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::parse::token::DelimToken;
  16 use syntax::source_map::{BytePos, SourceMap, Span};
  17 use syntax::{ast, ptr};
  18
  19 use chains::rewrite_chain;
  20 use closures;
  21 use comment::{
  22     combine_strs_with_missing_comments, contains_comment, recover_comment_removed, rewrite_comment,
  23     rewrite_missing_comment, CharClasses, FindUncommented,
  24 };
  25 use config::{Config, ControlBraceStyle, IndentStyle};
  26 use lists::{
  27     definitive_tactic, itemize_list, shape_for_tactic, struct_lit_formatting, struct_lit_shape,
  28     struct_lit_tactic, write_list, ListFormatting, ListItem, Separator,
  29 };
  30 use macros::{rewrite_macro, MacroPosition};
  31 use matches::rewrite_match;
  32 use overflow::{self, IntoOverflowableItem, OverflowableItem};
  33 use pairs::{rewrite_all_pairs, rewrite_pair, PairParts};
  34 use patterns::is_short_pattern;
  35 use rewrite::{Rewrite, RewriteContext};
  36 use shape::{Indent, Shape};
  37 use source_map::{LineRangeUtils, SpanUtils};
  38 use spanned::Spanned;
  39 use string::{rewrite_string, StringFormat};
  40 use types::{rewrite_path, PathContext};
  41 use utils::{
  42     colon_spaces, contains_skip, count_newlines, first_line_ends_with, inner_attributes,
  43     last_line_extendable, last_line_width, mk_sp, outer_attributes, ptr_vec_to_ref_vec,
  44     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             expr_vec.iter(),
  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(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, items.iter(), expr.span, shape, items.len() == 1)
 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) => {
 183             if let Some(ref expr) = *opt_expr {
 184                 rewrite_unary_prefix(context, "yield ", &**expr, shape)
 185             } else {
 186                 Some("yield".to_string())
 187             }
 188         }
 189         ast::ExprKind::Closure(capture, asyncness, movability, ref fn_decl, ref body, _) => {
 190             closures::rewrite_closure(
 191                 capture, asyncness, movability, fn_decl, body, expr.span, context, shape,
 192             )
 193         }
 194         ast::ExprKind::Try(..) | ast::ExprKind::Field(..) | ast::ExprKind::MethodCall(..) => {
 195             rewrite_chain(expr, context, shape)
 196         }
 197         ast::ExprKind::Mac(ref mac) => {
 198             rewrite_macro(mac, None, context, shape, MacroPosition::Expression).or_else(|| {
 199                 wrap_str(
 200                     context.snippet(expr.span).to_owned(),
 201                     context.config.max_width(),
 202                     shape,
 203                 )
 204             })
 205         }
 206         ast::ExprKind::Ret(None) => Some("return".to_owned()),
 207         ast::ExprKind::Ret(Some(ref expr)) => {
 208             rewrite_unary_prefix(context, "return ", &**expr, shape)
 209         }
 210         ast::ExprKind::Box(ref expr) => rewrite_unary_prefix(context, "box ", &**expr, shape),
 211         ast::ExprKind::AddrOf(mutability, ref expr) => {
 212             rewrite_expr_addrof(context, mutability, expr, shape)
 213         }
 214         ast::ExprKind::Cast(ref expr, ref ty) => rewrite_pair(
 215             &**expr,
 216             &**ty,
 217             PairParts::infix(" as "),
 218             context,
 219             shape,
 220             SeparatorPlace::Front,
 221         ),
 222         ast::ExprKind::Type(ref expr, ref ty) => rewrite_pair(
 223             &**expr,
 224             &**ty,
 225             PairParts::infix(": "),
 226             context,
 227             shape,
 228             SeparatorPlace::Back,
 229         ),
 230         ast::ExprKind::Index(ref expr, ref index) => {
 231             rewrite_index(&**expr, &**index, context, shape)
 232         }
 233         ast::ExprKind::Repeat(ref expr, ref repeats) => rewrite_pair(
 234             &**expr,
 235             &*repeats.value,
 236             PairParts::new("[", "; ", "]"),
 237             context,
 238             shape,
 239             SeparatorPlace::Back,
 240         ),
 241         ast::ExprKind::Range(ref lhs, ref rhs, limits) => {
 242             let delim = match limits {
 243                 ast::RangeLimits::HalfOpen => "..",
 244                 ast::RangeLimits::Closed => "..=",
 245             };
 246
 247             fn needs_space_before_range(context: &RewriteContext, lhs: &ast::Expr) -> bool {
 248                 match lhs.node {
 249                     ast::ExprKind::Lit(ref lit) => match lit.node {
 250                         ast::LitKind::FloatUnsuffixed(..) => {
 251                             context.snippet(lit.span).ends_with('.')
 252                         }
 253                         _ => false,
 254                     },
 255                     _ => false,
 256                 }
 257             }
 258
 259             fn needs_space_after_range(rhs: &ast::Expr) -> bool {
 260                 match rhs.node {
 261                     // Don't format `.. ..` into `....`, which is invalid.
 262                     //
 263                     // This check is unnecessary for `lhs`, because a range
 264                     // starting from another range needs parentheses as `(x ..) ..`
 265                     // (`x .. ..` is a range from `x` to `..`).
 266                     ast::ExprKind::Range(None, _, _) => true,
 267                     _ => false,
 268                 }
 269             }
 270
 271             let default_sp_delim = |lhs: Option<&ast::Expr>, rhs: Option<&ast::Expr>| {
 272                 let space_if = |b: bool| if b { " " } else { "" };
 273
 274                 format!(
 275                     "{}{}{}",
 276                     lhs.map_or("", |lhs| space_if(needs_space_before_range(context, lhs))),
 277                     delim,
 278                     rhs.map_or("", |rhs| space_if(needs_space_after_range(rhs))),
 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::TryBlock(ref block) => {
 321             if let rw @ Some(_) =
 322                 rewrite_single_line_block(context, "try ", block, Some(&expr.attrs), None, shape)
 323             {
 324                 rw
 325             } else {
 326                 // 9 = `try `
 327                 let budget = shape.width.saturating_sub(9);
 328                 Some(format!(
 329                     "{}{}",
 330                     "try ",
 331                     rewrite_block(
 332                         block,
 333                         Some(&expr.attrs),
 334                         None,
 335                         context,
 336                         Shape::legacy(budget, shape.indent)
 337                     )?
 338                 ))
 339             }
 340         }
 341         ast::ExprKind::ObsoleteInPlace(ref lhs, ref rhs) => lhs
 342             .rewrite(context, shape)
 343             .map(|s| s + " <-")
 344             .and_then(|lhs| rewrite_assign_rhs(context, lhs, &**rhs, shape)),
 345         ast::ExprKind::Async(capture_by, _node_id, ref block) => {
 346             let mover = if capture_by == ast::CaptureBy::Value {
 347                 "move "
 348             } else {
 349                 ""
 350             };
 351             if let rw @ Some(_) = rewrite_single_line_block(
 352                 context,
 353                 format!("{}{}", "async ", mover).as_str(),
 354                 block,
 355                 Some(&expr.attrs),
 356                 None,
 357                 shape,
 358             ) {
 359                 rw
 360             } else {
 361                 // 6 = `async `
 362                 let budget = shape.width.saturating_sub(6);
 363                 Some(format!(
 364                     "{}{}{}",
 365                     "async ",
 366                     mover,
 367                     rewrite_block(
 368                         block,
 369                         Some(&expr.attrs),
 370                         None,
 371                         context,
 372                         Shape::legacy(budget, shape.indent)
 373                     )?
