::Less(expr, input.parse()?, Expr::term(input)?));
} else if input.peek(Punct!["<="]) {
expr = Expr::binary(Binary::LessEqual(expr, input.parse()?, Expr::term(input)?));
} else {
break Ok(expr);
}
}
}
fn term(input: ParseStream<'_>) -> Result<Self> {
let mut expr = Expr::factor(input)?;
loop {
if input.peek(Punct!["+"]) {
expr = Expr::binary(Binary::Add(expr, input.parse()?, Expr::factor(input)?));
} else if input.peek(Punct!["-"]) {
expr = Expr::binary(Binary::Sub(expr, input.parse()?, Expr::factor(input)?));
} else {
break Ok(expr);
}
}
}
fn factor(input: ParseStream<'_>) -> Result<Self> {
let mut expr = Expr::unary(input)?;
loop {
if input.peek(Punct!["*"]) {
expr = Expr::binary(Binary::Mul(expr, input.parse()?, Expr::unary(input)?));
} else if input.peek(Punct!["/"]) {
expr = Expr::binary(Binary::Div(expr, input.parse()?, Expr::unary(input)?));
} else {
break Ok(expr);
}
}
}
fn unary(input: ParseStream<'_>) -> Result<Self> {
if input.peek(Punct!["-"]) {
Ok(Expr::Unary(Box::new(Unary::Neg(
input.parse()?,
Expr::unary(input)?,
))))
} else if input.peek(Punct!["!"]) {
Ok(Expr::Unary(Box::new(Unary::Not(
input.parse()?,
Expr::unary(input)?,
))))
} else {
Expr::call(input)
}
}
fn call(input: ParseStream<'_>) -> Result<Self> {
let mut expr = Expr::primary(input)?;
loop {
if input.peek(Punct!["("]) {
expr = Expr::finish_call(input, expr)?;
} else if input.peek(Punct!["."]) {
let _: Punct!["."] = input.parse()?;
let name: Ident = input.parse()?;
expr = Expr::Get {
object: Box::new(expr),
name,
};
} else {
break Ok(expr);
}
}
}
fn finish_call(input: ParseStream<'_>, callee: Expr) -> Result<Self> {
let mut contents: Group<Parentheses> = input.parse()?;
contents.remove_whitespace();
let paren = contents.delimiters();
let arguments: Punctuated<Expr, Punct![","]> =
Punctuated::parse_separated_trailing.parse(contents.into_token_stream())?;
let arguments: Vec<_> = arguments.into_iter().collect();
if arguments.len() >= 255 {
input.add_error(input.new_error(
"Can't have more than 254 arguments".to_string(),
paren.0.clone(),
error_codes::TOO_MANY_ARGS,
));
}
Ok(Expr::Call {
callee: Box::new(callee),
paren,
arguments,
})
}
fn primary(input: ParseStream<'_>) -> Result<Self> {
let lookahead = input.lookahead();
if lookahead.peek(kw::keyword_false) {
Ok(Expr::Literal(Literal::False(input.parse()?)))
} else if lookahead.peek(kw::keyword_true) {
Ok(Expr::Literal(Literal::True(input.parse()?)))
} else if lookahead.peek(kw::keyword_nil) {
Ok(Expr::Literal(Literal::Nil(input.parse()?)))
} else if lookahead.peek(LitFloat) {
Ok(Expr::Literal(Literal::Float(input.parse()?)))
} else if lookahead.peek(LitInt) {
Ok(Expr::Literal(Literal::Int(input.parse()?)))
} else if lookahead.peek(LitStr) {
Ok(Expr::Literal(Literal::String(input.parse()?)))
} else if input.peek(kw::keyword_super) {
Ok(Expr::Super {
keyword: input.parse()?,
distance: Cell::new(None),
dot: input.parse()?,
method: input.parse()?,
})
} else if input.peek(kw::keyword_this) {
Ok(Expr::This {
keyword: input.parse()?,
distance: Cell::new(None),
})
} else if lookahead.peek(Ident) {
Ok(Expr::Variable {
name: kw::ident(input)?,
distance: Cell::new(None),
})
} else if lookahead.peek(Punct!["("]) {
let group: Group<Parentheses> = input.parse()?;
Ok(Expr::Group(Box::new(parse(group.into_token_stream())?)))
