compiler/rustc_ast_pretty/src/pprust/state/expr.rs

   1 use crate::pp::Breaks::Inconsistent;
   2 use crate::pprust::state::{AnnNode, IterDelimited, PrintState, State, INDENT_UNIT};
   3
   4 use rustc_ast::ptr::P;
   5 use rustc_ast::token;
   6 use rustc_ast::util::literal::escape_byte_str_symbol;
   7 use rustc_ast::util::parser::{self, AssocOp, Fixity};
   8 use rustc_ast::{self as ast, BlockCheckMode};
   9
  10 impl<'a> State<'a> {
  11     fn print_else(&mut self, els: Option<&ast::Expr>) {
  12         if let Some(_else) = els {
  13             match &_else.kind {
  14                 // Another `else if` block.
  15                 ast::ExprKind::If(i, then, e) => {
  16                     self.cbox(INDENT_UNIT - 1);
  17                     self.ibox(0);
  18                     self.word(" else if ");
  19                     self.print_expr_as_cond(i);
  20                     self.space();
  21                     self.print_block(then);
  22                     self.print_else(e.as_deref())
  23                 }
  24                 // Final `else` block.
  25                 ast::ExprKind::Block(b, _) => {
  26                     self.cbox(INDENT_UNIT - 1);
  27                     self.ibox(0);
  28                     self.word(" else ");
  29                     self.print_block(b)
  30                 }
  31                 // Constraints would be great here!
  32                 _ => {
  33                     panic!("print_if saw if with weird alternative");
  34                 }
  35             }
  36         }
  37     }
  38
  39     fn print_if(&mut self, test: &ast::Expr, blk: &ast::Block, elseopt: Option<&ast::Expr>) {
  40         self.head("if");
  41         self.print_expr_as_cond(test);
  42         self.space();
  43         self.print_block(blk);
  44         self.print_else(elseopt)
  45     }
  46
  47     fn print_call_post(&mut self, args: &[P<ast::Expr>]) {
  48         self.popen();
  49         self.commasep_exprs(Inconsistent, args);
  50         self.pclose()
  51     }
  52
  53     fn print_expr_maybe_paren(&mut self, expr: &ast::Expr, prec: i8) {
  54         self.print_expr_cond_paren(expr, expr.precedence().order() < prec)
  55     }
  56
  57     /// Prints an expr using syntax that's acceptable in a condition position, such as the `cond` in
  58     /// `if cond { ... }`.
  59     fn print_expr_as_cond(&mut self, expr: &ast::Expr) {
  60         self.print_expr_cond_paren(expr, Self::cond_needs_par(expr))
  61     }
  62
  63     /// Does `expr` need parentheses when printed in a condition position?
  64     ///
  65     /// These cases need parens due to the parse error observed in #26461: `if return {}`
  66     /// parses as the erroneous construct `if (return {})`, not `if (return) {}`.
  67     pub(super) fn cond_needs_par(expr: &ast::Expr) -> bool {
  68         match expr.kind {
  69             ast::ExprKind::Break(..)
  70             | ast::ExprKind::Closure(..)
  71             | ast::ExprKind::Ret(..)
  72             | ast::ExprKind::Yeet(..) => true,
  73             _ => parser::contains_exterior_struct_lit(expr),
  74         }
  75     }
  76
  77     /// Prints `expr` or `(expr)` when `needs_par` holds.
