src/expr.rs

   1 // Copyright 2015 The Rust Project Developers. See the COPYRIGHT
   2 // file at the top-level directory of this distribution and at
   3 // http://rust-lang.org/COPYRIGHT.
   4 //
   5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
   6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
   7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
   8 // option. This file may not be copied, modified, or distributed
   9 // except according to those terms.
  10
  11 use std::borrow::Cow;
  12 use std::cmp::min;
  13
  14 use config::lists::*;
  15 use syntax::codemap::{BytePos, CodeMap, Span};
  16 use syntax::parse::token::DelimToken;
  17 use syntax::{ast, ptr};
  18
  19 use chains::rewrite_chain;
  20 use closures;
  21 use codemap::{LineRangeUtils, SpanUtils};
  22 use comment::{
  23     combine_strs_with_missing_comments, contains_comment, recover_comment_removed, rewrite_comment,
  24     rewrite_missing_comment, CharClasses, FindUncommented,
  25 };
  26 use config::{Config, ControlBraceStyle, IndentStyle};
  27 use lists::{
  28     definitive_tactic, itemize_list, shape_for_tactic, struct_lit_formatting, struct_lit_shape,
  29     struct_lit_tactic, write_list, ListFormatting, ListItem, Separator,
  30 };
  31 use macros::{rewrite_macro, MacroArg, MacroPosition};
  32 use matches::rewrite_match;
  33 use overflow;
  34 use pairs::{rewrite_all_pairs, rewrite_pair, PairParts};
  35 use patterns::{can_be_overflowed_pat, is_short_pattern, TuplePatField};
  36 use rewrite::{Rewrite, RewriteContext};
  37 use shape::{Indent, Shape};
  38 use spanned::Spanned;
  39 use string::{rewrite_string, StringFormat};
  40 use types::{can_be_overflowed_type, rewrite_path, PathContext};
  41 use utils::{
  42     colon_spaces, contains_skip, count_newlines, first_line_ends_with, first_line_width,
  43     inner_attributes, last_line_extendable, last_line_width, mk_sp, outer_attributes,
  44     ptr_vec_to_ref_vec, semicolon_for_stmt, wrap_str,
  45 };
  46 use vertical::rewrite_with_alignment;
  47 use visitor::FmtVisitor;
  48
  49 impl Rewrite for ast::Expr {
  50     fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
  51         format_expr(self, ExprType::SubExpression, context, shape)
  52     }
  53 }
  54
  55 #[derive(Copy, Clone, PartialEq)]
  56 pub enum ExprType {
  57     Statement,
  58     SubExpression,
  59 }
  60
  61 pub fn format_expr(
  62     expr: &ast::Expr,
  63     expr_type: ExprType,
  64     context: &RewriteContext,
  65     shape: Shape,
  66 ) -> Option<String> {
  67     skip_out_of_file_lines_range!(context, expr.span);
  68
  69     if contains_skip(&*expr.attrs) {
  70         return Some(context.snippet(expr.span()).to_owned());
  71     }
  72
  73     let expr_rw = match expr.node {
  74         ast::ExprKind::Array(ref expr_vec) => rewrite_array(
  75             "",
  76             &ptr_vec_to_ref_vec(expr_vec),
  77             expr.span,
  78             context,
  79             shape,
  80             choose_separator_tactic(context, expr.span),
  81             None,
  82         ),
  83         ast::ExprKind::Lit(ref l) => rewrite_literal(context, l, shape),
  84         ast::ExprKind::Call(ref callee, ref args) => {
  85             let inner_span = mk_sp(callee.span.hi(), expr.span.hi());
  86             let callee_str = callee.rewrite(context, shape)?;
  87             rewrite_call(context, &callee_str, args, inner_span, shape)
  88         }
  89         ast::ExprKind::Paren(ref subexpr) => rewrite_paren(context, subexpr, shape, expr.span),
  90         ast::ExprKind::Binary(op, ref lhs, ref rhs) => {
  91             // FIXME: format comments between operands and operator
  92             rewrite_all_pairs(expr, shape, context).or_else(|| {
  93                 rewrite_pair(
  94                     &**lhs,
  95                     &**rhs,
  96                     PairParts::infix(&format!(" {} ", context.snippet(op.span))),
  97                     context,
  98                     shape,
  99                     context.config.binop_separator(),
 100                 )
 101             })
 102         }
 103         ast::ExprKind::Unary(ref op, ref subexpr) => rewrite_unary_op(context, op, subexpr, shape),
 104         ast::ExprKind::Struct(ref path, ref fields, ref base) => rewrite_struct_lit(
 105             context,
 106             path,
 107             fields,
 108             base.as_ref().map(|e| &**e),
 109             expr.span,
 110             shape,
 111         ),
 112         ast::ExprKind::Tup(ref items) => {
 113             rewrite_tuple(context, &ptr_vec_to_ref_vec(items), expr.span, shape)
 114         }
 115         ast::ExprKind::If(..)
 116         | ast::ExprKind::IfLet(..)
 117         | ast::ExprKind::ForLoop(..)
 118         | ast::ExprKind::Loop(..)
 119         | ast::ExprKind::While(..)
 120         | ast::ExprKind::WhileLet(..) => to_control_flow(expr, expr_type)
 121             .and_then(|control_flow| control_flow.rewrite(context, shape)),
 122         ast::ExprKind::Block(ref block, opt_label) => {
 123             match expr_type {
 124                 ExprType::Statement => {
 125                     if is_unsafe_block(block) {
 126                         rewrite_block(block, Some(&expr.attrs), opt_label, context, shape)
 127                     } else if let rw @ Some(_) =
 128                         rewrite_empty_block(context, block, Some(&expr.attrs), opt_label, "", shape)
 129                     {
 130                         // Rewrite block without trying to put it in a single line.
 131                         rw
 132                     } else {
 133                         let prefix = block_prefix(context, block, shape)?;
 134
 135                         rewrite_block_with_visitor(
 136                             context,
 137                             &prefix,
 138                             block,
 139                             Some(&expr.attrs),
 140                             opt_label,
 141                             shape,
 142                             true,
 143                         )
 144                     }
 145                 }
 146                 ExprType::SubExpression => {
 147                     rewrite_block(block, Some(&expr.attrs), opt_label, context, shape)
 148                 }
 149             }
 150         }
 151         ast::ExprKind::Match(ref cond, ref arms) => {
 152             rewrite_match(context, cond, arms, shape, expr.span, &expr.attrs)
 153         }
 154         ast::ExprKind::Path(ref qself, ref path) => {
 155             rewrite_path(context, PathContext::Expr, qself.as_ref(), path, shape)
 156         }
 157         ast::ExprKind::Assign(ref lhs, ref rhs) => {
 158             rewrite_assignment(context, lhs, rhs, None, shape)
 159         }
 160         ast::ExprKind::AssignOp(ref op, ref lhs, ref rhs) => {
 161             rewrite_assignment(context, lhs, rhs, Some(op), shape)
 162         }
 163         ast::ExprKind::Continue(ref opt_label) => {
 164             let id_str = match *opt_label {
 165                 Some(label) => format!(" {}", label.ident),
 166                 None => String::new(),
 167             };
 168             Some(format!("continue{}", id_str))
 169         }
 170         ast::ExprKind::Break(ref opt_label, ref opt_expr) => {
 171             let id_str = match *opt_label {
 172                 Some(label) => format!(" {}", label.ident),
 173                 None => String::new(),
 174             };
 175
 176             if let Some(ref expr) = *opt_expr {
 177                 rewrite_unary_prefix(context, &format!("break{} ", id_str), &**expr, shape)
 178             } else {
 179                 Some(format!("break{}", id_str))
 180             }
 181         }
 182         ast::ExprKind::Yield(ref opt_expr) => if let Some(ref expr) = *opt_expr {
 183             rewrite_unary_prefix(context, "yield ", &**expr, shape)
 184         } else {
 185             Some("yield".to_string())
 186         },
 187         ast::ExprKind::Closure(capture, asyncness, movability, ref fn_decl, ref body, _) => {
 188             closures::rewrite_closure(
 189                 capture, asyncness, movability, fn_decl, body, expr.span, context, shape,
 190             )
 191         }
 192         ast::ExprKind::Try(..) | ast::ExprKind::Field(..) | ast::ExprKind::MethodCall(..) => {
 193             rewrite_chain(expr, context, shape)
 194         }
 195         ast::ExprKind::Mac(ref mac) => {
 196             rewrite_macro(mac, None, context, shape, MacroPosition::Expression).or_else(|| {
 197                 wrap_str(
 198                     context.snippet(expr.span).to_owned(),
 199                     context.config.max_width(),
 200                     shape,
 201                 )
 202             })
 203         }
 204         ast::ExprKind::Ret(None) => Some("return".to_owned()),
 205         ast::ExprKind::Ret(Some(ref expr)) => {
 206             rewrite_unary_prefix(context, "return ", &**expr, shape)
 207         }
 208         ast::ExprKind::Box(ref expr) => rewrite_unary_prefix(context, "box ", &**expr, shape),
 209         ast::ExprKind::AddrOf(mutability, ref expr) => {
 210             rewrite_expr_addrof(context, mutability, expr, shape)
 211         }
 212         ast::ExprKind::Cast(ref expr, ref ty) => rewrite_pair(
 213             &**expr,
 214             &**ty,
 215             PairParts::infix(" as "),
 216             context,
 217             shape,
 218             SeparatorPlace::Front,
 219         ),
 220         ast::ExprKind::Type(ref expr, ref ty) => rewrite_pair(
 221             &**expr,
 222             &**ty,
 223             PairParts::infix(": "),
 224             context,
 225             shape,
 226             SeparatorPlace::Back,
 227         ),
 228         ast::ExprKind::Index(ref expr, ref index) => {
 229             rewrite_index(&**expr, &**index, context, shape)
 230         }
 231         ast::ExprKind::Repeat(ref expr, ref repeats) => rewrite_pair(
 232             &**expr,
 233             &*repeats.value,
 234             PairParts::new("[", "; ", "]"),
 235             context,
 236             shape,
 237             SeparatorPlace::Back,
 238         ),
 239         ast::ExprKind::Range(ref lhs, ref rhs, limits) => {
 240             let delim = match limits {
 241                 ast::RangeLimits::HalfOpen => "..",
 242                 ast::RangeLimits::Closed => "..=",
 243             };
 244
 245             fn needs_space_before_range(context: &RewriteContext, lhs: &ast::Expr) -> bool {
 246                 match lhs.node {
 247                     ast::ExprKind::Lit(ref lit) => match lit.node {
 248                         ast::LitKind::FloatUnsuffixed(..) => {
 249                             context.snippet(lit.span).ends_with('.')