} else {
Err(lookahead.error())
}
}
}
impl Parse for Expr {
fn parse(input: ParseStream<'_>) -> Result<Self> {
Expr::assignment(input)
}
}
#[derive(Debug, Clone, PartialEq)]
struct Function {
name: Ident,
params: Vec<Ident>,
body: Vec<Stmt>,
}
impl Parse for Function {
fn parse(input: ParseStream<'_>) -> Result<Self> {
let name: Ident = input.parse()?;
let mut contents: Group<Parentheses> = input.parse()?;
contents.remove_whitespace();
let Parentheses(span) = contents.delimiters();
let tokens = contents.into_token_stream();
let params: Vec<Ident> = if tokens.is_empty() {
vec![]
} else {
let params: Punctuated<Ident, Punct![","]> =
Punctuated::parse_separated.parse(tokens)?;
params.into_iter().collect()
};
if params.len() >= 255 {
input.add_error(input.new_error(
"Can't have more than 254 parameters".to_string(),
span,
error_codes::TOO_MANY_ARGS,
));
}
let mut contents: Group<Braces> = input.parse()?;
contents.remove_whitespace();
let body = block.parse(contents.into_token_stream())?;
Ok(Function { name, params, body })
}
}
#[derive(Debug, Clone, PartialEq)]
enum Stmt {
Block(Vec<Stmt>),
Class {
name: Ident,
superclass: Option<Ident>,
superclass_distance: Cell<Option<usize>>,
methods: Vec<Function>,
},
Expr(Expr),
Function(Function),
If {
condition: Expr,
then_branch: Box<Stmt>,
else_branch: Option<Box<Stmt>>,
},
Print(Expr),
Return {
keyword: kw::keyword_return,
value: Option<Expr>,
},
Variable {
name: Ident,
initialiser: Option<Expr>,
},
While {
condition: Expr,
body: Box<Stmt>,
},
}
fn block(input: ParseStream<'_>) -> Result<Vec<Stmt>> {
let mut statements = vec![];
while !input.is_empty() {
statements.push(Stmt::declaration(input)?);
}
Ok(statements)
}
impl Stmt {
fn declaration(input: ParseStream<'_>) -> Result<Self> {
if input.peek(kw::keyword_class) {
Stmt::class_declaration(input)
} else if input.peek(kw::keyword_fun) {
let _: kw::keyword_fun = input.parse()?;
Ok(Stmt::Function(Function::parse(input)?))
} else if input.peek(kw::keyword_var) {
Stmt::var_declaration(input)
} else {
Stmt::statement(input)
}
}
fn class_declaration(input: ParseStream<'_>) -> Result<Self> {
let _: kw::keyword_class = input.parse()?;
let name: Ident = input.parse()?;
let superclass = if input.peek(Punct!["<"]) {
let _: Punct!["<"] = input.parse()?;
Some(input.parse()?)
} else {
None
};
let mut contents: Group<Braces> = input.parse()?;
contents.remove_whitespace();
let methods = parse_repeated.parse(contents.into_token_stream())?;
Ok(Stmt::Class {
name,
superclass,
superclass_distance: Cell::new(None),
methods,
})
}
fn var_declaration(input: ParseStream<'_>) -> Result<Self> {
let _: kw::keyword_var = input.parse()?;
let name = kw::ident(input)?;
let initialiser = if input.peek(Punct!["="]) {
let _: Punct!["="] = input.parse()?;
Some(input.parse()?)
} else {
None
};
let _: Punct![";"] = input.parse()?;
Ok(Stmt::Variable { name, initialiser })
}
fn statement(input: ParseStream<'_>) -> Result<Self> {
if input.peek(kw::keyword_if) {
Stmt::if_statement(input)
} else if input.peek(kw::keyword_for) {
Stmt::for_statement(input)
} else if input.peek(kw::keyword_print) {
Stmt::print_statement(input)
} else if input.peek(kw::keyword_return) {
Stmt::return_statement(input)
} else if input.peek(kw::keyword_while) {
Stmt::while_statement(input)
} else if input.peek(Punct!["{"]) {
let mut group: Group<Braces> = input.parse()?;
group.remove_whitespace();
Ok(Stmt::Block(block.parse(group.into_token_stream())?))
