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(
 594     context: &RewriteContext<'_>,
 595     expr: &ast::Expr,
 596     shape: Shape,
 597 ) -> Option<String> {
 598     match expr.node {
 599         ast::ExprKind::Match(ref cond, _) => {
 600             // `match `cond` {`
 601             let cond_shape = match context.config.indent_style() {
 602                 IndentStyle::Visual => shape.shrink_left(6).and_then(|s| s.sub_width(2))?,
 603                 IndentStyle::Block => shape.offset_left(8)?,
 604             };
 605             cond.rewrite(context, cond_shape)
 606         }
 607         _ => to_control_flow(expr, ExprType::SubExpression).and_then(|control_flow| {
 608             let alt_block_sep =
 609                 String::from("\n") + &shape.indent.block_only().to_string(context.config);
 610             control_flow
 611                 .rewrite_cond(context, shape, &alt_block_sep)
 612                 .and_then(|rw| Some(rw.0))
 613         }),
 614     }
 615 }
 616
 617 // Abstraction over control flow expressions
 618 #[derive(Debug)]
 619 struct ControlFlow<'a> {
 620     cond: Option<&'a ast::Expr>,
 621     block: &'a ast::Block,
 622     else_block: Option<&'a ast::Expr>,
 623     label: Option<ast::Label>,
 624     pats: Vec<&'a ast::Pat>,
 625     keyword: &'a str,
 626     matcher: &'a str,
 627     connector: &'a str,
 628     allow_single_line: bool,
 629     // True if this is an `if` expression in an `else if` :-( hacky
 630     nested_if: bool,
 631     span: Span,
 632 }
 633
 634 fn to_control_flow(expr: &ast::Expr, expr_type: ExprType) -> Option<ControlFlow<'_>> {
 635     match expr.node {
 636         ast::ExprKind::If(ref cond, ref if_block, ref else_block) => Some(ControlFlow::new_if(
 637             cond,
 638             vec![],
 639             if_block,
 640             else_block.as_ref().map(|e| &**e),
 641             expr_type == ExprType::SubExpression,
 642             false,
 643             expr.span,
 644         )),
 645         ast::ExprKind::IfLet(ref pat, ref cond, ref if_block, ref else_block) => {
 646             Some(ControlFlow::new_if(
 647                 cond,
 648                 ptr_vec_to_ref_vec(pat),
 649                 if_block,
 650                 else_block.as_ref().map(|e| &**e),
 651                 expr_type == ExprType::SubExpression,
 652                 false,
 653                 expr.span,
 654             ))
 655         }
 656         ast::ExprKind::ForLoop(ref pat, ref cond, ref block, label) => {
 657             Some(ControlFlow::new_for(pat, cond, block, label, expr.span))
 658         }
 659         ast::ExprKind::Loop(ref block, label) => {
 660             Some(ControlFlow::new_loop(block, label, expr.span))
 661         }
 662         ast::ExprKind::While(ref cond, ref block, label) => Some(ControlFlow::new_while(
 663             vec![],
 664             cond,
 665             block,
 666             label,
 667             expr.span,
 668         )),
 669         ast::ExprKind::WhileLet(ref pat, ref cond, ref block, label) => Some(
 670             ControlFlow::new_while(ptr_vec_to_ref_vec(pat), cond, block, label, expr.span),
 671         ),
 672         _ => None,
 673     }
 674 }
 675
 676 fn choose_matcher(pats: &[&ast::Pat]) -> &'static str {
 677     if pats.is_empty() {
 678         ""
 679     } else {
 680         "let"
 681     }
 682 }
 683
 684 impl<'a> ControlFlow<'a> {
 685     fn new_if(
 686         cond: &'a ast::Expr,
 687         pats: Vec<&'a ast::Pat>,
 688         block: &'a ast::Block,
 689         else_block: Option<&'a ast::Expr>,
 690         allow_single_line: bool,
 691         nested_if: bool,
 692         span: Span,
 693     ) -> ControlFlow<'a> {
 694         let matcher = choose_matcher(&pats);
 695         ControlFlow {
 696             cond: Some(cond),
 697             block,
 698             else_block,
 699             label: None,
 700             pats,
 701             keyword: "if",
 702             matcher,
 703             connector: " =",
 704             allow_single_line,
 705             nested_if,
 706             span,
 707         }
 708     }
 709
 710     fn new_loop(block: &'a ast::Block, label: Option<ast::Label>, span: Span) -> ControlFlow<'a> {
 711         ControlFlow {
 712             cond: None,
 713             block,
 714             else_block: None,
 715             label,
 716             pats: vec![],
 717             keyword: "loop",
 718             matcher: "",
 719             connector: "",
 720             allow_single_line: false,
 721             nested_if: false,
 722             span,
 723         }
 724     }
 725
 726     fn new_while(
 727         pats: Vec<&'a ast::Pat>,
 728         cond: &'a ast::Expr,
 729         block: &'a ast::Block,
 730         label: Option<ast::Label>,
 731         span: Span,
 732     ) -> ControlFlow<'a> {
 733         let matcher = choose_matcher(&pats);
 734         ControlFlow {
 735             cond: Some(cond),
 736             block,
 737             else_block: None,
 738             label,
 739             pats,
 740             keyword: "while",
 741             matcher,
 742             connector: " =",
 743             allow_single_line: false,
 744             nested_if: false,
 745             span,
 746         }
 747     }
 748
 749     fn new_for(
 750         pat: &'a ast::Pat,
 751         cond: &'a ast::Expr,
 752         block: &'a ast::Block,
 753         label: Option<ast::Label>,
 754         span: Span,
 755     ) -> ControlFlow<'a> {
 756         ControlFlow {
 757             cond: Some(cond),
 758             block,
 759             else_block: None,
 760             label,
 761             pats: vec![pat],
 762             keyword: "for",
 763             matcher: "",
 764             connector: " in",
 765             allow_single_line: false,
 766             nested_if: false,
 767             span,
 768         }
 769     }
 770
 771     fn rewrite_single_line(
 772         &self,
 773         pat_expr_str: &str,
 774         context: &RewriteContext<'_>,
 775         width: usize,
 776     ) -> Option<String> {
 777         assert!(self.allow_single_line);
 778         let else_block = self.else_block?;
 779         let fixed_cost = self.keyword.len() + "  {  } else {  }".len();
 780
 781         if let ast::ExprKind::Block(ref else_node, _) = else_block.node {
 782             if !is_simple_block(self.block, None, context.source_map)
 783                 || !is_simple_block(else_node, None, context.source_map)
 784                 || pat_expr_str.contains('\n')
 785             {
 786                 return None;
 787             }
 788
 789             let new_width = width.checked_sub(pat_expr_str.len() + fixed_cost)?;
 790             let expr = &self.block.stmts[0];
 791             let if_str = expr.rewrite(context, Shape::legacy(new_width, Indent::empty()))?;
 792
 793             let new_width = new_width.checked_sub(if_str.len())?;
 794             let else_expr = &else_node.stmts[0];
 795             let else_str = else_expr.rewrite(context, Shape::legacy(new_width, Indent::empty()))?;
 796
 797             if if_str.contains('\n') || else_str.contains('\n') {
 798                 return None;
 799             }
 800
 801             let result = format!(
 802                 "{} {} {{ {} }} else {{ {} }}",
 803                 self.keyword, pat_expr_str, if_str, else_str
 804             );
 805
 806             if result.len() <= width {
 807                 return Some(result);
 808             }
 809         }
 810
 811         None
 812     }
 813 }
 814
 815 /// Returns true if the last line of pat_str has leading whitespace and it is wider than the
 816 /// shape's indent.