 250                         }
 251                         _ => false,
 252                     },
 253                     _ => false,
 254                 }
 255             }
 256
 257             fn needs_space_after_range(rhs: &ast::Expr) -> bool {
 258                 match rhs.node {
 259                     // Don't format `.. ..` into `....`, which is invalid.
 260                     //
 261                     // This check is unnecessary for `lhs`, because a range
 262                     // starting from another range needs parentheses as `(x ..) ..`
 263                     // (`x .. ..` is a range from `x` to `..`).
 264                     ast::ExprKind::Range(None, _, _) => true,
 265                     _ => false,
 266                 }
 267             }
 268
 269             let default_sp_delim = |lhs: Option<&ast::Expr>, rhs: Option<&ast::Expr>| {
 270                 let space_if = |b: bool| if b { " " } else { "" };
 271
 272                 format!(
 273                     "{}{}{}",
 274                     lhs.map(|lhs| space_if(needs_space_before_range(context, lhs)))
 275                         .unwrap_or(""),
 276                     delim,
 277                     rhs.map(|rhs| space_if(needs_space_after_range(rhs)))
 278                         .unwrap_or(""),
 279                 )
 280             };
 281
 282             match (lhs.as_ref().map(|x| &**x), rhs.as_ref().map(|x| &**x)) {
 283                 (Some(lhs), Some(rhs)) => {
 284                     let sp_delim = if context.config.spaces_around_ranges() {
 285                         format!(" {} ", delim)
 286                     } else {
 287                         default_sp_delim(Some(lhs), Some(rhs))
 288                     };
 289                     rewrite_pair(
 290                         &*lhs,
 291                         &*rhs,
 292                         PairParts::infix(&sp_delim),
 293                         context,
 294                         shape,
 295                         context.config.binop_separator(),
 296                     )
 297                 }
 298                 (None, Some(rhs)) => {
 299                     let sp_delim = if context.config.spaces_around_ranges() {
 300                         format!("{} ", delim)
 301                     } else {
 302                         default_sp_delim(None, Some(rhs))
 303                     };
 304                     rewrite_unary_prefix(context, &sp_delim, &*rhs, shape)
 305                 }
 306                 (Some(lhs), None) => {
 307                     let sp_delim = if context.config.spaces_around_ranges() {
 308                         format!(" {}", delim)
 309                     } else {
 310                         default_sp_delim(Some(lhs), None)
 311                     };
 312                     rewrite_unary_suffix(context, &sp_delim, &*lhs, shape)
 313                 }
 314                 (None, None) => Some(delim.to_owned()),
 315             }
 316         }
 317         // We do not format these expressions yet, but they should still
 318         // satisfy our width restrictions.
 319         ast::ExprKind::InlineAsm(..) => Some(context.snippet(expr.span).to_owned()),
 320         ast::ExprKind::Catch(ref block) => {
 321             if let rw @ Some(_) = rewrite_single_line_block(
 322                 context,
 323                 "do catch ",
 324                 block,
 325                 Some(&expr.attrs),
 326                 None,
 327                 shape,
 328             ) {
 329                 rw
 330             } else {
 331                 // 9 = `do catch `
 332                 let budget = shape.width.saturating_sub(9);
 333                 Some(format!(
 334                     "{}{}",
 335                     "do catch ",
 336                     rewrite_block(
 337                         block,
 338                         Some(&expr.attrs),
 339                         None,
 340                         context,
 341                         Shape::legacy(budget, shape.indent)
 342                     )?
 343                 ))
 344             }
 345         }
 346         // FIXME(#2743)
 347         ast::ExprKind::ObsoleteInPlace(..) => unimplemented!(),
 348         ast::ExprKind::Async(capture_by, _node_id, ref block) => {
 349             let mover = if capture_by == ast::CaptureBy::Value {
 350                 "move "
 351             } else {
 352                 ""
 353             };
 354             if let rw @ Some(_) = rewrite_single_line_block(
 355                 context,
 356                 format!("{}{}", "async ", mover).as_str(),
 357                 block,
 358                 Some(&expr.attrs),
 359                 None,
 360                 shape,
 361             ) {
 362                 rw
 363             } else {
 364                 // 6 = `async `
 365                 let budget = shape.width.saturating_sub(6);
 366                 Some(format!(
 367                     "{}{}{}",
 368                     "async ",
 369                     mover,
 370                     rewrite_block(
 371                         block,
 372                         Some(&expr.attrs),
 373                         None,
 374                         context,
 375                         Shape::legacy(budget, shape.indent)
 376                     )?
 377                 ))
 378             }
 379         }
 380     };
 381
 382     expr_rw
 383         .and_then(|expr_str| recover_comment_removed(expr_str, expr.span, context))
 384         .and_then(|expr_str| {
 385             let attrs = outer_attributes(&expr.attrs);
 386             let attrs_str = attrs.rewrite(context, shape)?;
 387             let span = mk_sp(
 388                 attrs.last().map_or(expr.span.lo(), |attr| attr.span.hi()),
 389                 expr.span.lo(),
 390             );
 391             combine_strs_with_missing_comments(context, &attrs_str, &expr_str, span, shape, false)
 392         })
 393 }
 394
 395 pub fn rewrite_array<T: Rewrite + Spanned + ToExpr>(
 396     name: &str,
 397     exprs: &[&T],
 398     span: Span,
 399     context: &RewriteContext,
 400     shape: Shape,
 401     force_separator_tactic: Option<SeparatorTactic>,
 402     delim_token: Option<DelimToken>,
 403 ) -> Option<String> {
 404     overflow::rewrite_with_square_brackets(
 405         context,
 406         name,
 407         exprs,
 408         shape,
 409         span,
 410         force_separator_tactic,
 411         delim_token,
 412     )
 413 }
 414
 415 fn rewrite_empty_block(
 416     context: &RewriteContext,
 417     block: &ast::Block,
 418     attrs: Option<&[ast::Attribute]>,
 419     label: Option<ast::Label>,
 420     prefix: &str,
 421     shape: Shape,
 422 ) -> Option<String> {
 423     let label_str = rewrite_label(label);
 424     if attrs.map_or(false, |a| !inner_attributes(a).is_empty()) {
 425         return None;
 426     }
 427
 428     if block.stmts.is_empty() && !block_contains_comment(block, context.codemap) && shape.width >= 2
 429     {
 430         return Some(format!("{}{}{{}}", prefix, label_str));
 431     }
 432
 433     // If a block contains only a single-line comment, then leave it on one line.
 434     let user_str = context.snippet(block.span);
 435     let user_str = user_str.trim();
 436     if user_str.starts_with('{') && user_str.ends_with('}') {
 437         let comment_str = user_str[1..user_str.len() - 1].trim();
 438         if block.stmts.is_empty()
 439             && !comment_str.contains('\n')
 440             && !comment_str.starts_with("//")
 441             && comment_str.len() + 4 <= shape.width
 442         {
 443             return Some(format!("{}{}{{ {} }}", prefix, label_str, comment_str));
 444         }
 445     }
 446
 447     None
 448 }
 449
 450 fn block_prefix(context: &RewriteContext, block: &ast::Block, shape: Shape) -> Option<String> {
 451     Some(match block.rules {
 452         ast::BlockCheckMode::Unsafe(..) => {
 453             let snippet = context.snippet(block.span);
 454             let open_pos = snippet.find_uncommented("{")?;
 455             // Extract comment between unsafe and block start.
 456             let trimmed = &snippet[6..open_pos].trim();
 457
 458             if !trimmed.is_empty() {
 459                 // 9 = "unsafe  {".len(), 7 = "unsafe ".len()
 460                 let budget = shape.width.checked_sub(9)?;
 461                 format!(
 462                     "unsafe {} ",
 463                     rewrite_comment(
 464                         trimmed,
 465                         true,
 466                         Shape::legacy(budget, shape.indent + 7),
 467                         context.config,
 468                     )?