 374                 ))
 375             }
 376         }
 377     };
 378
 379     expr_rw
 380         .and_then(|expr_str| recover_comment_removed(expr_str, expr.span, context))
 381         .and_then(|expr_str| {
 382             let attrs = outer_attributes(&expr.attrs);
 383             let attrs_str = attrs.rewrite(context, shape)?;
 384             let span = mk_sp(
 385                 attrs.last().map_or(expr.span.lo(), |attr| attr.span.hi()),
 386                 expr.span.lo(),
 387             );
 388             combine_strs_with_missing_comments(context, &attrs_str, &expr_str, span, shape, false)
 389         })
 390 }
 391
 392 pub fn rewrite_array<'a, T: 'a + IntoOverflowableItem<'a>>(
 393     name: &'a str,
 394     exprs: impl Iterator<Item = &'a T>,
 395     span: Span,
 396     context: &'a RewriteContext,
 397     shape: Shape,
 398     force_separator_tactic: Option<SeparatorTactic>,
 399     delim_token: Option<DelimToken>,
 400 ) -> Option<String> {
 401     overflow::rewrite_with_square_brackets(
 402         context,
 403         name,
 404         exprs,
 405         shape,
 406         span,
 407         force_separator_tactic,
 408         delim_token,
 409     )
 410 }
 411
 412 fn rewrite_empty_block(
 413     context: &RewriteContext,
 414     block: &ast::Block,
 415     attrs: Option<&[ast::Attribute]>,
 416     label: Option<ast::Label>,
 417     prefix: &str,
 418     shape: Shape,
 419 ) -> Option<String> {
 420     if !block.stmts.is_empty() {
 421         return None;
 422     }
 423
 424     let label_str = rewrite_label(label);
 425     if attrs.map_or(false, |a| !inner_attributes(a).is_empty()) {
 426         return None;
 427     }
 428
 429     if !block_contains_comment(block, context.source_map) && shape.width >= 2 {
 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.source_map) {
 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, label) {
 515         (ast::BlockCheckMode::Unsafe(..), _) | (ast::BlockCheckMode::Default, Some(_)) => {
 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, None) => 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.source_map)
 773                 || !is_simple_block(else_node, None, context.source_map)
 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 /// Returns true if the last line of pat_str has leading whitespace and it is wider than the
 806 /// shape's indent.
 807 fn last_line_offsetted(start_column: usize, pat_str: &str) -> bool {
 808     let mut leading_whitespaces = 0;
 809     for c in pat_str.chars().rev() {
 810         match c {
 811             '\n' => break,
 812             _ if c.is_whitespace() => leading_whitespaces += 1,
 813             _ => leading_whitespaces = 0,
 814         }
 815     }
 816     leading_whitespaces > start_column
 817 }
 818
 819 impl<'a> ControlFlow<'a> {
 820     fn rewrite_pat_expr(
 821         &self,
 822         context: &RewriteContext,
 823         expr: &ast::Expr,
 824         shape: Shape,
 825         offset: usize,
 826     ) -> Option<String> {
 827         debug!("rewrite_pat_expr {:?} {:?} {:?}", shape, self.pats, expr);
 828
 829         let cond_shape = shape.offset_left(offset)?;
 830         if !self.pats.is_empty() {
 831             let matcher = if self.matcher.is_empty() {
 832                 self.matcher.to_owned()
 833             } else {
 834                 format!("{} ", self.matcher)
 835             };
 836             let pat_shape = cond_shape
 837                 .offset_left(matcher.len())?
 838                 .sub_width(self.connector.len())?;
 839             let pat_string = rewrite_multiple_patterns(context, &self.pats, pat_shape)?;
 840             let result = format!("{}{}{}", matcher, pat_string, self.connector);
 841             return rewrite_assign_rhs(context, result, expr, cond_shape);
 842         }
 843
 844         let expr_rw = expr.rewrite(context, cond_shape);
 845         // The expression may (partially) fit on the current line.
 846         // We do not allow splitting between `if` and condition.
 847         if self.keyword == "if" || expr_rw.is_some() {
 848             return expr_rw;
 849         }
 850
 851         // The expression won't fit on the current line, jump to next.
 852         let nested_shape = shape
 853             .block_indent(context.config.tab_spaces())
 854             .with_max_width(context.config);
 855         let nested_indent_str = nested_shape.indent.to_string_with_newline(context.config);
 856         expr.rewrite(context, nested_shape)
 857             .map(|expr_rw| format!("{}{}", nested_indent_str, expr_rw))
 858     }
 859
 860     fn rewrite_cond(
 861         &self,
 862         context: &RewriteContext,
 863         shape: Shape,
 864         alt_block_sep: &str,
 865     ) -> Option<(String, usize)> {
 866         // Do not take the rhs overhead from the upper expressions into account
 867         // when rewriting pattern.
 868         let new_width = context.budget(shape.used_width());
 869         let fresh_shape = Shape {
 870             width: new_width,
 871             ..shape
 872         };
 873         let constr_shape = if self.nested_if {
 874             // We are part of an if-elseif-else chain. Our constraints are tightened.
 875             // 7 = "} else " .len()
 876             fresh_shape.offset_left(7)?
 877         } else {
 878             fresh_shape
 879         };
 880
 881         let label_string = rewrite_label(self.label);
 882         // 1 = space after keyword.
 883         let offset = self.keyword.len() + label_string.len() + 1;
 884
 885         let pat_expr_string = match self.cond {
 886             Some(cond) => self.rewrite_pat_expr(context, cond, constr_shape, offset)?,
 887             None => String::new(),
 888         };
 889
 890         let brace_overhead =
 891             if context.config.control_brace_style() != ControlBraceStyle::AlwaysNextLine {
 892                 // 2 = ` {`
 893                 2
 894             } else {
 895                 0
 896             };
 897         let one_line_budget = context
 898             .config
 899             .max_width()
 900             .saturating_sub(constr_shape.used_width() + offset + brace_overhead);
 901         let force_newline_brace = (pat_expr_string.contains('\n')
 902             || pat_expr_string.len() > one_line_budget)
 903             && (!last_line_extendable(&pat_expr_string)
 904                 || last_line_offsetted(shape.used_width(), &pat_expr_string));
 905
 906         // Try to format if-else on single line.
 907         if self.allow_single_line
 908             && context
 909                 .config
 910                 .width_heuristics()
 911                 .single_line_if_else_max_width
 912                 > 0
 913         {
 914             let trial = self.rewrite_single_line(&pat_expr_string, context, shape.width);
 915
 916             if let Some(cond_str) = trial {
 917                 if cond_str.len()
 918                     <= context
 919                         .config
 920                         .width_heuristics()
 921                         .single_line_if_else_max_width
 922                 {
 923                     return Some((cond_str, 0));
 924                 }
 925             }
 926         }
 927
 928         let cond_span = if let Some(cond) = self.cond {
 929             cond.span
 930         } else {
 931             mk_sp(self.block.span.lo(), self.block.span.lo())
 932         };
 933
 934         // `for event in event`
 935         // Do not include label in the span.