 817 fn last_line_offsetted(start_column: usize, pat_str: &str) -> bool {
 818     let mut leading_whitespaces = 0;
 819     for c in pat_str.chars().rev() {
 820         match c {
 821             '\n' => break,
 822             _ if c.is_whitespace() => leading_whitespaces += 1,
 823             _ => leading_whitespaces = 0,
 824         }
 825     }
 826     leading_whitespaces > start_column
 827 }
 828
 829 impl<'a> ControlFlow<'a> {
 830     fn rewrite_pat_expr(
 831         &self,
 832         context: &RewriteContext<'_>,
 833         expr: &ast::Expr,
 834         shape: Shape,
 835         offset: usize,
 836     ) -> Option<String> {
 837         debug!("rewrite_pat_expr {:?} {:?} {:?}", shape, self.pats, expr);
 838
 839         let cond_shape = shape.offset_left(offset)?;
 840         if !self.pats.is_empty() {
 841             let matcher = if self.matcher.is_empty() {
 842                 self.matcher.to_owned()
 843             } else {
 844                 format!("{} ", self.matcher)
 845             };
 846             let pat_shape = cond_shape
 847                 .offset_left(matcher.len())?
 848                 .sub_width(self.connector.len())?;
 849             let pat_string = rewrite_multiple_patterns(context, &self.pats, pat_shape)?;
 850             let result = format!("{}{}{}", matcher, pat_string, self.connector);
 851             return rewrite_assign_rhs(context, result, expr, cond_shape);
 852         }
 853
 854         let expr_rw = expr.rewrite(context, cond_shape);
 855         // The expression may (partially) fit on the current line.
 856         // We do not allow splitting between `if` and condition.
 857         if self.keyword == "if" || expr_rw.is_some() {
 858             return expr_rw;
 859         }
 860
 861         // The expression won't fit on the current line, jump to next.
 862         let nested_shape = shape
 863             .block_indent(context.config.tab_spaces())
 864             .with_max_width(context.config);
 865         let nested_indent_str = nested_shape.indent.to_string_with_newline(context.config);
 866         expr.rewrite(context, nested_shape)
 867             .map(|expr_rw| format!("{}{}", nested_indent_str, expr_rw))
 868     }
 869
 870     fn rewrite_cond(
 871         &self,
 872         context: &RewriteContext<'_>,
 873         shape: Shape,
 874         alt_block_sep: &str,
 875     ) -> Option<(String, usize)> {
 876         // Do not take the rhs overhead from the upper expressions into account
 877         // when rewriting pattern.
 878         let new_width = context.budget(shape.used_width());
 879         let fresh_shape = Shape {
 880             width: new_width,
 881             ..shape
 882         };
 883         let constr_shape = if self.nested_if {
 884             // We are part of an if-elseif-else chain. Our constraints are tightened.
 885             // 7 = "} else " .len()
 886             fresh_shape.offset_left(7)?
 887         } else {
 888             fresh_shape
 889         };
 890
 891         let label_string = rewrite_label(self.label);
 892         // 1 = space after keyword.
 893         let offset = self.keyword.len() + label_string.len() + 1;
 894
 895         let pat_expr_string = match self.cond {
 896             Some(cond) => self.rewrite_pat_expr(context, cond, constr_shape, offset)?,
 897             None => String::new(),
 898         };
 899
 900         let brace_overhead =
 901             if context.config.control_brace_style() != ControlBraceStyle::AlwaysNextLine {
 902                 // 2 = ` {`
 903                 2
 904             } else {
 905                 0
 906             };
 907         let one_line_budget = context
 908             .config
 909             .max_width()
 910             .saturating_sub(constr_shape.used_width() + offset + brace_overhead);
 911         let force_newline_brace = (pat_expr_string.contains('\n')
 912             || pat_expr_string.len() > one_line_budget)
 913             && (!last_line_extendable(&pat_expr_string)
 914                 || last_line_offsetted(shape.used_width(), &pat_expr_string));
 915
 916         // Try to format if-else on single line.
 917         if self.allow_single_line
 918             && context
 919                 .config
 920                 .width_heuristics()
 921                 .single_line_if_else_max_width
 922                 > 0
 923         {
 924             let trial = self.rewrite_single_line(&pat_expr_string, context, shape.width);
 925
 926             if let Some(cond_str) = trial {
 927                 if cond_str.len()
 928                     <= context
 929                         .config
 930                         .width_heuristics()
 931                         .single_line_if_else_max_width
 932                 {
 933                     return Some((cond_str, 0));
 934                 }
 935             }
 936         }
 937
 938         let cond_span = if let Some(cond) = self.cond {
 939             cond.span
 940         } else {
 941             mk_sp(self.block.span.lo(), self.block.span.lo())
 942         };
 943
 944         // `for event in event`
 945         // Do not include label in the span.
 946         let lo = self
 947             .label
 948             .map_or(self.span.lo(), |label| label.ident.span.hi());
 949         let between_kwd_cond = mk_sp(
 950             context
 951                 .snippet_provider
 952                 .span_after(mk_sp(lo, self.span.hi()), self.keyword.trim()),
 953             if self.pats.is_empty() {
 954                 cond_span.lo()
 955             } else if self.matcher.is_empty() {
 956                 self.pats[0].span.lo()
 957             } else {
 958                 context
 959                     .snippet_provider
 960                     .span_before(self.span, self.matcher.trim())
 961             },
 962         );
 963
 964         let between_kwd_cond_comment = extract_comment(between_kwd_cond, context, shape);
 965
 966         let after_cond_comment =
 967             extract_comment(mk_sp(cond_span.hi(), self.block.span.lo()), context, shape);
 968
 969         let block_sep = if self.cond.is_none() && between_kwd_cond_comment.is_some() {
 970             ""
 971         } else if context.config.control_brace_style() == ControlBraceStyle::AlwaysNextLine
 972             || force_newline_brace
 973         {
 974             alt_block_sep
 975         } else {
 976             " "
 977         };
 978
 979         let used_width = if pat_expr_string.contains('\n') {
 980             last_line_width(&pat_expr_string)
 981         } else {
 982             // 2 = spaces after keyword and condition.
