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     let label_str = rewrite_label(label);
 421     if attrs.map_or(false, |a| !inner_attributes(a).is_empty()) {
 422         return None;
 423     }
 424
 425     if block.stmts.is_empty()
 426         && !block_contains_comment(block, context.source_map)
 427         && shape.width >= 2
 428     {
 429         return Some(format!("{}{}{{}}", prefix, label_str));
 430     }
 431
 432     // If a block contains only a single-line comment, then leave it on one line.
 433     let user_str = context.snippet(block.span);
 434     let user_str = user_str.trim();
 435     if user_str.starts_with('{') && user_str.ends_with('}') {
 436         let comment_str = user_str[1..user_str.len() - 1].trim();
 437         if block.stmts.is_empty()
 438             && !comment_str.contains('\n')
 439             && !comment_str.starts_with("//")
 440             && comment_str.len() + 4 <= shape.width
 441         {
 442             return Some(format!("{}{}{{ {} }}", prefix, label_str, comment_str));
 443         }
 444     }
 445
 446     None
 447 }
 448
 449 fn block_prefix(context: &RewriteContext, block: &ast::Block, shape: Shape) -> Option<String> {
 450     Some(match block.rules {
 451         ast::BlockCheckMode::Unsafe(..) => {
 452             let snippet = context.snippet(block.span);
 453             let open_pos = snippet.find_uncommented("{")?;
 454             // Extract comment between unsafe and block start.
 455             let trimmed = &snippet[6..open_pos].trim();
 456
 457             if !trimmed.is_empty() {
 458                 // 9 = "unsafe  {".len(), 7 = "unsafe ".len()
 459                 let budget = shape.width.checked_sub(9)?;
 460                 format!(
 461                     "unsafe {} ",
 462                     rewrite_comment(
 463                         trimmed,
 464                         true,
 465                         Shape::legacy(budget, shape.indent + 7),
 466                         context.config,
 467                     )?
 468                 )
 469             } else {
 470                 "unsafe ".to_owned()
 471             }
 472         }
 473         ast::BlockCheckMode::Default => String::new(),
 474     })
 475 }
 476
 477 fn rewrite_single_line_block(
 478     context: &RewriteContext,
 479     prefix: &str,
 480     block: &ast::Block,
 481     attrs: Option<&[ast::Attribute]>,
 482     label: Option<ast::Label>,
 483     shape: Shape,
 484 ) -> Option<String> {
 485     if is_simple_block(block, attrs, context.source_map) {
 486         let expr_shape = shape.offset_left(last_line_width(prefix))?;
 487         let expr_str = block.stmts[0].rewrite(context, expr_shape)?;
 488         let label_str = rewrite_label(label);
 489         let result = format!("{}{}{{ {} }}", prefix, label_str, expr_str);
 490         if result.len() <= shape.width && !result.contains('\n') {
 491             return Some(result);
 492         }
 493     }
 494     None
 495 }
 496
 497 pub fn rewrite_block_with_visitor(
 498     context: &RewriteContext,
 499     prefix: &str,
 500     block: &ast::Block,
 501     attrs: Option<&[ast::Attribute]>,
 502     label: Option<ast::Label>,
 503     shape: Shape,
 504     has_braces: bool,
 505 ) -> Option<String> {
 506     if let rw @ Some(_) = rewrite_empty_block(context, block, attrs, label, prefix, shape) {
 507         return rw;
 508     }
 509
 510     let mut visitor = FmtVisitor::from_context(context);
 511     visitor.block_indent = shape.indent;
 512     visitor.is_if_else_block = context.is_if_else_block();
 513     match block.rules {
 514         ast::BlockCheckMode::Unsafe(..) => {
 515             let snippet = context.snippet(block.span);
 516             let open_pos = snippet.find_uncommented("{")?;
 517             visitor.last_pos = block.span.lo() + BytePos(open_pos as u32)
 518         }
 519         ast::BlockCheckMode::Default => visitor.last_pos = block.span.lo(),
 520     }
 521
 522     let inner_attrs = attrs.map(inner_attributes);
 523     let label_str = rewrite_label(label);
 524     visitor.visit_block(block, inner_attrs.as_ref().map(|a| &**a), has_braces);
 525     Some(format!("{}{}{}", prefix, label_str, visitor.buffer))
 526 }
 527
 528 impl Rewrite for ast::Block {
 529     fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
 530         rewrite_block(self, None, None, context, shape)
 531     }
 532 }
 533
 534 fn rewrite_block(
 535     block: &ast::Block,
 536     attrs: Option<&[ast::Attribute]>,
 537     label: Option<ast::Label>,
 538     context: &RewriteContext,
 539     shape: Shape,
 540 ) -> Option<String> {
 541     let prefix = block_prefix(context, block, shape)?;
 542
 543     // shape.width is used only for the single line case: either the empty block `{}`,
 544     // or an unsafe expression `unsafe { e }`.
 545     if let rw @ Some(_) = rewrite_empty_block(context, block, attrs, label, &prefix, shape) {
 546         return rw;
 547     }
 548
 549     let result = rewrite_block_with_visitor(context, &prefix, block, attrs, label, shape, true);
 550     if let Some(ref result_str) = result {
 551         if result_str.lines().count() <= 3 {
 552             if let rw @ Some(_) =
 553                 rewrite_single_line_block(context, &prefix, block, attrs, label, shape)
 554             {
 555                 return rw;
 556             }
 557         }
 558     }
 559
 560     result
 561 }
 562
 563 impl Rewrite for ast::Stmt {
 564     fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
 565         skip_out_of_file_lines_range!(context, self.span());
 566
 567         let result = match self.node {
 568             ast::StmtKind::Local(ref local) => local.rewrite(context, shape),
 569             ast::StmtKind::Expr(ref ex) | ast::StmtKind::Semi(ref ex) => {
 570                 let suffix = if semicolon_for_stmt(context, self) {
 571                     ";"
 572                 } else {
 573                     ""
 574                 };
 575
 576                 let shape = shape.sub_width(suffix.len())?;
 577                 format_expr(ex, ExprType::Statement, context, shape).map(|s| s + suffix)
 578             }
 579             ast::StmtKind::Mac(..) | ast::StmtKind::Item(..) => None,
 580         };
 581         result.and_then(|res| recover_comment_removed(res, self.span(), context))
 582     }
 583 }
 584
 585 // Rewrite condition if the given expression has one.
