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         ast::ExprKind::Err => None,
 383     };
 384
 385     expr_rw
 386         .and_then(|expr_str| recover_comment_removed(expr_str, expr.span, context))
 387         .and_then(|expr_str| {
 388             let attrs = outer_attributes(&expr.attrs);
 389             let attrs_str = attrs.rewrite(context, shape)?;
 390             let span = mk_sp(
 391                 attrs.last().map_or(expr.span.lo(), |attr| attr.span.hi()),
 392                 expr.span.lo(),
 393             );
 394             combine_strs_with_missing_comments(context, &attrs_str, &expr_str, span, shape, false)
 395         })
 396 }
 397
 398 pub fn rewrite_array<'a, T: 'a + IntoOverflowableItem<'a>>(
 399     name: &'a str,
 400     exprs: impl Iterator<Item = &'a T>,
 401     span: Span,
 402     context: &'a RewriteContext,
 403     shape: Shape,
 404     force_separator_tactic: Option<SeparatorTactic>,
 405     delim_token: Option<DelimToken>,
 406 ) -> Option<String> {
 407     overflow::rewrite_with_square_brackets(
 408         context,
 409         name,
 410         exprs,
 411         shape,
 412         span,
 413         force_separator_tactic,
 414         delim_token,
 415     )
 416 }
 417
 418 fn rewrite_empty_block(
 419     context: &RewriteContext,
 420     block: &ast::Block,
 421     attrs: Option<&[ast::Attribute]>,
 422     label: Option<ast::Label>,
 423     prefix: &str,
 424     shape: Shape,
 425 ) -> Option<String> {
 426     if !block.stmts.is_empty() {
 427         return None;
 428     }
 429
 430     let label_str = rewrite_label(label);
 431     if attrs.map_or(false, |a| !inner_attributes(a).is_empty()) {
 432         return None;
 433     }
 434
 435     if !block_contains_comment(block, context.source_map) && shape.width >= 2 {
 436         return Some(format!("{}{}{{}}", prefix, label_str));
 437     }
 438
 439     // If a block contains only a single-line comment, then leave it on one line.
 440     let user_str = context.snippet(block.span);
 441     let user_str = user_str.trim();
 442     if user_str.starts_with('{') && user_str.ends_with('}') {
 443         let comment_str = user_str[1..user_str.len() - 1].trim();
 444         if block.stmts.is_empty()
 445             && !comment_str.contains('\n')
 446             && !comment_str.starts_with("//")
 447             && comment_str.len() + 4 <= shape.width
 448         {
 449             return Some(format!("{}{}{{ {} }}", prefix, label_str, comment_str));
 450         }
 451     }
 452
 453     None
 454 }
 455
 456 fn block_prefix(context: &RewriteContext, block: &ast::Block, shape: Shape) -> Option<String> {
 457     Some(match block.rules {
 458         ast::BlockCheckMode::Unsafe(..) => {
 459             let snippet = context.snippet(block.span);
 460             let open_pos = snippet.find_uncommented("{")?;
 461             // Extract comment between unsafe and block start.
 462             let trimmed = &snippet[6..open_pos].trim();
 463
 464             if !trimmed.is_empty() {
 465                 // 9 = "unsafe  {".len(), 7 = "unsafe ".len()
 466                 let budget = shape.width.checked_sub(9)?;
 467                 format!(
 468                     "unsafe {} ",
 469                     rewrite_comment(
 470                         trimmed,
 471                         true,
 472                         Shape::legacy(budget, shape.indent + 7),
 473                         context.config,
 474                     )?
 475                 )
 476             } else {
 477                 "unsafe ".to_owned()
 478             }
 479         }
 480         ast::BlockCheckMode::Default => String::new(),
 481     })
 482 }
 483
 484 fn rewrite_single_line_block(
 485     context: &RewriteContext,
 486     prefix: &str,
 487     block: &ast::Block,
 488     attrs: Option<&[ast::Attribute]>,
 489     label: Option<ast::Label>,
 490     shape: Shape,
 491 ) -> Option<String> {
 492     if is_simple_block(block, attrs, context.source_map) {
 493         let expr_shape = shape.offset_left(last_line_width(prefix))?;
 494         let expr_str = block.stmts[0].rewrite(context, expr_shape)?;
 495         let label_str = rewrite_label(label);
 496         let result = format!("{}{}{{ {} }}", prefix, label_str, expr_str);
 497         if result.len() <= shape.width && !result.contains('\n') {
 498             return Some(result);
 499         }
 500     }
 501     None
 502 }
 503
 504 pub fn rewrite_block_with_visitor(
 505     context: &RewriteContext,
 506     prefix: &str,
 507     block: &ast::Block,
 508     attrs: Option<&[ast::Attribute]>,
 509     label: Option<ast::Label>,
 510     shape: Shape,
 511     has_braces: bool,
 512 ) -> Option<String> {
 513     if let rw @ Some(_) = rewrite_empty_block(context, block, attrs, label, prefix, shape) {
 514         return rw;
 515     }
 516
 517     let mut visitor = FmtVisitor::from_context(context);
 518     visitor.block_indent = shape.indent;
 519     visitor.is_if_else_block = context.is_if_else_block();
 520     match (block.rules, label) {
 521         (ast::BlockCheckMode::Unsafe(..), _) | (ast::BlockCheckMode::Default, Some(_)) => {
 522             let snippet = context.snippet(block.span);
 523             let open_pos = snippet.find_uncommented("{")?;
 524             visitor.last_pos = block.span.lo() + BytePos(open_pos as u32)
 525         }
 526         (ast::BlockCheckMode::Default, None) => visitor.last_pos = block.span.lo(),
 527     }
 528
 529     let inner_attrs = attrs.map(inner_attributes);
 530     let label_str = rewrite_label(label);
 531     visitor.visit_block(block, inner_attrs.as_ref().map(|a| &**a), has_braces);
 532     Some(format!("{}{}{}", prefix, label_str, visitor.buffer))
 533 }
 534
 535 impl Rewrite for ast::Block {
 536     fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
 537         rewrite_block(self, None, None, context, shape)
 538     }
 539 }
 540
 541 fn rewrite_block(
 542     block: &ast::Block,
 543     attrs: Option<&[ast::Attribute]>,
 544     label: Option<ast::Label>,
 545     context: &RewriteContext,
 546     shape: Shape,
 547 ) -> Option<String> {
 548     let prefix = block_prefix(context, block, shape)?;
 549
 550     // shape.width is used only for the single line case: either the empty block `{}`,
 551     // or an unsafe expression `unsafe { e }`.
 552     if let rw @ Some(_) = rewrite_empty_block(context, block, attrs, label, &prefix, shape) {
 553         return rw;
 554     }
 555
 556     let result = rewrite_block_with_visitor(context, &prefix, block, attrs, label, shape, true);
 557     if let Some(ref result_str) = result {
 558         if result_str.lines().count() <= 3 {
 559             if let rw @ Some(_) =
 560                 rewrite_single_line_block(context, &prefix, block, attrs, label, shape)
 561             {
 562                 return rw;
 563             }
 564         }
 565     }
 566
 567     result
 568 }
 569
 570 impl Rewrite for ast::Stmt {
 571     fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
 572         skip_out_of_file_lines_range!(context, self.span());
 573
 574         let result = match self.node {
 575             ast::StmtKind::Local(ref local) => local.rewrite(context, shape),
 576             ast::StmtKind::Expr(ref ex) | ast::StmtKind::Semi(ref ex) => {
 577                 let suffix = if semicolon_for_stmt(context, self) {
 578                     ";"
 579                 } else {
 580                     ""
 581                 };
 582
 583                 let shape = shape.sub_width(suffix.len())?;
 584                 format_expr(ex, ExprType::Statement, context, shape).map(|s| s + suffix)
 585             }
 586             ast::StmtKind::Mac(..) | ast::StmtKind::Item(..) => None,
 587         };
 588         result.and_then(|res| recover_comment_removed(res, self.span(), context))
 589     }
 590 }
 591
 592 // Rewrite condition if the given expression has one.