} else {
Stmt::expression_statement(input)
}
}
fn for_statement(input: ParseStream<'_>) -> Result<Self> {
struct ForInner(Option<Stmt>, Expr, Option<Expr>);
impl Parse for ForInner {
fn parse(input: ParseStream<'_>) -> Result<Self> {
let initialiser = if input.peek(Punct![";"]) {
let _: Punct![";"] = input.parse()?;
None
} else if input.peek(kw::keyword_var) {
Some(Stmt::var_declaration(input)?)
} else {
Some(Stmt::expression_statement(input)?)
};
let condition = if input.peek(Punct![";"]) {
Expr::Literal(Literal::True(kw::keyword_true::new(input)))
} else {
Expr::parse(input)?
};
let _: Punct![";"] = input.parse()?;
let increment = if input.is_empty() {
None
} else {
Some(Expr::parse(input)?)
};
Ok(ForInner(initialiser, condition, increment))
}
}
let _: kw::keyword_for = input.parse()?;
let mut inner: Group<Parentheses> = input.parse()?;
inner.remove_whitespace();
let ForInner(initialiser, condition, increment) = parse(inner.into_token_stream())?;
let mut body = Stmt::statement(input)?;
if let Some(increment) = increment {
body = Stmt::Block(vec![body, Stmt::Expr(increment)]);
}
body = Stmt::While {
condition,
body: Box::new(body),
};
if let Some(initialiser) = initialiser {
body = Stmt::Block(vec![initialiser, body]);
}
Ok(body)
}
fn if_statement(input: ParseStream<'_>) -> Result<Self> {
let _: kw::keyword_if = input.parse()?;
let condition: Group<Parentheses> = input.parse()?;
let condition = parse(condition.into_token_stream())?;
let then_branch = Box::new(Stmt::statement(input)?);
let else_branch = if input.peek(kw::keyword_else) {
Some(Box::new(Stmt::statement(input)?))
} else {
None
};
Ok(Stmt::If {
condition,
then_branch,
else_branch,
})
}
fn print_statement(input: ParseStream<'_>) -> Result<Self> {
let _: kw::keyword_print = input.parse()?;
let value = input.parse()?;
let _: Punct![";"] = input.parse()?;
Ok(Self::Print(value))
}
fn return_statement(input: ParseStream<'_>) -> Result<Self> {
let keyword: kw::keyword_return = input.parse()?;
let value = if input.peek(Punct![";"]) {
None
} else {
Some(input.parse()?)
};
let _: Punct![";"] = input.parse()?;
Ok(Stmt::Return { keyword, value })
}
fn while_statement(input: ParseStream<'_>) -> Result<Self> {
let _: kw::keyword_while = input.parse()?;
let condition: Group<Parentheses> = input.parse()?;
let condition = parse(condition.into_token_stream())?;
let body = Box::new(Stmt::statement(input)?);
Ok(Stmt::While { condition, body })
}
fn expression_statement(input: ParseStream<'_>) -> Result<Self> {
let expr = input.parse()?;
let _: Punct![";"] = input.parse()?;
Ok(Self::Expr(expr))
}
}
impl Parse for Stmt {
fn parse(input: ParseStream<'_>) -> Result<Self> {
Stmt::declaration(input)
}
}
struct Ast(Vec<Stmt>);
impl Ast {
fn synchronise(input: ParseStream<'_>) {
input.synchronise(|input| {
use kw::*;
input.peek(Punct![";"])
|| peek2_any!(
input,
keyword_class,
keyword_for,
keyword_fun,
keyword_if,
keyword_print,
keyword_return,
keyword_var,
keyword_while
)
});
}sourcepub fn peek2<T: Peek>(&self, token: T) -> bool
pub fn peek2<T: Peek>(&self, token: T) -> bool
Returns true if the next token is an instance of T.
Note that for the purposes of this function, multi-character punctuation
like += is considered to be two tokens, and float literals are
considered to be three tokens (start, ., end).
sourcepub fn current_span(&self) -> Result<Span>
pub fn current_span(&self) -> Result<Span>
Gets the span of the current token, unless self is empty.
sourcepub fn fork(&self) -> ParseBuffer<'a>
pub fn fork(&self) -> ParseBuffer<'a>
Creates a new ParseBuffer at the same position as self.