 983             label_string.len() + self.keyword.len() + pat_expr_string.len() + 2
 984         };
 985
 986         Some((
 987             format!(
 988                 "{}{}{}{}{}",
 989                 label_string,
 990                 self.keyword,
 991                 between_kwd_cond_comment.as_ref().map_or(
 992                     if pat_expr_string.is_empty() || pat_expr_string.starts_with('\n') {
 993                         ""
 994                     } else {
 995                         " "
 996                     },
 997                     |s| &**s,
 998                 ),
 999                 pat_expr_string,
1000                 after_cond_comment.as_ref().map_or(block_sep, |s| &**s)
1001             ),
1002             used_width,
1003         ))
1004     }
1005 }
1006
1007 impl<'a> Rewrite for ControlFlow<'a> {
1008     fn rewrite(&self, context: &RewriteContext<'_>, shape: Shape) -> Option<String> {
1009         debug!("ControlFlow::rewrite {:?} {:?}", self, shape);
1010
1011         let alt_block_sep = &shape.indent.to_string_with_newline(context.config);
1012         let (cond_str, used_width) = self.rewrite_cond(context, shape, alt_block_sep)?;
1013         // If `used_width` is 0, it indicates that whole control flow is written in a single line.
1014         if used_width == 0 {
1015             return Some(cond_str);
1016         }
1017
1018         let block_width = shape.width.saturating_sub(used_width);
1019         // This is used only for the empty block case: `{}`. So, we use 1 if we know
1020         // we should avoid the single line case.
1021         let block_width = if self.else_block.is_some() || self.nested_if {
1022             min(1, block_width)
1023         } else {
1024             block_width
1025         };
1026         let block_shape = Shape {
1027             width: block_width,
1028             ..shape
1029         };
1030         let block_str = {
1031             let old_val = context.is_if_else_block.replace(self.else_block.is_some());
1032             let result =
1033                 rewrite_block_with_visitor(context, "", self.block, None, None, block_shape, true);
1034             context.is_if_else_block.replace(old_val);
1035             result?
1036         };
1037
1038         let mut result = format!("{}{}", cond_str, block_str);
1039
1040         if let Some(else_block) = self.else_block {
1041             let shape = Shape::indented(shape.indent, context.config);
1042             let mut last_in_chain = false;
1043             let rewrite = match else_block.node {
1044                 // If the else expression is another if-else expression, prevent it
1045                 // from being formatted on a single line.
1046                 // Note how we're passing the original shape, as the
1047                 // cost of "else" should not cascade.
1048                 ast::ExprKind::IfLet(ref pat, ref cond, ref if_block, ref next_else_block) => {
1049                     ControlFlow::new_if(
1050                         cond,
1051                         ptr_vec_to_ref_vec(pat),
1052                         if_block,
1053                         next_else_block.as_ref().map(|e| &**e),
1054                         false,
1055                         true,
1056                         mk_sp(else_block.span.lo(), self.span.hi()),
1057                     )
1058                     .rewrite(context, shape)
1059                 }
1060                 ast::ExprKind::If(ref cond, ref if_block, ref next_else_block) => {
1061                     ControlFlow::new_if(
1062                         cond,
1063                         vec![],
1064                         if_block,
1065                         next_else_block.as_ref().map(|e| &**e),
1066                         false,
1067                         true,
1068                         mk_sp(else_block.span.lo(), self.span.hi()),
1069                     )
1070                     .rewrite(context, shape)
1071                 }
1072                 _ => {
1073                     last_in_chain = true;
1074                     // When rewriting a block, the width is only used for single line
1075                     // blocks, passing 1 lets us avoid that.
1076                     let else_shape = Shape {
1077                         width: min(1, shape.width),
1078                         ..shape
1079                     };
1080                     format_expr(else_block, ExprType::Statement, context, else_shape)
1081                 }
1082             };
1083
1084             let between_kwd_else_block = mk_sp(
1085                 self.block.span.hi(),
1086                 context
1087                     .snippet_provider
1088                     .span_before(mk_sp(self.block.span.hi(), else_block.span.lo()), "else"),
1089             );
1090             let between_kwd_else_block_comment =
1091                 extract_comment(between_kwd_else_block, context, shape);
1092
1093             let after_else = mk_sp(
1094                 context
1095                     .snippet_provider
1096                     .span_after(mk_sp(self.block.span.hi(), else_block.span.lo()), "else"),
1097                 else_block.span.lo(),
1098             );
1099             let after_else_comment = extract_comment(after_else, context, shape);
1100
1101             let between_sep = match context.config.control_brace_style() {
1102                 ControlBraceStyle::AlwaysNextLine | ControlBraceStyle::ClosingNextLine => {
1103                     &*alt_block_sep
1104                 }
1105                 ControlBraceStyle::AlwaysSameLine => " ",
1106             };
1107             let after_sep = match context.config.control_brace_style() {
1108                 ControlBraceStyle::AlwaysNextLine if last_in_chain => &*alt_block_sep,
1109                 _ => " ",
1110             };
1111
1112             result.push_str(&format!(
1113                 "{}else{}",
1114                 between_kwd_else_block_comment
1115                     .as_ref()
1116                     .map_or(between_sep, |s| &**s),
1117                 after_else_comment.as_ref().map_or(after_sep, |s| &**s),
1118             ));
1119             result.push_str(&rewrite?);
1120         }
1121
1122         Some(result)
1123     }
1124 }
1125
1126 fn rewrite_label(opt_label: Option<ast::Label>) -> Cow<'static, str> {
1127     match opt_label {
1128         Some(label) => Cow::from(format!("{}: ", label.ident)),
1129         None => Cow::from(""),
1130     }
1131 }
1132
1133 fn extract_comment(span: Span, context: &RewriteContext<'_>, shape: Shape) -> Option<String> {
1134     match rewrite_missing_comment(span, shape, context) {
1135         Some(ref comment) if !comment.is_empty() => Some(format!(
1136             "{indent}{}{indent}",
1137             comment,
1138             indent = shape.indent.to_string_with_newline(context.config)
1139         )),
1140         _ => None,
1141     }
1142 }
1143
1144 pub fn block_contains_comment(block: &ast::Block, source_map: &SourceMap) -> bool {
1145     let snippet = source_map.span_to_snippet(block.span).unwrap();
1146     contains_comment(&snippet)
1147 }
1148
1149 // Checks that a block contains no statements, an expression and no comments or
1150 // attributes.
1151 // FIXME: incorrectly returns false when comment is contained completely within
1152 // the expression.
1153 pub fn is_simple_block(
1154     block: &ast::Block,
1155     attrs: Option<&[ast::Attribute]>,
1156     source_map: &SourceMap,
1157 ) -> bool {
1158     (block.stmts.len() == 1
1159         && stmt_is_expr(&block.stmts[0])
1160         && !block_contains_comment(block, source_map)
1161         && attrs.map_or(true, |a| a.is_empty()))
1162 }
1163
1164 /// Checks whether a block contains at most one statement or expression, and no
1165 /// comments or attributes.