 593 pub fn rewrite_cond(context: &RewriteContext, expr: &ast::Expr, shape: Shape) -> Option<String> {
 594     match expr.node {
 595         ast::ExprKind::Match(ref cond, _) => {
 596             // `match `cond` {`
 597             let cond_shape = match context.config.indent_style() {
 598                 IndentStyle::Visual => shape.shrink_left(6).and_then(|s| s.sub_width(2))?,
 599                 IndentStyle::Block => shape.offset_left(8)?,
 600             };
 601             cond.rewrite(context, cond_shape)
 602         }
 603         _ => to_control_flow(expr, ExprType::SubExpression).and_then(|control_flow| {
 604             let alt_block_sep =
 605                 String::from("\n") + &shape.indent.block_only().to_string(context.config);
 606             control_flow
 607                 .rewrite_cond(context, shape, &alt_block_sep)
 608                 .and_then(|rw| Some(rw.0))
 609         }),
 610     }
 611 }
 612
 613 // Abstraction over control flow expressions
 614 #[derive(Debug)]
 615 struct ControlFlow<'a> {
 616     cond: Option<&'a ast::Expr>,
 617     block: &'a ast::Block,
 618     else_block: Option<&'a ast::Expr>,
 619     label: Option<ast::Label>,
 620     pats: Vec<&'a ast::Pat>,
 621     keyword: &'a str,
 622     matcher: &'a str,
 623     connector: &'a str,
 624     allow_single_line: bool,
 625     // True if this is an `if` expression in an `else if` :-( hacky
 626     nested_if: bool,
 627     span: Span,
 628 }
 629
 630 fn to_control_flow(expr: &ast::Expr, expr_type: ExprType) -> Option<ControlFlow> {
 631     match expr.node {
 632         ast::ExprKind::If(ref cond, ref if_block, ref else_block) => Some(ControlFlow::new_if(
 633             cond,
 634             vec![],
 635             if_block,
 636             else_block.as_ref().map(|e| &**e),
 637             expr_type == ExprType::SubExpression,
 638             false,
 639             expr.span,
 640         )),
 641         ast::ExprKind::IfLet(ref pat, ref cond, ref if_block, ref else_block) => {
 642             Some(ControlFlow::new_if(
 643                 cond,
 644                 ptr_vec_to_ref_vec(pat),
 645                 if_block,
 646                 else_block.as_ref().map(|e| &**e),
 647                 expr_type == ExprType::SubExpression,
 648                 false,
 649                 expr.span,
 650             ))
 651         }
 652         ast::ExprKind::ForLoop(ref pat, ref cond, ref block, label) => {
 653             Some(ControlFlow::new_for(pat, cond, block, label, expr.span))
 654         }
 655         ast::ExprKind::Loop(ref block, label) => {
 656             Some(ControlFlow::new_loop(block, label, expr.span))
 657         }
 658         ast::ExprKind::While(ref cond, ref block, label) => Some(ControlFlow::new_while(
 659             vec![],
 660             cond,
 661             block,
 662             label,
 663             expr.span,
 664         )),
 665         ast::ExprKind::WhileLet(ref pat, ref cond, ref block, label) => Some(
 666             ControlFlow::new_while(ptr_vec_to_ref_vec(pat), cond, block, label, expr.span),
 667         ),
 668         _ => None,
 669     }
 670 }
 671
 672 fn choose_matcher(pats: &[&ast::Pat]) -> &'static str {
 673     if pats.is_empty() {
 674         ""
 675     } else {
 676         "let"
 677     }
 678 }
 679
 680 impl<'a> ControlFlow<'a> {
 681     fn new_if(
 682         cond: &'a ast::Expr,
 683         pats: Vec<&'a ast::Pat>,
 684         block: &'a ast::Block,
 685         else_block: Option<&'a ast::Expr>,
 686         allow_single_line: bool,
 687         nested_if: bool,
 688         span: Span,
 689     ) -> ControlFlow<'a> {
 690         let matcher = choose_matcher(&pats);
 691         ControlFlow {
 692             cond: Some(cond),
 693             block,
 694             else_block,
 695             label: None,
 696             pats,
 697             keyword: "if",
 698             matcher,
 699             connector: " =",
 700             allow_single_line,
 701             nested_if,
 702             span,
 703         }
 704     }
 705
 706     fn new_loop(block: &'a ast::Block, label: Option<ast::Label>, span: Span) -> ControlFlow<'a> {
 707         ControlFlow {
 708             cond: None,
 709             block,
 710             else_block: None,
 711             label,
 712             pats: vec![],
 713             keyword: "loop",
 714             matcher: "",
 715             connector: "",
 716             allow_single_line: false,
 717             nested_if: false,
 718             span,
 719         }
 720     }
 721
 722     fn new_while(
 723         pats: Vec<&'a ast::Pat>,
 724         cond: &'a ast::Expr,
 725         block: &'a ast::Block,
 726         label: Option<ast::Label>,
 727         span: Span,
 728     ) -> ControlFlow<'a> {
 729         let matcher = choose_matcher(&pats);
 730         ControlFlow {
 731             cond: Some(cond),
 732             block,
 733             else_block: None,
 734             label,
 735             pats,
 736             keyword: "while",
 737             matcher,
 738             connector: " =",
 739             allow_single_line: false,
 740             nested_if: false,
 741             span,
 742         }
 743     }
 744
 745     fn new_for(
 746         pat: &'a ast::Pat,
 747         cond: &'a ast::Expr,
 748         block: &'a ast::Block,
 749         label: Option<ast::Label>,
 750         span: Span,
 751     ) -> ControlFlow<'a> {
 752         ControlFlow {
 753             cond: Some(cond),
 754             block,
 755             else_block: None,
 756             label,
 757             pats: vec![pat],
 758             keyword: "for",
 759             matcher: "",
 760             connector: " in",
 761             allow_single_line: false,
 762             nested_if: false,
 763             span,
 764         }
 765     }
 766
 767     fn rewrite_single_line(
 768         &self,
 769         pat_expr_str: &str,
 770         context: &RewriteContext,
 771         width: usize,
 772     ) -> Option<String> {
 773         assert!(self.allow_single_line);
 774         let else_block = self.else_block?;
 775         let fixed_cost = self.keyword.len() + "  {  } else {  }".len();
 776
 777         if let ast::ExprKind::Block(ref else_node, _) = else_block.node {
 778             if !is_simple_block(self.block, None, context.source_map)
 779                 || !is_simple_block(else_node, None, context.source_map)
 780                 || pat_expr_str.contains('\n')
 781             {
 782                 return None;
 783             }
 784
 785             let new_width = width.checked_sub(pat_expr_str.len() + fixed_cost)?;
 786             let expr = &self.block.stmts[0];
 787             let if_str = expr.rewrite(context, Shape::legacy(new_width, Indent::empty()))?;
 788
 789             let new_width = new_width.checked_sub(if_str.len())?;
 790             let else_expr = &else_node.stmts[0];
 791             let else_str = else_expr.rewrite(context, Shape::legacy(new_width, Indent::empty()))?;
 792
 793             if if_str.contains('\n') || else_str.contains('\n') {
 794                 return None;
 795             }
 796
 797             let result = format!(
 798                 "{} {} {{ {} }} else {{ {} }}",
 799                 self.keyword, pat_expr_str, if_str, else_str
 800             );
 801
 802             if result.len() <= width {
 803                 return Some(result);
 804             }
 805         }
 806
 807         None
 808     }
 809 }
 810
 811 /// Returns true if the last line of pat_str has leading whitespace and it is wider than the
 812 /// shape's indent.