 586 pub fn rewrite_cond(context: &RewriteContext, expr: &ast::Expr, shape: Shape) -> Option<String> {
 587     match expr.node {
 588         ast::ExprKind::Match(ref cond, _) => {
 589             // `match `cond` {`
 590             let cond_shape = match context.config.indent_style() {
 591                 IndentStyle::Visual => shape.shrink_left(6).and_then(|s| s.sub_width(2))?,
 592                 IndentStyle::Block => shape.offset_left(8)?,
 593             };
 594             cond.rewrite(context, cond_shape)
 595         }
 596         _ => to_control_flow(expr, ExprType::SubExpression).and_then(|control_flow| {
 597             let alt_block_sep =
 598                 String::from("\n") + &shape.indent.block_only().to_string(context.config);
 599             control_flow
 600                 .rewrite_cond(context, shape, &alt_block_sep)
 601                 .and_then(|rw| Some(rw.0))
 602         }),
 603     }
 604 }
 605
 606 // Abstraction over control flow expressions
 607 #[derive(Debug)]
 608 struct ControlFlow<'a> {
 609     cond: Option<&'a ast::Expr>,
 610     block: &'a ast::Block,
 611     else_block: Option<&'a ast::Expr>,
 612     label: Option<ast::Label>,
 613     pats: Vec<&'a ast::Pat>,
 614     keyword: &'a str,
 615     matcher: &'a str,
 616     connector: &'a str,
 617     allow_single_line: bool,
 618     // True if this is an `if` expression in an `else if` :-( hacky
 619     nested_if: bool,
 620     span: Span,
 621 }
 622
 623 fn to_control_flow(expr: &ast::Expr, expr_type: ExprType) -> Option<ControlFlow> {
 624     match expr.node {
 625         ast::ExprKind::If(ref cond, ref if_block, ref else_block) => Some(ControlFlow::new_if(
 626             cond,
 627             vec![],
 628             if_block,
 629             else_block.as_ref().map(|e| &**e),
 630             expr_type == ExprType::SubExpression,
 631             false,
 632             expr.span,
 633         )),
 634         ast::ExprKind::IfLet(ref pat, ref cond, ref if_block, ref else_block) => {
 635             Some(ControlFlow::new_if(
 636                 cond,
 637                 ptr_vec_to_ref_vec(pat),
 638                 if_block,
 639                 else_block.as_ref().map(|e| &**e),
 640                 expr_type == ExprType::SubExpression,
 641                 false,
 642                 expr.span,
 643             ))
 644         }
 645         ast::ExprKind::ForLoop(ref pat, ref cond, ref block, label) => {
 646             Some(ControlFlow::new_for(pat, cond, block, label, expr.span))
 647         }
 648         ast::ExprKind::Loop(ref block, label) => {
 649             Some(ControlFlow::new_loop(block, label, expr.span))
 650         }
 651         ast::ExprKind::While(ref cond, ref block, label) => Some(ControlFlow::new_while(
 652             vec![],
 653             cond,
 654             block,
 655             label,
 656             expr.span,
 657         )),
 658         ast::ExprKind::WhileLet(ref pat, ref cond, ref block, label) => Some(
 659             ControlFlow::new_while(ptr_vec_to_ref_vec(pat), cond, block, label, expr.span),
 660         ),
 661         _ => None,
 662     }
 663 }
 664
 665 fn choose_matcher(pats: &[&ast::Pat]) -> &'static str {
 666     if pats.is_empty() {
 667         ""
 668     } else {
 669         "let"
 670     }
 671 }
 672
 673 impl<'a> ControlFlow<'a> {
 674     fn new_if(
 675         cond: &'a ast::Expr,
 676         pats: Vec<&'a ast::Pat>,
 677         block: &'a ast::Block,
 678         else_block: Option<&'a ast::Expr>,
 679         allow_single_line: bool,
 680         nested_if: bool,
 681         span: Span,
 682     ) -> ControlFlow<'a> {
 683         let matcher = choose_matcher(&pats);
 684         ControlFlow {
 685             cond: Some(cond),
 686             block,
 687             else_block,
 688             label: None,
 689             pats,
 690             keyword: "if",
 691             matcher,
 692             connector: " =",
 693             allow_single_line,
 694             nested_if,
 695             span,
 696         }
 697     }
 698
 699     fn new_loop(block: &'a ast::Block, label: Option<ast::Label>, span: Span) -> ControlFlow<'a> {
 700         ControlFlow {
 701             cond: None,
 702             block,
 703             else_block: None,
 704             label,
 705             pats: vec![],
 706             keyword: "loop",
 707             matcher: "",
 708             connector: "",
 709             allow_single_line: false,
 710             nested_if: false,
 711             span,
 712         }
 713     }
 714
 715     fn new_while(
 716         pats: Vec<&'a ast::Pat>,
 717         cond: &'a ast::Expr,
 718         block: &'a ast::Block,
 719         label: Option<ast::Label>,
 720         span: Span,
 721     ) -> ControlFlow<'a> {
 722         let matcher = choose_matcher(&pats);
 723         ControlFlow {
 724             cond: Some(cond),
 725             block,
 726             else_block: None,
 727             label,
 728             pats,
 729             keyword: "while",
 730             matcher,
 731             connector: " =",
 732             allow_single_line: false,
 733             nested_if: false,
 734             span,
 735         }
 736     }
 737
 738     fn new_for(
 739         pat: &'a ast::Pat,
 740         cond: &'a ast::Expr,
 741         block: &'a ast::Block,
 742         label: Option<ast::Label>,
 743         span: Span,
 744     ) -> ControlFlow<'a> {
 745         ControlFlow {
 746             cond: Some(cond),
 747             block,
 748             else_block: None,
 749             label,
 750             pats: vec![pat],
 751             keyword: "for",
 752             matcher: "",
 753             connector: " in",
 754             allow_single_line: false,
 755             nested_if: false,
 756             span,
 757         }
 758     }
 759
 760     fn rewrite_single_line(
 761         &self,
 762         pat_expr_str: &str,
 763         context: &RewriteContext,
 764         width: usize,
 765     ) -> Option<String> {
 766         assert!(self.allow_single_line);
 767         let else_block = self.else_block?;
 768         let fixed_cost = self.keyword.len() + "  {  } else {  }".len();
 769
 770         if let ast::ExprKind::Block(ref else_node, _) = else_block.node {
 771             if !is_simple_block(self.block, None, context.source_map)
 772                 || !is_simple_block(else_node, None, context.source_map)
 773                 || pat_expr_str.contains('\n')
 774             {
 775                 return None;
 776             }
 777
 778             let new_width = width.checked_sub(pat_expr_str.len() + fixed_cost)?;
 779             let expr = &self.block.stmts[0];
 780             let if_str = expr.rewrite(context, Shape::legacy(new_width, Indent::empty()))?;
 781
 782             let new_width = new_width.checked_sub(if_str.len())?;
 783             let else_expr = &else_node.stmts[0];
 784             let else_str = else_expr.rewrite(context, Shape::legacy(new_width, Indent::empty()))?;
 785
 786             if if_str.contains('\n') || else_str.contains('\n') {
 787                 return None;
 788             }
 789
 790             let result = format!(
 791                 "{} {} {{ {} }} else {{ {} }}",
 792                 self.keyword, pat_expr_str, if_str, else_str
 793             );
 794
 795             if result.len() <= width {
 796                 return Some(result);
 797             }
 798         }
 799
 800         None
 801     }
 802 }
 803
 804 /// Returns true if the last line of pat_str has leading whitespace and it is wider than the
 805 /// shape's indent.
 806 fn last_line_offsetted(start_column: usize, pat_str: &str) -> bool {
 807     let mut leading_whitespaces = 0;
 808     for c in pat_str.chars().rev() {
 809         match c {
 810             '\n' => break,
 811             _ if c.is_whitespace() => leading_whitespaces += 1,
 812             _ => leading_whitespaces = 0,
 813         }
 814     }
 815     leading_whitespaces > start_column
 816 }
 817
 818 impl<'a> ControlFlow<'a> {
 819     fn rewrite_pat_expr(
 820         &self,
 821         context: &RewriteContext,
 822         expr: &ast::Expr,
 823         shape: Shape,
 824         offset: usize,
 825     ) -> Option<String> {
 826         debug!("rewrite_pat_expr {:?} {:?} {:?}", shape, self.pats, expr);
 827
 828         let cond_shape = shape.offset_left(offset)?;
 829         if !self.pats.is_empty() {
 830             let matcher = if self.matcher.is_empty() {
 831                 self.matcher.to_owned()
 832             } else {
 833                 format!("{} ", self.matcher)
 834             };
 835             let pat_shape = cond_shape
 836                 .offset_left(matcher.len())?
 837                 .sub_width(self.connector.len())?;
 838             let pat_string = rewrite_multiple_patterns(context, &self.pats, pat_shape)?;
 839             let result = format!("{}{}{}", matcher, pat_string, self.connector);
 840             return rewrite_assign_rhs(context, result, expr, cond_shape);
 841         }
 842
 843         let expr_rw = expr.rewrite(context, cond_shape);
 844         // The expression may (partially) fit on the current line.