 936         let lo = self
 937             .label
 938             .map_or(self.span.lo(), |label| label.ident.span.hi());
 939         let between_kwd_cond = mk_sp(
 940             context
 941                 .snippet_provider
 942                 .span_after(mk_sp(lo, self.span.hi()), self.keyword.trim()),
 943             if self.pats.is_empty() {
 944                 cond_span.lo()
 945             } else if self.matcher.is_empty() {
 946                 self.pats[0].span.lo()
 947             } else {
 948                 context
 949                     .snippet_provider
 950                     .span_before(self.span, self.matcher.trim())
 951             },
 952         );
 953
 954         let between_kwd_cond_comment = extract_comment(between_kwd_cond, context, shape);
 955
 956         let after_cond_comment =
 957             extract_comment(mk_sp(cond_span.hi(), self.block.span.lo()), context, shape);
 958
 959         let block_sep = if self.cond.is_none() && between_kwd_cond_comment.is_some() {
 960             ""
 961         } else if context.config.control_brace_style() == ControlBraceStyle::AlwaysNextLine
 962             || force_newline_brace
 963         {
 964             alt_block_sep
 965         } else {
 966             " "
 967         };
 968
 969         let used_width = if pat_expr_string.contains('\n') {
 970             last_line_width(&pat_expr_string)
 971         } else {
 972             // 2 = spaces after keyword and condition.
 973             label_string.len() + self.keyword.len() + pat_expr_string.len() + 2
 974         };
 975
 976         Some((
 977             format!(
 978                 "{}{}{}{}{}",
 979                 label_string,
 980                 self.keyword,
 981                 between_kwd_cond_comment.as_ref().map_or(
 982                     if pat_expr_string.is_empty() || pat_expr_string.starts_with('\n') {
 983                         ""
 984                     } else {
 985                         " "
 986                     },
 987                     |s| &**s,
 988                 ),
 989                 pat_expr_string,
 990                 after_cond_comment.as_ref().map_or(block_sep, |s| &**s)
 991             ),
 992             used_width,
 993         ))
 994     }
 995 }
 996
 997 impl<'a> Rewrite for ControlFlow<'a> {
 998     fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
 999         debug!("ControlFlow::rewrite {:?} {:?}", self, shape);
1000
1001         let alt_block_sep = &shape.indent.to_string_with_newline(context.config);
1002         let (cond_str, used_width) = self.rewrite_cond(context, shape, alt_block_sep)?;
1003         // If `used_width` is 0, it indicates that whole control flow is written in a single line.
1004         if used_width == 0 {
1005             return Some(cond_str);
1006         }
1007
1008         let block_width = shape.width.saturating_sub(used_width);
1009         // This is used only for the empty block case: `{}`. So, we use 1 if we know
1010         // we should avoid the single line case.
1011         let block_width = if self.else_block.is_some() || self.nested_if {
1012             min(1, block_width)
1013         } else {
1014             block_width
1015         };
1016         let block_shape = Shape {
1017             width: block_width,
1018             ..shape
1019         };
1020         let block_str = {
1021             let old_val = context.is_if_else_block.replace(self.else_block.is_some());
1022             let result =
1023                 rewrite_block_with_visitor(context, "", self.block, None, None, block_shape, true);
1024             context.is_if_else_block.replace(old_val);
1025             result?
1026         };
1027
1028         let mut result = format!("{}{}", cond_str, block_str);
1029
1030         if let Some(else_block) = self.else_block {
1031             let shape = Shape::indented(shape.indent, context.config);
1032             let mut last_in_chain = false;
1033             let rewrite = match else_block.node {
1034                 // If the else expression is another if-else expression, prevent it
1035                 // from being formatted on a single line.
1036                 // Note how we're passing the original shape, as the
1037                 // cost of "else" should not cascade.
1038                 ast::ExprKind::IfLet(ref pat, ref cond, ref if_block, ref next_else_block) => {
1039                     ControlFlow::new_if(
1040                         cond,
1041                         ptr_vec_to_ref_vec(pat),
1042                         if_block,
1043                         next_else_block.as_ref().map(|e| &**e),
1044                         false,
1045                         true,
1046                         mk_sp(else_block.span.lo(), self.span.hi()),
1047                     )
1048                     .rewrite(context, shape)
1049                 }
1050                 ast::ExprKind::If(ref cond, ref if_block, ref next_else_block) => {
1051                     ControlFlow::new_if(
1052                         cond,
1053                         vec![],
1054                         if_block,
1055                         next_else_block.as_ref().map(|e| &**e),
1056                         false,
1057                         true,
1058                         mk_sp(else_block.span.lo(), self.span.hi()),
1059                     )
1060                     .rewrite(context, shape)
1061                 }
1062                 _ => {
1063                     last_in_chain = true;
1064                     // When rewriting a block, the width is only used for single line
1065                     // blocks, passing 1 lets us avoid that.
1066                     let else_shape = Shape {
1067                         width: min(1, shape.width),
1068                         ..shape
1069                     };
1070                     format_expr(else_block, ExprType::Statement, context, else_shape)
1071                 }
1072             };
1073
1074             let between_kwd_else_block = mk_sp(
1075                 self.block.span.hi(),
1076                 context
1077                     .snippet_provider
1078                     .span_before(mk_sp(self.block.span.hi(), else_block.span.lo()), "else"),
1079             );
1080             let between_kwd_else_block_comment =
1081                 extract_comment(between_kwd_else_block, context, shape);
1082
1083             let after_else = mk_sp(
1084                 context
1085                     .snippet_provider
1086                     .span_after(mk_sp(self.block.span.hi(), else_block.span.lo()), "else"),
1087                 else_block.span.lo(),
1088             );
1089             let after_else_comment = extract_comment(after_else, context, shape);
1090
1091             let between_sep = match context.config.control_brace_style() {
1092                 ControlBraceStyle::AlwaysNextLine | ControlBraceStyle::ClosingNextLine => {
1093                     &*alt_block_sep
1094                 }
1095                 ControlBraceStyle::AlwaysSameLine => " ",
1096             };
1097             let after_sep = match context.config.control_brace_style() {
1098                 ControlBraceStyle::AlwaysNextLine if last_in_chain => &*alt_block_sep,
1099                 _ => " ",
1100             };
1101
1102             result.push_str(&format!(
1103                 "{}else{}",
1104                 between_kwd_else_block_comment
1105                     .as_ref()
1106                     .map_or(between_sep, |s| &**s),
1107                 after_else_comment.as_ref().map_or(after_sep, |s| &**s),
1108             ));
1109             result.push_str(&rewrite?);
1110         }
1111
1112         Some(result)
1113     }
1114 }
1115
1116 fn rewrite_label(opt_label: Option<ast::Label>) -> Cow<'static, str> {
1117     match opt_label {
1118         Some(label) => Cow::from(format!("{}: ", label.ident)),
1119         None => Cow::from(""),
1120     }
1121 }
1122
1123 fn extract_comment(span: Span, context: &RewriteContext, shape: Shape) -> Option<String> {
1124     match rewrite_missing_comment(span, shape, context) {
1125         Some(ref comment) if !comment.is_empty() => Some(format!(
1126             "{indent}{}{indent}",
1127             comment,
1128             indent = shape.indent.to_string_with_newline(context.config)
1129         )),
1130         _ => None,
1131     }
1132 }
1133
1134 pub fn block_contains_comment(block: &ast::Block, source_map: &SourceMap) -> bool {
1135     let snippet = source_map.span_to_snippet(block.span).unwrap();
1136     contains_comment(&snippet)
1137 }
1138
1139 // Checks that a block contains no statements, an expression and no comments or
1140 // attributes.