 469                 )
 470             } else {
 471                 "unsafe ".to_owned()
 472             }
 473         }
 474         ast::BlockCheckMode::Default => String::new(),
 475     })
 476 }
 477
 478 fn rewrite_single_line_block(
 479     context: &RewriteContext,
 480     prefix: &str,
 481     block: &ast::Block,
 482     attrs: Option<&[ast::Attribute]>,
 483     label: Option<ast::Label>,
 484     shape: Shape,
 485 ) -> Option<String> {
 486     if is_simple_block(block, attrs, context.codemap) {
 487         let expr_shape = shape.offset_left(last_line_width(prefix))?;
 488         let expr_str = block.stmts[0].rewrite(context, expr_shape)?;
 489         let label_str = rewrite_label(label);
 490         let result = format!("{}{}{{ {} }}", prefix, label_str, expr_str);
 491         if result.len() <= shape.width && !result.contains('\n') {
 492             return Some(result);
 493         }
 494     }
 495     None
 496 }
 497
 498 pub fn rewrite_block_with_visitor(
 499     context: &RewriteContext,
 500     prefix: &str,
 501     block: &ast::Block,
 502     attrs: Option<&[ast::Attribute]>,
 503     label: Option<ast::Label>,
 504     shape: Shape,
 505     has_braces: bool,
 506 ) -> Option<String> {
 507     if let rw @ Some(_) = rewrite_empty_block(context, block, attrs, label, prefix, shape) {
 508         return rw;
 509     }
 510
 511     let mut visitor = FmtVisitor::from_context(context);
 512     visitor.block_indent = shape.indent;
 513     visitor.is_if_else_block = context.is_if_else_block();
 514     match block.rules {
 515         ast::BlockCheckMode::Unsafe(..) => {
 516             let snippet = context.snippet(block.span);
 517             let open_pos = snippet.find_uncommented("{")?;
 518             visitor.last_pos = block.span.lo() + BytePos(open_pos as u32)
 519         }
 520         ast::BlockCheckMode::Default => visitor.last_pos = block.span.lo(),
 521     }
 522
 523     let inner_attrs = attrs.map(inner_attributes);
 524     let label_str = rewrite_label(label);
 525     visitor.visit_block(block, inner_attrs.as_ref().map(|a| &**a), has_braces);
 526     Some(format!("{}{}{}", prefix, label_str, visitor.buffer))
 527 }
 528
 529 impl Rewrite for ast::Block {
 530     fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
 531         rewrite_block(self, None, None, context, shape)
 532     }
 533 }
 534
 535 fn rewrite_block(
 536     block: &ast::Block,
 537     attrs: Option<&[ast::Attribute]>,
 538     label: Option<ast::Label>,
 539     context: &RewriteContext,
 540     shape: Shape,
 541 ) -> Option<String> {
 542     let prefix = block_prefix(context, block, shape)?;
 543
 544     // shape.width is used only for the single line case: either the empty block `{}`,
 545     // or an unsafe expression `unsafe { e }`.
 546     if let rw @ Some(_) = rewrite_empty_block(context, block, attrs, label, &prefix, shape) {
 547         return rw;
 548     }
 549
 550     let result = rewrite_block_with_visitor(context, &prefix, block, attrs, label, shape, true);
 551     if let Some(ref result_str) = result {
 552         if result_str.lines().count() <= 3 {
 553             if let rw @ Some(_) =
 554                 rewrite_single_line_block(context, &prefix, block, attrs, label, shape)
 555             {
 556                 return rw;
 557             }
 558         }
 559     }
 560
 561     result
 562 }
 563
 564 impl Rewrite for ast::Stmt {
 565     fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
 566         skip_out_of_file_lines_range!(context, self.span());
 567
 568         let result = match self.node {
 569             ast::StmtKind::Local(ref local) => local.rewrite(context, shape),
 570             ast::StmtKind::Expr(ref ex) | ast::StmtKind::Semi(ref ex) => {
 571                 let suffix = if semicolon_for_stmt(context, self) {
 572                     ";"
 573                 } else {
 574                     ""
 575                 };
 576
 577                 let shape = shape.sub_width(suffix.len())?;
 578                 format_expr(ex, ExprType::Statement, context, shape).map(|s| s + suffix)
 579             }
 580             ast::StmtKind::Mac(..) | ast::StmtKind::Item(..) => None,
 581         };
 582         result.and_then(|res| recover_comment_removed(res, self.span(), context))
 583     }
 584 }
 585
 586 // Rewrite condition if the given expression has one.
 587 pub fn rewrite_cond(context: &RewriteContext, expr: &ast::Expr, shape: Shape) -> Option<String> {
 588     match expr.node {
 589         ast::ExprKind::Match(ref cond, _) => {
 590             // `match `cond` {`
 591             let cond_shape = match context.config.indent_style() {
 592                 IndentStyle::Visual => shape.shrink_left(6).and_then(|s| s.sub_width(2))?,
 593                 IndentStyle::Block => shape.offset_left(8)?,
 594             };
 595             cond.rewrite(context, cond_shape)
 596         }
 597         _ => to_control_flow(expr, ExprType::SubExpression).and_then(|control_flow| {
 598             let alt_block_sep =
 599                 String::from("\n") + &shape.indent.block_only().to_string(context.config);
 600             control_flow
 601                 .rewrite_cond(context, shape, &alt_block_sep)
 602                 .and_then(|rw| Some(rw.0))
 603         }),
 604     }
 605 }
 606
 607 // Abstraction over control flow expressions
 608 #[derive(Debug)]
 609 struct ControlFlow<'a> {
 610     cond: Option<&'a ast::Expr>,
 611     block: &'a ast::Block,
 612     else_block: Option<&'a ast::Expr>,
 613     label: Option<ast::Label>,
 614     pats: Vec<&'a ast::Pat>,
 615     keyword: &'a str,
 616     matcher: &'a str,
 617     connector: &'a str,
 618     allow_single_line: bool,
 619     // True if this is an `if` expression in an `else if` :-( hacky
 620     nested_if: bool,
 621     span: Span,
 622 }
 623
 624 fn to_control_flow(expr: &ast::Expr, expr_type: ExprType) -> Option<ControlFlow> {
 625     match expr.node {
 626         ast::ExprKind::If(ref cond, ref if_block, ref else_block) => Some(ControlFlow::new_if(
 627             cond,
 628             vec![],
 629             if_block,
 630             else_block.as_ref().map(|e| &**e),
 631             expr_type == ExprType::SubExpression,
 632             false,
 633             expr.span,
 634         )),
 635         ast::ExprKind::IfLet(ref pat, ref cond, ref if_block, ref else_block) => {
 636             Some(ControlFlow::new_if(
 637                 cond,
 638                 ptr_vec_to_ref_vec(pat),
 639                 if_block,
 640                 else_block.as_ref().map(|e| &**e),
 641                 expr_type == ExprType::SubExpression,
 642                 false,
 643                 expr.span,
 644             ))
 645         }
 646         ast::ExprKind::ForLoop(ref pat, ref cond, ref block, label) => {
 647             Some(ControlFlow::new_for(pat, cond, block, label, expr.span))
 648         }
 649         ast::ExprKind::Loop(ref block, label) => {
 650             Some(ControlFlow::new_loop(block, label, expr.span))
 651         }
 652         ast::ExprKind::While(ref cond, ref block, label) => Some(ControlFlow::new_while(
 653             vec![],
 654             cond,
 655             block,
 656             label,
 657             expr.span,
 658         )),
 659         ast::ExprKind::WhileLet(ref pat, ref cond, ref block, label) => Some(
 660             ControlFlow::new_while(ptr_vec_to_ref_vec(pat), cond, block, label, expr.span),
 661         ),
 662         _ => None,
 663     }
 664 }
 665
 666 fn choose_matcher(pats: &[&ast::Pat]) -> &'static str {
 667     if pats.is_empty() {
 668         ""
 669     } else {
 670         "let"
 671     }
 672 }
 673
 674 impl<'a> ControlFlow<'a> {
 675     fn new_if(
 676         cond: &'a ast::Expr,
 677         pats: Vec<&'a ast::Pat>,
 678         block: &'a ast::Block,
 679         else_block: Option<&'a ast::Expr>,
 680         allow_single_line: bool,
 681         nested_if: bool,
 682         span: Span,
 683     ) -> ControlFlow<'a> {
 684         let matcher = choose_matcher(&pats);
 685         ControlFlow {
 686             cond: Some(cond),
 687             block,
 688             else_block,
 689             label: None,
 690             pats,
 691             keyword: "if",
 692             matcher,
 693             connector: " =",
 694             allow_single_line,
 695             nested_if,
 696             span,
 697         }
 698     }
 699
 700     fn new_loop(block: &'a ast::Block, label: Option<ast::Label>, span: Span) -> ControlFlow<'a> {
 701         ControlFlow {
 702             cond: None,
 703             block,
 704             else_block: None,
 705             label,
 706             pats: vec![],
 707             keyword: "loop",
 708             matcher: "",
 709             connector: "",
 710             allow_single_line: false,
 711             nested_if: false,
 712             span,
 713         }
 714     }
 715
 716     fn new_while(
 717         pats: Vec<&'a ast::Pat>,
 718         cond: &'a ast::Expr,
 719         block: &'a ast::Block,
 720         label: Option<ast::Label>,
 721         span: Span,
 722     ) -> ControlFlow<'a> {
 723         let matcher = choose_matcher(&pats);
 724         ControlFlow {
 725             cond: Some(cond),
 726             block,
 727             else_block: None,
 728             label,
 729             pats,
 730             keyword: "while",
 731             matcher,
 732             connector: " =",
 733             allow_single_line: false,
 734             nested_if: false,
 735             span,
 736         }
 737     }
 738
 739     fn new_for(
 740         pat: &'a ast::Pat,
 741         cond: &'a ast::Expr,
 742         block: &'a ast::Block,
 743         label: Option<ast::Label>,
 744         span: Span,
 745     ) -> ControlFlow<'a> {
 746         ControlFlow {
 747             cond: Some(cond),
 748             block,
 749             else_block: None,
 750             label,
 751             pats: vec![pat],
 752             keyword: "for",
 753             matcher: "",
 754             connector: " in",
 755             allow_single_line: false,
 756             nested_if: false,
 757             span,
 758         }
 759     }
 760
 761     fn rewrite_single_line(
 762         &self,
 763         pat_expr_str: &str,
 764         context: &RewriteContext,
 765         width: usize,
 766     ) -> Option<String> {
 767         assert!(self.allow_single_line);
 768         let else_block = self.else_block?;
 769         let fixed_cost = self.keyword.len() + "  {  } else {  }".len();
 770
 771         if let ast::ExprKind::Block(ref else_node, _) = else_block.node {
 772             if !is_simple_block(self.block, None, context.codemap)
 773                 || !is_simple_block(else_node, None, context.codemap)
 774                 || pat_expr_str.contains('\n')
 775             {
 776                 return None;
 777             }
 778
 779             let new_width = width.checked_sub(pat_expr_str.len() + fixed_cost)?;
 780             let expr = &self.block.stmts[0];
 781             let if_str = expr.rewrite(context, Shape::legacy(new_width, Indent::empty()))?;
 782
 783             let new_width = new_width.checked_sub(if_str.len())?;
 784             let else_expr = &else_node.stmts[0];
 785             let else_str = else_expr.rewrite(context, Shape::legacy(new_width, Indent::empty()))?;
 786
 787             if if_str.contains('\n') || else_str.contains('\n') {
 788                 return None;
 789             }
 790
 791             let result = format!(
 792                 "{} {} {{ {} }} else {{ {} }}",
 793                 self.keyword, pat_expr_str, if_str, else_str
 794             );
 795
 796             if result.len() <= width {
 797                 return Some(result);
 798             }
 799         }
 800
 801         None
 802     }
 803 }
 804
 805 impl<'a> ControlFlow<'a> {
 806     fn rewrite_pat_expr(
 807         &self,
 808         context: &RewriteContext,
 809         expr: &ast::Expr,
 810         shape: Shape,
 811         offset: usize,
 812     ) -> Option<String> {
 813         debug!("rewrite_pat_expr {:?} {:?} {:?}", shape, self.pats, expr);
 814
 815         let cond_shape = shape.offset_left(offset)?;
 816         if !self.pats.is_empty() {
 817             let matcher = if self.matcher.is_empty() {
 818                 self.matcher.to_owned()
 819             } else {
 820                 format!("{} ", self.matcher)
 821             };
 822             let pat_shape = cond_shape
 823                 .offset_left(matcher.len())?