Changes to self will not affect the fork, and vice versa.
sourcepub fn commit(&self, fork: &Self)
pub fn commit(&self, fork: &Self)
Commits a forked buffer into self, updating self to reflect fork.
Panics
This function will panic if fork wasn’t forked from self or if
self is further ahead than fork.
sourcepub fn unexpected_token(&self, expected: HashSet<String>) -> Error
pub fn unexpected_token(&self, expected: HashSet<String>) -> Error
Creates an error with the message Unexpected token and the given
expected tokens.
Use of this function is generally discouraged in favour of
Lookahead::error.
sourcepub fn lookahead(&self) -> Lookahead<'a>
pub fn lookahead(&self) -> Lookahead<'a>
Creates a helper struct for peeking at the next token.
Examples found in repository?
examples/calc.rs (line 83)
82 83 84 85 86 87 88 89 90 91 92 93 94
fn primary(input: ParseStream<'_>) -> Result<Expr> {
let lookahead = input.lookahead();
if lookahead.peek(token::LitFloat) {
Ok(Expr::Num(input.parse::<token::LitFloat>()?.value()))
} else if lookahead.peek(token::LitInt) {
Ok(Expr::Num(input.parse::<token::LitInt>()?.value() as f64))
} else if lookahead.peek(token::LeftParen) {
let group: Group<Parentheses> = input.parse()?;
parse(group.into_token_stream())
} else {
Err(lookahead.error())
}
}More examples
examples/lox/main.rs (line 377)
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fn primary(input: ParseStream<'_>) -> Result<Self> {
let lookahead = input.lookahead();
if lookahead.peek(kw::keyword_false) {
Ok(Expr::Literal(Literal::False(input.parse()?)))
} else if lookahead.peek(kw::keyword_true) {
Ok(Expr::Literal(Literal::True(input.parse()?)))
} else if lookahead.peek(kw::keyword_nil) {
Ok(Expr::Literal(Literal::Nil(input.parse()?)))
} else if lookahead.peek(LitFloat) {
Ok(Expr::Literal(Literal::Float(input.parse()?)))
} else if lookahead.peek(LitInt) {
Ok(Expr::Literal(Literal::Int(input.parse()?)))
} else if lookahead.peek(LitStr) {
Ok(Expr::Literal(Literal::String(input.parse()?)))
} else if input.peek(kw::keyword_super) {
Ok(Expr::Super {
keyword: input.parse()?,
distance: Cell::new(None),
dot: input.parse()?,
method: input.parse()?,
})
} else if input.peek(kw::keyword_this) {
Ok(Expr::This {
keyword: input.parse()?,
distance: Cell::new(None),
})
} else if lookahead.peek(Ident) {
Ok(Expr::Variable {
name: kw::ident(input)?,
distance: Cell::new(None),
})
} else if lookahead.peek(Punct!["("]) {
let group: Group<Parentheses> = input.parse()?;
Ok(Expr::Group(Box::new(parse(group.into_token_stream())?)))
} else {
Err(lookahead.error())
}
}sourcepub fn skip_whitespace(&self)
pub fn skip_whitespace(&self)
Skips over all whitespace tokens before the next non-whitespace token.
This method will not skip newlines.
sourcepub fn empty_span(&self) -> Span
pub fn empty_span(&self) -> Span
Creates a new empty Span with this stream’s source file.
Trait Implementations§
Auto Trait Implementations§
impl<'a> !RefUnwindSafe for ParseBuffer<'a>
impl<'a> !Send for ParseBuffer<'a>
impl<'a> !Sync for ParseBuffer<'a>
impl<'a> Unpin for ParseBuffer<'a>
impl<'a> UnwindSafe for ParseBuffer<'a>
Blanket Implementations§
source§impl<T> BorrowMut<T> for Twhere
T: ?Sized,
impl<T> BorrowMut<T> for Twhere T: ?Sized,
source§fn borrow_mut(&mut self) -> &mut T
fn borrow_mut(&mut self) -> &mut T
Mutably borrows from an owned value. Read more