1166 pub fn is_simple_block_stmt(
1167     block: &ast::Block,
1168     attrs: Option<&[ast::Attribute]>,
1169     source_map: &SourceMap,
1170 ) -> bool {
1171     block.stmts.len() <= 1
1172         && !block_contains_comment(block, source_map)
1173         && attrs.map_or(true, |a| a.is_empty())
1174 }
1175
1176 /// Checks whether a block contains no statements, expressions, comments, or
1177 /// inner attributes.
1178 pub fn is_empty_block(
1179     block: &ast::Block,
1180     attrs: Option<&[ast::Attribute]>,
1181     source_map: &SourceMap,
1182 ) -> bool {
1183     block.stmts.is_empty()
1184         && !block_contains_comment(block, source_map)
1185         && attrs.map_or(true, |a| inner_attributes(a).is_empty())
1186 }
1187
1188 pub fn stmt_is_expr(stmt: &ast::Stmt) -> bool {
1189     match stmt.node {
1190         ast::StmtKind::Expr(..) => true,
1191         _ => false,
1192     }
1193 }
1194
1195 pub fn is_unsafe_block(block: &ast::Block) -> bool {
1196     if let ast::BlockCheckMode::Unsafe(..) = block.rules {
1197         true
1198     } else {
1199         false
1200     }
1201 }
1202
1203 pub fn rewrite_multiple_patterns(
1204     context: &RewriteContext<'_>,
1205     pats: &[&ast::Pat],
1206     shape: Shape,
1207 ) -> Option<String> {
1208     let pat_strs = pats
1209         .iter()
1210         .map(|p| p.rewrite(context, shape))
1211         .collect::<Option<Vec<_>>>()?;
1212
1213     let use_mixed_layout = pats
1214         .iter()
1215         .zip(pat_strs.iter())
1216         .all(|(pat, pat_str)| is_short_pattern(pat, pat_str));
1217     let items: Vec<_> = pat_strs.into_iter().map(ListItem::from_str).collect();
1218     let tactic = if use_mixed_layout {
1219         DefinitiveListTactic::Mixed
1220     } else {
1221         definitive_tactic(
1222             &items,
1223             ListTactic::HorizontalVertical,
1224             Separator::VerticalBar,
1225             shape.width,
1226         )
1227     };
1228     let fmt = ListFormatting::new(shape, context.config)
1229         .tactic(tactic)
1230         .separator(" |")
1231         .separator_place(context.config.binop_separator())
1232         .ends_with_newline(false);
1233     write_list(&items, &fmt)
1234 }
1235
1236 pub fn rewrite_literal(context: &RewriteContext<'_>, l: &ast::Lit, shape: Shape) -> Option<String> {
1237     match l.node {
1238         ast::LitKind::Str(_, ast::StrStyle::Cooked) => rewrite_string_lit(context, l.span, shape),
1239         _ => wrap_str(
1240             context.snippet(l.span).to_owned(),
1241             context.config.max_width(),
1242             shape,
1243         ),
1244     }
1245 }
1246
1247 fn rewrite_string_lit(context: &RewriteContext<'_>, span: Span, shape: Shape) -> Option<String> {
1248     let string_lit = context.snippet(span);
1249
1250     if !context.config.format_strings() {
1251         if string_lit
1252             .lines()
1253             .rev()
1254             .skip(1)
1255             .all(|line| line.ends_with('\\'))
1256         {
1257             let new_indent = shape.visual_indent(1).indent;
1258             let indented_string_lit = String::from(
1259                 string_lit
1260                     .lines()
1261                     .map(|line| {
1262                         format!(
1263                             "{}{}",
1264                             new_indent.to_string(context.config),
1265                             line.trim_start()
1266                         )
1267                     })
1268                     .collect::<Vec<_>>()
1269                     .join("\n")
1270                     .trim_start(),
1271             );
1272             return if context.config.version() == Version::Two {
1273                 Some(indented_string_lit)
1274             } else {
1275                 wrap_str(indented_string_lit, context.config.max_width(), shape)
1276             };
1277         } else {
1278             return wrap_str(string_lit.to_owned(), context.config.max_width(), shape);
1279         }
1280     }
1281
1282     // Remove the quote characters.
1283     let str_lit = &string_lit[1..string_lit.len() - 1];
1284
1285     rewrite_string(
1286         str_lit,
1287         &StringFormat::new(shape.visual_indent(0), context.config),
1288         shape.width.saturating_sub(2),
1289     )
1290 }
1291
1292 fn choose_separator_tactic(context: &RewriteContext<'_>, span: Span) -> Option<SeparatorTactic> {
1293     if context.inside_macro() {
1294         if span_ends_with_comma(context, span) {
1295             Some(SeparatorTactic::Always)
1296         } else {
1297             Some(SeparatorTactic::Never)
1298         }
1299     } else {
1300         None
1301     }
1302 }
1303
1304 pub fn rewrite_call(
1305     context: &RewriteContext<'_>,
1306     callee: &str,
1307     args: &[ptr::P<ast::Expr>],
1308     span: Span,
1309     shape: Shape,
1310 ) -> Option<String> {
1311     overflow::rewrite_with_parens(
1312         context,
1313         callee,
1314         args.iter(),
1315         shape,
1316         span,
1317         context.config.width_heuristics().fn_call_width,
1318         choose_separator_tactic(context, span),
1319     )
1320 }
1321
1322 pub fn is_simple_expr(expr: &ast::Expr) -> bool {
1323     match expr.node {
1324         ast::ExprKind::Lit(..) => true,
1325         ast::ExprKind::Path(ref qself, ref path) => qself.is_none() && path.segments.len() <= 1,
1326         ast::ExprKind::AddrOf(_, ref expr)
1327         | ast::ExprKind::Box(ref expr)
1328         | ast::ExprKind::Cast(ref expr, _)
1329         | ast::ExprKind::Field(ref expr, _)
1330         | ast::ExprKind::Try(ref expr)
1331         | ast::ExprKind::Unary(_, ref expr) => is_simple_expr(expr),
1332         ast::ExprKind::Index(ref lhs, ref rhs) => is_simple_expr(lhs) && is_simple_expr(rhs),
1333         ast::ExprKind::Repeat(ref lhs, ref rhs) => {
1334             is_simple_expr(lhs) && is_simple_expr(&*rhs.value)
1335         }
1336         _ => false,
1337     }
1338 }
1339
1340 pub fn is_every_expr_simple(lists: &[OverflowableItem<'_>]) -> bool {
1341     lists.iter().all(OverflowableItem::is_simple)
1342 }
1343
1344 pub fn can_be_overflowed_expr(
1345     context: &RewriteContext<'_>,
1346     expr: &ast::Expr,
1347     args_len: usize,
1348 ) -> bool {
1349     match expr.node {
1350         ast::ExprKind::Match(..) => {
1351             (context.use_block_indent() && args_len == 1)
1352                 || (context.config.indent_style() == IndentStyle::Visual && args_len > 1)
1353         }
1354         ast::ExprKind::If(..)
1355         | ast::ExprKind::IfLet(..)
1356         | ast::ExprKind::ForLoop(..)
1357         | ast::ExprKind::Loop(..)
1358         | ast::ExprKind::While(..)