1141 // FIXME: incorrectly returns false when comment is contained completely within
1142 // the expression.
1143 pub fn is_simple_block(
1144     block: &ast::Block,
1145     attrs: Option<&[ast::Attribute]>,
1146     source_map: &SourceMap,
1147 ) -> bool {
1148     (block.stmts.len() == 1
1149         && stmt_is_expr(&block.stmts[0])
1150         && !block_contains_comment(block, source_map)
1151         && attrs.map_or(true, |a| a.is_empty()))
1152 }
1153
1154 /// Checks whether a block contains at most one statement or expression, and no
1155 /// comments or attributes.
1156 pub fn is_simple_block_stmt(
1157     block: &ast::Block,
1158     attrs: Option<&[ast::Attribute]>,
1159     source_map: &SourceMap,
1160 ) -> bool {
1161     block.stmts.len() <= 1
1162         && !block_contains_comment(block, source_map)
1163         && attrs.map_or(true, |a| a.is_empty())
1164 }
1165
1166 /// Checks whether a block contains no statements, expressions, comments, or
1167 /// inner attributes.
1168 pub fn is_empty_block(
1169     block: &ast::Block,
1170     attrs: Option<&[ast::Attribute]>,
1171     source_map: &SourceMap,
1172 ) -> bool {
1173     block.stmts.is_empty()
1174         && !block_contains_comment(block, source_map)
1175         && attrs.map_or(true, |a| inner_attributes(a).is_empty())
1176 }
1177
1178 pub fn stmt_is_expr(stmt: &ast::Stmt) -> bool {
1179     match stmt.node {
1180         ast::StmtKind::Expr(..) => true,
1181         _ => false,
1182     }
1183 }
1184
1185 pub fn is_unsafe_block(block: &ast::Block) -> bool {
1186     if let ast::BlockCheckMode::Unsafe(..) = block.rules {
1187         true
1188     } else {
1189         false
1190     }
1191 }
1192
1193 pub fn rewrite_multiple_patterns(
1194     context: &RewriteContext,
1195     pats: &[&ast::Pat],
1196     shape: Shape,
1197 ) -> Option<String> {
1198     let pat_strs = pats
1199         .iter()
1200         .map(|p| p.rewrite(context, shape))
1201         .collect::<Option<Vec<_>>>()?;
1202
1203     let use_mixed_layout = pats
1204         .iter()
1205         .zip(pat_strs.iter())
1206         .all(|(pat, pat_str)| is_short_pattern(pat, pat_str));
1207     let items: Vec<_> = pat_strs.into_iter().map(ListItem::from_str).collect();
1208     let tactic = if use_mixed_layout {
1209         DefinitiveListTactic::Mixed
1210     } else {
1211         definitive_tactic(
1212             &items,
1213             ListTactic::HorizontalVertical,
1214             Separator::VerticalBar,
1215             shape.width,
1216         )
1217     };
1218     let fmt = ListFormatting::new(shape, context.config)
1219         .tactic(tactic)
1220         .separator(" |")
1221         .separator_place(context.config.binop_separator())
1222         .ends_with_newline(false);
1223     write_list(&items, &fmt)
1224 }
1225
1226 pub fn rewrite_literal(context: &RewriteContext, l: &ast::Lit, shape: Shape) -> Option<String> {
1227     match l.node {
1228         ast::LitKind::Str(_, ast::StrStyle::Cooked) => rewrite_string_lit(context, l.span, shape),
1229         _ => wrap_str(
1230             context.snippet(l.span).to_owned(),
1231             context.config.max_width(),
1232             shape,
1233         ),
1234     }
1235 }
1236
1237 fn rewrite_string_lit(context: &RewriteContext, span: Span, shape: Shape) -> Option<String> {
1238     let string_lit = context.snippet(span);
1239
1240     if !context.config.format_strings() {
1241         if string_lit
1242             .lines()
1243             .rev()
1244             .skip(1)
1245             .all(|line| line.ends_with('\\'))
1246         {
1247             let new_indent = shape.visual_indent(1).indent;
1248             let indented_string_lit = String::from(
1249                 string_lit
1250                     .lines()
1251                     .map(|line| {
1252                         format!(
1253                             "{}{}",
1254                             new_indent.to_string(context.config),
1255                             line.trim_start()
1256                         )
1257                     })
1258                     .collect::<Vec<_>>()
1259                     .join("\n")
1260                     .trim_start(),
1261             );
1262             return wrap_str(indented_string_lit, context.config.max_width(), shape);
1263         } else {
1264             return wrap_str(string_lit.to_owned(), context.config.max_width(), shape);
1265         }
1266     }
1267
1268     // Remove the quote characters.
1269     let str_lit = &string_lit[1..string_lit.len() - 1];
1270
1271     rewrite_string(
1272         str_lit,
1273         &StringFormat::new(shape.visual_indent(0), context.config),
1274         shape.width.saturating_sub(2),
1275     )
1276 }
1277
1278 fn choose_separator_tactic(context: &RewriteContext, span: Span) -> Option<SeparatorTactic> {
1279     if context.inside_macro() {
1280         if span_ends_with_comma(context, span) {
1281             Some(SeparatorTactic::Always)
1282         } else {
1283             Some(SeparatorTactic::Never)
1284         }
1285     } else {
1286         None
1287     }
1288 }
1289
1290 pub fn rewrite_call(
1291     context: &RewriteContext,
1292     callee: &str,
1293     args: &[ptr::P<ast::Expr>],
1294     span: Span,
1295     shape: Shape,
1296 ) -> Option<String> {
1297     overflow::rewrite_with_parens(
1298         context,
1299         callee,
1300         args.iter(),
1301         shape,
1302         span,
1303         context.config.width_heuristics().fn_call_width,
1304         choose_separator_tactic(context, span),
1305     )
1306 }
1307
1308 pub fn is_simple_expr(expr: &ast::Expr) -> bool {
1309     match expr.node {
1310         ast::ExprKind::Lit(..) => true,
1311         ast::ExprKind::Path(ref qself, ref path) => qself.is_none() && path.segments.len() <= 1,
1312         ast::ExprKind::AddrOf(_, ref expr)
1313         | ast::ExprKind::Box(ref expr)
1314         | ast::ExprKind::Cast(ref expr, _)
1315         | ast::ExprKind::Field(ref expr, _)
1316         | ast::ExprKind::Try(ref expr)
1317         | ast::ExprKind::Unary(_, ref expr) => is_simple_expr(expr),
1318         ast::ExprKind::Index(ref lhs, ref rhs) => is_simple_expr(lhs) && is_simple_expr(rhs),
1319         ast::ExprKind::Repeat(ref lhs, ref rhs) => {
1320             is_simple_expr(lhs) && is_simple_expr(&*rhs.value)
1321         }
1322         _ => false,
1323     }
1324 }
1325
1326 pub fn is_every_expr_simple(lists: &[OverflowableItem]) -> bool {
1327     lists.iter().all(OverflowableItem::is_simple)
1328 }
1329
1330 pub fn can_be_overflowed_expr(context: &RewriteContext, expr: &ast::Expr, args_len: usize) -> bool {
1331     match expr.node {
1332         ast::ExprKind::Match(..) => {
1333             (context.use_block_indent() && args_len == 1)
1334                 || (context.config.indent_style() == IndentStyle::Visual && args_len > 1)
1335         }
1336         ast::ExprKind::If(..)