 845         // We do not allow splitting between `if` and condition.
 846         if self.keyword == "if" || expr_rw.is_some() {
 847             return expr_rw;
 848         }
 849
 850         // The expression won't fit on the current line, jump to next.
 851         let nested_shape = shape
 852             .block_indent(context.config.tab_spaces())
 853             .with_max_width(context.config);
 854         let nested_indent_str = nested_shape.indent.to_string_with_newline(context.config);
 855         expr.rewrite(context, nested_shape)
 856             .map(|expr_rw| format!("{}{}", nested_indent_str, expr_rw))
 857     }
 858
 859     fn rewrite_cond(
 860         &self,
 861         context: &RewriteContext,
 862         shape: Shape,
 863         alt_block_sep: &str,
 864     ) -> Option<(String, usize)> {
 865         // Do not take the rhs overhead from the upper expressions into account
 866         // when rewriting pattern.
 867         let new_width = context.budget(shape.used_width());
 868         let fresh_shape = Shape {
 869             width: new_width,
 870             ..shape
 871         };
 872         let constr_shape = if self.nested_if {
 873             // We are part of an if-elseif-else chain. Our constraints are tightened.
 874             // 7 = "} else " .len()
 875             fresh_shape.offset_left(7)?
 876         } else {
 877             fresh_shape
 878         };
 879
 880         let label_string = rewrite_label(self.label);
 881         // 1 = space after keyword.
 882         let offset = self.keyword.len() + label_string.len() + 1;
 883
 884         let pat_expr_string = match self.cond {
 885             Some(cond) => self.rewrite_pat_expr(context, cond, constr_shape, offset)?,
 886             None => String::new(),
 887         };
 888
 889         let brace_overhead =
 890             if context.config.control_brace_style() != ControlBraceStyle::AlwaysNextLine {
 891                 // 2 = ` {`
 892                 2
 893             } else {
 894                 0
 895             };
 896         let one_line_budget = context
 897             .config
 898             .max_width()
 899             .saturating_sub(constr_shape.used_width() + offset + brace_overhead);
 900         let force_newline_brace = (pat_expr_string.contains('\n')
 901             || pat_expr_string.len() > one_line_budget)
 902             && (!last_line_extendable(&pat_expr_string)
 903                 || last_line_offsetted(shape.used_width(), &pat_expr_string));
 904
 905         // Try to format if-else on single line.
 906         if self.allow_single_line
 907             && context
 908                 .config
 909                 .width_heuristics()
 910                 .single_line_if_else_max_width
 911                 > 0
 912         {
 913             let trial = self.rewrite_single_line(&pat_expr_string, context, shape.width);
 914
 915             if let Some(cond_str) = trial {
 916                 if cond_str.len()
 917                     <= context
 918                         .config
 919                         .width_heuristics()
 920                         .single_line_if_else_max_width
 921                 {
 922                     return Some((cond_str, 0));
 923                 }
 924             }
 925         }
 926
 927         let cond_span = if let Some(cond) = self.cond {
 928             cond.span
 929         } else {
 930             mk_sp(self.block.span.lo(), self.block.span.lo())
 931         };
 932
 933         // `for event in event`
 934         // Do not include label in the span.
 935         let lo = self
 936             .label
 937             .map_or(self.span.lo(), |label| label.ident.span.hi());
 938         let between_kwd_cond = mk_sp(
 939             context
 940                 .snippet_provider
 941                 .span_after(mk_sp(lo, self.span.hi()), self.keyword.trim()),
 942             if self.pats.is_empty() {
 943                 cond_span.lo()
 944             } else if self.matcher.is_empty() {
 945                 self.pats[0].span.lo()
 946             } else {
 947                 context
 948                     .snippet_provider
 949                     .span_before(self.span, self.matcher.trim())
 950             },
 951         );
 952
 953         let between_kwd_cond_comment = extract_comment(between_kwd_cond, context, shape);
 954
 955         let after_cond_comment =
 956             extract_comment(mk_sp(cond_span.hi(), self.block.span.lo()), context, shape);
 957
 958         let block_sep = if self.cond.is_none() && between_kwd_cond_comment.is_some() {
 959             ""
 960         } else if context.config.control_brace_style() == ControlBraceStyle::AlwaysNextLine
 961             || force_newline_brace
 962         {
 963             alt_block_sep
 964         } else {
 965             " "
 966         };
 967
 968         let used_width = if pat_expr_string.contains('\n') {
 969             last_line_width(&pat_expr_string)
 970         } else {
 971             // 2 = spaces after keyword and condition.
 972             label_string.len() + self.keyword.len() + pat_expr_string.len() + 2
 973         };
 974
 975         Some((
 976             format!(
 977                 "{}{}{}{}{}",
 978                 label_string,
 979                 self.keyword,
 980                 between_kwd_cond_comment.as_ref().map_or(
 981                     if pat_expr_string.is_empty() || pat_expr_string.starts_with('\n') {
 982                         ""
 983                     } else {
 984                         " "
 985                     },
 986                     |s| &**s,
 987                 ),
 988                 pat_expr_string,
 989                 after_cond_comment.as_ref().map_or(block_sep, |s| &**s)
 990             ),
 991             used_width,
 992         ))
 993     }
 994 }
 995
 996 impl<'a> Rewrite for ControlFlow<'a> {
 997     fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
 998         debug!("ControlFlow::rewrite {:?} {:?}", self, shape);
 999
1000         let alt_block_sep = &shape.indent.to_string_with_newline(context.config);
1001         let (cond_str, used_width) = self.rewrite_cond(context, shape, alt_block_sep)?;
1002         // If `used_width` is 0, it indicates that whole control flow is written in a single line.
1003         if used_width == 0 {
1004             return Some(cond_str);
1005         }
1006
1007         let block_width = shape.width.saturating_sub(used_width);
1008         // This is used only for the empty block case: `{}`. So, we use 1 if we know
1009         // we should avoid the single line case.
1010         let block_width = if self.else_block.is_some() || self.nested_if {
1011             min(1, block_width)
1012         } else {
1013             block_width
1014         };
1015         let block_shape = Shape {
1016             width: block_width,
1017             ..shape
1018         };
1019         let block_str = {
1020             let old_val = context.is_if_else_block.replace(self.else_block.is_some());
1021             let result =
1022                 rewrite_block_with_visitor(context, "", self.block, None, None, block_shape, true);
1023             context.is_if_else_block.replace(old_val);
1024             result?
1025         };
1026
1027         let mut result = format!("{}{}", cond_str, block_str);
1028
1029         if let Some(else_block) = self.else_block {
1030             let shape = Shape::indented(shape.indent, context.config);
1031             let mut last_in_chain = false;
1032             let rewrite = match else_block.node {
1033                 // If the else expression is another if-else expression, prevent it
1034                 // from being formatted on a single line.
1035                 // Note how we're passing the original shape, as the
1036                 // cost of "else" should not cascade.
1037                 ast::ExprKind::IfLet(ref pat, ref cond, ref if_block, ref next_else_block) => {
1038                     ControlFlow::new_if(
1039                         cond,
1040                         ptr_vec_to_ref_vec(pat),
1041                         if_block,
1042                         next_else_block.as_ref().map(|e| &**e),
1043                         false,
1044                         true,
1045                         mk_sp(else_block.span.lo(), self.span.hi()),
1046                     )
1047                     .rewrite(context, shape)
1048                 }
1049                 ast::ExprKind::If(ref cond, ref if_block, ref next_else_block) => {
1050                     ControlFlow::new_if(
1051                         cond,
1052                         vec![],
1053                         if_block,
1054                         next_else_block.as_ref().map(|e| &**e),
1055                         false,
1056                         true,
1057                         mk_sp(else_block.span.lo(), self.span.hi()),
1058                     )
1059                     .rewrite(context, shape)
1060                 }
1061                 _ => {
1062                     last_in_chain = true;
1063                     // When rewriting a block, the width is only used for single line
1064                     // blocks, passing 1 lets us avoid that.