 824                 .sub_width(self.connector.len())?;
 825             let pat_string = rewrite_multiple_patterns(context, &self.pats, pat_shape)?;
 826             let result = format!("{}{}{}", matcher, pat_string, self.connector);
 827             return rewrite_assign_rhs(context, result, expr, cond_shape);
 828         }
 829
 830         let expr_rw = expr.rewrite(context, cond_shape);
 831         // The expression may (partially) fit on the current line.
 832         // We do not allow splitting between `if` and condition.
 833         if self.keyword == "if" || expr_rw.is_some() {
 834             return expr_rw;
 835         }
 836
 837         // The expression won't fit on the current line, jump to next.
 838         let nested_shape = shape
 839             .block_indent(context.config.tab_spaces())
 840             .with_max_width(context.config);
 841         let nested_indent_str = nested_shape.indent.to_string_with_newline(context.config);
 842         expr.rewrite(context, nested_shape)
 843             .map(|expr_rw| format!("{}{}", nested_indent_str, expr_rw))
 844     }
 845
 846     fn rewrite_cond(
 847         &self,
 848         context: &RewriteContext,
 849         shape: Shape,
 850         alt_block_sep: &str,
 851     ) -> Option<(String, usize)> {
 852         // Do not take the rhs overhead from the upper expressions into account
 853         // when rewriting pattern.
 854         let new_width = context.budget(shape.used_width());
 855         let fresh_shape = Shape {
 856             width: new_width,
 857             ..shape
 858         };
 859         let constr_shape = if self.nested_if {
 860             // We are part of an if-elseif-else chain. Our constraints are tightened.
 861             // 7 = "} else " .len()
 862             fresh_shape.offset_left(7)?
 863         } else {
 864             fresh_shape
 865         };
 866
 867         let label_string = rewrite_label(self.label);
 868         // 1 = space after keyword.
 869         let offset = self.keyword.len() + label_string.len() + 1;
 870
 871         let pat_expr_string = match self.cond {
 872             Some(cond) => self.rewrite_pat_expr(context, cond, constr_shape, offset)?,
 873             None => String::new(),
 874         };
 875
 876         let brace_overhead =
 877             if context.config.control_brace_style() != ControlBraceStyle::AlwaysNextLine {
 878                 // 2 = ` {`
 879                 2
 880             } else {
 881                 0
 882             };
 883         let one_line_budget = context
 884             .config
 885             .max_width()
 886             .saturating_sub(constr_shape.used_width() + offset + brace_overhead);
 887         let force_newline_brace = (pat_expr_string.contains('\n')
 888             || pat_expr_string.len() > one_line_budget)
 889             && !last_line_extendable(&pat_expr_string);
 890
 891         // Try to format if-else on single line.
 892         if self.allow_single_line
 893             && context
 894                 .config
 895                 .width_heuristics()
 896                 .single_line_if_else_max_width
 897                 > 0
 898         {
 899             let trial = self.rewrite_single_line(&pat_expr_string, context, shape.width);
 900
 901             if let Some(cond_str) = trial {
 902                 if cond_str.len() <= context
 903                     .config
 904                     .width_heuristics()
 905                     .single_line_if_else_max_width
 906                 {
 907                     return Some((cond_str, 0));
 908                 }
 909             }
 910         }
 911
 912         let cond_span = if let Some(cond) = self.cond {
 913             cond.span
 914         } else {
 915             mk_sp(self.block.span.lo(), self.block.span.lo())
 916         };
 917
 918         // `for event in event`
 919         // Do not include label in the span.
 920         let lo = self
 921             .label
 922             .map_or(self.span.lo(), |label| label.ident.span.hi());
 923         let between_kwd_cond = mk_sp(
 924             context
 925                 .snippet_provider
 926                 .span_after(mk_sp(lo, self.span.hi()), self.keyword.trim()),
 927             if self.pats.is_empty() {
 928                 cond_span.lo()
 929             } else if self.matcher.is_empty() {
 930                 self.pats[0].span.lo()
 931             } else {
 932                 context
 933                     .snippet_provider
 934                     .span_before(self.span, self.matcher.trim())
 935             },
 936         );
 937
 938         let between_kwd_cond_comment = extract_comment(between_kwd_cond, context, shape);
 939
 940         let after_cond_comment =
 941             extract_comment(mk_sp(cond_span.hi(), self.block.span.lo()), context, shape);
 942
 943         let block_sep = if self.cond.is_none() && between_kwd_cond_comment.is_some() {
 944             ""
 945         } else if context.config.control_brace_style() == ControlBraceStyle::AlwaysNextLine
 946             || force_newline_brace
 947         {
 948             alt_block_sep
 949         } else {
 950             " "
 951         };
 952
 953         let used_width = if pat_expr_string.contains('\n') {
 954             last_line_width(&pat_expr_string)
 955         } else {
 956             // 2 = spaces after keyword and condition.
 957             label_string.len() + self.keyword.len() + pat_expr_string.len() + 2
 958         };
 959
 960         Some((
 961             format!(
 962                 "{}{}{}{}{}",
 963                 label_string,
 964                 self.keyword,
 965                 between_kwd_cond_comment.as_ref().map_or(
 966                     if pat_expr_string.is_empty() || pat_expr_string.starts_with('\n') {
 967                         ""
 968                     } else {
 969                         " "
 970                     },
 971                     |s| &**s,
 972                 ),
 973                 pat_expr_string,
 974                 after_cond_comment.as_ref().map_or(block_sep, |s| &**s)
 975             ),
 976             used_width,
 977         ))
 978     }
 979 }
 980
 981 impl<'a> Rewrite for ControlFlow<'a> {
 982     fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
 983         debug!("ControlFlow::rewrite {:?} {:?}", self, shape);
 984
 985         let alt_block_sep = &shape.indent.to_string_with_newline(context.config);
 986         let (cond_str, used_width) = self.rewrite_cond(context, shape, alt_block_sep)?;
 987         // If `used_width` is 0, it indicates that whole control flow is written in a single line.
 988         if used_width == 0 {
 989             return Some(cond_str);
 990         }
 991
 992         let block_width = shape.width.saturating_sub(used_width);
 993         // This is used only for the empty block case: `{}`. So, we use 1 if we know
 994         // we should avoid the single line case.
 995         let block_width = if self.else_block.is_some() || self.nested_if {
 996             min(1, block_width)
 997         } else {
 998             block_width
 999         };
1000         let block_shape = Shape {
1001             width: block_width,
1002             ..shape
1003         };
1004         let block_str = {
1005             let old_val = context.is_if_else_block.replace(self.else_block.is_some());
1006             let result =
1007                 rewrite_block_with_visitor(context, "", self.block, None, None, block_shape, true);
1008             context.is_if_else_block.replace(old_val);
1009             result?
1010         };
1011
1012         let mut result = format!("{}{}", cond_str, block_str);
1013
1014         if let Some(else_block) = self.else_block {
1015             let shape = Shape::indented(shape.indent, context.config);
1016             let mut last_in_chain = false;
1017             let rewrite = match else_block.node {
1018                 // If the else expression is another if-else expression, prevent it
1019                 // from being formatted on a single line.
1020                 // Note how we're passing the original shape, as the
1021                 // cost of "else" should not cascade.
1022                 ast::ExprKind::IfLet(ref pat, ref cond, ref if_block, ref next_else_block) => {
1023                     ControlFlow::new_if(
1024                         cond,
1025                         ptr_vec_to_ref_vec(pat),
1026                         if_block,
1027                         next_else_block.as_ref().map(|e| &**e),
1028                         false,
1029                         true,
1030                         mk_sp(else_block.span.lo(), self.span.hi()),
1031                     ).rewrite(context, shape)
1032                 }
1033                 ast::ExprKind::If(ref cond, ref if_block, ref next_else_block) => {
1034                     ControlFlow::new_if(
1035                         cond,
1036                         vec![],
1037                         if_block,
1038                         next_else_block.as_ref().map(|e| &**e),
1039                         false,
1040                         true,
1041                         mk_sp(else_block.span.lo(), self.span.hi()),
1042                     ).rewrite(context, shape)
1043                 }
1044                 _ => {
1045                     last_in_chain = true;
1046                     // When rewriting a block, the width is only used for single line
1047                     // blocks, passing 1 lets us avoid that.