1359         | ast::ExprKind::WhileLet(..) => {
1360             context.config.combine_control_expr() && context.use_block_indent() && args_len == 1
1361         }
1362
1363         // Handle always block-like expressions
1364         ast::ExprKind::Block(..) | ast::ExprKind::Closure(..) => true,
1365
1366         // Handle `[]` and `{}`-like expressions
1367         ast::ExprKind::Array(..) | ast::ExprKind::Struct(..) => {
1368             context.config.overflow_delimited_expr()
1369                 || (context.use_block_indent() && args_len == 1)
1370         }
1371         ast::ExprKind::Mac(ref macro_) => {
1372             match (macro_.node.delim, context.config.overflow_delimited_expr()) {
1373                 (ast::MacDelimiter::Bracket, true) | (ast::MacDelimiter::Brace, true) => true,
1374                 _ => context.use_block_indent() && args_len == 1,
1375             }
1376         }
1377
1378         // Handle parenthetical expressions
1379         ast::ExprKind::Call(..) | ast::ExprKind::MethodCall(..) | ast::ExprKind::Tup(..) => {
1380             context.use_block_indent() && args_len == 1
1381         }
1382
1383         // Handle unary-like expressions
1384         ast::ExprKind::AddrOf(_, ref expr)
1385         | ast::ExprKind::Box(ref expr)
1386         | ast::ExprKind::Try(ref expr)
1387         | ast::ExprKind::Unary(_, ref expr)
1388         | ast::ExprKind::Cast(ref expr, _) => can_be_overflowed_expr(context, expr, args_len),
1389         _ => false,
1390     }
1391 }
1392
1393 pub fn is_nested_call(expr: &ast::Expr) -> bool {
1394     match expr.node {
1395         ast::ExprKind::Call(..) | ast::ExprKind::Mac(..) => true,
1396         ast::ExprKind::AddrOf(_, ref expr)
1397         | ast::ExprKind::Box(ref expr)
1398         | ast::ExprKind::Try(ref expr)
1399         | ast::ExprKind::Unary(_, ref expr)
1400         | ast::ExprKind::Cast(ref expr, _) => is_nested_call(expr),
1401         _ => false,
1402     }
1403 }
1404
1405 /// Return true if a function call or a method call represented by the given span ends with a
1406 /// trailing comma. This function is used when rewriting macro, as adding or removing a trailing
1407 /// comma from macro can potentially break the code.
1408 pub fn span_ends_with_comma(context: &RewriteContext<'_>, span: Span) -> bool {
1409     let mut result: bool = Default::default();
1410     let mut prev_char: char = Default::default();
1411     let closing_delimiters = &[')', '}', ']'];
1412
1413     for (kind, c) in CharClasses::new(context.snippet(span).chars()) {
1414         match c {
1415             _ if kind.is_comment() || c.is_whitespace() => continue,
1416             c if closing_delimiters.contains(&c) => {
1417                 result &= !closing_delimiters.contains(&prev_char);
1418             }
1419             ',' => result = true,
1420             _ => result = false,
1421         }
1422         prev_char = c;
1423     }
1424
1425     result
1426 }
1427
1428 fn rewrite_paren(
1429     context: &RewriteContext<'_>,
1430     mut subexpr: &ast::Expr,
1431     shape: Shape,
1432     mut span: Span,
1433 ) -> Option<String> {
1434     debug!("rewrite_paren, shape: {:?}", shape);
1435
1436     // Extract comments within parens.
1437     let mut pre_span;
1438     let mut post_span;
1439     let mut pre_comment;
1440     let mut post_comment;
1441     let remove_nested_parens = context.config.remove_nested_parens();
1442     loop {
1443         // 1 = "(" or ")"
1444         pre_span = mk_sp(span.lo() + BytePos(1), subexpr.span.lo());
1445         post_span = mk_sp(subexpr.span.hi(), span.hi() - BytePos(1));
1446         pre_comment = rewrite_missing_comment(pre_span, shape, context)?;
1447         post_comment = rewrite_missing_comment(post_span, shape, context)?;
1448
1449         // Remove nested parens if there are no comments.
1450         if let ast::ExprKind::Paren(ref subsubexpr) = subexpr.node {
1451             if remove_nested_parens && pre_comment.is_empty() && post_comment.is_empty() {
1452                 span = subexpr.span;
1453                 subexpr = subsubexpr;
1454                 continue;
1455             }
1456         }
1457
1458         break;
1459     }
1460
1461     // 1 = `(` and `)`
1462     let sub_shape = shape.offset_left(1)?.sub_width(1)?;
1463     let subexpr_str = subexpr.rewrite(context, sub_shape)?;
1464     let fits_single_line = !pre_comment.contains("//") && !post_comment.contains("//");
1465     if fits_single_line {
1466         Some(format!("({}{}{})", pre_comment, &subexpr_str, post_comment))
1467     } else {
1468         rewrite_paren_in_multi_line(context, subexpr, shape, pre_span, post_span)
1469     }
1470 }
1471
1472 fn rewrite_paren_in_multi_line(
1473     context: &RewriteContext<'_>,
1474     subexpr: &ast::Expr,
1475     shape: Shape,
1476     pre_span: Span,
1477     post_span: Span,
1478 ) -> Option<String> {
1479     let nested_indent = shape.indent.block_indent(context.config);
1480     let nested_shape = Shape::indented(nested_indent, context.config);
1481     let pre_comment = rewrite_missing_comment(pre_span, nested_shape, context)?;
1482     let post_comment = rewrite_missing_comment(post_span, nested_shape, context)?;
1483     let subexpr_str = subexpr.rewrite(context, nested_shape)?;
1484
1485     let mut result = String::with_capacity(subexpr_str.len() * 2);
1486     result.push('(');
1487     if !pre_comment.is_empty() {
1488         result.push_str(&nested_indent.to_string_with_newline(context.config));
1489         result.push_str(&pre_comment);
1490     }
1491     result.push_str(&nested_indent.to_string_with_newline(context.config));
1492     result.push_str(&subexpr_str);
1493     if !post_comment.is_empty() {
1494         result.push_str(&nested_indent.to_string_with_newline(context.config));
1495         result.push_str(&post_comment);
1496     }
1497     result.push_str(&shape.indent.to_string_with_newline(context.config));
1498     result.push(')');
1499
1500     Some(result)
1501 }
1502
1503 fn rewrite_index(
1504     expr: &ast::Expr,
1505     index: &ast::Expr,
1506     context: &RewriteContext<'_>,
1507     shape: Shape,
1508 ) -> Option<String> {
1509     let expr_str = expr.rewrite(context, shape)?;
1510
1511     let offset = last_line_width(&expr_str) + 1;
1512     let rhs_overhead = shape.rhs_overhead(context.config);
1513     let index_shape = if expr_str.contains('\n') {
1514         Shape::legacy(context.config.max_width(), shape.indent)
1515             .offset_left(offset)
1516             .and_then(|shape| shape.sub_width(1 + rhs_overhead))
1517     } else {
1518         match context.config.indent_style() {
1519             IndentStyle::Block => shape
1520                 .offset_left(offset)
1521                 .and_then(|shape| shape.sub_width(1)),
1522             IndentStyle::Visual => shape.visual_indent(offset).sub_width(offset + 1),
1523         }
1524     };
1525     let orig_index_rw = index_shape.and_then(|s| index.rewrite(context, s));
1526
1527     // Return if index fits in a single line.