 813 fn last_line_offsetted(start_column: usize, pat_str: &str) -> bool {
 814     let mut leading_whitespaces = 0;
 815     for c in pat_str.chars().rev() {
 816         match c {
 817             '\n' => break,
 818             _ if c.is_whitespace() => leading_whitespaces += 1,
 819             _ => leading_whitespaces = 0,
 820         }
 821     }
 822     leading_whitespaces > start_column
 823 }
 824
 825 impl<'a> ControlFlow<'a> {
 826     fn rewrite_pat_expr(
 827         &self,
 828         context: &RewriteContext,
 829         expr: &ast::Expr,
 830         shape: Shape,
 831         offset: usize,
 832     ) -> Option<String> {
 833         debug!("rewrite_pat_expr {:?} {:?} {:?}", shape, self.pats, expr);
 834
 835         let cond_shape = shape.offset_left(offset)?;
 836         if !self.pats.is_empty() {
 837             let matcher = if self.matcher.is_empty() {
 838                 self.matcher.to_owned()
 839             } else {
 840                 format!("{} ", self.matcher)
 841             };
 842             let pat_shape = cond_shape
 843                 .offset_left(matcher.len())?
 844                 .sub_width(self.connector.len())?;
 845             let pat_string = rewrite_multiple_patterns(context, &self.pats, pat_shape)?;
 846             let result = format!("{}{}{}", matcher, pat_string, self.connector);
 847             return rewrite_assign_rhs(context, result, expr, cond_shape);
 848         }
 849
 850         let expr_rw = expr.rewrite(context, cond_shape);
 851         // The expression may (partially) fit on the current line.
 852         // We do not allow splitting between `if` and condition.
 853         if self.keyword == "if" || expr_rw.is_some() {
 854             return expr_rw;
 855         }
 856
 857         // The expression won't fit on the current line, jump to next.
 858         let nested_shape = shape
 859             .block_indent(context.config.tab_spaces())
 860             .with_max_width(context.config);
 861         let nested_indent_str = nested_shape.indent.to_string_with_newline(context.config);
 862         expr.rewrite(context, nested_shape)
 863             .map(|expr_rw| format!("{}{}", nested_indent_str, expr_rw))
 864     }
 865
 866     fn rewrite_cond(
 867         &self,
 868         context: &RewriteContext,
 869         shape: Shape,
 870         alt_block_sep: &str,
 871     ) -> Option<(String, usize)> {
 872         // Do not take the rhs overhead from the upper expressions into account
 873         // when rewriting pattern.
 874         let new_width = context.budget(shape.used_width());
 875         let fresh_shape = Shape {
 876             width: new_width,
 877             ..shape
 878         };
 879         let constr_shape = if self.nested_if {
 880             // We are part of an if-elseif-else chain. Our constraints are tightened.
 881             // 7 = "} else " .len()
 882             fresh_shape.offset_left(7)?
 883         } else {
 884             fresh_shape
 885         };
 886
 887         let label_string = rewrite_label(self.label);
 888         // 1 = space after keyword.
 889         let offset = self.keyword.len() + label_string.len() + 1;
 890
 891         let pat_expr_string = match self.cond {
 892             Some(cond) => self.rewrite_pat_expr(context, cond, constr_shape, offset)?,
 893             None => String::new(),
 894         };
 895
 896         let brace_overhead =
 897             if context.config.control_brace_style() != ControlBraceStyle::AlwaysNextLine {
 898                 // 2 = ` {`
 899                 2
 900             } else {
 901                 0
 902             };
 903         let one_line_budget = context
 904             .config
 905             .max_width()
 906             .saturating_sub(constr_shape.used_width() + offset + brace_overhead);
 907         let force_newline_brace = (pat_expr_string.contains('\n')
 908             || pat_expr_string.len() > one_line_budget)
 909             && (!last_line_extendable(&pat_expr_string)
 910                 || last_line_offsetted(shape.used_width(), &pat_expr_string));
 911
 912         // Try to format if-else on single line.
 913         if self.allow_single_line
 914             && context
 915                 .config
 916                 .width_heuristics()
 917                 .single_line_if_else_max_width
 918                 > 0
 919         {
 920             let trial = self.rewrite_single_line(&pat_expr_string, context, shape.width);
 921
 922             if let Some(cond_str) = trial {
 923                 if cond_str.len()
 924                     <= context
 925                         .config
 926                         .width_heuristics()
 927                         .single_line_if_else_max_width
 928                 {
 929                     return Some((cond_str, 0));
 930                 }
 931             }
 932         }
 933
 934         let cond_span = if let Some(cond) = self.cond {
 935             cond.span
 936         } else {
 937             mk_sp(self.block.span.lo(), self.block.span.lo())
 938         };
 939
 940         // `for event in event`
 941         // Do not include label in the span.
 942         let lo = self
 943             .label
 944             .map_or(self.span.lo(), |label| label.ident.span.hi());
 945         let between_kwd_cond = mk_sp(
 946             context
 947                 .snippet_provider
 948                 .span_after(mk_sp(lo, self.span.hi()), self.keyword.trim()),
 949             if self.pats.is_empty() {
 950                 cond_span.lo()
 951             } else if self.matcher.is_empty() {
 952                 self.pats[0].span.lo()
 953             } else {
 954                 context
 955                     .snippet_provider
 956                     .span_before(self.span, self.matcher.trim())
 957             },
 958         );
 959
 960         let between_kwd_cond_comment = extract_comment(between_kwd_cond, context, shape);
 961
 962         let after_cond_comment =
 963             extract_comment(mk_sp(cond_span.hi(), self.block.span.lo()), context, shape);
 964
 965         let block_sep = if self.cond.is_none() && between_kwd_cond_comment.is_some() {
 966             ""
 967         } else if context.config.control_brace_style() == ControlBraceStyle::AlwaysNextLine
 968             || force_newline_brace
 969         {
 970             alt_block_sep
 971         } else {
 972             " "
 973         };
 974
 975         let used_width = if pat_expr_string.contains('\n') {
 976             last_line_width(&pat_expr_string)
 977         } else {
 978             // 2 = spaces after keyword and condition.
 979             label_string.len() + self.keyword.len() + pat_expr_string.len() + 2
 980         };
 981
 982         Some((
 983             format!(
 984                 "{}{}{}{}{}",
 985                 label_string,
 986                 self.keyword,
 987                 between_kwd_cond_comment.as_ref().map_or(
 988                     if pat_expr_string.is_empty() || pat_expr_string.starts_with('\n') {
 989                         ""
 990                     } else {
 991                         " "
 992                     },
 993                     |s| &**s,
 994                 ),
 995                 pat_expr_string,
 996                 after_cond_comment.as_ref().map_or(block_sep, |s| &**s)
 997             ),
 998             used_width,
 999         ))
1000     }
1001 }
1002
1003 impl<'a> Rewrite for ControlFlow<'a> {
1004     fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
1005         debug!("ControlFlow::rewrite {:?} {:?}", self, shape);
1006
1007         let alt_block_sep = &shape.indent.to_string_with_newline(context.config);
1008         let (cond_str, used_width) = self.rewrite_cond(context, shape, alt_block_sep)?;
1009         // If `used_width` is 0, it indicates that whole control flow is written in a single line.
1010         if used_width == 0 {
1011             return Some(cond_str);
1012         }
1013
1014         let block_width = shape.width.saturating_sub(used_width);
1015         // This is used only for the empty block case: `{}`. So, we use 1 if we know
1016         // we should avoid the single line case.
1017         let block_width = if self.else_block.is_some() || self.nested_if {
1018             min(1, block_width)
1019         } else {
1020             block_width
1021         };
1022         let block_shape = Shape {
1023             width: block_width,
1024             ..shape
1025         };
1026         let block_str = {
1027             let old_val = context.is_if_else_block.replace(self.else_block.is_some());
1028             let result =
1029                 rewrite_block_with_visitor(context, "", self.block, None, None, block_shape, true);
1030             context.is_if_else_block.replace(old_val);
1031             result?