1337         | ast::ExprKind::IfLet(..)
1338         | ast::ExprKind::ForLoop(..)
1339         | ast::ExprKind::Loop(..)
1340         | ast::ExprKind::While(..)
1341         | ast::ExprKind::WhileLet(..) => {
1342             context.config.combine_control_expr() && context.use_block_indent() && args_len == 1
1343         }
1344
1345         // Handle always block-like expressions
1346         ast::ExprKind::Block(..) | ast::ExprKind::Closure(..) => true,
1347
1348         // Handle `[]` and `{}`-like expressions
1349         ast::ExprKind::Array(..) | ast::ExprKind::Struct(..) => {
1350             context.config.overflow_delimited_expr()
1351                 || (context.use_block_indent() && args_len == 1)
1352         }
1353         ast::ExprKind::Mac(ref macro_) => {
1354             match (macro_.node.delim, context.config.overflow_delimited_expr()) {
1355                 (ast::MacDelimiter::Bracket, true) | (ast::MacDelimiter::Brace, true) => true,
1356                 _ => context.use_block_indent() && args_len == 1,
1357             }
1358         }
1359
1360         // Handle parenthetical expressions
1361         ast::ExprKind::Call(..) | ast::ExprKind::MethodCall(..) | ast::ExprKind::Tup(..) => {
1362             context.use_block_indent() && args_len == 1
1363         }
1364
1365         // Handle unary-like expressions
1366         ast::ExprKind::AddrOf(_, ref expr)
1367         | ast::ExprKind::Box(ref expr)
1368         | ast::ExprKind::Try(ref expr)
1369         | ast::ExprKind::Unary(_, ref expr)
1370         | ast::ExprKind::Cast(ref expr, _) => can_be_overflowed_expr(context, expr, args_len),
1371         _ => false,
1372     }
1373 }
1374
1375 pub fn is_nested_call(expr: &ast::Expr) -> bool {
1376     match expr.node {
1377         ast::ExprKind::Call(..) | ast::ExprKind::Mac(..) => true,
1378         ast::ExprKind::AddrOf(_, ref expr)
1379         | ast::ExprKind::Box(ref expr)
1380         | ast::ExprKind::Try(ref expr)
1381         | ast::ExprKind::Unary(_, ref expr)
1382         | ast::ExprKind::Cast(ref expr, _) => is_nested_call(expr),
1383         _ => false,
1384     }
1385 }
1386
1387 /// Return true if a function call or a method call represented by the given span ends with a
1388 /// trailing comma. This function is used when rewriting macro, as adding or removing a trailing
1389 /// comma from macro can potentially break the code.
1390 pub fn span_ends_with_comma(context: &RewriteContext, span: Span) -> bool {
1391     let mut result: bool = Default::default();
1392     let mut prev_char: char = Default::default();
1393     let closing_delimiters = &[')', '}', ']'];
1394
1395     for (kind, c) in CharClasses::new(context.snippet(span).chars()) {
1396         match c {
1397             _ if kind.is_comment() || c.is_whitespace() => continue,
1398             c if closing_delimiters.contains(&c) => {
1399                 result &= !closing_delimiters.contains(&prev_char);
1400             }
1401             ',' => result = true,
1402             _ => result = false,
1403         }
1404         prev_char = c;
1405     }
1406
1407     result
1408 }
1409
1410 fn rewrite_paren(
1411     context: &RewriteContext,
1412     mut subexpr: &ast::Expr,
1413     shape: Shape,
1414     mut span: Span,
1415 ) -> Option<String> {
1416     debug!("rewrite_paren, shape: {:?}", shape);
1417
1418     // Extract comments within parens.
1419     let mut pre_span;
1420     let mut post_span;
1421     let mut pre_comment;
1422     let mut post_comment;
1423     let remove_nested_parens = context.config.remove_nested_parens();
1424     loop {
1425         // 1 = "(" or ")"
1426         pre_span = mk_sp(span.lo() + BytePos(1), subexpr.span.lo());
1427         post_span = mk_sp(subexpr.span.hi(), span.hi() - BytePos(1));
1428         pre_comment = rewrite_missing_comment(pre_span, shape, context)?;
1429         post_comment = rewrite_missing_comment(post_span, shape, context)?;
1430
1431         // Remove nested parens if there are no comments.
1432         if let ast::ExprKind::Paren(ref subsubexpr) = subexpr.node {
1433             if remove_nested_parens && pre_comment.is_empty() && post_comment.is_empty() {
1434                 span = subexpr.span;
1435                 subexpr = subsubexpr;
1436                 continue;
1437             }
1438         }
1439
1440         break;
1441     }
1442
1443     // 1 = `(` and `)`
1444     let sub_shape = shape.offset_left(1)?.sub_width(1)?;
1445     let subexpr_str = subexpr.rewrite(context, sub_shape)?;
1446     let fits_single_line = !pre_comment.contains("//") && !post_comment.contains("//");
1447     if fits_single_line {
1448         Some(format!("({}{}{})", pre_comment, &subexpr_str, post_comment))
1449     } else {
1450         rewrite_paren_in_multi_line(context, subexpr, shape, pre_span, post_span)
1451     }
1452 }
1453
1454 fn rewrite_paren_in_multi_line(
1455     context: &RewriteContext,
1456     subexpr: &ast::Expr,
1457     shape: Shape,
1458     pre_span: Span,
1459     post_span: Span,
1460 ) -> Option<String> {
1461     let nested_indent = shape.indent.block_indent(context.config);
1462     let nested_shape = Shape::indented(nested_indent, context.config);
1463     let pre_comment = rewrite_missing_comment(pre_span, nested_shape, context)?;
1464     let post_comment = rewrite_missing_comment(post_span, nested_shape, context)?;
1465     let subexpr_str = subexpr.rewrite(context, nested_shape)?;
1466
1467     let mut result = String::with_capacity(subexpr_str.len() * 2);
1468     result.push('(');
1469     if !pre_comment.is_empty() {
1470         result.push_str(&nested_indent.to_string_with_newline(context.config));
1471         result.push_str(&pre_comment);
1472     }
1473     result.push_str(&nested_indent.to_string_with_newline(context.config));
1474     result.push_str(&subexpr_str);
1475     if !post_comment.is_empty() {
1476         result.push_str(&nested_indent.to_string_with_newline(context.config));
1477         result.push_str(&post_comment);
1478     }
1479     result.push_str(&shape.indent.to_string_with_newline(context.config));
1480     result.push(')');
1481
1482     Some(result)
1483 }
1484
1485 fn rewrite_index(
1486     expr: &ast::Expr,
1487     index: &ast::Expr,
1488     context: &RewriteContext,
1489     shape: Shape,
1490 ) -> Option<String> {
1491     let expr_str = expr.rewrite(context, shape)?;
1492
1493     let offset = last_line_width(&expr_str) + 1;
1494     let rhs_overhead = shape.rhs_overhead(context.config);
1495     let index_shape = if expr_str.contains('\n') {
1496         Shape::legacy(context.config.max_width(), shape.indent)
1497             .offset_left(offset)
1498             .and_then(|shape| shape.sub_width(1 + rhs_overhead))
1499     } else {
1500         match context.config.indent_style() {
1501             IndentStyle::Block => shape
1502                 .offset_left(offset)
1503                 .and_then(|shape| shape.sub_width(1)),
1504             IndentStyle::Visual => shape.visual_indent(offset).sub_width(offset + 1),
1505         }
1506     };
1507     let orig_index_rw = index_shape.and_then(|s| index.rewrite(context, s));
1508
1509     // Return if index fits in a single line.