1528     match orig_index_rw {
1529         Some(ref index_str) if !index_str.contains('\n') => {
1530             return Some(format!("{}[{}]", expr_str, index_str));
1531         }
1532         _ => (),
1533     }
1534
1535     // Try putting index on the next line and see if it fits in a single line.
1536     let indent = shape.indent.block_indent(context.config);
1537     let index_shape = Shape::indented(indent, context.config).offset_left(1)?;
1538     let index_shape = index_shape.sub_width(1 + rhs_overhead)?;
1539     let new_index_rw = index.rewrite(context, index_shape);
1540     match (orig_index_rw, new_index_rw) {
1541         (_, Some(ref new_index_str)) if !new_index_str.contains('\n') => Some(format!(
1542             "{}{}[{}]",
1543             expr_str,
1544             indent.to_string_with_newline(context.config),
1545             new_index_str,
1546         )),
1547         (None, Some(ref new_index_str)) => Some(format!(
1548             "{}{}[{}]",
1549             expr_str,
1550             indent.to_string_with_newline(context.config),
1551             new_index_str,
1552         )),
1553         (Some(ref index_str), _) => Some(format!("{}[{}]", expr_str, index_str)),
1554         _ => None,
1555     }
1556 }
1557
1558 fn struct_lit_can_be_aligned(fields: &[ast::Field], base: Option<&ast::Expr>) -> bool {
1559     if base.is_some() {
1560         return false;
1561     }
1562
1563     fields.iter().all(|field| !field.is_shorthand)
1564 }
1565
1566 fn rewrite_struct_lit<'a>(
1567     context: &RewriteContext<'_>,
1568     path: &ast::Path,
1569     fields: &'a [ast::Field],
1570     base: Option<&'a ast::Expr>,
1571     span: Span,
1572     shape: Shape,
1573 ) -> Option<String> {
1574     debug!("rewrite_struct_lit: shape {:?}", shape);
1575
1576     enum StructLitField<'a> {
1577         Regular(&'a ast::Field),
1578         Base(&'a ast::Expr),
1579     }
1580
1581     // 2 = " {".len()
1582     let path_shape = shape.sub_width(2)?;
1583     let path_str = rewrite_path(context, PathContext::Expr, None, path, path_shape)?;
1584
1585     if fields.is_empty() && base.is_none() {
1586         return Some(format!("{} {{}}", path_str));
1587     }
1588
1589     // Foo { a: Foo } - indent is +3, width is -5.
1590     let (h_shape, v_shape) = struct_lit_shape(shape, context, path_str.len() + 3, 2)?;
1591
1592     let one_line_width = h_shape.map_or(0, |shape| shape.width);
1593     let body_lo = context.snippet_provider.span_after(span, "{");
1594     let fields_str = if struct_lit_can_be_aligned(fields, base)
1595         && context.config.struct_field_align_threshold() > 0
1596     {
1597         rewrite_with_alignment(
1598             fields,
1599             context,
1600             v_shape,
1601             mk_sp(body_lo, span.hi()),
1602             one_line_width,
1603         )?
1604     } else {
1605         let field_iter = fields
1606             .iter()
1607             .map(StructLitField::Regular)
1608             .chain(base.into_iter().map(StructLitField::Base));
1609
1610         let span_lo = |item: &StructLitField<'_>| match *item {
1611             StructLitField::Regular(field) => field.span().lo(),
1612             StructLitField::Base(expr) => {
1613                 let last_field_hi = fields.last().map_or(span.lo(), |field| field.span.hi());
1614                 let snippet = context.snippet(mk_sp(last_field_hi, expr.span.lo()));
1615                 let pos = snippet.find_uncommented("..").unwrap();
1616                 last_field_hi + BytePos(pos as u32)
1617             }
1618         };
1619         let span_hi = |item: &StructLitField<'_>| match *item {
1620             StructLitField::Regular(field) => field.span().hi(),
1621             StructLitField::Base(expr) => expr.span.hi(),
1622         };
1623         let rewrite = |item: &StructLitField<'_>| match *item {
1624             StructLitField::Regular(field) => {
1625                 // The 1 taken from the v_budget is for the comma.
1626                 rewrite_field(context, field, v_shape.sub_width(1)?, 0)
1627             }
1628             StructLitField::Base(expr) => {
1629                 // 2 = ..
1630                 expr.rewrite(context, v_shape.offset_left(2)?)
1631                     .map(|s| format!("..{}", s))
1632             }
1633         };
1634
1635         let items = itemize_list(
1636             context.snippet_provider,
1637             field_iter,
1638             "}",
1639             ",",
1640             span_lo,
1641             span_hi,
1642             rewrite,
1643             body_lo,
1644             span.hi(),
1645             false,
1646         );
1647         let item_vec = items.collect::<Vec<_>>();
1648
1649         let tactic = struct_lit_tactic(h_shape, context, &item_vec);
1650         let nested_shape = shape_for_tactic(tactic, h_shape, v_shape);
1651
1652         let ends_with_comma = span_ends_with_comma(context, span);
1653         let force_no_trailing_comma = context.inside_macro() && !ends_with_comma;
1654
1655         let fmt = struct_lit_formatting(
1656             nested_shape,
1657             tactic,
1658             context,
1659             force_no_trailing_comma || base.is_some() || !context.use_block_indent(),
1660         );
1661
1662         write_list(&item_vec, &fmt)?
1663     };
1664
1665     let fields_str = wrap_struct_field(context, &fields_str, shape, v_shape, one_line_width);
1666     Some(format!("{} {{{}}}", path_str, fields_str))
1667
1668     // FIXME if context.config.indent_style() == Visual, but we run out
1669     // of space, we should fall back to BlockIndent.
1670 }
1671
1672 pub fn wrap_struct_field(
1673     context: &RewriteContext<'_>,
1674     fields_str: &str,
1675     shape: Shape,
1676     nested_shape: Shape,
1677     one_line_width: usize,
1678 ) -> String {
1679     if context.config.indent_style() == IndentStyle::Block
1680         && (fields_str.contains('\n')
1681             || !context.config.struct_lit_single_line()
1682             || fields_str.len() > one_line_width)
1683     {
1684         format!(
1685             "{}{}{}",
1686             nested_shape.indent.to_string_with_newline(context.config),
1687             fields_str,
1688             shape.indent.to_string_with_newline(context.config)
1689         )
1690     } else {
1691         // One liner or visual indent.