1032         };
1033
1034         let mut result = format!("{}{}", cond_str, block_str);
1035
1036         if let Some(else_block) = self.else_block {
1037             let shape = Shape::indented(shape.indent, context.config);
1038             let mut last_in_chain = false;
1039             let rewrite = match else_block.node {
1040                 // If the else expression is another if-else expression, prevent it
1041                 // from being formatted on a single line.
1042                 // Note how we're passing the original shape, as the
1043                 // cost of "else" should not cascade.
1044                 ast::ExprKind::IfLet(ref pat, ref cond, ref if_block, ref next_else_block) => {
1045                     ControlFlow::new_if(
1046                         cond,
1047                         ptr_vec_to_ref_vec(pat),
1048                         if_block,
1049                         next_else_block.as_ref().map(|e| &**e),
1050                         false,
1051                         true,
1052                         mk_sp(else_block.span.lo(), self.span.hi()),
1053                     )
1054                     .rewrite(context, shape)
1055                 }
1056                 ast::ExprKind::If(ref cond, ref if_block, ref next_else_block) => {
1057                     ControlFlow::new_if(
1058                         cond,
1059                         vec![],
1060                         if_block,
1061                         next_else_block.as_ref().map(|e| &**e),
1062                         false,
1063                         true,
1064                         mk_sp(else_block.span.lo(), self.span.hi()),
1065                     )
1066                     .rewrite(context, shape)
1067                 }
1068                 _ => {
1069                     last_in_chain = true;
1070                     // When rewriting a block, the width is only used for single line
1071                     // blocks, passing 1 lets us avoid that.
1072                     let else_shape = Shape {
1073                         width: min(1, shape.width),
1074                         ..shape
1075                     };
1076                     format_expr(else_block, ExprType::Statement, context, else_shape)
1077                 }
1078             };
1079
1080             let between_kwd_else_block = mk_sp(
1081                 self.block.span.hi(),
1082                 context
1083                     .snippet_provider
1084                     .span_before(mk_sp(self.block.span.hi(), else_block.span.lo()), "else"),
1085             );
1086             let between_kwd_else_block_comment =
1087                 extract_comment(between_kwd_else_block, context, shape);
1088
1089             let after_else = mk_sp(
1090                 context
1091                     .snippet_provider
1092                     .span_after(mk_sp(self.block.span.hi(), else_block.span.lo()), "else"),
1093                 else_block.span.lo(),
1094             );
1095             let after_else_comment = extract_comment(after_else, context, shape);
1096
1097             let between_sep = match context.config.control_brace_style() {
1098                 ControlBraceStyle::AlwaysNextLine | ControlBraceStyle::ClosingNextLine => {
1099                     &*alt_block_sep
1100                 }
1101                 ControlBraceStyle::AlwaysSameLine => " ",
1102             };
1103             let after_sep = match context.config.control_brace_style() {
1104                 ControlBraceStyle::AlwaysNextLine if last_in_chain => &*alt_block_sep,
1105                 _ => " ",
1106             };
1107
1108             result.push_str(&format!(
1109                 "{}else{}",
1110                 between_kwd_else_block_comment
1111                     .as_ref()
1112                     .map_or(between_sep, |s| &**s),
1113                 after_else_comment.as_ref().map_or(after_sep, |s| &**s),
1114             ));
1115             result.push_str(&rewrite?);
1116         }
1117
1118         Some(result)
1119     }
1120 }
1121
1122 fn rewrite_label(opt_label: Option<ast::Label>) -> Cow<'static, str> {
1123     match opt_label {
1124         Some(label) => Cow::from(format!("{}: ", label.ident)),
1125         None => Cow::from(""),
1126     }
1127 }
1128
1129 fn extract_comment(span: Span, context: &RewriteContext, shape: Shape) -> Option<String> {
1130     match rewrite_missing_comment(span, shape, context) {
1131         Some(ref comment) if !comment.is_empty() => Some(format!(
1132             "{indent}{}{indent}",
1133             comment,
1134             indent = shape.indent.to_string_with_newline(context.config)
1135         )),
1136         _ => None,
1137     }
1138 }
1139
1140 pub fn block_contains_comment(block: &ast::Block, source_map: &SourceMap) -> bool {
1141     let snippet = source_map.span_to_snippet(block.span).unwrap();
1142     contains_comment(&snippet)
1143 }
1144
1145 // Checks that a block contains no statements, an expression and no comments or
1146 // attributes.
1147 // FIXME: incorrectly returns false when comment is contained completely within
1148 // the expression.
1149 pub fn is_simple_block(
1150     block: &ast::Block,
1151     attrs: Option<&[ast::Attribute]>,
1152     source_map: &SourceMap,
1153 ) -> bool {
1154     (block.stmts.len() == 1
1155         && stmt_is_expr(&block.stmts[0])
1156         && !block_contains_comment(block, source_map)
1157         && attrs.map_or(true, |a| a.is_empty()))
1158 }
1159
1160 /// Checks whether a block contains at most one statement or expression, and no
1161 /// comments or attributes.
1162 pub fn is_simple_block_stmt(
1163     block: &ast::Block,
1164     attrs: Option<&[ast::Attribute]>,
1165     source_map: &SourceMap,
1166 ) -> bool {
1167     block.stmts.len() <= 1
1168         && !block_contains_comment(block, source_map)
1169         && attrs.map_or(true, |a| a.is_empty())
1170 }
1171
1172 /// Checks whether a block contains no statements, expressions, comments, or
1173 /// inner attributes.
1174 pub fn is_empty_block(
1175     block: &ast::Block,
1176     attrs: Option<&[ast::Attribute]>,
1177     source_map: &SourceMap,
1178 ) -> bool {
1179     block.stmts.is_empty()
1180         && !block_contains_comment(block, source_map)
1181         && attrs.map_or(true, |a| inner_attributes(a).is_empty())
1182 }
1183
1184 pub fn stmt_is_expr(stmt: &ast::Stmt) -> bool {
1185     match stmt.node {
1186         ast::StmtKind::Expr(..) => true,
1187         _ => false,
1188     }
1189 }
1190
1191 pub fn is_unsafe_block(block: &ast::Block) -> bool {
1192     if let ast::BlockCheckMode::Unsafe(..) = block.rules {
1193         true
1194     } else {
1195         false
1196     }
1197 }
1198
1199 pub fn rewrite_multiple_patterns(
1200     context: &RewriteContext,
1201     pats: &[&ast::Pat],
1202     shape: Shape,
1203 ) -> Option<String> {
1204     let pat_strs = pats
1205         .iter()
1206         .map(|p| p.rewrite(context, shape))
1207         .collect::<Option<Vec<_>>>()?;
1208
1209     let use_mixed_layout = pats
1210         .iter()
1211         .zip(pat_strs.iter())
1212         .all(|(pat, pat_str)| is_short_pattern(pat, pat_str));
1213     let items: Vec<_> = pat_strs.into_iter().map(ListItem::from_str).collect();
1214     let tactic = if use_mixed_layout {
1215         DefinitiveListTactic::Mixed
1216     } else {
1217         definitive_tactic(
1218             &items,
1219             ListTactic::HorizontalVertical,
1220             Separator::VerticalBar,
1221             shape.width,
1222         )
1223     };
1224     let fmt = ListFormatting::new(shape, context.config)
1225         .tactic(tactic)
1226         .separator(" |")
1227         .separator_place(context.config.binop_separator())
1228         .ends_with_newline(false);
1229     write_list(&items, &fmt)
1230 }
1231
1232 pub fn rewrite_literal(context: &RewriteContext, l: &ast::Lit, shape: Shape) -> Option<String> {
1233     match l.node {
1234         ast::LitKind::Str(_, ast::StrStyle::Cooked) => rewrite_string_lit(context, l.span, shape),
1235         _ => wrap_str(
1236             context.snippet(l.span).to_owned(),
1237             context.config.max_width(),
1238             shape,
1239         ),
1240     }
1241 }
1242
1243 fn rewrite_string_lit(context: &RewriteContext, span: Span, shape: Shape) -> Option<String> {
1244     let string_lit = context.snippet(span);
1245
1246     if !context.config.format_strings() {
1247         if string_lit
1248             .lines()
1249             .rev()
1250             .skip(1)
1251             .all(|line| line.ends_with('\\'))
1252         {
1253             let new_indent = shape.visual_indent(1).indent;
1254             let indented_string_lit = String::from(
1255                 string_lit
1256                     .lines()
1257                     .map(|line| {
1258                         format!(
1259                             "{}{}",
1260                             new_indent.to_string(context.config),
1261                             line.trim_start()
1262                         )
1263                     })
1264                     .collect::<Vec<_>>()
1265                     .join("\n")
1266                     .trim_start(),
1267             );
1268             return if context.config.version() == Version::Two {
1269                 Some(indented_string_lit)
1270             } else {
1271                 wrap_str(indented_string_lit, context.config.max_width(), shape)
1272             };
1273         } else {
1274             return wrap_str(string_lit.to_owned(), context.config.max_width(), shape);
1275         }
1276     }
1277
1278     // Remove the quote characters.