1065                     let else_shape = Shape {
1066                         width: min(1, shape.width),
1067                         ..shape
1068                     };
1069                     format_expr(else_block, ExprType::Statement, context, else_shape)
1070                 }
1071             };
1072
1073             let between_kwd_else_block = mk_sp(
1074                 self.block.span.hi(),
1075                 context
1076                     .snippet_provider
1077                     .span_before(mk_sp(self.block.span.hi(), else_block.span.lo()), "else"),
1078             );
1079             let between_kwd_else_block_comment =
1080                 extract_comment(between_kwd_else_block, context, shape);
1081
1082             let after_else = mk_sp(
1083                 context
1084                     .snippet_provider
1085                     .span_after(mk_sp(self.block.span.hi(), else_block.span.lo()), "else"),
1086                 else_block.span.lo(),
1087             );
1088             let after_else_comment = extract_comment(after_else, context, shape);
1089
1090             let between_sep = match context.config.control_brace_style() {
1091                 ControlBraceStyle::AlwaysNextLine | ControlBraceStyle::ClosingNextLine => {
1092                     &*alt_block_sep
1093                 }
1094                 ControlBraceStyle::AlwaysSameLine => " ",
1095             };
1096             let after_sep = match context.config.control_brace_style() {
1097                 ControlBraceStyle::AlwaysNextLine if last_in_chain => &*alt_block_sep,
1098                 _ => " ",
1099             };
1100
1101             result.push_str(&format!(
1102                 "{}else{}",
1103                 between_kwd_else_block_comment
1104                     .as_ref()
1105                     .map_or(between_sep, |s| &**s),
1106                 after_else_comment.as_ref().map_or(after_sep, |s| &**s),
1107             ));
1108             result.push_str(&rewrite?);
1109         }
1110
1111         Some(result)
1112     }
1113 }
1114
1115 fn rewrite_label(opt_label: Option<ast::Label>) -> Cow<'static, str> {
1116     match opt_label {
1117         Some(label) => Cow::from(format!("{}: ", label.ident)),
1118         None => Cow::from(""),
1119     }
1120 }
1121
1122 fn extract_comment(span: Span, context: &RewriteContext, shape: Shape) -> Option<String> {
1123     match rewrite_missing_comment(span, shape, context) {
1124         Some(ref comment) if !comment.is_empty() => Some(format!(
1125             "{indent}{}{indent}",
1126             comment,
1127             indent = shape.indent.to_string_with_newline(context.config)
1128         )),
1129         _ => None,
1130     }
1131 }
1132
1133 pub fn block_contains_comment(block: &ast::Block, source_map: &SourceMap) -> bool {
1134     let snippet = source_map.span_to_snippet(block.span).unwrap();
1135     contains_comment(&snippet)
1136 }
1137
1138 // Checks that a block contains no statements, an expression and no comments or
1139 // attributes.
1140 // FIXME: incorrectly returns false when comment is contained completely within
1141 // the expression.
1142 pub fn is_simple_block(
1143     block: &ast::Block,
1144     attrs: Option<&[ast::Attribute]>,
1145     source_map: &SourceMap,
1146 ) -> bool {
1147     (block.stmts.len() == 1
1148         && stmt_is_expr(&block.stmts[0])
1149         && !block_contains_comment(block, source_map)
1150         && attrs.map_or(true, |a| a.is_empty()))
1151 }
1152
1153 /// Checks whether a block contains at most one statement or expression, and no
1154 /// comments or attributes.
1155 pub fn is_simple_block_stmt(
1156     block: &ast::Block,
1157     attrs: Option<&[ast::Attribute]>,
1158     source_map: &SourceMap,
1159 ) -> bool {
1160     block.stmts.len() <= 1
1161         && !block_contains_comment(block, source_map)
1162         && attrs.map_or(true, |a| a.is_empty())
1163 }
1164
1165 /// Checks whether a block contains no statements, expressions, comments, or
1166 /// inner attributes.
1167 pub fn is_empty_block(
1168     block: &ast::Block,
1169     attrs: Option<&[ast::Attribute]>,
1170     source_map: &SourceMap,
1171 ) -> bool {
1172     block.stmts.is_empty()
1173         && !block_contains_comment(block, source_map)
1174         && attrs.map_or(true, |a| inner_attributes(a).is_empty())
1175 }
1176
1177 pub fn stmt_is_expr(stmt: &ast::Stmt) -> bool {
1178     match stmt.node {
1179         ast::StmtKind::Expr(..) => true,
1180         _ => false,
1181     }
1182 }
1183
1184 pub fn is_unsafe_block(block: &ast::Block) -> bool {
1185     if let ast::BlockCheckMode::Unsafe(..) = block.rules {
1186         true
1187     } else {
1188         false
1189     }
1190 }
1191
1192 pub fn rewrite_multiple_patterns(
1193     context: &RewriteContext,
1194     pats: &[&ast::Pat],
1195     shape: Shape,
1196 ) -> Option<String> {
1197     let pat_strs = pats
1198         .iter()
1199         .map(|p| p.rewrite(context, shape))
1200         .collect::<Option<Vec<_>>>()?;
1201
1202     let use_mixed_layout = pats
1203         .iter()
1204         .zip(pat_strs.iter())
1205         .all(|(pat, pat_str)| is_short_pattern(pat, pat_str));
1206     let items: Vec<_> = pat_strs.into_iter().map(ListItem::from_str).collect();
1207     let tactic = if use_mixed_layout {
1208         DefinitiveListTactic::Mixed
1209     } else {
1210         definitive_tactic(
1211             &items,
1212             ListTactic::HorizontalVertical,
1213             Separator::VerticalBar,
1214             shape.width,
1215         )
1216     };
1217     let fmt = ListFormatting::new(shape, context.config)
1218         .tactic(tactic)
1219         .separator(" |")
1220         .separator_place(context.config.binop_separator())
1221         .ends_with_newline(false);
1222     write_list(&items, &fmt)
1223 }
1224
1225 pub fn rewrite_literal(context: &RewriteContext, l: &ast::Lit, shape: Shape) -> Option<String> {
1226     match l.node {
1227         ast::LitKind::Str(_, ast::StrStyle::Cooked) => rewrite_string_lit(context, l.span, shape),
1228         _ => wrap_str(
1229             context.snippet(l.span).to_owned(),
1230             context.config.max_width(),
1231             shape,
1232         ),
1233     }
1234 }
1235
1236 fn rewrite_string_lit(context: &RewriteContext, span: Span, shape: Shape) -> Option<String> {
1237     let string_lit = context.snippet(span);
1238
1239     if !context.config.format_strings() {
1240         if string_lit
1241             .lines()
1242             .rev()
1243             .skip(1)
1244             .all(|line| line.ends_with('\\'))
1245         {
1246             let new_indent = shape.visual_indent(1).indent;
1247             let indented_string_lit = String::from(
1248                 string_lit
1249                     .lines()
1250                     .map(|line| {
1251                         format!(
1252                             "{}{}",
1253                             new_indent.to_string(context.config),
1254                             line.trim_left()
1255                         )
1256                     })
1257                     .collect::<Vec<_>>()
1258                     .join("\n")
1259                     .trim_left(),
1260             );
1261             return wrap_str(indented_string_lit, context.config.max_width(), shape);
1262         } else {
1263             return wrap_str(string_lit.to_owned(), context.config.max_width(), shape);
1264         }
1265     }
1266
1267     // Remove the quote characters.