1692         format!(" {} ", fields_str)
1693     }
1694 }
1695
1696 pub fn struct_lit_field_separator(config: &Config) -> &str {
1697     colon_spaces(config.space_before_colon(), config.space_after_colon())
1698 }
1699
1700 pub fn rewrite_field(
1701     context: &RewriteContext<'_>,
1702     field: &ast::Field,
1703     shape: Shape,
1704     prefix_max_width: usize,
1705 ) -> Option<String> {
1706     if contains_skip(&field.attrs) {
1707         return Some(context.snippet(field.span()).to_owned());
1708     }
1709     let mut attrs_str = field.attrs.rewrite(context, shape)?;
1710     if !attrs_str.is_empty() {
1711         attrs_str.push_str(&shape.indent.to_string_with_newline(context.config));
1712     };
1713     let name = context.snippet(field.ident.span);
1714     if field.is_shorthand {
1715         Some(attrs_str + name)
1716     } else {
1717         let mut separator = String::from(struct_lit_field_separator(context.config));
1718         for _ in 0..prefix_max_width.saturating_sub(name.len()) {
1719             separator.push(' ');
1720         }
1721         let overhead = name.len() + separator.len();
1722         let expr_shape = shape.offset_left(overhead)?;
1723         let expr = field.expr.rewrite(context, expr_shape);
1724
1725         match expr {
1726             Some(ref e) if e.as_str() == name && context.config.use_field_init_shorthand() => {
1727                 Some(attrs_str + name)
1728             }
1729             Some(e) => Some(format!("{}{}{}{}", attrs_str, name, separator, e)),
1730             None => {
1731                 let expr_offset = shape.indent.block_indent(context.config);
1732                 let expr = field
1733                     .expr
1734                     .rewrite(context, Shape::indented(expr_offset, context.config));
1735                 expr.map(|s| {
1736                     format!(
1737                         "{}{}:\n{}{}",
1738                         attrs_str,
1739                         name,
1740                         expr_offset.to_string(context.config),
1741                         s
1742                     )
1743                 })
1744             }
1745         }
1746     }
1747 }
1748
1749 fn rewrite_tuple_in_visual_indent_style<'a, T: 'a + IntoOverflowableItem<'a>>(
1750     context: &RewriteContext<'_>,
1751     mut items: impl Iterator<Item = &'a T>,
1752     span: Span,
1753     shape: Shape,
1754     is_singleton_tuple: bool,
1755 ) -> Option<String> {
1756     // In case of length 1, need a trailing comma
1757     debug!("rewrite_tuple_in_visual_indent_style {:?}", shape);
1758     if is_singleton_tuple {
1759         // 3 = "(" + ",)"
1760         let nested_shape = shape.sub_width(3)?.visual_indent(1);
1761         return items
1762             .next()
1763             .unwrap()
1764             .rewrite(context, nested_shape)
1765             .map(|s| format!("({},)", s));
1766     }
1767
1768     let list_lo = context.snippet_provider.span_after(span, "(");
1769     let nested_shape = shape.sub_width(2)?.visual_indent(1);
1770     let items = itemize_list(
1771         context.snippet_provider,
1772         items,
1773         ")",
1774         ",",
1775         |item| item.span().lo(),
1776         |item| item.span().hi(),
1777         |item| item.rewrite(context, nested_shape),
1778         list_lo,
1779         span.hi() - BytePos(1),
1780         false,
1781     );
1782     let item_vec: Vec<_> = items.collect();
1783     let tactic = definitive_tactic(
1784         &item_vec,
1785         ListTactic::HorizontalVertical,
1786         Separator::Comma,
1787         nested_shape.width,
1788     );
1789     let fmt = ListFormatting::new(nested_shape, context.config)
1790         .tactic(tactic)
1791         .ends_with_newline(false);
1792     let list_str = write_list(&item_vec, &fmt)?;
1793
1794     Some(format!("({})", list_str))
1795 }
1796
1797 pub fn rewrite_tuple<'a, T: 'a + IntoOverflowableItem<'a>>(
1798     context: &'a RewriteContext<'_>,
1799     items: impl Iterator<Item = &'a T>,
1800     span: Span,
1801     shape: Shape,
1802     is_singleton_tuple: bool,
1803 ) -> Option<String> {
1804     debug!("rewrite_tuple {:?}", shape);
1805     if context.use_block_indent() {
1806         // We use the same rule as function calls for rewriting tuples.
1807         let force_tactic = if context.inside_macro() {
1808             if span_ends_with_comma(context, span) {
1809                 Some(SeparatorTactic::Always)
1810             } else {
1811                 Some(SeparatorTactic::Never)
1812             }
1813         } else if is_singleton_tuple {
1814             Some(SeparatorTactic::Always)
1815         } else {
1816             None
1817         };
1818         overflow::rewrite_with_parens(
1819             context,
1820             "",
1821             items,
1822             shape,
1823             span,
1824             context.config.width_heuristics().fn_call_width,
1825             force_tactic,
1826         )
1827     } else {
1828         rewrite_tuple_in_visual_indent_style(context, items, span, shape, is_singleton_tuple)
1829     }
1830 }
1831
1832 pub fn rewrite_unary_prefix<R: Rewrite>(
1833     context: &RewriteContext<'_>,
1834     prefix: &str,
1835     rewrite: &R,
1836     shape: Shape,
1837 ) -> Option<String> {
1838     rewrite
1839         .rewrite(context, shape.offset_left(prefix.len())?)
1840         .map(|r| format!("{}{}", prefix, r))
1841 }
1842
1843 // FIXME: this is probably not correct for multi-line Rewrites. we should
1844 // subtract suffix.len() from the last line budget, not the first!
1845 pub fn rewrite_unary_suffix<R: Rewrite>(
1846     context: &RewriteContext<'_>,
1847     suffix: &str,
1848     rewrite: &R,
1849     shape: Shape,
1850 ) -> Option<String> {
1851     rewrite
1852         .rewrite(context, shape.sub_width(suffix.len())?)
1853         .map(|mut r| {
1854             r.push_str(suffix);
1855             r
1856         })
1857 }
1858
1859 fn rewrite_unary_op(
1860     context: &RewriteContext<'_>,
1861     op: ast::UnOp,
1862     expr: &ast::Expr,
1863     shape: Shape,
1864 ) -> Option<String> {
1865     // For some reason, an UnOp is not spanned like BinOp!
1866     rewrite_unary_prefix(context, ast::UnOp::to_string(op), expr, shape)
1867 }
1868
1869 fn rewrite_assignment(
1870     context: &RewriteContext<'_>,
1871     lhs: &ast::Expr,
1872     rhs: &ast::Expr,
1873     op: Option<&ast::BinOp>,
1874     shape: Shape,
1875 ) -> Option<String> {
1876     let operator_str = match op {
1877         Some(op) => context.snippet(op.span),
1878         None => "=",
1879     };
1880
1881     // 1 = space between lhs and operator.
1882     let lhs_shape = shape.sub_width(operator_str.len() + 1)?;
1883     let lhs_str = format!("{} {}", lhs.rewrite(context, lhs_shape)?, operator_str);
1884
1885     rewrite_assign_rhs(context, lhs_str, rhs, shape)
1886 }
1887
1888 /// Controls where to put the rhs.