1510     match orig_index_rw {
1511         Some(ref index_str) if !index_str.contains('\n') => {
1512             return Some(format!("{}[{}]", expr_str, index_str));
1513         }
1514         _ => (),
1515     }
1516
1517     // Try putting index on the next line and see if it fits in a single line.
1518     let indent = shape.indent.block_indent(context.config);
1519     let index_shape = Shape::indented(indent, context.config).offset_left(1)?;
1520     let index_shape = index_shape.sub_width(1 + rhs_overhead)?;
1521     let new_index_rw = index.rewrite(context, index_shape);
1522     match (orig_index_rw, new_index_rw) {
1523         (_, Some(ref new_index_str)) if !new_index_str.contains('\n') => Some(format!(
1524             "{}{}[{}]",
1525             expr_str,
1526             indent.to_string_with_newline(context.config),
1527             new_index_str,
1528         )),
1529         (None, Some(ref new_index_str)) => Some(format!(
1530             "{}{}[{}]",
1531             expr_str,
1532             indent.to_string_with_newline(context.config),
1533             new_index_str,
1534         )),
1535         (Some(ref index_str), _) => Some(format!("{}[{}]", expr_str, index_str)),
1536         _ => None,
1537     }
1538 }
1539
1540 fn struct_lit_can_be_aligned(fields: &[ast::Field], base: Option<&ast::Expr>) -> bool {
1541     if base.is_some() {
1542         return false;
1543     }
1544
1545     fields.iter().all(|field| !field.is_shorthand)
1546 }
1547
1548 fn rewrite_struct_lit<'a>(
1549     context: &RewriteContext,
1550     path: &ast::Path,
1551     fields: &'a [ast::Field],
1552     base: Option<&'a ast::Expr>,
1553     span: Span,
1554     shape: Shape,
1555 ) -> Option<String> {
1556     debug!("rewrite_struct_lit: shape {:?}", shape);
1557
1558     enum StructLitField<'a> {
1559         Regular(&'a ast::Field),
1560         Base(&'a ast::Expr),
1561     }
1562
1563     // 2 = " {".len()
1564     let path_shape = shape.sub_width(2)?;
1565     let path_str = rewrite_path(context, PathContext::Expr, None, path, path_shape)?;
1566
1567     if fields.is_empty() && base.is_none() {
1568         return Some(format!("{} {{}}", path_str));
1569     }
1570
1571     // Foo { a: Foo } - indent is +3, width is -5.
1572     let (h_shape, v_shape) = struct_lit_shape(shape, context, path_str.len() + 3, 2)?;
1573
1574     let one_line_width = h_shape.map_or(0, |shape| shape.width);
1575     let body_lo = context.snippet_provider.span_after(span, "{");
1576     let fields_str = if struct_lit_can_be_aligned(fields, base)
1577         && context.config.struct_field_align_threshold() > 0
1578     {
1579         rewrite_with_alignment(
1580             fields,
1581             context,
1582             v_shape,
1583             mk_sp(body_lo, span.hi()),
1584             one_line_width,
1585         )?
1586     } else {
1587         let field_iter = fields
1588             .iter()
1589             .map(StructLitField::Regular)
1590             .chain(base.into_iter().map(StructLitField::Base));
1591
1592         let span_lo = |item: &StructLitField| match *item {
1593             StructLitField::Regular(field) => field.span().lo(),
1594             StructLitField::Base(expr) => {
1595                 let last_field_hi = fields.last().map_or(span.lo(), |field| field.span.hi());
1596                 let snippet = context.snippet(mk_sp(last_field_hi, expr.span.lo()));
1597                 let pos = snippet.find_uncommented("..").unwrap();
1598                 last_field_hi + BytePos(pos as u32)
1599             }
1600         };
1601         let span_hi = |item: &StructLitField| match *item {
1602             StructLitField::Regular(field) => field.span().hi(),
1603             StructLitField::Base(expr) => expr.span.hi(),
1604         };
1605         let rewrite = |item: &StructLitField| match *item {
1606             StructLitField::Regular(field) => {
1607                 // The 1 taken from the v_budget is for the comma.
1608                 rewrite_field(context, field, v_shape.sub_width(1)?, 0)
1609             }
1610             StructLitField::Base(expr) => {
1611                 // 2 = ..
1612                 expr.rewrite(context, v_shape.offset_left(2)?)
1613                     .map(|s| format!("..{}", s))
1614             }
1615         };
1616
1617         let items = itemize_list(
1618             context.snippet_provider,
1619             field_iter,
1620             "}",
1621             ",",
1622             span_lo,
1623             span_hi,
1624             rewrite,
1625             body_lo,
1626             span.hi(),
1627             false,
1628         );
1629         let item_vec = items.collect::<Vec<_>>();
1630
1631         let tactic = struct_lit_tactic(h_shape, context, &item_vec);
1632         let nested_shape = shape_for_tactic(tactic, h_shape, v_shape);
1633
1634         let ends_with_comma = span_ends_with_comma(context, span);
1635         let force_no_trailing_comma = context.inside_macro() && !ends_with_comma;
1636
1637         let fmt = struct_lit_formatting(
1638             nested_shape,
1639             tactic,
1640             context,
1641             force_no_trailing_comma || base.is_some() || !context.use_block_indent(),
1642         );
1643
1644         write_list(&item_vec, &fmt)?
1645     };
1646
1647     let fields_str = wrap_struct_field(context, &fields_str, shape, v_shape, one_line_width);
1648     Some(format!("{} {{{}}}", path_str, fields_str))
1649
1650     // FIXME if context.config.indent_style() == Visual, but we run out
1651     // of space, we should fall back to BlockIndent.