1268     let str_lit = &string_lit[1..string_lit.len() - 1];
1269
1270     rewrite_string(
1271         str_lit,
1272         &StringFormat::new(shape.visual_indent(0), context.config),
1273         shape.width.saturating_sub(2),
1274     )
1275 }
1276
1277 fn choose_separator_tactic(context: &RewriteContext, span: Span) -> Option<SeparatorTactic> {
1278     if context.inside_macro() {
1279         if span_ends_with_comma(context, span) {
1280             Some(SeparatorTactic::Always)
1281         } else {
1282             Some(SeparatorTactic::Never)
1283         }
1284     } else {
1285         None
1286     }
1287 }
1288
1289 pub fn rewrite_call(
1290     context: &RewriteContext,
1291     callee: &str,
1292     args: &[ptr::P<ast::Expr>],
1293     span: Span,
1294     shape: Shape,
1295 ) -> Option<String> {
1296     overflow::rewrite_with_parens(
1297         context,
1298         callee,
1299         args.iter(),
1300         shape,
1301         span,
1302         context.config.width_heuristics().fn_call_width,
1303         choose_separator_tactic(context, span),
1304     )
1305 }
1306
1307 pub fn is_simple_expr(expr: &ast::Expr) -> bool {
1308     match expr.node {
1309         ast::ExprKind::Lit(..) => true,
1310         ast::ExprKind::Path(ref qself, ref path) => qself.is_none() && path.segments.len() <= 1,
1311         ast::ExprKind::AddrOf(_, ref expr)
1312         | ast::ExprKind::Box(ref expr)
1313         | ast::ExprKind::Cast(ref expr, _)
1314         | ast::ExprKind::Field(ref expr, _)
1315         | ast::ExprKind::Try(ref expr)
1316         | ast::ExprKind::Unary(_, ref expr) => is_simple_expr(expr),
1317         ast::ExprKind::Index(ref lhs, ref rhs) => is_simple_expr(lhs) && is_simple_expr(rhs),
1318         ast::ExprKind::Repeat(ref lhs, ref rhs) => {
1319             is_simple_expr(lhs) && is_simple_expr(&*rhs.value)
1320         }
1321         _ => false,
1322     }
1323 }
1324
1325 pub fn is_every_expr_simple(lists: &[OverflowableItem]) -> bool {
1326     lists.iter().all(OverflowableItem::is_simple)
1327 }
1328
1329 pub fn can_be_overflowed_expr(context: &RewriteContext, expr: &ast::Expr, args_len: usize) -> bool {
1330     match expr.node {
1331         ast::ExprKind::Match(..) => {
1332             (context.use_block_indent() && args_len == 1)
1333                 || (context.config.indent_style() == IndentStyle::Visual && args_len > 1)
1334         }
1335         ast::ExprKind::If(..)
1336         | ast::ExprKind::IfLet(..)
1337         | ast::ExprKind::ForLoop(..)
1338         | ast::ExprKind::Loop(..)
1339         | ast::ExprKind::While(..)
1340         | ast::ExprKind::WhileLet(..) => {
1341             context.config.combine_control_expr() && context.use_block_indent() && args_len == 1
1342         }
1343
1344         // Handle always block-like expressions
1345         ast::ExprKind::Block(..) | ast::ExprKind::Closure(..) => true,
1346
1347         // Handle `[]` and `{}`-like expressions
1348         ast::ExprKind::Array(..) | ast::ExprKind::Struct(..) => {
1349             context.config.overflow_delimited_expr()
1350                 || (context.use_block_indent() && args_len == 1)
1351         }
1352         ast::ExprKind::Mac(ref macro_) => {
1353             match (macro_.node.delim, context.config.overflow_delimited_expr()) {
1354                 (ast::MacDelimiter::Bracket, true) | (ast::MacDelimiter::Brace, true) => true,
1355                 _ => context.use_block_indent() && args_len == 1,
1356             }
1357         }
1358
1359         // Handle parenthetical expressions
1360         ast::ExprKind::Call(..) | ast::ExprKind::MethodCall(..) | ast::ExprKind::Tup(..) => {
1361             context.use_block_indent() && args_len == 1
1362         }
1363
1364         // Handle unary-like expressions
1365         ast::ExprKind::AddrOf(_, ref expr)
1366         | ast::ExprKind::Box(ref expr)
1367         | ast::ExprKind::Try(ref expr)
1368         | ast::ExprKind::Unary(_, ref expr)
1369         | ast::ExprKind::Cast(ref expr, _) => can_be_overflowed_expr(context, expr, args_len),
1370         _ => false,
1371     }
1372 }
1373
1374 pub fn is_nested_call(expr: &ast::Expr) -> bool {
1375     match expr.node {
1376         ast::ExprKind::Call(..) | ast::ExprKind::Mac(..) => true,
1377         ast::ExprKind::AddrOf(_, ref expr)
1378         | ast::ExprKind::Box(ref expr)
1379         | ast::ExprKind::Try(ref expr)
1380         | ast::ExprKind::Unary(_, ref expr)
1381         | ast::ExprKind::Cast(ref expr, _) => is_nested_call(expr),
1382         _ => false,
1383     }
1384 }
1385
1386 /// Return true if a function call or a method call represented by the given span ends with a
1387 /// trailing comma. This function is used when rewriting macro, as adding or removing a trailing
1388 /// comma from macro can potentially break the code.
1389 pub fn span_ends_with_comma(context: &RewriteContext, span: Span) -> bool {
1390     let mut result: bool = Default::default();
1391     let mut prev_char: char = Default::default();
1392     let closing_delimiters = &[')', '}', ']'];
1393
1394     for (kind, c) in CharClasses::new(context.snippet(span).chars()) {
1395         match c {
1396             _ if kind.is_comment() || c.is_whitespace() => continue,
1397             c if closing_delimiters.contains(&c) => {
1398                 result &= !closing_delimiters.contains(&prev_char);
1399             }
1400             ',' => result = true,
1401             _ => result = false,
1402         }
1403         prev_char = c;
1404     }
1405
1406     result
1407 }
1408
1409 fn rewrite_paren(
1410     context: &RewriteContext,
1411     mut subexpr: &ast::Expr,
1412     shape: Shape,
1413     mut span: Span,
1414 ) -> Option<String> {
1415     debug!("rewrite_paren, shape: {:?}", shape);
1416
1417     // Extract comments within parens.
1418     let mut pre_span;
1419     let mut post_span;
1420     let mut pre_comment;
1421     let mut post_comment;
1422     let remove_nested_parens = context.config.remove_nested_parens();
1423     loop {
1424         // 1 = "(" or ")"
1425         pre_span = mk_sp(span.lo() + BytePos(1), subexpr.span.lo());
1426         post_span = mk_sp(subexpr.span.hi(), span.hi() - BytePos(1));
1427         pre_comment = rewrite_missing_comment(pre_span, shape, context)?;
1428         post_comment = rewrite_missing_comment(post_span, shape, context)?;
1429
1430         // Remove nested parens if there are no comments.