  78     pub(super) fn print_expr_cond_paren(&mut self, expr: &ast::Expr, needs_par: bool) {
  79         if needs_par {
  80             self.popen();
  81         }
  82         self.print_expr(expr);
  83         if needs_par {
  84             self.pclose();
  85         }
  86     }
  87
  88     fn print_expr_vec(&mut self, exprs: &[P<ast::Expr>]) {
  89         self.ibox(INDENT_UNIT);
  90         self.word("[");
  91         self.commasep_exprs(Inconsistent, exprs);
  92         self.word("]");
  93         self.end();
  94     }
  95
  96     pub(super) fn print_expr_anon_const(
  97         &mut self,
  98         expr: &ast::AnonConst,
  99         attrs: &[ast::Attribute],
 100     ) {
 101         self.ibox(INDENT_UNIT);
 102         self.word("const");
 103         self.nbsp();
 104         if let ast::ExprKind::Block(block, None) = &expr.value.kind {
 105             self.cbox(0);
 106             self.ibox(0);
 107             self.print_block_with_attrs(block, attrs);
 108         } else {
 109             self.print_expr(&expr.value);
 110         }
 111         self.end();
 112     }
 113
 114     fn print_expr_repeat(&mut self, element: &ast::Expr, count: &ast::AnonConst) {
 115         self.ibox(INDENT_UNIT);
 116         self.word("[");
 117         self.print_expr(element);
 118         self.word_space(";");
 119         self.print_expr(&count.value);
 120         self.word("]");
 121         self.end();
 122     }
 123
 124     fn print_expr_struct(
 125         &mut self,
 126         qself: &Option<P<ast::QSelf>>,
 127         path: &ast::Path,
 128         fields: &[ast::ExprField],
 129         rest: &ast::StructRest,
 130     ) {
 131         if let Some(qself) = qself {
 132             self.print_qpath(path, qself, true);
 133         } else {
 134             self.print_path(path, true, 0);
 135         }
 136         self.nbsp();
 137         self.word("{");
 138         let has_rest = match rest {
 139             ast::StructRest::Base(_) | ast::StructRest::Rest(_) => true,
 140             ast::StructRest::None => false,
 141         };
 142         if fields.is_empty() && !has_rest {
 143             self.word("}");
 144             return;
 145         }
 146         self.cbox(0);
 147         for field in fields.iter().delimited() {
 148             self.maybe_print_comment(field.span.hi());
 149             self.print_outer_attributes(&field.attrs);
 150             if field.is_first {
 151                 self.space_if_not_bol();
 152             }
 153             if !field.is_shorthand {
 154                 self.print_ident(field.ident);
 155                 self.word_nbsp(":");
 156             }
 157             self.print_expr(&field.expr);
 158             if !field.is_last || has_rest {
 159                 self.word_space(",");
 160             } else {
 161                 self.trailing_comma_or_space();
 162             }
 163         }
 164         if has_rest {
 165             if fields.is_empty() {
 166                 self.space();
 167             }
 168             self.word("..");
 169             if let ast::StructRest::Base(expr) = rest {
 170                 self.print_expr(expr);
 171             }
 172             self.space();
 173         }
 174         self.offset(-INDENT_UNIT);
 175         self.end();
 176         self.word("}");
 177     }
 178
 179     fn print_expr_tup(&mut self, exprs: &[P<ast::Expr>]) {
 180         self.popen();
 181         self.commasep_exprs(Inconsistent, exprs);
 182         if exprs.len() == 1 {
 183             self.word(",");
 184         }
 185         self.pclose()
 186     }
 187
 188     fn print_expr_call(&mut self, func: &ast::Expr, args: &[P<ast::Expr>]) {
 189         let prec = match func.kind {
 190             ast::ExprKind::Field(..) => parser::PREC_FORCE_PAREN,
 191             _ => parser::PREC_POSTFIX,
 192         };
 193
 194         self.print_expr_maybe_paren(func, prec);
 195         self.print_call_post(args)
 196     }
 197
 198     fn print_expr_method_call(
 199         &mut self,
 200         segment: &ast::PathSegment,
 201         receiver: &ast::Expr,
 202         base_args: &[P<ast::Expr>],
 203     ) {
 204         self.print_expr_maybe_paren(receiver, parser::PREC_POSTFIX);
 205         self.word(".");
 206         self.print_ident(segment.ident);
 207         if let Some(args) = &segment.args {
 208             self.print_generic_args(args, true);
 209         }
 210         self.print_call_post(base_args)
 211     }
 212
 213     fn print_expr_binary(&mut self, op: ast::BinOp, lhs: &ast::Expr, rhs: &ast::Expr) {
 214         let assoc_op = AssocOp::from_ast_binop(op.node);
 215         let prec = assoc_op.precedence() as i8;
 216         let fixity = assoc_op.fixity();
 217
 218         let (left_prec, right_prec) = match fixity {
 219             Fixity::Left => (prec, prec + 1),
 220             Fixity::Right => (prec + 1, prec),
 221             Fixity::None => (prec + 1, prec + 1),
 222         };
 223
 224         let left_prec = match (&lhs.kind, op.node) {
 225             // These cases need parens: `x as i32 < y` has the parser thinking that `i32 < y` is
 226             // the beginning of a path type. It starts trying to parse `x as (i32 < y ...` instead
 227             // of `(x as i32) < ...`. We need to convince it _not_ to do that.