1652 }
1653
1654 pub fn wrap_struct_field(
1655     context: &RewriteContext,
1656     fields_str: &str,
1657     shape: Shape,
1658     nested_shape: Shape,
1659     one_line_width: usize,
1660 ) -> String {
1661     if context.config.indent_style() == IndentStyle::Block
1662         && (fields_str.contains('\n')
1663             || !context.config.struct_lit_single_line()
1664             || fields_str.len() > one_line_width)
1665     {
1666         format!(
1667             "{}{}{}",
1668             nested_shape.indent.to_string_with_newline(context.config),
1669             fields_str,
1670             shape.indent.to_string_with_newline(context.config)
1671         )
1672     } else {
1673         // One liner or visual indent.
1674         format!(" {} ", fields_str)
1675     }
1676 }
1677
1678 pub fn struct_lit_field_separator(config: &Config) -> &str {
1679     colon_spaces(config.space_before_colon(), config.space_after_colon())
1680 }
1681
1682 pub fn rewrite_field(
1683     context: &RewriteContext,
1684     field: &ast::Field,
1685     shape: Shape,
1686     prefix_max_width: usize,
1687 ) -> Option<String> {
1688     if contains_skip(&field.attrs) {
1689         return Some(context.snippet(field.span()).to_owned());
1690     }
1691     let mut attrs_str = field.attrs.rewrite(context, shape)?;
1692     if !attrs_str.is_empty() {
1693         attrs_str.push_str(&shape.indent.to_string_with_newline(context.config));
1694     };
1695     let name = context.snippet(field.ident.span);
1696     if field.is_shorthand {
1697         Some(attrs_str + name)
1698     } else {
1699         let mut separator = String::from(struct_lit_field_separator(context.config));
1700         for _ in 0..prefix_max_width.saturating_sub(name.len()) {
1701             separator.push(' ');
1702         }
1703         let overhead = name.len() + separator.len();
1704         let expr_shape = shape.offset_left(overhead)?;
1705         let expr = field.expr.rewrite(context, expr_shape);
1706
1707         match expr {
1708             Some(ref e) if e.as_str() == name && context.config.use_field_init_shorthand() => {
1709                 Some(attrs_str + name)
1710             }
1711             Some(e) => Some(format!("{}{}{}{}", attrs_str, name, separator, e)),
1712             None => {
1713                 let expr_offset = shape.indent.block_indent(context.config);
1714                 let expr = field
1715                     .expr
1716                     .rewrite(context, Shape::indented(expr_offset, context.config));
1717                 expr.map(|s| {
1718                     format!(
1719                         "{}{}:\n{}{}",
1720                         attrs_str,
1721                         name,
1722                         expr_offset.to_string(context.config),
1723                         s
1724                     )
1725                 })
1726             }
1727         }
1728     }
1729 }
1730
1731 fn rewrite_tuple_in_visual_indent_style<'a, T: 'a + IntoOverflowableItem<'a>>(
1732     context: &RewriteContext,
1733     mut items: impl Iterator<Item = &'a T>,
1734     span: Span,
1735     shape: Shape,
1736     is_singleton_tuple: bool,
1737 ) -> Option<String> {
1738     // In case of length 1, need a trailing comma
1739     debug!("rewrite_tuple_in_visual_indent_style {:?}", shape);
1740     if is_singleton_tuple {
1741         // 3 = "(" + ",)"
1742         let nested_shape = shape.sub_width(3)?.visual_indent(1);
1743         return items
1744             .next()
1745             .unwrap()
1746             .rewrite(context, nested_shape)
1747             .map(|s| format!("({},)", s));
1748     }
1749
1750     let list_lo = context.snippet_provider.span_after(span, "(");
1751     let nested_shape = shape.sub_width(2)?.visual_indent(1);
1752     let items = itemize_list(
1753         context.snippet_provider,
1754         items,
1755         ")",
1756         ",",
1757         |item| item.span().lo(),
1758         |item| item.span().hi(),
1759         |item| item.rewrite(context, nested_shape),
1760         list_lo,
1761         span.hi() - BytePos(1),
1762         false,
1763     );
1764     let item_vec: Vec<_> = items.collect();
1765     let tactic = definitive_tactic(
1766         &item_vec,
1767         ListTactic::HorizontalVertical,
1768         Separator::Comma,
1769         nested_shape.width,
1770     );
1771     let fmt = ListFormatting::new(nested_shape, context.config)
1772         .tactic(tactic)
1773         .ends_with_newline(false);
1774     let list_str = write_list(&item_vec, &fmt)?;
1775
1776     Some(format!("({})", list_str))
1777 }
1778
1779 pub fn rewrite_tuple<'a, T: 'a + IntoOverflowableItem<'a>>(
1780     context: &'a RewriteContext,
1781     items: impl Iterator<Item = &'a T>,
1782     span: Span,
1783     shape: Shape,
1784     is_singleton_tuple: bool,
1785 ) -> Option<String> {
1786     debug!("rewrite_tuple {:?}", shape);
1787     if context.use_block_indent() {
1788         // We use the same rule as function calls for rewriting tuples.
1789         let force_tactic = if context.inside_macro() {
1790             if span_ends_with_comma(context, span) {
1791                 Some(SeparatorTactic::Always)
1792             } else {
1793                 Some(SeparatorTactic::Never)
1794             }
1795         } else if is_singleton_tuple {
1796             Some(SeparatorTactic::Always)
1797         } else {
1798             None
1799         };
1800         overflow::rewrite_with_parens(
1801             context,
1802             "",
1803             items,
1804             shape,
1805             span,
1806             context.config.width_heuristics().fn_call_width,
1807             force_tactic,
1808         )
1809     } else {
1810         rewrite_tuple_in_visual_indent_style(context, items, span, shape, is_singleton_tuple)
1811     }
1812 }
1813
1814 pub fn rewrite_unary_prefix<R: Rewrite>(
1815     context: &RewriteContext,
1816     prefix: &str,
1817     rewrite: &R,
1818     shape: Shape,
1819 ) -> Option<String> {
1820     rewrite
1821         .rewrite(context, shape.offset_left(prefix.len())?)
1822         .map(|r| format!("{}{}", prefix, r))
1823 }
1824
1825 // FIXME: this is probably not correct for multi-line Rewrites. we should
1826 // subtract suffix.len() from the last line budget, not the first!
1827 pub fn rewrite_unary_suffix<R: Rewrite>(
1828     context: &RewriteContext,
1829     suffix: &str,
1830     rewrite: &R,
1831     shape: Shape,
1832 ) -> Option<String> {
1833     rewrite
1834         .rewrite(context, shape.sub_width(suffix.len())?)
1835         .map(|mut r| {
1836             r.push_str(suffix);
1837             r
1838         })
1839 }
1840
1841 fn rewrite_unary_op(
1842     context: &RewriteContext,
1843     op: ast::UnOp,
1844     expr: &ast::Expr,
1845     shape: Shape,
1846 ) -> Option<String> {
1847     // For some reason, an UnOp is not spanned like BinOp!
1848     rewrite_unary_prefix(context, ast::UnOp::to_string(op), expr, shape)
1849 }
1850
1851 fn rewrite_assignment(
1852     context: &RewriteContext,
1853     lhs: &ast::Expr,
1854     rhs: &ast::Expr,
1855     op: Option<&ast::BinOp>,
1856     shape: Shape,
1857 ) -> Option<String> {
1858     let operator_str = match op {
1859         Some(op) => context.snippet(op.span),
1860         None => "=",
1861     };
1862
1863     // 1 = space between lhs and operator.