1279     let str_lit = &string_lit[1..string_lit.len() - 1];
1280
1281     rewrite_string(
1282         str_lit,
1283         &StringFormat::new(shape.visual_indent(0), context.config),
1284         shape.width.saturating_sub(2),
1285     )
1286 }
1287
1288 fn choose_separator_tactic(context: &RewriteContext, span: Span) -> Option<SeparatorTactic> {
1289     if context.inside_macro() {
1290         if span_ends_with_comma(context, span) {
1291             Some(SeparatorTactic::Always)
1292         } else {
1293             Some(SeparatorTactic::Never)
1294         }
1295     } else {
1296         None
1297     }
1298 }
1299
1300 pub fn rewrite_call(
1301     context: &RewriteContext,
1302     callee: &str,
1303     args: &[ptr::P<ast::Expr>],
1304     span: Span,
1305     shape: Shape,
1306 ) -> Option<String> {
1307     overflow::rewrite_with_parens(
1308         context,
1309         callee,
1310         args.iter(),
1311         shape,
1312         span,
1313         context.config.width_heuristics().fn_call_width,
1314         choose_separator_tactic(context, span),
1315     )
1316 }
1317
1318 pub fn is_simple_expr(expr: &ast::Expr) -> bool {
1319     match expr.node {
1320         ast::ExprKind::Lit(..) => true,
1321         ast::ExprKind::Path(ref qself, ref path) => qself.is_none() && path.segments.len() <= 1,
1322         ast::ExprKind::AddrOf(_, ref expr)
1323         | ast::ExprKind::Box(ref expr)
1324         | ast::ExprKind::Cast(ref expr, _)
1325         | ast::ExprKind::Field(ref expr, _)
1326         | ast::ExprKind::Try(ref expr)
1327         | ast::ExprKind::Unary(_, ref expr) => is_simple_expr(expr),
1328         ast::ExprKind::Index(ref lhs, ref rhs) => is_simple_expr(lhs) && is_simple_expr(rhs),
1329         ast::ExprKind::Repeat(ref lhs, ref rhs) => {
1330             is_simple_expr(lhs) && is_simple_expr(&*rhs.value)
1331         }
1332         _ => false,
1333     }
1334 }
1335
1336 pub fn is_every_expr_simple(lists: &[OverflowableItem]) -> bool {
1337     lists.iter().all(OverflowableItem::is_simple)
1338 }
1339
1340 pub fn can_be_overflowed_expr(context: &RewriteContext, expr: &ast::Expr, args_len: usize) -> bool {
1341     match expr.node {
1342         ast::ExprKind::Match(..) => {
1343             (context.use_block_indent() && args_len == 1)
1344                 || (context.config.indent_style() == IndentStyle::Visual && args_len > 1)
1345         }
1346         ast::ExprKind::If(..)
1347         | ast::ExprKind::IfLet(..)
1348         | ast::ExprKind::ForLoop(..)
1349         | ast::ExprKind::Loop(..)
1350         | ast::ExprKind::While(..)
1351         | ast::ExprKind::WhileLet(..) => {
1352             context.config.combine_control_expr() && context.use_block_indent() && args_len == 1
1353         }
1354
1355         // Handle always block-like expressions
1356         ast::ExprKind::Block(..) | ast::ExprKind::Closure(..) => true,
1357
1358         // Handle `[]` and `{}`-like expressions
1359         ast::ExprKind::Array(..) | ast::ExprKind::Struct(..) => {
1360             context.config.overflow_delimited_expr()
1361                 || (context.use_block_indent() && args_len == 1)
1362         }
1363         ast::ExprKind::Mac(ref macro_) => {
1364             match (macro_.node.delim, context.config.overflow_delimited_expr()) {
1365                 (ast::MacDelimiter::Bracket, true) | (ast::MacDelimiter::Brace, true) => true,
1366                 _ => context.use_block_indent() && args_len == 1,
1367             }
1368         }
1369
1370         // Handle parenthetical expressions
1371         ast::ExprKind::Call(..) | ast::ExprKind::MethodCall(..) | ast::ExprKind::Tup(..) => {
1372             context.use_block_indent() && args_len == 1
1373         }
1374
1375         // Handle unary-like expressions
1376         ast::ExprKind::AddrOf(_, ref expr)
1377         | ast::ExprKind::Box(ref expr)
1378         | ast::ExprKind::Try(ref expr)
1379         | ast::ExprKind::Unary(_, ref expr)
1380         | ast::ExprKind::Cast(ref expr, _) => can_be_overflowed_expr(context, expr, args_len),
1381         _ => false,
1382     }
1383 }
1384
1385 pub fn is_nested_call(expr: &ast::Expr) -> bool {
1386     match expr.node {
1387         ast::ExprKind::Call(..) | ast::ExprKind::Mac(..) => true,
1388         ast::ExprKind::AddrOf(_, ref expr)
1389         | ast::ExprKind::Box(ref expr)
1390         | ast::ExprKind::Try(ref expr)
1391         | ast::ExprKind::Unary(_, ref expr)
1392         | ast::ExprKind::Cast(ref expr, _) => is_nested_call(expr),
1393         _ => false,
1394     }
1395 }
1396
1397 /// Return true if a function call or a method call represented by the given span ends with a
1398 /// trailing comma. This function is used when rewriting macro, as adding or removing a trailing
1399 /// comma from macro can potentially break the code.
1400 pub fn span_ends_with_comma(context: &RewriteContext, span: Span) -> bool {
1401     let mut result: bool = Default::default();
1402     let mut prev_char: char = Default::default();
1403     let closing_delimiters = &[')', '}', ']'];
1404
1405     for (kind, c) in CharClasses::new(context.snippet(span).chars()) {
1406         match c {
1407             _ if kind.is_comment() || c.is_whitespace() => continue,
1408             c if closing_delimiters.contains(&c) => {
1409                 result &= !closing_delimiters.contains(&prev_char);
1410             }
1411             ',' => result = true,
1412             _ => result = false,
1413         }
1414         prev_char = c;
1415     }
1416
1417     result
1418 }
1419
1420 fn rewrite_paren(
1421     context: &RewriteContext,
1422     mut subexpr: &ast::Expr,
1423     shape: Shape,
1424     mut span: Span,
1425 ) -> Option<String> {
1426     debug!("rewrite_paren, shape: {:?}", shape);
1427
1428     // Extract comments within parens.
1429     let mut pre_span;
1430     let mut post_span;
1431     let mut pre_comment;
1432     let mut post_comment;
1433     let remove_nested_parens = context.config.remove_nested_parens();
1434     loop {
1435         // 1 = "(" or ")"
1436         pre_span = mk_sp(span.lo() + BytePos(1), subexpr.span.lo());
1437         post_span = mk_sp(subexpr.span.hi(), span.hi() - BytePos(1));
1438         pre_comment = rewrite_missing_comment(pre_span, shape, context)?;
1439         post_comment = rewrite_missing_comment(post_span, shape, context)?;
1440
1441         // Remove nested parens if there are no comments.
