| 278 | } |
| 279 | |
| 280 | fn range<'a, I, E>(expr: E) -> impl Parser<'a, I, Expr, ParserError<'a>> + Clone + 'a |
| 281 | where |
| 282 | I: Input<'a, Token = lr::Token, Span = Span> + BorrowInput<'a>, |
| 283 | E: Parser<'a, I, Expr, ParserError<'a>> + Clone + 'a, |
| 284 | { |
| 285 | // Ranges have five cases we need to parse: |
| 286 | // x..y (bounded) |
| 287 | // x.. (only start bound) |
| 288 | // x (no-op) |
| 289 | // ..y (only end bound) |
| 290 | // .. (unbounded) |
| 291 | #[derive(Clone)] |
| 292 | enum RangeCase { |
| 293 | NoOp(Expr), |
| 294 | Range(Option<Expr>, Option<Expr>), |
| 295 | } |
| 296 | choice(( |
| 297 | // with start bound (first 3 cases) |
| 298 | expr.clone() |
| 299 | .then(choice(( |
| 300 | // range and end bound |
| 301 | select_ref! { lr::Token { kind: TokenKind::Range { bind_left: true, bind_right: true }, .. } => () } |
| 302 | .ignore_then(expr.clone()) |
| 303 | .map(|x| Some(Some(x))), |
| 304 | // range and no end bound |
| 305 | select_ref! { lr::Token { kind: TokenKind::Range { bind_left: true, .. }, .. } => Some(None) }, |
| 306 | // no range |
| 307 | empty().to(None), |
| 308 | ))) |
| 309 | .map(|(start, range)| { |
| 310 | if let Some(end) = range { |
| 311 | RangeCase::Range(Some(start), end) |
| 312 | } else { |
| 313 | RangeCase::NoOp(start) |
| 314 | } |
| 315 | }), |
| 316 | // only end bound |
| 317 | select_ref! { lr::Token { kind: TokenKind::Range { bind_right: true, .. }, .. } => () } |
| 318 | .ignore_then(expr) |
| 319 | .map(|range| RangeCase::Range(None, Some(range))), |
| 320 | // unbounded |
| 321 | select_ref! { lr::Token { kind: TokenKind::Range { .. }, .. } => RangeCase::Range(None, None) }, |
| 322 | )) |
| 323 | .map_with(|case, extra| { |
| 324 | let span = extra.span(); |
| 325 | match case { |
| 326 | RangeCase::NoOp(x) => x, |
| 327 | RangeCase::Range(start, end) => { |
| 328 | let kind = ExprKind::Range(Range { |
| 329 | start: start.map(Box::new), |
| 330 | end: end.map(Box::new), |
| 331 | }); |
| 332 | kind.into_expr(span) |
| 333 | } |
| 334 | } |
| 335 | }) |
| 336 | .boxed() |
| 337 | } |