 228             (&ast::ExprKind::Cast { .. }, ast::BinOpKind::Lt | ast::BinOpKind::Shl) => {
 229                 parser::PREC_FORCE_PAREN
 230             }
 231             // We are given `(let _ = a) OP b`.
 232             //
 233             // - When `OP <= LAnd` we should print `let _ = a OP b` to avoid redundant parens
 234             //   as the parser will interpret this as `(let _ = a) OP b`.
 235             //
 236             // - Otherwise, e.g. when we have `(let a = b) < c` in AST,
 237             //   parens are required since the parser would interpret `let a = b < c` as
 238             //   `let a = (b < c)`. To achieve this, we force parens.
 239             (&ast::ExprKind::Let { .. }, _) if !parser::needs_par_as_let_scrutinee(prec) => {
 240                 parser::PREC_FORCE_PAREN
 241             }
 242             _ => left_prec,
 243         };
 244
 245         self.print_expr_maybe_paren(lhs, left_prec);
 246         self.space();
 247         self.word_space(op.node.to_string());
 248         self.print_expr_maybe_paren(rhs, right_prec)
 249     }
 250
 251     fn print_expr_unary(&mut self, op: ast::UnOp, expr: &ast::Expr) {
 252         self.word(ast::UnOp::to_string(op));
 253         self.print_expr_maybe_paren(expr, parser::PREC_PREFIX)
 254     }
 255
 256     fn print_expr_addr_of(
 257         &mut self,
 258         kind: ast::BorrowKind,
 259         mutability: ast::Mutability,
 260         expr: &ast::Expr,
 261     ) {
 262         self.word("&");
 263         match kind {
 264             ast::BorrowKind::Ref => self.print_mutability(mutability, false),
 265             ast::BorrowKind::Raw => {
 266                 self.word_nbsp("raw");
 267                 self.print_mutability(mutability, true);
 268             }
 269         }
 270         self.print_expr_maybe_paren(expr, parser::PREC_PREFIX)
 271     }
 272
 273     pub fn print_expr(&mut self, expr: &ast::Expr) {
 274         self.print_expr_outer_attr_style(expr, true)
 275     }
 276
 277     pub(super) fn print_expr_outer_attr_style(&mut self, expr: &ast::Expr, is_inline: bool) {
 278         self.maybe_print_comment(expr.span.lo());
 279
 280         let attrs = &expr.attrs;
 281         if is_inline {
 282             self.print_outer_attributes_inline(attrs);
 283         } else {
 284             self.print_outer_attributes(attrs);
 285         }
 286
 287         self.ibox(INDENT_UNIT);
 288         self.ann.pre(self, AnnNode::Expr(expr));
 289         match &expr.kind {
 290             ast::ExprKind::Box(expr) => {
 291                 self.word_space("box");
 292                 self.print_expr_maybe_paren(expr, parser::PREC_PREFIX);
 293             }
 294             ast::ExprKind::Array(exprs) => {
 295                 self.print_expr_vec(exprs);
 296             }
 297             ast::ExprKind::ConstBlock(anon_const) => {
 298                 self.print_expr_anon_const(anon_const, attrs);
 299             }
 300             ast::ExprKind::Repeat(element, count) => {
 301                 self.print_expr_repeat(element, count);
 302             }
 303             ast::ExprKind::Struct(se) => {
 304                 self.print_expr_struct(&se.qself, &se.path, &se.fields, &se.rest);
 305             }
 306             ast::ExprKind::Tup(exprs) => {
 307                 self.print_expr_tup(exprs);
 308             }
 309             ast::ExprKind::Call(func, args) => {
 310                 self.print_expr_call(func, args);
 311             }
 312             ast::ExprKind::MethodCall(box ast::MethodCall { seg, receiver, args, .. }) => {
 313                 self.print_expr_method_call(seg, receiver, args);
 314             }
 315             ast::ExprKind::Binary(op, lhs, rhs) => {
 316                 self.print_expr_binary(*op, lhs, rhs);
 317             }
 318             ast::ExprKind::Unary(op, expr) => {
 319                 self.print_expr_unary(*op, expr);
 320             }
 321             ast::ExprKind::AddrOf(k, m, expr) => {
 322                 self.print_expr_addr_of(*k, *m, expr);
 323             }
 324             ast::ExprKind::Lit(token_lit) => {
 325                 self.print_token_literal(*token_lit, expr.span);
 326             }
 327             ast::ExprKind::IncludedBytes(bytes) => {