1431         if let ast::ExprKind::Paren(ref subsubexpr) = subexpr.node {
1432             if remove_nested_parens && pre_comment.is_empty() && post_comment.is_empty() {
1433                 span = subexpr.span;
1434                 subexpr = subsubexpr;
1435                 continue;
1436             }
1437         }
1438
1439         break;
1440     }
1441
1442     // 1 = `(` and `)`
1443     let sub_shape = shape.offset_left(1)?.sub_width(1)?;
1444     let subexpr_str = subexpr.rewrite(context, sub_shape)?;
1445     let fits_single_line = !pre_comment.contains("//") && !post_comment.contains("//");
1446     if fits_single_line {
1447         Some(format!("({}{}{})", pre_comment, &subexpr_str, post_comment))
1448     } else {
1449         rewrite_paren_in_multi_line(context, subexpr, shape, pre_span, post_span)
1450     }
1451 }
1452
1453 fn rewrite_paren_in_multi_line(
1454     context: &RewriteContext,
1455     subexpr: &ast::Expr,
1456     shape: Shape,
1457     pre_span: Span,
1458     post_span: Span,
1459 ) -> Option<String> {
1460     let nested_indent = shape.indent.block_indent(context.config);
1461     let nested_shape = Shape::indented(nested_indent, context.config);
1462     let pre_comment = rewrite_missing_comment(pre_span, nested_shape, context)?;
1463     let post_comment = rewrite_missing_comment(post_span, nested_shape, context)?;
1464     let subexpr_str = subexpr.rewrite(context, nested_shape)?;
1465
1466     let mut result = String::with_capacity(subexpr_str.len() * 2);
1467     result.push('(');
1468     if !pre_comment.is_empty() {
1469         result.push_str(&nested_indent.to_string_with_newline(context.config));
1470         result.push_str(&pre_comment);
1471     }
1472     result.push_str(&nested_indent.to_string_with_newline(context.config));
1473     result.push_str(&subexpr_str);
1474     if !post_comment.is_empty() {
1475         result.push_str(&nested_indent.to_string_with_newline(context.config));
1476         result.push_str(&post_comment);
1477     }
1478     result.push_str(&shape.indent.to_string_with_newline(context.config));
1479     result.push(')');
1480
1481     Some(result)
1482 }
1483
1484 fn rewrite_index(
1485     expr: &ast::Expr,
1486     index: &ast::Expr,
1487     context: &RewriteContext,
1488     shape: Shape,
1489 ) -> Option<String> {
1490     let expr_str = expr.rewrite(context, shape)?;
1491
1492     let offset = last_line_width(&expr_str) + 1;
1493     let rhs_overhead = shape.rhs_overhead(context.config);
1494     let index_shape = if expr_str.contains('\n') {
1495         Shape::legacy(context.config.max_width(), shape.indent)
1496             .offset_left(offset)
1497             .and_then(|shape| shape.sub_width(1 + rhs_overhead))
1498     } else {
1499         match context.config.indent_style() {
1500             IndentStyle::Block => shape
1501                 .offset_left(offset)
1502                 .and_then(|shape| shape.sub_width(1)),
1503             IndentStyle::Visual => shape.visual_indent(offset).sub_width(offset + 1),
1504         }
1505     };
1506     let orig_index_rw = index_shape.and_then(|s| index.rewrite(context, s));
1507
1508     // Return if index fits in a single line.
1509     match orig_index_rw {
1510         Some(ref index_str) if !index_str.contains('\n') => {
1511             return Some(format!("{}[{}]", expr_str, index_str));
1512         }
1513         _ => (),
1514     }
1515
1516     // Try putting index on the next line and see if it fits in a single line.
1517     let indent = shape.indent.block_indent(context.config);
1518     let index_shape = Shape::indented(indent, context.config).offset_left(1)?;
1519     let index_shape = index_shape.sub_width(1 + rhs_overhead)?;
1520     let new_index_rw = index.rewrite(context, index_shape);
1521     match (orig_index_rw, new_index_rw) {
1522         (_, Some(ref new_index_str)) if !new_index_str.contains('\n') => Some(format!(
1523             "{}{}[{}]",
1524             expr_str,
1525             indent.to_string_with_newline(context.config),
1526             new_index_str,
1527         )),
1528         (None, Some(ref new_index_str)) => Some(format!(
1529             "{}{}[{}]",
1530             expr_str,
1531             indent.to_string_with_newline(context.config),
1532             new_index_str,
1533         )),
1534         (Some(ref index_str), _) => Some(format!("{}[{}]", expr_str, index_str)),
1535         _ => None,
1536     }
1537 }
1538
1539 fn struct_lit_can_be_aligned(fields: &[ast::Field], base: Option<&ast::Expr>) -> bool {
1540     if base.is_some() {
1541         return false;
1542     }
1543
1544     fields.iter().all(|field| !field.is_shorthand)
1545 }
1546
1547 fn rewrite_struct_lit<'a>(
1548     context: &RewriteContext,
1549     path: &ast::Path,
1550     fields: &'a [ast::Field],
1551     base: Option<&'a ast::Expr>,
1552     span: Span,
1553     shape: Shape,
1554 ) -> Option<String> {
1555     debug!("rewrite_struct_lit: shape {:?}", shape);
1556
1557     enum StructLitField<'a> {
1558         Regular(&'a ast::Field),
1559         Base(&'a ast::Expr),
1560     }
1561
1562     // 2 = " {".len()
1563     let path_shape = shape.sub_width(2)?;
1564     let path_str = rewrite_path(context, PathContext::Expr, None, path, path_shape)?;
1565
1566     if fields.is_empty() && base.is_none() {
1567         return Some(format!("{} {{}}", path_str));
1568     }
1569
1570     // Foo { a: Foo } - indent is +3, width is -5.
1571     let (h_shape, v_shape) = struct_lit_shape(shape, context, path_str.len() + 3, 2)?;
1572
1573     let one_line_width = h_shape.map_or(0, |shape| shape.width);
1574     let body_lo = context.snippet_provider.span_after(span, "{");
1575     let fields_str = if struct_lit_can_be_aligned(fields, base)
1576         && context.config.struct_field_align_threshold() > 0
1577     {
1578         rewrite_with_alignment(
1579             fields,
1580             context,
1581             v_shape,
1582             mk_sp(body_lo, span.hi()),
1583             one_line_width,
1584         )?
1585     } else {
1586         let field_iter = fields
1587             .into_iter()
1588             .map(StructLitField::Regular)
1589             .chain(base.into_iter().map(StructLitField::Base));
1590
1591         let span_lo = |item: &StructLitField| match *item {
1592             StructLitField::Regular(field) => field.span().lo(),
1593             StructLitField::Base(expr) => {
1594                 let last_field_hi = fields.last().map_or(span.lo(), |field| field.span.hi());
1595                 let snippet = context.snippet(mk_sp(last_field_hi, expr.span.lo()));
1596                 let pos = snippet.find_uncommented("..").unwrap();
1597                 last_field_hi + BytePos(pos as u32)
1598             }
1599         };
1600         let span_hi = |item: &StructLitField| match *item {
1601             StructLitField::Regular(field) => field.span().hi(),
1602             StructLitField::Base(expr) => expr.span.hi(),
1603         };
1604         let rewrite = |item: &StructLitField| match *item {
1605             StructLitField::Regular(field) => {
1606                 // The 1 taken from the v_budget is for the comma.
1607                 rewrite_field(context, field, v_shape.sub_width(1)?, 0)
1608             }
1609             StructLitField::Base(expr) => {
1610                 // 2 = ..
1611                 expr.rewrite(context, v_shape.offset_left(2)?)