1048                     let else_shape = Shape {
1049                         width: min(1, shape.width),
1050                         ..shape
1051                     };
1052                     format_expr(else_block, ExprType::Statement, context, else_shape)
1053                 }
1054             };
1055
1056             let between_kwd_else_block = mk_sp(
1057                 self.block.span.hi(),
1058                 context
1059                     .snippet_provider
1060                     .span_before(mk_sp(self.block.span.hi(), else_block.span.lo()), "else"),
1061             );
1062             let between_kwd_else_block_comment =
1063                 extract_comment(between_kwd_else_block, context, shape);
1064
1065             let after_else = mk_sp(
1066                 context
1067                     .snippet_provider
1068                     .span_after(mk_sp(self.block.span.hi(), else_block.span.lo()), "else"),
1069                 else_block.span.lo(),
1070             );
1071             let after_else_comment = extract_comment(after_else, context, shape);
1072
1073             let between_sep = match context.config.control_brace_style() {
1074                 ControlBraceStyle::AlwaysNextLine | ControlBraceStyle::ClosingNextLine => {
1075                     &*alt_block_sep
1076                 }
1077                 ControlBraceStyle::AlwaysSameLine => " ",
1078             };
1079             let after_sep = match context.config.control_brace_style() {
1080                 ControlBraceStyle::AlwaysNextLine if last_in_chain => &*alt_block_sep,
1081                 _ => " ",
1082             };
1083
1084             result.push_str(&format!(
1085                 "{}else{}",
1086                 between_kwd_else_block_comment
1087                     .as_ref()
1088                     .map_or(between_sep, |s| &**s),
1089                 after_else_comment.as_ref().map_or(after_sep, |s| &**s),
1090             ));
1091             result.push_str(&rewrite?);
1092         }
1093
1094         Some(result)
1095     }
1096 }
1097
1098 fn rewrite_label(opt_label: Option<ast::Label>) -> Cow<'static, str> {
1099     match opt_label {
1100         Some(label) => Cow::from(format!("{}: ", label.ident)),
1101         None => Cow::from(""),
1102     }
1103 }
1104
1105 fn extract_comment(span: Span, context: &RewriteContext, shape: Shape) -> Option<String> {
1106     match rewrite_missing_comment(span, shape, context) {
1107         Some(ref comment) if !comment.is_empty() => Some(format!(
1108             "{indent}{}{indent}",
1109             comment,
1110             indent = shape.indent.to_string_with_newline(context.config)
1111         )),
1112         _ => None,
1113     }
1114 }
1115
1116 pub fn block_contains_comment(block: &ast::Block, codemap: &CodeMap) -> bool {
1117     let snippet = codemap.span_to_snippet(block.span).unwrap();
1118     contains_comment(&snippet)
1119 }
1120
1121 // Checks that a block contains no statements, an expression and no comments or
1122 // attributes.
1123 // FIXME: incorrectly returns false when comment is contained completely within
1124 // the expression.
1125 pub fn is_simple_block(
1126     block: &ast::Block,
1127     attrs: Option<&[ast::Attribute]>,
1128     codemap: &CodeMap,
1129 ) -> bool {
1130     (block.stmts.len() == 1
1131         && stmt_is_expr(&block.stmts[0])
1132         && !block_contains_comment(block, codemap)
1133         && attrs.map_or(true, |a| a.is_empty()))
1134 }
1135
1136 /// Checks whether a block contains at most one statement or expression, and no
1137 /// comments or attributes.
1138 pub fn is_simple_block_stmt(
1139     block: &ast::Block,
1140     attrs: Option<&[ast::Attribute]>,
1141     codemap: &CodeMap,
1142 ) -> bool {
1143     block.stmts.len() <= 1
1144         && !block_contains_comment(block, codemap)
1145         && attrs.map_or(true, |a| a.is_empty())
1146 }
1147
1148 /// Checks whether a block contains no statements, expressions, comments, or
1149 /// inner attributes.
1150 pub fn is_empty_block(
1151     block: &ast::Block,
1152     attrs: Option<&[ast::Attribute]>,
1153     codemap: &CodeMap,
1154 ) -> bool {
1155     block.stmts.is_empty()
1156         && !block_contains_comment(block, codemap)
1157         && attrs.map_or(true, |a| inner_attributes(a).is_empty())
1158 }
1159
1160 pub fn stmt_is_expr(stmt: &ast::Stmt) -> bool {
1161     match stmt.node {
1162         ast::StmtKind::Expr(..) => true,
1163         _ => false,
1164     }
1165 }
1166
1167 pub fn is_unsafe_block(block: &ast::Block) -> bool {
1168     if let ast::BlockCheckMode::Unsafe(..) = block.rules {
1169         true
1170     } else {
1171         false
1172     }
1173 }
1174
1175 pub fn rewrite_multiple_patterns(
1176     context: &RewriteContext,
1177     pats: &[&ast::Pat],
1178     shape: Shape,
1179 ) -> Option<String> {
1180     let pat_strs = pats
1181         .iter()
1182         .map(|p| p.rewrite(context, shape))
1183         .collect::<Option<Vec<_>>>()?;
1184
1185     let use_mixed_layout = pats
1186         .iter()
1187         .zip(pat_strs.iter())
1188         .all(|(pat, pat_str)| is_short_pattern(pat, pat_str));
1189     let items: Vec<_> = pat_strs.into_iter().map(ListItem::from_str).collect();
1190     let tactic = if use_mixed_layout {
1191         DefinitiveListTactic::Mixed
1192     } else {
1193         definitive_tactic(
1194             &items,
1195             ListTactic::HorizontalVertical,
1196             Separator::VerticalBar,
1197             shape.width,
1198         )
1199     };
1200     let fmt = ListFormatting {
1201         tactic,
1202         separator: " |",
1203         trailing_separator: SeparatorTactic::Never,
1204         separator_place: context.config.binop_separator(),
1205         shape,
1206         ends_with_newline: false,
1207         preserve_newline: false,
1208         nested: false,
1209         config: context.config,
1210     };
1211     write_list(&items, &fmt)
1212 }
1213
1214 pub fn rewrite_literal(context: &RewriteContext, l: &ast::Lit, shape: Shape) -> Option<String> {
1215     match l.node {
1216         ast::LitKind::Str(_, ast::StrStyle::Cooked) => rewrite_string_lit(context, l.span, shape),
1217         _ => wrap_str(
1218             context.snippet(l.span).to_owned(),
1219             context.config.max_width(),
1220             shape,
1221         ),
1222     }
1223 }
1224
1225 fn rewrite_string_lit(context: &RewriteContext, span: Span, shape: Shape) -> Option<String> {
1226     let string_lit = context.snippet(span);
1227
1228     if !context.config.format_strings() {
1229         if string_lit
1230             .lines()
1231             .rev()
1232             .skip(1)
1233             .all(|line| line.ends_with('\\'))
1234         {
1235             let new_indent = shape.visual_indent(1).indent;
1236             let indented_string_lit = String::from(
1237                 string_lit
1238                     .lines()
1239                     .map(|line| {
1240                         format!(
1241                             "{}{}",
1242                             new_indent.to_string(context.config),
1243                             line.trim_left()
1244                         )
1245                     }).collect::<Vec<_>>()
1246                     .join("\n")
1247                     .trim_left(),
1248             );
1249             return wrap_str(indented_string_lit, context.config.max_width(), shape);
1250         } else {
1251             return wrap_str(string_lit.to_owned(), context.config.max_width(), shape);
1252         }
1253     }
1254
1255     // Remove the quote characters.
1256     let str_lit = &string_lit[1..string_lit.len() - 1];
1257
1258     rewrite_string(
1259         str_lit,
1260         &StringFormat::new(shape.visual_indent(0), context.config),
1261     )
1262 }
1263
1264 /// In case special-case style is required, returns an offset from which we start horizontal layout.
1265 pub fn maybe_get_args_offset<T: ToExpr>(callee_str: &str, args: &[&T]) -> Option<(bool, usize)> {
1266     if let Some(&(_, num_args_before)) = SPECIAL_MACRO_WHITELIST
1267         .iter()
1268         .find(|&&(s, _)| s == callee_str)
1269     {
1270         let all_simple = args.len() > num_args_before && is_every_expr_simple(args);
1271
1272         Some((all_simple, num_args_before))
1273     } else {
1274         None
1275     }
1276 }
1277
1278 /// A list of `format!`-like macros, that take a long format string and a list of arguments to
1279 /// format.
1280 ///
1281 /// Organized as a list of `(&str, usize)` tuples, giving the name of the macro and the number of
1282 /// arguments before the format string (none for `format!("format", ...)`, one for `assert!(result,
1283 /// "format", ...)`, two for `assert_eq!(left, right, "format", ...)`).
1284 const SPECIAL_MACRO_WHITELIST: &[(&str, usize)] = &[
1285     // format! like macros
1286     // From the Rust Standard Library.
1287     ("eprint!", 0),
1288     ("eprintln!", 0),
1289     ("format!", 0),
1290     ("format_args!", 0),
1291     ("print!", 0),
1292     ("println!", 0),
1293     ("panic!", 0),
1294     ("unreachable!", 0),
1295     // From the `log` crate.