 328                 let lit = token::Lit::new(token::ByteStr, escape_byte_str_symbol(bytes), None);
 329                 self.print_token_literal(lit, expr.span)
 330             }
 331             ast::ExprKind::Cast(expr, ty) => {
 332                 let prec = AssocOp::As.precedence() as i8;
 333                 self.print_expr_maybe_paren(expr, prec);
 334                 self.space();
 335                 self.word_space("as");
 336                 self.print_type(ty);
 337             }
 338             ast::ExprKind::Type(expr, ty) => {
 339                 let prec = AssocOp::Colon.precedence() as i8;
 340                 self.print_expr_maybe_paren(expr, prec);
 341                 self.word_space(":");
 342                 self.print_type(ty);
 343             }
 344             ast::ExprKind::Let(pat, scrutinee, _) => {
 345                 self.print_let(pat, scrutinee);
 346             }
 347             ast::ExprKind::If(test, blk, elseopt) => self.print_if(test, blk, elseopt.as_deref()),
 348             ast::ExprKind::While(test, blk, opt_label) => {
 349                 if let Some(label) = opt_label {
 350                     self.print_ident(label.ident);
 351                     self.word_space(":");
 352                 }
 353                 self.cbox(0);
 354                 self.ibox(0);
 355                 self.word_nbsp("while");
 356                 self.print_expr_as_cond(test);
 357                 self.space();
 358                 self.print_block_with_attrs(blk, attrs);
 359             }
 360             ast::ExprKind::ForLoop(pat, iter, blk, opt_label) => {
 361                 if let Some(label) = opt_label {
 362                     self.print_ident(label.ident);
 363                     self.word_space(":");
 364                 }
 365                 self.cbox(0);
 366                 self.ibox(0);
 367                 self.word_nbsp("for");
 368                 self.print_pat(pat);
 369                 self.space();
 370                 self.word_space("in");
 371                 self.print_expr_as_cond(iter);
 372                 self.space();
 373                 self.print_block_with_attrs(blk, attrs);
 374             }
 375             ast::ExprKind::Loop(blk, opt_label, _) => {
 376                 if let Some(label) = opt_label {
 377                     self.print_ident(label.ident);
 378                     self.word_space(":");
 379                 }
 380                 self.cbox(0);
 381                 self.ibox(0);
 382                 self.word_nbsp("loop");
 383                 self.print_block_with_attrs(blk, attrs);
 384             }
 385             ast::ExprKind::Match(expr, arms) => {
 386                 self.cbox(0);
 387                 self.ibox(0);
 388                 self.word_nbsp("match");
 389                 self.print_expr_as_cond(expr);
 390                 self.space();
 391                 self.bopen();
 392                 self.print_inner_attributes_no_trailing_hardbreak(attrs);
 393                 for arm in arms {
 394                     self.print_arm(arm);
 395                 }
 396                 let empty = attrs.is_empty() && arms.is_empty();
 397                 self.bclose(expr.span, empty);
 398             }
 399             ast::ExprKind::Closure(box ast::Closure {
 400                 binder,
 401                 capture_clause,
 402                 constness,
 403                 asyncness,
 404                 movability,
 405                 fn_decl,
 406                 body,
 407                 fn_decl_span: _,
 408                 fn_arg_span: _,
 409             }) => {
 410                 self.print_closure_binder(binder);
 411                 self.print_constness(*constness);
 412                 self.print_movability(*movability);
 413                 self.print_asyncness(*asyncness);
 414                 self.print_capture_clause(*capture_clause);
 415
 416                 self.print_fn_params_and_ret(fn_decl, true);
 417                 self.space();
 418                 self.print_expr(body);
 419                 self.end(); // need to close a box
 420
 421                 // a box will be closed by print_expr, but we didn't want an overall
 422                 // wrapper so we closed the corresponding opening. so create an
 423                 // empty box to satisfy the close.