1612                     .map(|s| format!("..{}", s))
1613             }
1614         };
1615
1616         let items = itemize_list(
1617             context.snippet_provider,
1618             field_iter,
1619             "}",
1620             ",",
1621             span_lo,
1622             span_hi,
1623             rewrite,
1624             body_lo,
1625             span.hi(),
1626             false,
1627         );
1628         let item_vec = items.collect::<Vec<_>>();
1629
1630         let tactic = struct_lit_tactic(h_shape, context, &item_vec);
1631         let nested_shape = shape_for_tactic(tactic, h_shape, v_shape);
1632
1633         let ends_with_comma = span_ends_with_comma(context, span);
1634         let force_no_trailing_comma = context.inside_macro() && !ends_with_comma;
1635
1636         let fmt = struct_lit_formatting(
1637             nested_shape,
1638             tactic,
1639             context,
1640             force_no_trailing_comma || base.is_some() || !context.use_block_indent(),
1641         );
1642
1643         write_list(&item_vec, &fmt)?
1644     };
1645
1646     let fields_str = wrap_struct_field(context, &fields_str, shape, v_shape, one_line_width);
1647     Some(format!("{} {{{}}}", path_str, fields_str))
1648
1649     // FIXME if context.config.indent_style() == Visual, but we run out
1650     // of space, we should fall back to BlockIndent.
1651 }
1652
1653 pub fn wrap_struct_field(
1654     context: &RewriteContext,
1655     fields_str: &str,
1656     shape: Shape,
1657     nested_shape: Shape,
1658     one_line_width: usize,
1659 ) -> String {
1660     if context.config.indent_style() == IndentStyle::Block
1661         && (fields_str.contains('\n')
1662             || !context.config.struct_lit_single_line()
1663             || fields_str.len() > one_line_width)
1664     {
1665         format!(
1666             "{}{}{}",
1667             nested_shape.indent.to_string_with_newline(context.config),
1668             fields_str,
1669             shape.indent.to_string_with_newline(context.config)
1670         )
1671     } else {
1672         // One liner or visual indent.
1673         format!(" {} ", fields_str)
1674     }
1675 }
1676
1677 pub fn struct_lit_field_separator(config: &Config) -> &str {
1678     colon_spaces(config.space_before_colon(), config.space_after_colon())
1679 }
1680
1681 pub fn rewrite_field(
1682     context: &RewriteContext,
1683     field: &ast::Field,
1684     shape: Shape,
1685     prefix_max_width: usize,
1686 ) -> Option<String> {
1687     if contains_skip(&field.attrs) {
1688         return Some(context.snippet(field.span()).to_owned());
1689     }
1690     let mut attrs_str = field.attrs.rewrite(context, shape)?;
1691     if !attrs_str.is_empty() {
1692         attrs_str.push_str(&shape.indent.to_string_with_newline(context.config));
1693     };
1694     let name = context.snippet(field.ident.span);
1695     if field.is_shorthand {
1696         Some(attrs_str + name)
1697     } else {
1698         let mut separator = String::from(struct_lit_field_separator(context.config));
1699         for _ in 0..prefix_max_width.saturating_sub(name.len()) {
1700             separator.push(' ');
1701         }
1702         let overhead = name.len() + separator.len();
1703         let expr_shape = shape.offset_left(overhead)?;
1704         let expr = field.expr.rewrite(context, expr_shape);
1705
1706         match expr {
1707             Some(ref e) if e.as_str() == name && context.config.use_field_init_shorthand() => {
1708                 Some(attrs_str + name)
1709             }
1710             Some(e) => Some(format!("{}{}{}{}", attrs_str, name, separator, e)),
1711             None => {
1712                 let expr_offset = shape.indent.block_indent(context.config);
1713                 let expr = field
1714                     .expr
1715                     .rewrite(context, Shape::indented(expr_offset, context.config));
1716                 expr.map(|s| {
1717                     format!(
1718                         "{}{}:\n{}{}",
1719                         attrs_str,
1720                         name,
1721                         expr_offset.to_string(context.config),
1722                         s
1723                     )
1724                 })
1725             }
1726         }
1727     }
1728 }
1729
1730 fn rewrite_tuple_in_visual_indent_style<'a, T: 'a + IntoOverflowableItem<'a>>(
1731     context: &RewriteContext,
1732     mut items: impl Iterator<Item = &'a T>,
1733     span: Span,
1734     shape: Shape,
1735     is_singleton_tuple: bool,
1736 ) -> Option<String> {
1737     // In case of length 1, need a trailing comma
1738     debug!("rewrite_tuple_in_visual_indent_style {:?}", shape);
1739     if is_singleton_tuple {
1740         // 3 = "(" + ",)"
1741         let nested_shape = shape.sub_width(3)?.visual_indent(1);
1742         return items
1743             .next()
1744             .unwrap()
1745             .rewrite(context, nested_shape)
1746             .map(|s| format!("({},)", s));
1747     }
1748
1749     let list_lo = context.snippet_provider.span_after(span, "(");
1750     let nested_shape = shape.sub_width(2)?.visual_indent(1);
1751     let items = itemize_list(
1752         context.snippet_provider,
1753         items,
1754         ")",
1755         ",",
1756         |item| item.span().lo(),
1757         |item| item.span().hi(),
1758         |item| item.rewrite(context, nested_shape),
1759         list_lo,
1760         span.hi() - BytePos(1),
1761         false,
1762     );
1763     let item_vec: Vec<_> = items.collect();
1764     let tactic = definitive_tactic(
1765         &item_vec,
1766         ListTactic::HorizontalVertical,
1767         Separator::Comma,
1768         nested_shape.width,
1769     );
1770     let fmt = ListFormatting::new(nested_shape, context.config)
1771         .tactic(tactic)
1772         .ends_with_newline(false);
1773     let list_str = write_list(&item_vec, &fmt)?;
1774
1775     Some(format!("({})", list_str))
1776 }
1777
1778 pub fn rewrite_tuple<'a, T: 'a + IntoOverflowableItem<'a>>(
1779     context: &'a RewriteContext,
1780     items: impl Iterator<Item = &'a T>,
1781     span: Span,
1782     shape: Shape,
1783     is_singleton_tuple: bool,
1784 ) -> Option<String> {
1785     debug!("rewrite_tuple {:?}", shape);
1786     if context.use_block_indent() {
1787         // We use the same rule as function calls for rewriting tuples.
1788         let force_tactic = if context.inside_macro() {
1789             if span_ends_with_comma(context, span) {
1790                 Some(SeparatorTactic::Always)
1791             } else {
1792                 Some(SeparatorTactic::Never)
1793             }
1794         } else if is_singleton_tuple {
1795             Some(SeparatorTactic::Always)
1796         } else {
1797             None
1798         };
1799         overflow::rewrite_with_parens(
1800             context,
1801             "",
1802             items,
1803             shape,
1804             span,
1805             context.config.width_heuristics().fn_call_width,
1806             force_tactic,
1807         )
1808     } else {
1809         rewrite_tuple_in_visual_indent_style(context, items, span, shape, is_singleton_tuple)
1810     }
1811 }
1812
1813 pub fn rewrite_unary_prefix<R: Rewrite>(
1814     context: &RewriteContext,
1815     prefix: &str,
1816     rewrite: &R,
1817     shape: Shape,
1818 ) -> Option<String> {
1819     rewrite
1820         .rewrite(context, shape.offset_left(prefix.len())?)
1821         .map(|r| format!("{}{}", prefix, r))
1822 }
1823
1824 // FIXME: this is probably not correct for multi-line Rewrites. we should
1825 // subtract suffix.len() from the last line budget, not the first!
1826 pub fn rewrite_unary_suffix<R: Rewrite>(
1827     context: &RewriteContext,
1828     suffix: &str,
1829     rewrite: &R,
1830     shape: Shape,
1831 ) -> Option<String> {
1832     rewrite
1833         .rewrite(context, shape.sub_width(suffix.len())?)
1834         .map(|mut r| {
1835             r.push_str(suffix);
1836             r
1837         })
1838 }
1839
1840 fn rewrite_unary_op(
1841     context: &RewriteContext,
1842     op: ast::UnOp,
1843     expr: &ast::Expr,
1844     shape: Shape,
1845 ) -> Option<String> {
1846     // For some reason, an UnOp is not spanned like BinOp!