1442         if let ast::ExprKind::Paren(ref subsubexpr) = subexpr.node {
1443             if remove_nested_parens && pre_comment.is_empty() && post_comment.is_empty() {
1444                 span = subexpr.span;
1445                 subexpr = subsubexpr;
1446                 continue;
1447             }
1448         }
1449
1450         break;
1451     }
1452
1453     // 1 = `(` and `)`
1454     let sub_shape = shape.offset_left(1)?.sub_width(1)?;
1455     let subexpr_str = subexpr.rewrite(context, sub_shape)?;
1456     let fits_single_line = !pre_comment.contains("//") && !post_comment.contains("//");
1457     if fits_single_line {
1458         Some(format!("({}{}{})", pre_comment, &subexpr_str, post_comment))
1459     } else {
1460         rewrite_paren_in_multi_line(context, subexpr, shape, pre_span, post_span)
1461     }
1462 }
1463
1464 fn rewrite_paren_in_multi_line(
1465     context: &RewriteContext,
1466     subexpr: &ast::Expr,
1467     shape: Shape,
1468     pre_span: Span,
1469     post_span: Span,
1470 ) -> Option<String> {
1471     let nested_indent = shape.indent.block_indent(context.config);
1472     let nested_shape = Shape::indented(nested_indent, context.config);
1473     let pre_comment = rewrite_missing_comment(pre_span, nested_shape, context)?;
1474     let post_comment = rewrite_missing_comment(post_span, nested_shape, context)?;
1475     let subexpr_str = subexpr.rewrite(context, nested_shape)?;
1476
1477     let mut result = String::with_capacity(subexpr_str.len() * 2);
1478     result.push('(');
1479     if !pre_comment.is_empty() {
1480         result.push_str(&nested_indent.to_string_with_newline(context.config));
1481         result.push_str(&pre_comment);
1482     }
1483     result.push_str(&nested_indent.to_string_with_newline(context.config));
1484     result.push_str(&subexpr_str);
1485     if !post_comment.is_empty() {
1486         result.push_str(&nested_indent.to_string_with_newline(context.config));
1487         result.push_str(&post_comment);
1488     }
1489     result.push_str(&shape.indent.to_string_with_newline(context.config));
1490     result.push(')');
1491
1492     Some(result)
1493 }
1494
1495 fn rewrite_index(
1496     expr: &ast::Expr,
1497     index: &ast::Expr,
1498     context: &RewriteContext,
1499     shape: Shape,
1500 ) -> Option<String> {
1501     let expr_str = expr.rewrite(context, shape)?;
1502
1503     let offset = last_line_width(&expr_str) + 1;
1504     let rhs_overhead = shape.rhs_overhead(context.config);
1505     let index_shape = if expr_str.contains('\n') {
1506         Shape::legacy(context.config.max_width(), shape.indent)
1507             .offset_left(offset)
1508             .and_then(|shape| shape.sub_width(1 + rhs_overhead))
1509     } else {
1510         match context.config.indent_style() {
1511             IndentStyle::Block => shape
1512                 .offset_left(offset)
1513                 .and_then(|shape| shape.sub_width(1)),
1514             IndentStyle::Visual => shape.visual_indent(offset).sub_width(offset + 1),
1515         }
1516     };
1517     let orig_index_rw = index_shape.and_then(|s| index.rewrite(context, s));
1518
1519     // Return if index fits in a single line.
1520     match orig_index_rw {
1521         Some(ref index_str) if !index_str.contains('\n') => {
1522             return Some(format!("{}[{}]", expr_str, index_str));
1523         }
1524         _ => (),
1525     }
1526
1527     // Try putting index on the next line and see if it fits in a single line.
1528     let indent = shape.indent.block_indent(context.config);
1529     let index_shape = Shape::indented(indent, context.config).offset_left(1)?;
1530     let index_shape = index_shape.sub_width(1 + rhs_overhead)?;
1531     let new_index_rw = index.rewrite(context, index_shape);
1532     match (orig_index_rw, new_index_rw) {
1533         (_, Some(ref new_index_str)) if !new_index_str.contains('\n') => Some(format!(
1534             "{}{}[{}]",
1535             expr_str,
1536             indent.to_string_with_newline(context.config),
1537             new_index_str,
1538         )),
1539         (None, Some(ref new_index_str)) => Some(format!(
1540             "{}{}[{}]",
1541             expr_str,
1542             indent.to_string_with_newline(context.config),
1543             new_index_str,
1544         )),
1545         (Some(ref index_str), _) => Some(format!("{}[{}]", expr_str, index_str)),
1546         _ => None,
1547     }
1548 }
1549
1550 fn struct_lit_can_be_aligned(fields: &[ast::Field], base: Option<&ast::Expr>) -> bool {
1551     if base.is_some() {
1552         return false;
1553     }
1554
1555     fields.iter().all(|field| !field.is_shorthand)
1556 }
1557
1558 fn rewrite_struct_lit<'a>(
1559     context: &RewriteContext,
1560     path: &ast::Path,
1561     fields: &'a [ast::Field],
1562     base: Option<&'a ast::Expr>,
1563     span: Span,
1564     shape: Shape,
1565 ) -> Option<String> {
1566     debug!("rewrite_struct_lit: shape {:?}", shape);
1567
1568     enum StructLitField<'a> {
1569         Regular(&'a ast::Field),
1570         Base(&'a ast::Expr),
1571     }
1572
1573     // 2 = " {".len()
1574     let path_shape = shape.sub_width(2)?;
1575     let path_str = rewrite_path(context, PathContext::Expr, None, path, path_shape)?;
1576
1577     if fields.is_empty() && base.is_none() {
1578         return Some(format!("{} {{}}", path_str));
1579     }
1580
1581     // Foo { a: Foo } - indent is +3, width is -5.
1582     let (h_shape, v_shape) = struct_lit_shape(shape, context, path_str.len() + 3, 2)?;
1583
1584     let one_line_width = h_shape.map_or(0, |shape| shape.width);
1585     let body_lo = context.snippet_provider.span_after(span, "{");
1586     let fields_str = if struct_lit_can_be_aligned(fields, base)
1587         && context.config.struct_field_align_threshold() > 0
1588     {
1589         rewrite_with_alignment(
1590             fields,
1591             context,
1592             v_shape,
1593             mk_sp(body_lo, span.hi()),
1594             one_line_width,
1595         )?
1596     } else {
1597         let field_iter = fields
1598             .iter()
1599             .map(StructLitField::Regular)
1600             .chain(base.into_iter().map(StructLitField::Base));
1601
1602         let span_lo = |item: &StructLitField| match *item {
1603             StructLitField::Regular(field) => field.span().lo(),
1604             StructLitField::Base(expr) => {
1605                 let last_field_hi = fields.last().map_or(span.lo(), |field| field.span.hi());
1606                 let snippet = context.snippet(mk_sp(last_field_hi, expr.span.lo()));
1607                 let pos = snippet.find_uncommented("..").unwrap();
1608                 last_field_hi + BytePos(pos as u32)
1609             }
1610         };
1611         let span_hi = |item: &StructLitField| match *item {
1612             StructLitField::Regular(field) => field.span().hi(),
1613             StructLitField::Base(expr) => expr.span.hi(),
1614         };
1615         let rewrite = |item: &StructLitField| match *item {
1616             StructLitField::Regular(field) => {
1617                 // The 1 taken from the v_budget is for the comma.
1618                 rewrite_field(context, field, v_shape.sub_width(1)?, 0)
1619             }
1620             StructLitField::Base(expr) => {
1621                 // 2 = ..
1622                 expr.rewrite(context, v_shape.offset_left(2)?)