 424                 self.ibox(0);
 425             }
 426             ast::ExprKind::Block(blk, opt_label) => {
 427                 if let Some(label) = opt_label {
 428                     self.print_ident(label.ident);
 429                     self.word_space(":");
 430                 }
 431                 // containing cbox, will be closed by print-block at }
 432                 self.cbox(0);
 433                 // head-box, will be closed by print-block after {
 434                 self.ibox(0);
 435                 self.print_block_with_attrs(blk, attrs);
 436             }
 437             ast::ExprKind::Async(capture_clause, _, blk) => {
 438                 self.word_nbsp("async");
 439                 self.print_capture_clause(*capture_clause);
 440                 // cbox/ibox in analogy to the `ExprKind::Block` arm above
 441                 self.cbox(0);
 442                 self.ibox(0);
 443                 self.print_block_with_attrs(blk, attrs);
 444             }
 445             ast::ExprKind::Await(expr) => {
 446                 self.print_expr_maybe_paren(expr, parser::PREC_POSTFIX);
 447                 self.word(".await");
 448             }
 449             ast::ExprKind::Assign(lhs, rhs, _) => {
 450                 let prec = AssocOp::Assign.precedence() as i8;
 451                 self.print_expr_maybe_paren(lhs, prec + 1);
 452                 self.space();
 453                 self.word_space("=");
 454                 self.print_expr_maybe_paren(rhs, prec);
 455             }
 456             ast::ExprKind::AssignOp(op, lhs, rhs) => {
 457                 let prec = AssocOp::Assign.precedence() as i8;
 458                 self.print_expr_maybe_paren(lhs, prec + 1);
 459                 self.space();
 460                 self.word(op.node.to_string());
 461                 self.word_space("=");
 462                 self.print_expr_maybe_paren(rhs, prec);
 463             }
 464             ast::ExprKind::Field(expr, ident) => {
 465                 self.print_expr_maybe_paren(expr, parser::PREC_POSTFIX);
 466                 self.word(".");
 467                 self.print_ident(*ident);
 468             }
 469             ast::ExprKind::Index(expr, index) => {
 470                 self.print_expr_maybe_paren(expr, parser::PREC_POSTFIX);
 471                 self.word("[");
 472                 self.print_expr(index);
 473                 self.word("]");
 474             }
 475             ast::ExprKind::Range(start, end, limits) => {
 476                 // Special case for `Range`. `AssocOp` claims that `Range` has higher precedence
 477                 // than `Assign`, but `x .. x = x` gives a parse error instead of `x .. (x = x)`.
 478                 // Here we use a fake precedence value so that any child with lower precedence than
 479                 // a "normal" binop gets parenthesized. (`LOr` is the lowest-precedence binop.)
 480                 let fake_prec = AssocOp::LOr.precedence() as i8;
 481                 if let Some(e) = start {
 482                     self.print_expr_maybe_paren(e, fake_prec);
 483                 }
 484                 match limits {
 485                     ast::RangeLimits::HalfOpen => self.word(".."),
 486                     ast::RangeLimits::Closed => self.word("..="),
 487                 }
 488                 if let Some(e) = end {
 489                     self.print_expr_maybe_paren(e, fake_prec);
 490                 }
 491             }
 492             ast::ExprKind::Underscore => self.word("_"),
 493             ast::ExprKind::Path(None, path) => self.print_path(path, true, 0),
 494             ast::ExprKind::Path(Some(qself), path) => self.print_qpath(path, qself, true),
 495             ast::ExprKind::Break(opt_label, opt_expr) => {
 496                 self.word("break");
 497                 if let Some(label) = opt_label {
 498                     self.space();
 499                     self.print_ident(label.ident);
 500                 }
 501                 if let Some(expr) = opt_expr {
 502                     self.space();
 503                     self.print_expr_maybe_paren(expr, parser::PREC_JUMP);
 504                 }
 505             }
 506             ast::ExprKind::Continue(opt_label) => {
 507                 self.word("continue");
 508                 if let Some(label) = opt_label {
 509                     self.space();
 510                     self.print_ident(label.ident);
 511                 }
 512             }