1847     rewrite_unary_prefix(context, ast::UnOp::to_string(op), expr, shape)
1848 }
1849
1850 fn rewrite_assignment(
1851     context: &RewriteContext,
1852     lhs: &ast::Expr,
1853     rhs: &ast::Expr,
1854     op: Option<&ast::BinOp>,
1855     shape: Shape,
1856 ) -> Option<String> {
1857     let operator_str = match op {
1858         Some(op) => context.snippet(op.span),
1859         None => "=",
1860     };
1861
1862     // 1 = space between lhs and operator.
1863     let lhs_shape = shape.sub_width(operator_str.len() + 1)?;
1864     let lhs_str = format!("{} {}", lhs.rewrite(context, lhs_shape)?, operator_str);
1865
1866     rewrite_assign_rhs(context, lhs_str, rhs, shape)
1867 }
1868
1869 /// Controls where to put the rhs.
1870 #[derive(Debug, Copy, Clone, PartialEq, Eq)]
1871 pub enum RhsTactics {
1872     /// Use heuristics.
1873     Default,
1874     /// Put the rhs on the next line if it uses multiple line, without extra indentation.
1875     ForceNextLineWithoutIndent,
1876 }
1877
1878 // The left hand side must contain everything up to, and including, the
1879 // assignment operator.
1880 pub fn rewrite_assign_rhs<S: Into<String>, R: Rewrite>(
1881     context: &RewriteContext,
1882     lhs: S,
1883     ex: &R,
1884     shape: Shape,
1885 ) -> Option<String> {
1886     rewrite_assign_rhs_with(context, lhs, ex, shape, RhsTactics::Default)
1887 }
1888
1889 pub fn rewrite_assign_rhs_with<S: Into<String>, R: Rewrite>(
1890     context: &RewriteContext,
1891     lhs: S,
1892     ex: &R,
1893     shape: Shape,
1894     rhs_tactics: RhsTactics,
1895 ) -> Option<String> {
1896     let lhs = lhs.into();
1897     let last_line_width = last_line_width(&lhs).saturating_sub(if lhs.contains('\n') {
1898         shape.indent.width()
1899     } else {
1900         0
1901     });
1902     // 1 = space between operator and rhs.
1903     let orig_shape = shape.offset_left(last_line_width + 1).unwrap_or(Shape {
1904         width: 0,
1905         offset: shape.offset + last_line_width + 1,
1906         ..shape
1907     });
1908     let rhs = choose_rhs(
1909         context,
1910         ex,
1911         orig_shape,
1912         ex.rewrite(context, orig_shape),
1913         rhs_tactics,
1914     )?;
1915     Some(lhs + &rhs)
1916 }
1917
1918 fn choose_rhs<R: Rewrite>(
1919     context: &RewriteContext,
1920     expr: &R,
1921     shape: Shape,
1922     orig_rhs: Option<String>,
1923     rhs_tactics: RhsTactics,
1924 ) -> Option<String> {
1925     match orig_rhs {
1926         Some(ref new_str) if !new_str.contains('\n') && new_str.len() <= shape.width => {
1927             Some(format!(" {}", new_str))
1928         }
1929         _ => {
1930             // Expression did not fit on the same line as the identifier.
1931             // Try splitting the line and see if that works better.
1932             let new_shape = shape_from_rhs_tactic(context, shape, rhs_tactics)?;
1933             let new_rhs = expr.rewrite(context, new_shape);
1934             let new_indent_str = &shape
1935                 .indent
1936                 .block_indent(context.config)
1937                 .to_string_with_newline(context.config);
1938
1939             match (orig_rhs, new_rhs) {
1940                 (Some(ref orig_rhs), Some(ref new_rhs))
1941                     if wrap_str(new_rhs.clone(), context.config.max_width(), new_shape)
1942                         .is_none() =>
1943                 {
1944                     Some(format!(" {}", orig_rhs))
1945                 }
1946                 (Some(ref orig_rhs), Some(ref new_rhs))
1947                     if prefer_next_line(orig_rhs, new_rhs, rhs_tactics) =>
1948                 {
1949                     Some(format!("{}{}", new_indent_str, new_rhs))
1950                 }
1951                 (None, Some(ref new_rhs)) => Some(format!("{}{}", new_indent_str, new_rhs)),
1952                 (None, None) => None,
1953                 (Some(orig_rhs), _) => Some(format!(" {}", orig_rhs)),
1954             }
1955         }
1956     }
1957 }
1958
1959 fn shape_from_rhs_tactic(
1960     context: &RewriteContext,
1961     shape: Shape,
1962     rhs_tactic: RhsTactics,
1963 ) -> Option<Shape> {
1964     match rhs_tactic {
1965         RhsTactics::ForceNextLineWithoutIndent => shape
1966             .with_max_width(context.config)
1967             .sub_width(shape.indent.width()),
1968         RhsTactics::Default => {
1969             Shape::indented(shape.indent.block_indent(context.config), context.config)
1970                 .sub_width(shape.rhs_overhead(context.config))
1971         }
1972     }
1973 }
1974
1975 pub fn prefer_next_line(orig_rhs: &str, next_line_rhs: &str, rhs_tactics: RhsTactics) -> bool {
1976     rhs_tactics == RhsTactics::ForceNextLineWithoutIndent
1977         || !next_line_rhs.contains('\n')
1978         || count_newlines(orig_rhs) > count_newlines(next_line_rhs) + 1
1979         || first_line_ends_with(orig_rhs, '(') && !first_line_ends_with(next_line_rhs, '(')
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 }
1983
1984 fn rewrite_expr_addrof(
1985     context: &RewriteContext,
1986     mutability: ast::Mutability,
1987     expr: &ast::Expr,
1988     shape: Shape,
1989 ) -> Option<String> {
1990     let operator_str = match mutability {
1991         ast::Mutability::Immutable => "&",
1992         ast::Mutability::Mutable => "&mut ",
1993     };
1994     rewrite_unary_prefix(context, operator_str, expr, shape)
1995 }
1996
1997 pub fn is_method_call(expr: &ast::Expr) -> bool {
1998     match expr.node {
1999         ast::ExprKind::MethodCall(..) => true,
2000         ast::ExprKind::AddrOf(_, ref expr)
2001         | ast::ExprKind::Box(ref expr)
2002         | ast::ExprKind::Cast(ref expr, _)
2003         | ast::ExprKind::Try(ref expr)
2004         | ast::ExprKind::Unary(_, ref expr) => is_method_call(expr),
2005         _ => false,
2006     }
2007 }
2008
2009 #[cfg(test)]
2010 mod test {
2011     use super::last_line_offsetted;
2012
2013     #[test]
2014     fn test_last_line_offsetted() {
2015         let lines = "one\n    two";
2016         assert_eq!(last_line_offsetted(2, lines), true);
2017         assert_eq!(last_line_offsetted(4, lines), false);
2018         assert_eq!(last_line_offsetted(6, lines), false);
2019
2020         let lines = "one    two";
2021         assert_eq!(last_line_offsetted(2, lines), false);
2022         assert_eq!(last_line_offsetted(0, lines), false);
2023
2024         let lines = "\ntwo";
2025         assert_eq!(last_line_offsetted(2, lines), false);
2026         assert_eq!(last_line_offsetted(0, lines), false);
2027
2028         let lines = "one\n    two      three";
2029         assert_eq!(last_line_offsetted(2, lines), true);
2030         let lines = "one\n two      three";
2031         assert_eq!(last_line_offsetted(2, lines), false);
2032     }
2033 }