1864     let lhs_shape = shape.sub_width(operator_str.len() + 1)?;
1865     let lhs_str = format!("{} {}", lhs.rewrite(context, lhs_shape)?, operator_str);
1866
1867     rewrite_assign_rhs(context, lhs_str, rhs, shape)
1868 }
1869
1870 /// Controls where to put the rhs.
1871 #[derive(Debug, Copy, Clone, PartialEq, Eq)]
1872 pub enum RhsTactics {
1873     /// Use heuristics.
1874     Default,
1875     /// Put the rhs on the next line if it uses multiple line, without extra indentation.
1876     ForceNextLineWithoutIndent,
1877 }
1878
1879 // The left hand side must contain everything up to, and including, the
1880 // assignment operator.
1881 pub fn rewrite_assign_rhs<S: Into<String>, R: Rewrite>(
1882     context: &RewriteContext,
1883     lhs: S,
1884     ex: &R,
1885     shape: Shape,
1886 ) -> Option<String> {
1887     rewrite_assign_rhs_with(context, lhs, ex, shape, RhsTactics::Default)
1888 }
1889
1890 pub fn rewrite_assign_rhs_with<S: Into<String>, R: Rewrite>(
1891     context: &RewriteContext,
1892     lhs: S,
1893     ex: &R,
1894     shape: Shape,
1895     rhs_tactics: RhsTactics,
1896 ) -> Option<String> {
1897     let lhs = lhs.into();
1898     let last_line_width = last_line_width(&lhs).saturating_sub(if lhs.contains('\n') {
1899         shape.indent.width()
1900     } else {
1901         0
1902     });
1903     // 1 = space between operator and rhs.
1904     let orig_shape = shape.offset_left(last_line_width + 1).unwrap_or(Shape {
1905         width: 0,
1906         offset: shape.offset + last_line_width + 1,
1907         ..shape
1908     });
1909     let rhs = choose_rhs(
1910         context,
1911         ex,
1912         orig_shape,
1913         ex.rewrite(context, orig_shape),
1914         rhs_tactics,
1915     )?;
1916     Some(lhs + &rhs)
1917 }
1918
1919 fn choose_rhs<R: Rewrite>(
1920     context: &RewriteContext,
1921     expr: &R,
1922     shape: Shape,
1923     orig_rhs: Option<String>,
1924     rhs_tactics: RhsTactics,
1925 ) -> Option<String> {
1926     match orig_rhs {
1927         Some(ref new_str) if !new_str.contains('\n') && new_str.len() <= shape.width => {
1928             Some(format!(" {}", new_str))
1929         }
1930         _ => {
1931             // Expression did not fit on the same line as the identifier.
1932             // Try splitting the line and see if that works better.
1933             let new_shape = shape_from_rhs_tactic(context, shape, rhs_tactics)?;
1934             let new_rhs = expr.rewrite(context, new_shape);
1935             let new_indent_str = &shape
1936                 .indent
1937                 .block_indent(context.config)
1938                 .to_string_with_newline(context.config);
1939
1940             match (orig_rhs, new_rhs) {
1941                 (Some(ref orig_rhs), Some(ref new_rhs))
1942                     if wrap_str(new_rhs.clone(), context.config.max_width(), new_shape)
1943                         .is_none() =>
1944                 {
1945                     Some(format!(" {}", orig_rhs))
1946                 }
1947                 (Some(ref orig_rhs), Some(ref new_rhs))
1948                     if prefer_next_line(orig_rhs, new_rhs, rhs_tactics) =>
1949                 {
1950                     Some(format!("{}{}", new_indent_str, new_rhs))
1951                 }
1952                 (None, Some(ref new_rhs)) => Some(format!("{}{}", new_indent_str, new_rhs)),
1953                 (None, None) => None,
1954                 (Some(orig_rhs), _) => Some(format!(" {}", orig_rhs)),
1955             }
1956         }
1957     }
1958 }
1959
1960 fn shape_from_rhs_tactic(
1961     context: &RewriteContext,
1962     shape: Shape,
1963     rhs_tactic: RhsTactics,
1964 ) -> Option<Shape> {
1965     match rhs_tactic {
1966         RhsTactics::ForceNextLineWithoutIndent => shape
1967             .with_max_width(context.config)
1968             .sub_width(shape.indent.width()),
1969         RhsTactics::Default => {
1970             Shape::indented(shape.indent.block_indent(context.config), context.config)
1971                 .sub_width(shape.rhs_overhead(context.config))
1972         }
1973     }
1974 }
1975
1976 pub fn prefer_next_line(orig_rhs: &str, next_line_rhs: &str, rhs_tactics: RhsTactics) -> bool {
1977     rhs_tactics == RhsTactics::ForceNextLineWithoutIndent
1978         || !next_line_rhs.contains('\n')
1979         || count_newlines(orig_rhs) > count_newlines(next_line_rhs) + 1
1980         || first_line_ends_with(orig_rhs, '(') && !first_line_ends_with(next_line_rhs, '(')
1981         || first_line_ends_with(orig_rhs, '{') && !first_line_ends_with(next_line_rhs, '{')
1982         || first_line_ends_with(orig_rhs, '[') && !first_line_ends_with(next_line_rhs, '[')
1983 }
1984
1985 fn rewrite_expr_addrof(
1986     context: &RewriteContext,
1987     mutability: ast::Mutability,
1988     expr: &ast::Expr,
1989     shape: Shape,
1990 ) -> Option<String> {
1991     let operator_str = match mutability {
1992         ast::Mutability::Immutable => "&",
1993         ast::Mutability::Mutable => "&mut ",
1994     };
1995     rewrite_unary_prefix(context, operator_str, expr, shape)
1996 }
1997
1998 pub fn is_method_call(expr: &ast::Expr) -> bool {
1999     match expr.node {
2000         ast::ExprKind::MethodCall(..) => true,
2001         ast::ExprKind::AddrOf(_, ref expr)
2002         | ast::ExprKind::Box(ref expr)
2003         | ast::ExprKind::Cast(ref expr, _)
2004         | ast::ExprKind::Try(ref expr)
2005         | ast::ExprKind::Unary(_, ref expr) => is_method_call(expr),
2006         _ => false,
2007     }
2008 }
2009
2010 #[cfg(test)]
2011 mod test {
2012     use super::last_line_offsetted;
2013
2014     #[test]
2015     fn test_last_line_offsetted() {
2016         let lines = "one\n    two";
2017         assert_eq!(last_line_offsetted(2, lines), true);
2018         assert_eq!(last_line_offsetted(4, lines), false);
2019         assert_eq!(last_line_offsetted(6, lines), false);
2020
2021         let lines = "one    two";
2022         assert_eq!(last_line_offsetted(2, lines), false);
2023         assert_eq!(last_line_offsetted(0, lines), false);
2024
2025         let lines = "\ntwo";
2026         assert_eq!(last_line_offsetted(2, lines), false);
2027         assert_eq!(last_line_offsetted(0, lines), false);
2028
2029         let lines = "one\n    two      three";
2030         assert_eq!(last_line_offsetted(2, lines), true);
2031         let lines = "one\n two      three";
2032         assert_eq!(last_line_offsetted(2, lines), false);
2033     }
2034 }