1889 #[derive(Debug, Copy, Clone, PartialEq, Eq)]
1890 pub enum RhsTactics {
1891     /// Use heuristics.
1892     Default,
1893     /// Put the rhs on the next line if it uses multiple line, without extra indentation.
1894     ForceNextLineWithoutIndent,
1895 }
1896
1897 // The left hand side must contain everything up to, and including, the
1898 // assignment operator.
1899 pub fn rewrite_assign_rhs<S: Into<String>, R: Rewrite>(
1900     context: &RewriteContext<'_>,
1901     lhs: S,
1902     ex: &R,
1903     shape: Shape,
1904 ) -> Option<String> {
1905     rewrite_assign_rhs_with(context, lhs, ex, shape, RhsTactics::Default)
1906 }
1907
1908 pub fn rewrite_assign_rhs_with<S: Into<String>, R: Rewrite>(
1909     context: &RewriteContext<'_>,
1910     lhs: S,
1911     ex: &R,
1912     shape: Shape,
1913     rhs_tactics: RhsTactics,
1914 ) -> Option<String> {
1915     let lhs = lhs.into();
1916     let last_line_width = last_line_width(&lhs).saturating_sub(if lhs.contains('\n') {
1917         shape.indent.width()
1918     } else {
1919         0
1920     });
1921     // 1 = space between operator and rhs.
1922     let orig_shape = shape.offset_left(last_line_width + 1).unwrap_or(Shape {
1923         width: 0,
1924         offset: shape.offset + last_line_width + 1,
1925         ..shape
1926     });
1927     let rhs = choose_rhs(
1928         context,
1929         ex,
1930         orig_shape,
1931         ex.rewrite(context, orig_shape),
1932         rhs_tactics,
1933     )?;
1934     Some(lhs + &rhs)
1935 }
1936
1937 fn choose_rhs<R: Rewrite>(
1938     context: &RewriteContext<'_>,
1939     expr: &R,
1940     shape: Shape,
1941     orig_rhs: Option<String>,
1942     rhs_tactics: RhsTactics,
1943 ) -> Option<String> {
1944     match orig_rhs {
1945         Some(ref new_str) if !new_str.contains('\n') && new_str.len() <= shape.width => {
1946             Some(format!(" {}", new_str))
1947         }
1948         _ => {
1949             // Expression did not fit on the same line as the identifier.
1950             // Try splitting the line and see if that works better.
1951             let new_shape = shape_from_rhs_tactic(context, shape, rhs_tactics)?;
1952             let new_rhs = expr.rewrite(context, new_shape);
1953             let new_indent_str = &shape
1954                 .indent
1955                 .block_indent(context.config)
1956                 .to_string_with_newline(context.config);
1957
1958             match (orig_rhs, new_rhs) {
1959                 (Some(ref orig_rhs), Some(ref new_rhs))
1960                     if wrap_str(new_rhs.clone(), context.config.max_width(), new_shape)
1961                         .is_none() =>
1962                 {
1963                     Some(format!(" {}", orig_rhs))
1964                 }
1965                 (Some(ref orig_rhs), Some(ref new_rhs))
1966                     if prefer_next_line(orig_rhs, new_rhs, rhs_tactics) =>
1967                 {
1968                     Some(format!("{}{}", new_indent_str, new_rhs))
1969                 }
1970                 (None, Some(ref new_rhs)) => Some(format!("{}{}", new_indent_str, new_rhs)),
1971                 (None, None) => None,
1972                 (Some(orig_rhs), _) => Some(format!(" {}", orig_rhs)),
1973             }
1974         }
1975     }
1976 }
1977
1978 fn shape_from_rhs_tactic(
1979     context: &RewriteContext<'_>,
1980     shape: Shape,
1981     rhs_tactic: RhsTactics,
1982 ) -> Option<Shape> {
1983     match rhs_tactic {
1984         RhsTactics::ForceNextLineWithoutIndent => shape
1985             .with_max_width(context.config)
1986             .sub_width(shape.indent.width()),
1987         RhsTactics::Default => {
1988             Shape::indented(shape.indent.block_indent(context.config), context.config)
1989                 .sub_width(shape.rhs_overhead(context.config))
1990         }
1991     }
1992 }
1993
1994 pub fn prefer_next_line(orig_rhs: &str, next_line_rhs: &str, rhs_tactics: RhsTactics) -> bool {
1995     rhs_tactics == RhsTactics::ForceNextLineWithoutIndent
1996         || !next_line_rhs.contains('\n')
1997         || count_newlines(orig_rhs) > count_newlines(next_line_rhs) + 1
1998         || first_line_ends_with(orig_rhs, '(') && !first_line_ends_with(next_line_rhs, '(')
1999         || first_line_ends_with(orig_rhs, '{') && !first_line_ends_with(next_line_rhs, '{')
2000         || first_line_ends_with(orig_rhs, '[') && !first_line_ends_with(next_line_rhs, '[')
2001 }
2002
2003 fn rewrite_expr_addrof(
2004     context: &RewriteContext<'_>,
2005     mutability: ast::Mutability,
2006     expr: &ast::Expr,
2007     shape: Shape,
2008 ) -> Option<String> {
2009     let operator_str = match mutability {
2010         ast::Mutability::Immutable => "&",
2011         ast::Mutability::Mutable => "&mut ",
2012     };
2013     rewrite_unary_prefix(context, operator_str, expr, shape)
2014 }
2015
2016 pub fn is_method_call(expr: &ast::Expr) -> bool {
2017     match expr.node {
2018         ast::ExprKind::MethodCall(..) => true,
2019         ast::ExprKind::AddrOf(_, ref expr)
2020         | ast::ExprKind::Box(ref expr)
2021         | ast::ExprKind::Cast(ref expr, _)
2022         | ast::ExprKind::Try(ref expr)
2023         | ast::ExprKind::Unary(_, ref expr) => is_method_call(expr),
2024         _ => false,
2025     }
2026 }
2027
2028 #[cfg(test)]
2029 mod test {
2030     use super::last_line_offsetted;
2031
2032     #[test]
2033     fn test_last_line_offsetted() {
2034         let lines = "one\n    two";
2035         assert_eq!(last_line_offsetted(2, lines), true);
2036         assert_eq!(last_line_offsetted(4, lines), false);
2037         assert_eq!(last_line_offsetted(6, lines), false);
2038
2039         let lines = "one    two";
2040         assert_eq!(last_line_offsetted(2, lines), false);
2041         assert_eq!(last_line_offsetted(0, lines), false);
2042
2043         let lines = "\ntwo";
2044         assert_eq!(last_line_offsetted(2, lines), false);
2045         assert_eq!(last_line_offsetted(0, lines), false);
2046
2047         let lines = "one\n    two      three";
2048         assert_eq!(last_line_offsetted(2, lines), true);
2049         let lines = "one\n two      three";
2050         assert_eq!(last_line_offsetted(2, lines), false);
2051     }
2052 }