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