 513             ast::ExprKind::Ret(result) => {
 514                 self.word("return");
 515                 if let Some(expr) = result {
 516                     self.word(" ");
 517                     self.print_expr_maybe_paren(expr, parser::PREC_JUMP);
 518                 }
 519             }
 520             ast::ExprKind::Yeet(result) => {
 521                 self.word("do");
 522                 self.word(" ");
 523                 self.word("yeet");
 524                 if let Some(expr) = result {
 525                     self.word(" ");
 526                     self.print_expr_maybe_paren(expr, parser::PREC_JUMP);
 527                 }
 528             }
 529             ast::ExprKind::InlineAsm(a) => {
 530                 self.word("asm!");
 531                 self.print_inline_asm(a);
 532             }
 533             ast::ExprKind::MacCall(m) => self.print_mac(m),
 534             ast::ExprKind::Paren(e) => {
 535                 self.popen();
 536                 self.print_expr(e);
 537                 self.pclose();
 538             }
 539             ast::ExprKind::Yield(e) => {
 540                 self.word("yield");
 541
 542                 if let Some(expr) = e {
 543                     self.space();
 544                     self.print_expr_maybe_paren(expr, parser::PREC_JUMP);
 545                 }
 546             }
 547             ast::ExprKind::Try(e) => {
 548                 self.print_expr_maybe_paren(e, parser::PREC_POSTFIX);
 549                 self.word("?")
 550             }
 551             ast::ExprKind::TryBlock(blk) => {
 552                 self.cbox(0);
 553                 self.ibox(0);
 554                 self.word_nbsp("try");
 555                 self.print_block_with_attrs(blk, attrs)
 556             }
 557             ast::ExprKind::Err => {
 558                 self.popen();
 559                 self.word("/*ERROR*/");
 560                 self.pclose()
 561             }
 562         }
 563         self.ann.post(self, AnnNode::Expr(expr));
 564         self.end();
 565     }
 566
 567     fn print_arm(&mut self, arm: &ast::Arm) {
 568         // Note, I have no idea why this check is necessary, but here it is.
 569         if arm.attrs.is_empty() {
 570             self.space();
 571         }
 572         self.cbox(INDENT_UNIT);
 573         self.ibox(0);
 574         self.maybe_print_comment(arm.pat.span.lo());
 575         self.print_outer_attributes(&arm.attrs);
 576         self.print_pat(&arm.pat);
 577         self.space();
 578         if let Some(e) = &arm.guard {
 579             self.word_space("if");
 580             self.print_expr(e);
 581             self.space();
 582         }
 583         self.word_space("=>");
 584
 585         match &arm.body.kind {
 586             ast::ExprKind::Block(blk, opt_label) => {
 587                 if let Some(label) = opt_label {
 588                     self.print_ident(label.ident);
 589                     self.word_space(":");
 590                 }
 591
 592                 // The block will close the pattern's ibox.
 593                 self.print_block_unclosed_indent(blk);
 594
 595                 // If it is a user-provided unsafe block, print a comma after it.
 596                 if let BlockCheckMode::Unsafe(ast::UserProvided) = blk.rules {
 597                     self.word(",");
 598                 }
 599             }
 600             _ => {
 601                 self.end(); // Close the ibox for the pattern.
 602                 self.print_expr(&arm.body);
 603                 self.word(",");
 604             }
 605         }
 606         self.end(); // Close enclosing cbox.
 607     }
 608
 609     fn print_closure_binder(&mut self, binder: &ast::ClosureBinder) {
 610         match binder {
 611             ast::ClosureBinder::NotPresent => {}
 612             ast::ClosureBinder::For { generic_params, .. } => {
 613                 self.print_formal_generic_params(generic_params)
 614             }
 615         }
 616     }
 617
 618     fn print_movability(&mut self, movability: ast::Movability) {
 619         match movability {
 620             ast::Movability::Static => self.word_space("static"),
 621             ast::Movability::Movable => {}
 622         }
 623     }
 624
 625     fn print_capture_clause(&mut self, capture_clause: ast::CaptureBy) {
 626         match capture_clause {
 627             ast::CaptureBy::Value => self.word_space("move"),
 628             ast::CaptureBy::Ref => {}
 629         }
 630     }
 631 }