1296     ("debug!", 0),
1297     ("error!", 0),
1298     ("info!", 0),
1299     ("warn!", 0),
1300     // write! like macros
1301     ("assert!", 1),
1302     ("debug_assert!", 1),
1303     ("write!", 1),
1304     ("writeln!", 1),
1305     // assert_eq! like macros
1306     ("assert_eq!", 2),
1307     ("assert_ne!", 2),
1308     ("debug_assert_eq!", 2),
1309     ("debug_assert_ne!", 2),
1310 ];
1311
1312 fn choose_separator_tactic(context: &RewriteContext, span: Span) -> Option<SeparatorTactic> {
1313     if context.inside_macro() {
1314         if span_ends_with_comma(context, span) {
1315             Some(SeparatorTactic::Always)
1316         } else {
1317             Some(SeparatorTactic::Never)
1318         }
1319     } else {
1320         None
1321     }
1322 }
1323
1324 pub fn rewrite_call(
1325     context: &RewriteContext,
1326     callee: &str,
1327     args: &[ptr::P<ast::Expr>],
1328     span: Span,
1329     shape: Shape,
1330 ) -> Option<String> {
1331     overflow::rewrite_with_parens(
1332         context,
1333         callee,
1334         &ptr_vec_to_ref_vec(args),
1335         shape,
1336         span,
1337         context.config.width_heuristics().fn_call_width,
1338         choose_separator_tactic(context, span),
1339     )
1340 }
1341
1342 fn is_simple_expr(expr: &ast::Expr) -> bool {
1343     match expr.node {
1344         ast::ExprKind::Lit(..) => true,
1345         ast::ExprKind::Path(ref qself, ref path) => qself.is_none() && path.segments.len() <= 1,
1346         ast::ExprKind::AddrOf(_, ref expr)
1347         | ast::ExprKind::Box(ref expr)
1348         | ast::ExprKind::Cast(ref expr, _)
1349         | ast::ExprKind::Field(ref expr, _)
1350         | ast::ExprKind::Try(ref expr)
1351         | ast::ExprKind::Unary(_, ref expr) => is_simple_expr(expr),
1352         ast::ExprKind::Index(ref lhs, ref rhs) => is_simple_expr(lhs) && is_simple_expr(rhs),
1353         ast::ExprKind::Repeat(ref lhs, ref rhs) => {
1354             is_simple_expr(lhs) && is_simple_expr(&*rhs.value)
1355         }
1356         _ => false,
1357     }
1358 }
1359
1360 pub fn is_every_expr_simple<T: ToExpr>(lists: &[&T]) -> bool {
1361     lists
1362         .iter()
1363         .all(|arg| arg.to_expr().map_or(false, is_simple_expr))
1364 }
1365
1366 pub fn can_be_overflowed_expr(context: &RewriteContext, expr: &ast::Expr, args_len: usize) -> bool {
1367     match expr.node {
1368         ast::ExprKind::Match(..) => {
1369             (context.use_block_indent() && args_len == 1)
1370                 || (context.config.indent_style() == IndentStyle::Visual && args_len > 1)
1371         }
1372         ast::ExprKind::If(..)
1373         | ast::ExprKind::IfLet(..)
1374         | ast::ExprKind::ForLoop(..)
1375         | ast::ExprKind::Loop(..)
1376         | ast::ExprKind::While(..)
1377         | ast::ExprKind::WhileLet(..) => {
1378             context.config.combine_control_expr() && context.use_block_indent() && args_len == 1
1379         }
1380         ast::ExprKind::Block(..) | ast::ExprKind::Closure(..) => {
1381             context.use_block_indent()
1382                 || context.config.indent_style() == IndentStyle::Visual && args_len > 1
1383         }
1384         ast::ExprKind::Array(..)
1385         | ast::ExprKind::Call(..)
1386         | ast::ExprKind::Mac(..)
1387         | ast::ExprKind::MethodCall(..)
1388         | ast::ExprKind::Struct(..)
1389         | ast::ExprKind::Tup(..) => context.use_block_indent() && args_len == 1,
1390         ast::ExprKind::AddrOf(_, ref expr)
1391         | ast::ExprKind::Box(ref expr)
1392         | ast::ExprKind::Try(ref expr)
1393         | ast::ExprKind::Unary(_, ref expr)
1394         | ast::ExprKind::Cast(ref expr, _) => can_be_overflowed_expr(context, expr, args_len),
1395         _ => false,
1396     }
1397 }
1398
1399 pub fn is_nested_call(expr: &ast::Expr) -> bool {
1400     match expr.node {
1401         ast::ExprKind::Call(..) | ast::ExprKind::Mac(..) => true,
1402         ast::ExprKind::AddrOf(_, ref expr)
1403         | ast::ExprKind::Box(ref expr)
1404         | ast::ExprKind::Try(ref expr)
1405         | ast::ExprKind::Unary(_, ref expr)
1406         | ast::ExprKind::Cast(ref expr, _) => is_nested_call(expr),
1407         _ => false,
1408     }
1409 }
1410
1411 /// Return true if a function call or a method call represented by the given span ends with a
1412 /// trailing comma. This function is used when rewriting macro, as adding or removing a trailing
1413 /// comma from macro can potentially break the code.
1414 pub fn span_ends_with_comma(context: &RewriteContext, span: Span) -> bool {
1415     let mut result: bool = Default::default();
1416     let mut prev_char: char = Default::default();
1417     let closing_delimiters = &[')', '}', ']'];
1418
1419     for (kind, c) in CharClasses::new(context.snippet(span).chars()) {
1420         match c {
1421             _ if kind.is_comment() || c.is_whitespace() => continue,
1422             c if closing_delimiters.contains(&c) => {
1423                 result &= !closing_delimiters.contains(&prev_char);
1424             }
1425             ',' => result = true,
1426             _ => result = false,
1427         }
1428         prev_char = c;
1429     }
1430
1431     result
1432 }
1433
1434 fn rewrite_paren(
1435     context: &RewriteContext,
1436     mut subexpr: &ast::Expr,
1437     shape: Shape,
1438     mut span: Span,
1439 ) -> Option<String> {
1440     debug!("rewrite_paren, shape: {:?}", shape);
1441
1442     // Extract comments within parens.
1443     let mut pre_comment;
1444     let mut post_comment;
1445     let remove_nested_parens = context.config.remove_nested_parens();
1446     loop {
1447         // 1 = "(" or ")"
1448         let pre_span = mk_sp(span.lo() + BytePos(1), subexpr.span.lo());
1449         let post_span = mk_sp(subexpr.span.hi(), span.hi() - BytePos(1));
1450         pre_comment = rewrite_missing_comment(pre_span, shape, context)?;
1451         post_comment = rewrite_missing_comment(post_span, shape, context)?;
1452
1453         // Remove nested parens if there are no comments.
1454         if let ast::ExprKind::Paren(ref subsubexpr) = subexpr.node {
1455             if remove_nested_parens && pre_comment.is_empty() && post_comment.is_empty() {
1456                 span = subexpr.span;
1457                 subexpr = subsubexpr;
1458                 continue;
1459             }
1460         }
1461
1462         break;
1463     }
1464
1465     // 1 `(`
1466     let sub_shape = shape.offset_left(1).and_then(|s| s.sub_width(1))?;
1467
1468     let subexpr_str = subexpr.rewrite(context, sub_shape)?;
1469     debug!("rewrite_paren, subexpr_str: `{:?}`", subexpr_str);
1470
1471     // 2 = `()`
1472     if subexpr_str.contains('\n') || first_line_width(&subexpr_str) + 2 <= shape.width {
1473         Some(format!("({}{}{})", pre_comment, &subexpr_str, post_comment))
1474     } else {
1475         None
1476     }
1477 }
1478
1479 fn rewrite_index(
1480     expr: &ast::Expr,
1481     index: &ast::Expr,
1482     context: &RewriteContext,
1483     shape: Shape,
1484 ) -> Option<String> {
1485     let expr_str = expr.rewrite(context, shape)?;
1486
1487     let offset = last_line_width(&expr_str) + 1;
1488     let rhs_overhead = shape.rhs_overhead(context.config);
1489     let index_shape = if expr_str.contains('\n') {
1490         Shape::legacy(context.config.max_width(), shape.indent)
1491             .offset_left(offset)
1492             .and_then(|shape| shape.sub_width(1 + rhs_overhead))
1493     } else {
1494         shape.visual_indent(offset).sub_width(offset + 1)
1495     };
1496     let orig_index_rw = index_shape.and_then(|s| index.rewrite(context, s));
1497
1498     // Return if index fits in a single line.
1499     match orig_index_rw {
1500         Some(ref index_str) if !index_str.contains('\n') => {
1501             return Some(format!("{}[{}]", expr_str, index_str));
1502         }
1503         _ => (),
1504     }
1505
1506     // Try putting index on the next line and see if it fits in a single line.
1507     let indent = shape.indent.block_indent(context.config);
1508     let index_shape = Shape::indented(indent, context.config).offset_left(1)?;
1509     let index_shape = index_shape.sub_width(1 + rhs_overhead)?;
1510     let new_index_rw = index.rewrite(context, index_shape);
1511     match (orig_index_rw, new_index_rw) {
1512         (_, Some(ref new_index_str)) if !new_index_str.contains('\n') => Some(format!(
1513             "{}{}[{}]",
1514             expr_str,
1515             indent.to_string_with_newline(context.config),
1516             new_index_str,
1517         )),
1518         (None, Some(ref new_index_str)) => Some(format!(
1519             "{}{}[{}]",
1520             expr_str,
1521             indent.to_string_with_newline(context.config),
1522             new_index_str,
1523         )),
1524         (Some(ref index_str), _) => Some(format!("{}[{}]", expr_str, index_str)),
1525         _ => None,
1526     }
1527 }
1528
1529 fn struct_lit_can_be_aligned(fields: &[ast::Field], base: &Option<&ast::Expr>) -> bool {
1530     if base.is_some() {
1531         return false;
1532     }
1533
1534     fields.iter().all(|field| !field.is_shorthand)
1535 }
1536
1537 fn rewrite_struct_lit<'a>(
1538     context: &RewriteContext,
1539     path: &ast::Path,
1540     fields: &'a [ast::Field],
1541     base: Option<&'a ast::Expr>,
1542     span: Span,
1543     shape: Shape,
1544 ) -> Option<String> {
1545     debug!("rewrite_struct_lit: shape {:?}", shape);
1546
1547     enum StructLitField<'a> {
1548         Regular(&'a ast::Field),
1549         Base(&'a ast::Expr),
1550     }
1551
1552     // 2 = " {".len()
1553     let path_shape = shape.sub_width(2)?;
1554     let path_str = rewrite_path(context, PathContext::Expr, None, path, path_shape)?;
1555
1556     if fields.is_empty() && base.is_none() {
1557         return Some(format!("{} {{}}", path_str));
1558     }
1559
1560     // Foo { a: Foo } - indent is +3, width is -5.