1623                     .map(|s| format!("..{}", s))
1624             }
1625         };
1626
1627         let items = itemize_list(
1628             context.snippet_provider,
1629             field_iter,
1630             "}",
1631             ",",
1632             span_lo,
1633             span_hi,
1634             rewrite,
1635             body_lo,
1636             span.hi(),
1637             false,
1638         );
1639         let item_vec = items.collect::<Vec<_>>();
1640
1641         let tactic = struct_lit_tactic(h_shape, context, &item_vec);
1642         let nested_shape = shape_for_tactic(tactic, h_shape, v_shape);
1643
1644         let ends_with_comma = span_ends_with_comma(context, span);
1645         let force_no_trailing_comma = context.inside_macro() && !ends_with_comma;
1646
1647         let fmt = struct_lit_formatting(
1648             nested_shape,
1649             tactic,
1650             context,
1651             force_no_trailing_comma || base.is_some() || !context.use_block_indent(),
1652         );
1653
1654         write_list(&item_vec, &fmt)?
1655     };
1656
1657     let fields_str = wrap_struct_field(context, &fields_str, shape, v_shape, one_line_width);
1658     Some(format!("{} {{{}}}", path_str, fields_str))
1659
1660     // FIXME if context.config.indent_style() == Visual, but we run out
1661     // of space, we should fall back to BlockIndent.
1662 }
1663
1664 pub fn wrap_struct_field(
1665     context: &RewriteContext,
1666     fields_str: &str,
1667     shape: Shape,
1668     nested_shape: Shape,
1669     one_line_width: usize,
1670 ) -> String {
1671     if context.config.indent_style() == IndentStyle::Block
1672         && (fields_str.contains('\n')
1673             || !context.config.struct_lit_single_line()
1674             || fields_str.len() > one_line_width)
1675     {
1676         format!(
1677             "{}{}{}",
1678             nested_shape.indent.to_string_with_newline(context.config),
1679             fields_str,
1680             shape.indent.to_string_with_newline(context.config)
1681         )
1682     } else {
1683         // One liner or visual indent.
1684         format!(" {} ", fields_str)
1685     }
1686 }
1687
1688 pub fn struct_lit_field_separator(config: &Config) -> &str {
1689     colon_spaces(config.space_before_colon(), config.space_after_colon())
1690 }
1691
1692 pub fn rewrite_field(
1693     context: &RewriteContext,
1694     field: &ast::Field,
1695     shape: Shape,
1696     prefix_max_width: usize,
1697 ) -> Option<String> {
1698     if contains_skip(&field.attrs) {
1699         return Some(context.snippet(field.span()).to_owned());
1700     }
1701     let mut attrs_str = field.attrs.rewrite(context, shape)?;
1702     if !attrs_str.is_empty() {
1703         attrs_str.push_str(&shape.indent.to_string_with_newline(context.config));
1704     };
1705     let name = context.snippet(field.ident.span);
1706     if field.is_shorthand {
1707         Some(attrs_str + name)
1708     } else {
1709         let mut separator = String::from(struct_lit_field_separator(context.config));
1710         for _ in 0..prefix_max_width.saturating_sub(name.len()) {
1711             separator.push(' ');
1712         }
1713         let overhead = name.len() + separator.len();
1714         let expr_shape = shape.offset_left(overhead)?;
1715         let expr = field.expr.rewrite(context, expr_shape);
1716
1717         match expr {
1718             Some(ref e) if e.as_str() == name && context.config.use_field_init_shorthand() => {
1719                 Some(attrs_str + name)
1720             }
1721             Some(e) => Some(format!("{}{}{}{}", attrs_str, name, separator, e)),
1722             None => {
1723                 let expr_offset = shape.indent.block_indent(context.config);
1724                 let expr = field
1725                     .expr
1726                     .rewrite(context, Shape::indented(expr_offset, context.config));
1727                 expr.map(|s| {
1728                     format!(
1729                         "{}{}:\n{}{}",
1730                         attrs_str,
1731                         name,
1732                         expr_offset.to_string(context.config),
1733                         s
1734                     )
1735                 })
1736             }
1737         }
1738     }
1739 }
1740
1741 fn rewrite_tuple_in_visual_indent_style<'a, T: 'a + IntoOverflowableItem<'a>>(
1742     context: &RewriteContext,
1743     mut items: impl Iterator<Item = &'a T>,
1744     span: Span,
1745     shape: Shape,
1746     is_singleton_tuple: bool,
1747 ) -> Option<String> {
1748     // In case of length 1, need a trailing comma
1749     debug!("rewrite_tuple_in_visual_indent_style {:?}", shape);
1750     if is_singleton_tuple {
1751         // 3 = "(" + ",)"
1752         let nested_shape = shape.sub_width(3)?.visual_indent(1);
1753         return items
1754             .next()
1755             .unwrap()
1756             .rewrite(context, nested_shape)
1757             .map(|s| format!("({},)", s));
1758     }
1759
1760     let list_lo = context.snippet_provider.span_after(span, "(");
1761     let nested_shape = shape.sub_width(2)?.visual_indent(1);
1762     let items = itemize_list(
1763         context.snippet_provider,
1764         items,
1765         ")",
1766         ",",
1767         |item| item.span().lo(),
1768         |item| item.span().hi(),
1769         |item| item.rewrite(context, nested_shape),
1770         list_lo,
1771         span.hi() - BytePos(1),
1772         false,
1773     );
1774     let item_vec: Vec<_> = items.collect();
1775     let tactic = definitive_tactic(
1776         &item_vec,
1777         ListTactic::HorizontalVertical,
1778         Separator::Comma,
1779         nested_shape.width,
1780     );
1781     let fmt = ListFormatting::new(nested_shape, context.config)
1782         .tactic(tactic)
1783         .ends_with_newline(false);
1784     let list_str = write_list(&item_vec, &fmt)?;
1785
1786     Some(format!("({})", list_str))
1787 }
1788
1789 pub fn rewrite_tuple<'a, T: 'a + IntoOverflowableItem<'a>>(
1790     context: &'a RewriteContext,
1791     items: impl Iterator<Item = &'a T>,
1792     span: Span,
1793     shape: Shape,
1794     is_singleton_tuple: bool,
1795 ) -> Option<String> {
1796     debug!("rewrite_tuple {:?}", shape);
1797     if context.use_block_indent() {
1798         // We use the same rule as function calls for rewriting tuples.
1799         let force_tactic = if context.inside_macro() {
1800             if span_ends_with_comma(context, span) {
1801                 Some(SeparatorTactic::Always)
1802             } else {
1803                 Some(SeparatorTactic::Never)
1804             }
1805         } else if is_singleton_tuple {
1806             Some(SeparatorTactic::Always)
1807         } else {
1808             None
1809         };
1810         overflow::rewrite_with_parens(
1811             context,
1812             "",
1813             items,
1814             shape,
1815             span,
1816             context.config.width_heuristics().fn_call_width,
1817             force_tactic,
1818         )
1819     } else {
1820         rewrite_tuple_in_visual_indent_style(context, items, span, shape, is_singleton_tuple)
1821     }
1822 }
1823
1824 pub fn rewrite_unary_prefix<R: Rewrite>(
1825     context: &RewriteContext,
1826     prefix: &str,
1827     rewrite: &R,
1828     shape: Shape,
1829 ) -> Option<String> {
1830     rewrite
1831         .rewrite(context, shape.offset_left(prefix.len())?)
1832         .map(|r| format!("{}{}", prefix, r))
1833 }
1834
1835 // FIXME: this is probably not correct for multi-line Rewrites. we should
1836 // subtract suffix.len() from the last line budget, not the first!
1837 pub fn rewrite_unary_suffix<R: Rewrite>(
1838     context: &RewriteContext,
1839     suffix: &str,
1840     rewrite: &R,
1841     shape: Shape,
1842 ) -> Option<String> {
1843     rewrite
1844         .rewrite(context, shape.sub_width(suffix.len())?)