1561     let (h_shape, v_shape) = struct_lit_shape(shape, context, path_str.len() + 3, 2)?;
1562
1563     let one_line_width = h_shape.map_or(0, |shape| shape.width);
1564     let body_lo = context.snippet_provider.span_after(span, "{");
1565     let fields_str = if struct_lit_can_be_aligned(fields, &base)
1566         && context.config.struct_field_align_threshold() > 0
1567     {
1568         rewrite_with_alignment(
1569             fields,
1570             context,
1571             shape,
1572             mk_sp(body_lo, span.hi()),
1573             one_line_width,
1574         )?
1575     } else {
1576         let field_iter = fields
1577             .into_iter()
1578             .map(StructLitField::Regular)
1579             .chain(base.into_iter().map(StructLitField::Base));
1580
1581         let span_lo = |item: &StructLitField| match *item {
1582             StructLitField::Regular(field) => field.span().lo(),
1583             StructLitField::Base(expr) => {
1584                 let last_field_hi = fields.last().map_or(span.lo(), |field| field.span.hi());
1585                 let snippet = context.snippet(mk_sp(last_field_hi, expr.span.lo()));
1586                 let pos = snippet.find_uncommented("..").unwrap();
1587                 last_field_hi + BytePos(pos as u32)
1588             }
1589         };
1590         let span_hi = |item: &StructLitField| match *item {
1591             StructLitField::Regular(field) => field.span().hi(),
1592             StructLitField::Base(expr) => expr.span.hi(),
1593         };
1594         let rewrite = |item: &StructLitField| match *item {
1595             StructLitField::Regular(field) => {
1596                 // The 1 taken from the v_budget is for the comma.
1597                 rewrite_field(context, field, v_shape.sub_width(1)?, 0)
1598             }
1599             StructLitField::Base(expr) => {
1600                 // 2 = ..
1601                 expr.rewrite(context, v_shape.offset_left(2)?)
1602                     .map(|s| format!("..{}", s))
1603             }
1604         };
1605
1606         let items = itemize_list(
1607             context.snippet_provider,
1608             field_iter,
1609             "}",
1610             ",",
1611             span_lo,
1612             span_hi,
1613             rewrite,
1614             body_lo,
1615             span.hi(),
1616             false,
1617         );
1618         let item_vec = items.collect::<Vec<_>>();
1619
1620         let tactic = struct_lit_tactic(h_shape, context, &item_vec);
1621         let nested_shape = shape_for_tactic(tactic, h_shape, v_shape);
1622
1623         let ends_with_comma = span_ends_with_comma(context, span);
1624         let force_no_trailing_comma = context.inside_macro() && !ends_with_comma;
1625
1626         let fmt = struct_lit_formatting(
1627             nested_shape,
1628             tactic,
1629             context,
1630             force_no_trailing_comma || base.is_some(),
1631         );
1632
1633         write_list(&item_vec, &fmt)?
1634     };
1635
1636     let fields_str = wrap_struct_field(context, &fields_str, shape, v_shape, one_line_width);
1637     Some(format!("{} {{{}}}", path_str, fields_str))
1638
1639     // FIXME if context.config.indent_style() == Visual, but we run out
1640     // of space, we should fall back to BlockIndent.
1641 }
1642
1643 pub fn wrap_struct_field(
1644     context: &RewriteContext,
1645     fields_str: &str,
1646     shape: Shape,
1647     nested_shape: Shape,
1648     one_line_width: usize,
1649 ) -> String {
1650     if context.config.indent_style() == IndentStyle::Block
1651         && (fields_str.contains('\n')
1652             || !context.config.struct_lit_single_line()
1653             || fields_str.len() > one_line_width)
1654     {
1655         format!(
1656             "{}{}{}",
1657             nested_shape.indent.to_string_with_newline(context.config),
1658             fields_str,
1659             shape.indent.to_string_with_newline(context.config)
1660         )
1661     } else {
1662         // One liner or visual indent.
1663         format!(" {} ", fields_str)
1664     }
1665 }
1666
1667 pub fn struct_lit_field_separator(config: &Config) -> &str {
1668     colon_spaces(config.space_before_colon(), config.space_after_colon())
1669 }
1670
1671 pub fn rewrite_field(
1672     context: &RewriteContext,
1673     field: &ast::Field,
1674     shape: Shape,
1675     prefix_max_width: usize,
1676 ) -> Option<String> {
1677     if contains_skip(&field.attrs) {
1678         return Some(context.snippet(field.span()).to_owned());
1679     }
1680     let mut attrs_str = field.attrs.rewrite(context, shape)?;
1681     if !attrs_str.is_empty() {
1682         attrs_str.push_str(&shape.indent.to_string_with_newline(context.config));
1683     };
1684     let name = context.snippet(field.ident.span);
1685     if field.is_shorthand {
1686         Some(attrs_str + &name)
1687     } else {
1688         let mut separator = String::from(struct_lit_field_separator(context.config));
1689         for _ in 0..prefix_max_width.saturating_sub(name.len()) {
1690             separator.push(' ');
1691         }
1692         let overhead = name.len() + separator.len();
1693         let expr_shape = shape.offset_left(overhead)?;
1694         let expr = field.expr.rewrite(context, expr_shape);
1695
1696         match expr {
1697             Some(ref e) if e.as_str() == name && context.config.use_field_init_shorthand() => {
1698                 Some(attrs_str + &name)
1699             }
1700             Some(e) => Some(format!("{}{}{}{}", attrs_str, name, separator, e)),
1701             None => {
1702                 let expr_offset = shape.indent.block_indent(context.config);
1703                 let expr = field
1704                     .expr
1705                     .rewrite(context, Shape::indented(expr_offset, context.config));
1706                 expr.map(|s| {
1707                     format!(
1708                         "{}{}:\n{}{}",
1709                         attrs_str,
1710                         name,
1711                         expr_offset.to_string(context.config),
1712                         s
1713                     )
1714                 })
1715             }
1716         }
1717     }
1718 }
1719
1720 fn rewrite_tuple_in_visual_indent_style<'a, T>(
1721     context: &RewriteContext,
1722     items: &[&T],
1723     span: Span,
1724     shape: Shape,
1725 ) -> Option<String>
1726 where
1727     T: Rewrite + Spanned + ToExpr + 'a,
1728 {
1729     let mut items = items.iter();
1730     // In case of length 1, need a trailing comma
1731     debug!("rewrite_tuple_in_visual_indent_style {:?}", shape);
1732     if items.len() == 1 {
1733         // 3 = "(" + ",)"
1734         let nested_shape = shape.sub_width(3)?.visual_indent(1);
1735         return items
1736             .next()
1737             .unwrap()
1738             .rewrite(context, nested_shape)
1739             .map(|s| format!("({},)", s));
1740     }
1741
1742     let list_lo = context.snippet_provider.span_after(span, "(");
1743     let nested_shape = shape.sub_width(2)?.visual_indent(1);
1744     let items = itemize_list(
1745         context.snippet_provider,
1746         items,
1747         ")",
1748         ",",
1749         |item| item.span().lo(),
1750         |item| item.span().hi(),
1751         |item| item.rewrite(context, nested_shape),
1752         list_lo,
1753         span.hi() - BytePos(1),
1754         false,
1755     );
1756     let item_vec: Vec<_> = items.collect();
1757     let tactic = definitive_tactic(
1758         &item_vec,
1759         ListTactic::HorizontalVertical,
1760         Separator::Comma,
1761         nested_shape.width,
1762     );
1763     let fmt = ListFormatting {
1764         tactic,
1765         separator: ",",
1766         trailing_separator: SeparatorTactic::Never,
1767         separator_place: SeparatorPlace::Back,
1768         shape,
1769         ends_with_newline: false,
1770         preserve_newline: false,
1771         nested: false,
1772         config: context.config,
1773     };
1774     let list_str = write_list(&item_vec, &fmt)?;
1775
1776     Some(format!("({})", list_str))
1777 }
1778
1779 pub fn rewrite_tuple<'a, T>(
1780     context: &RewriteContext,
1781     items: &[&T],
1782     span: Span,
1783     shape: Shape,
1784 ) -> Option<String>
1785 where
1786     T: Rewrite + Spanned + ToExpr + 'a,
1787 {
1788     debug!("rewrite_tuple {:?}", shape);
1789     if context.use_block_indent() {
1790         // We use the same rule as function calls for rewriting tuples.
1791         let force_tactic = if context.inside_macro() {
1792             if span_ends_with_comma(context, span) {
1793                 Some(SeparatorTactic::Always)
1794             } else {
1795                 Some(SeparatorTactic::Never)
1796             }
1797         } else if items.len() == 1 {
1798             Some(SeparatorTactic::Always)
1799         } else {
1800             None
1801         };
1802         overflow::rewrite_with_parens(
1803             context,
1804             "",
1805             items,
1806             shape,
1807             span,
1808             context.config.width_heuristics().fn_call_width,
1809             force_tactic,
1810         )
1811     } else {
1812         rewrite_tuple_in_visual_indent_style(context, items, span, shape)
1813     }
1814 }
1815
1816 pub fn rewrite_unary_prefix<R: Rewrite>(
1817     context: &RewriteContext,
1818     prefix: &str,
1819     rewrite: &R,
1820     shape: Shape,
1821 ) -> Option<String> {
1822     rewrite
1823         .rewrite(context, shape.offset_left(prefix.len())?)
1824         .map(|r| format!("{}{}", prefix, r))
1825 }
1826
1827 // FIXME: this is probably not correct for multi-line Rewrites. we should
1828 // subtract suffix.len() from the last line budget, not the first!
1829 pub fn rewrite_unary_suffix<R: Rewrite>(
1830     context: &RewriteContext,
1831     suffix: &str,
1832     rewrite: &R,
1833     shape: Shape,
1834 ) -> Option<String> {
1835     rewrite
1836         .rewrite(context, shape.sub_width(suffix.len())?)
1837         .map(|mut r| {
1838             r.push_str(suffix);
1839             r
1840         })
1841 }
1842
1843 fn rewrite_unary_op(
1844     context: &RewriteContext,
1845     op: &ast::UnOp,
1846     expr: &ast::Expr,
1847     shape: Shape,
1848 ) -> Option<String> {
1849     // For some reason, an UnOp is not spanned like BinOp!
1850     let operator_str = match *op {
1851         ast::UnOp::Deref => "*",
1852         ast::UnOp::Not => "!",
1853         ast::UnOp::Neg => "-",
1854     };
1855     rewrite_unary_prefix(context, operator_str, expr, shape)
1856 }
1857
1858 fn rewrite_assignment(
1859     context: &RewriteContext,
1860     lhs: &ast::Expr,
1861     rhs: &ast::Expr,
1862     op: Option<&ast::BinOp>,
1863     shape: Shape,
1864 ) -> Option<String> {
1865     let operator_str = match op {
1866         Some(op) => context.snippet(op.span),
1867         None => "=",
1868     };
1869
1870     // 1 = space between lhs and operator.
1871     let lhs_shape = shape.sub_width(operator_str.len() + 1)?;
1872     let lhs_str = format!("{} {}", lhs.rewrite(context, lhs_shape)?, operator_str);
1873
1874     rewrite_assign_rhs(context, lhs_str, rhs, shape)
1875 }
1876
1877 /// Controls where to put the rhs.
1878 #[derive(Debug, Copy, Clone, PartialEq, Eq)]
1879 pub enum RhsTactics {
1880     /// Use heuristics.
1881     Default,
1882     /// Put the rhs on the next line if it uses multiple line, without extra indentation.
1883     ForceNextLineWithoutIndent,
1884 }
1885
1886 // The left hand side must contain everything up to, and including, the
1887 // assignment operator.
1888 pub fn rewrite_assign_rhs<S: Into<String>, R: Rewrite>(
1889     context: &RewriteContext,
1890     lhs: S,
1891     ex: &R,
1892     shape: Shape,
1893 ) -> Option<String> {
1894     rewrite_assign_rhs_with(context, lhs, ex, shape, RhsTactics::Default)
1895 }
1896
1897 pub fn rewrite_assign_rhs_with<S: Into<String>, R: Rewrite>(
1898     context: &RewriteContext,
1899     lhs: S,
1900     ex: &R,
1901     shape: Shape,
1902     rhs_tactics: RhsTactics,
1903 ) -> Option<String> {
1904     let lhs = lhs.into();
1905     let last_line_width = last_line_width(&lhs).saturating_sub(if lhs.contains('\n') {
1906         shape.indent.width()
1907     } else {
1908         0
1909     });
1910     // 1 = space between operator and rhs.
1911     let orig_shape = shape.offset_left(last_line_width + 1).unwrap_or(Shape {
1912         width: 0,
1913         offset: shape.offset + last_line_width + 1,
1914         ..shape
1915     });
1916     let rhs = choose_rhs(
1917         context,
1918         ex,
1919         orig_shape,
1920         ex.rewrite(context, orig_shape),
1921         rhs_tactics,
1922     )?;
1923     Some(lhs + &rhs)
1924 }
1925
1926 fn choose_rhs<R: Rewrite>(
1927     context: &RewriteContext,
1928     expr: &R,
1929     shape: Shape,
1930     orig_rhs: Option<String>,
1931     rhs_tactics: RhsTactics,
1932 ) -> Option<String> {
1933     match orig_rhs {
1934         Some(ref new_str) if !new_str.contains('\n') && new_str.len() <= shape.width => {
1935             Some(format!(" {}", new_str))
1936         }
1937         _ => {
1938             // Expression did not fit on the same line as the identifier.
1939             // Try splitting the line and see if that works better.
1940             let new_shape = shape_from_rhs_tactic(context, shape, rhs_tactics)?;
1941             let new_rhs = expr.rewrite(context, new_shape);
1942             let new_indent_str = &shape
1943                 .indent
1944                 .block_indent(context.config)
1945                 .to_string_with_newline(context.config);
1946
1947             match (orig_rhs, new_rhs) {
1948                 (Some(ref orig_rhs), Some(ref new_rhs))
1949                     if wrap_str(new_rhs.clone(), context.config.max_width(), new_shape)
1950                         .is_none() =>
1951                 {
1952                     Some(format!(" {}", orig_rhs))
1953                 }
1954                 (Some(ref orig_rhs), Some(ref new_rhs))
1955                     if prefer_next_line(orig_rhs, new_rhs, rhs_tactics) =>
1956                 {
1957                     Some(format!("{}{}", new_indent_str, new_rhs))
1958                 }
1959                 (None, Some(ref new_rhs)) => Some(format!("{}{}", new_indent_str, new_rhs)),
1960                 (None, None) => None,
1961                 (Some(orig_rhs), _) => Some(format!(" {}", orig_rhs)),
1962             }
1963         }
1964     }
1965 }
1966
1967 fn shape_from_rhs_tactic(
1968     context: &RewriteContext,
1969     shape: Shape,
1970     rhs_tactic: RhsTactics,
1971 ) -> Option<Shape> {
1972     match rhs_tactic {
1973         RhsTactics::ForceNextLineWithoutIndent => Some(shape.with_max_width(context.config)),
1974         RhsTactics::Default => {
1975             Shape::indented(shape.indent.block_indent(context.config), context.config)
1976                 .sub_width(shape.rhs_overhead(context.config))
1977         }
1978     }
1979 }
1980
1981 pub fn prefer_next_line(orig_rhs: &str, next_line_rhs: &str, rhs_tactics: RhsTactics) -> bool {
1982     rhs_tactics == RhsTactics::ForceNextLineWithoutIndent
1983         || !next_line_rhs.contains('\n')
1984         || count_newlines(orig_rhs) > count_newlines(next_line_rhs) + 1
1985         || first_line_ends_with(orig_rhs, '(') && !first_line_ends_with(next_line_rhs, '(')
1986         || first_line_ends_with(orig_rhs, '{') && !first_line_ends_with(next_line_rhs, '{')
1987         || first_line_ends_with(orig_rhs, '[') && !first_line_ends_with(next_line_rhs, '[')
1988 }
1989
1990 fn rewrite_expr_addrof(
1991     context: &RewriteContext,
1992     mutability: ast::Mutability,
1993     expr: &ast::Expr,
1994     shape: Shape,
1995 ) -> Option<String> {
1996     let operator_str = match mutability {
1997         ast::Mutability::Immutable => "&",
1998         ast::Mutability::Mutable => "&mut ",
1999     };
2000     rewrite_unary_prefix(context, operator_str, expr, shape)
2001 }
2002
2003 pub trait ToExpr {
2004     fn to_expr(&self) -> Option<&ast::Expr>;
2005     fn can_be_overflowed(&self, context: &RewriteContext, len: usize) -> bool;
2006 }
2007
2008 impl ToExpr for ast::Expr {
2009     fn to_expr(&self) -> Option<&ast::Expr> {
2010         Some(self)
2011     }
2012
2013     fn can_be_overflowed(&self, context: &RewriteContext, len: usize) -> bool {
2014         can_be_overflowed_expr(context, self, len)
2015     }
2016 }
2017
2018 impl ToExpr for ast::Ty {
2019     fn to_expr(&self) -> Option<&ast::Expr> {
2020         None
2021     }
2022
2023     fn can_be_overflowed(&self, context: &RewriteContext, len: usize) -> bool {
2024         can_be_overflowed_type(context, self, len)
2025     }
2026 }
2027
2028 impl<'a> ToExpr for TuplePatField<'a> {
2029     fn to_expr(&self) -> Option<&ast::Expr> {
2030         None
2031     }
2032
2033     fn can_be_overflowed(&self, context: &RewriteContext, len: usize) -> bool {
2034         can_be_overflowed_pat(context, self, len)
2035     }
2036 }
2037
2038 impl<'a> ToExpr for ast::StructField {
2039     fn to_expr(&self) -> Option<&ast::Expr> {
2040         None
2041     }
2042
2043     fn can_be_overflowed(&self, _: &RewriteContext, _: usize) -> bool {
2044         false
2045     }
2046 }
2047
2048 impl<'a> ToExpr for MacroArg {
2049     fn to_expr(&self) -> Option<&ast::Expr> {
2050         match *self {
2051             MacroArg::Expr(ref expr) => Some(expr),
2052             _ => None,
2053         }
2054     }
2055
2056     fn can_be_overflowed(&self, context: &RewriteContext, len: usize) -> bool {
2057         match *self {
2058             MacroArg::Expr(ref expr) => can_be_overflowed_expr(context, expr, len),
2059             MacroArg::Ty(ref ty) => can_be_overflowed_type(context, ty, len),
2060             MacroArg::Pat(..) => false,
2061             MacroArg::Item(..) => len == 1,
2062         }
2063     }
2064 }
2065
2066 impl ToExpr for ast::GenericParam {
2067     fn to_expr(&self) -> Option<&ast::Expr> {
2068         None
2069     }
2070
2071     fn can_be_overflowed(&self, _: &RewriteContext, _: usize) -> bool {
2072         false
2073     }
2074 }
2075
2076 pub fn is_method_call(expr: &ast::Expr) -> bool {
2077     match expr.node {
2078         ast::ExprKind::MethodCall(..) => true,
2079         ast::ExprKind::AddrOf(_, ref expr)
2080         | ast::ExprKind::Box(ref expr)
2081         | ast::ExprKind::Cast(ref expr, _)
2082         | ast::ExprKind::Try(ref expr)
2083         | ast::ExprKind::Unary(_, ref expr) => is_method_call(expr),
2084         _ => false,
2085     }
2086 }