1845         .map(|mut r| {
1846             r.push_str(suffix);
1847             r
1848         })
1849 }
1850
1851 fn rewrite_unary_op(
1852     context: &RewriteContext,
1853     op: ast::UnOp,
1854     expr: &ast::Expr,
1855     shape: Shape,
1856 ) -> Option<String> {
1857     // For some reason, an UnOp is not spanned like BinOp!
1858     rewrite_unary_prefix(context, ast::UnOp::to_string(op), expr, shape)
1859 }
1860
1861 fn rewrite_assignment(
1862     context: &RewriteContext,
1863     lhs: &ast::Expr,
1864     rhs: &ast::Expr,
1865     op: Option<&ast::BinOp>,
1866     shape: Shape,
1867 ) -> Option<String> {
1868     let operator_str = match op {
1869         Some(op) => context.snippet(op.span),
1870         None => "=",
1871     };
1872
1873     // 1 = space between lhs and operator.
1874     let lhs_shape = shape.sub_width(operator_str.len() + 1)?;
1875     let lhs_str = format!("{} {}", lhs.rewrite(context, lhs_shape)?, operator_str);
1876
1877     rewrite_assign_rhs(context, lhs_str, rhs, shape)
1878 }
1879
1880 /// Controls where to put the rhs.
1881 #[derive(Debug, Copy, Clone, PartialEq, Eq)]
1882 pub enum RhsTactics {
1883     /// Use heuristics.
1884     Default,
1885     /// Put the rhs on the next line if it uses multiple line, without extra indentation.
1886     ForceNextLineWithoutIndent,
1887 }
1888
1889 // The left hand side must contain everything up to, and including, the
1890 // assignment operator.
1891 pub fn rewrite_assign_rhs<S: Into<String>, R: Rewrite>(
1892     context: &RewriteContext,
1893     lhs: S,
1894     ex: &R,
1895     shape: Shape,
1896 ) -> Option<String> {
1897     rewrite_assign_rhs_with(context, lhs, ex, shape, RhsTactics::Default)
1898 }
1899
1900 pub fn rewrite_assign_rhs_with<S: Into<String>, R: Rewrite>(
1901     context: &RewriteContext,
1902     lhs: S,
1903     ex: &R,
1904     shape: Shape,
1905     rhs_tactics: RhsTactics,
1906 ) -> Option<String> {
1907     let lhs = lhs.into();
1908     let last_line_width = last_line_width(&lhs).saturating_sub(if lhs.contains('\n') {
1909         shape.indent.width()
1910     } else {
1911         0
1912     });
1913     // 1 = space between operator and rhs.
1914     let orig_shape = shape.offset_left(last_line_width + 1).unwrap_or(Shape {
1915         width: 0,
1916         offset: shape.offset + last_line_width + 1,
1917         ..shape
1918     });
1919     let rhs = choose_rhs(
1920         context,
1921         ex,
1922         orig_shape,
1923         ex.rewrite(context, orig_shape),
1924         rhs_tactics,
1925     )?;
1926     Some(lhs + &rhs)
1927 }
1928
1929 fn choose_rhs<R: Rewrite>(
1930     context: &RewriteContext,
1931     expr: &R,
1932     shape: Shape,
1933     orig_rhs: Option<String>,
1934     rhs_tactics: RhsTactics,
1935 ) -> Option<String> {
1936     match orig_rhs {
1937         Some(ref new_str) if !new_str.contains('\n') && new_str.len() <= shape.width => {
1938             Some(format!(" {}", new_str))
1939         }
1940         _ => {
1941             // Expression did not fit on the same line as the identifier.
1942             // Try splitting the line and see if that works better.
1943             let new_shape = shape_from_rhs_tactic(context, shape, rhs_tactics)?;
1944             let new_rhs = expr.rewrite(context, new_shape);
1945             let new_indent_str = &shape
1946                 .indent
1947                 .block_indent(context.config)
1948                 .to_string_with_newline(context.config);
1949
1950             match (orig_rhs, new_rhs) {
1951                 (Some(ref orig_rhs), Some(ref new_rhs))
1952                     if wrap_str(new_rhs.clone(), context.config.max_width(), new_shape)
1953                         .is_none() =>
1954                 {
1955                     Some(format!(" {}", orig_rhs))
1956                 }
1957                 (Some(ref orig_rhs), Some(ref new_rhs))
1958                     if prefer_next_line(orig_rhs, new_rhs, rhs_tactics) =>
1959                 {
1960                     Some(format!("{}{}", new_indent_str, new_rhs))
1961                 }
1962                 (None, Some(ref new_rhs)) => Some(format!("{}{}", new_indent_str, new_rhs)),
1963                 (None, None) => None,
1964                 (Some(orig_rhs), _) => Some(format!(" {}", orig_rhs)),
1965             }
1966         }
1967     }
1968 }
1969
1970 fn shape_from_rhs_tactic(
1971     context: &RewriteContext,
1972     shape: Shape,
1973     rhs_tactic: RhsTactics,
1974 ) -> Option<Shape> {
1975     match rhs_tactic {
1976         RhsTactics::ForceNextLineWithoutIndent => shape
1977             .with_max_width(context.config)
1978             .sub_width(shape.indent.width()),
1979         RhsTactics::Default => {
1980             Shape::indented(shape.indent.block_indent(context.config), context.config)
1981                 .sub_width(shape.rhs_overhead(context.config))
1982         }
1983     }
1984 }
1985
1986 pub fn prefer_next_line(orig_rhs: &str, next_line_rhs: &str, rhs_tactics: RhsTactics) -> bool {
1987     rhs_tactics == RhsTactics::ForceNextLineWithoutIndent
1988         || !next_line_rhs.contains('\n')
1989         || count_newlines(orig_rhs) > count_newlines(next_line_rhs) + 1
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         || first_line_ends_with(orig_rhs, '[') && !first_line_ends_with(next_line_rhs, '[')
1993 }
1994
1995 fn rewrite_expr_addrof(
1996     context: &RewriteContext,
1997     mutability: ast::Mutability,
1998     expr: &ast::Expr,
1999     shape: Shape,
2000 ) -> Option<String> {
2001     let operator_str = match mutability {
2002         ast::Mutability::Immutable => "&",
2003         ast::Mutability::Mutable => "&mut ",
2004     };
2005     rewrite_unary_prefix(context, operator_str, expr, shape)
2006 }
2007
2008 pub fn is_method_call(expr: &ast::Expr) -> bool {
2009     match expr.node {
2010         ast::ExprKind::MethodCall(..) => true,
2011         ast::ExprKind::AddrOf(_, ref expr)
2012         | ast::ExprKind::Box(ref expr)
2013         | ast::ExprKind::Cast(ref expr, _)
2014         | ast::ExprKind::Try(ref expr)
2015         | ast::ExprKind::Unary(_, ref expr) => is_method_call(expr),
2016         _ => false,
2017     }
2018 }
2019
2020 #[cfg(test)]
2021 mod test {
2022     use super::last_line_offsetted;
2023
2024     #[test]
2025     fn test_last_line_offsetted() {
2026         let lines = "one\n    two";
2027         assert_eq!(last_line_offsetted(2, lines), true);
2028         assert_eq!(last_line_offsetted(4, lines), false);
2029         assert_eq!(last_line_offsetted(6, lines), false);
2030
2031         let lines = "one    two";
2032         assert_eq!(last_line_offsetted(2, lines), false);
2033         assert_eq!(last_line_offsetted(0, lines), false);
2034
2035         let lines = "\ntwo";
2036         assert_eq!(last_line_offsetted(2, lines), false);
2037         assert_eq!(last_line_offsetted(0, lines), false);
2038
2039         let lines = "one\n    two      three";
2040         assert_eq!(last_line_offsetted(2, lines), true);
2041         let lines = "one\n two      three";
2042         assert_eq!(last_line_offsetted(2, lines), false);
2043     }
2044 }