src/expr.rs

   1 use std::borrow::Cow;
   2 use std::cmp::min;
   3 use std::iter;
   4
   5 use itertools::Itertools;
   6 use syntax::parse::token::DelimToken;
   7 use syntax::source_map::{BytePos, SourceMap, Span};
   8 use syntax::{ast, ptr};
   9
  10 use crate::chains::rewrite_chain;
  11 use crate::closures;
  12 use crate::comment::{
  13     combine_strs_with_missing_comments, contains_comment, recover_comment_removed, rewrite_comment,
  14     rewrite_missing_comment, CharClasses, FindUncommented,
  15 };
  16 use crate::config::lists::*;
  17 use crate::config::{Config, ControlBraceStyle, IndentStyle, Version};
  18 use crate::lists::{
  19     definitive_tactic, itemize_list, shape_for_tactic, struct_lit_formatting, struct_lit_shape,
  20     struct_lit_tactic, write_list, ListFormatting, ListItem, Separator,
  21 };
  22 use crate::macros::{rewrite_macro, MacroPosition};
  23 use crate::matches::rewrite_match;
  24 use crate::overflow::{self, IntoOverflowableItem, OverflowableItem};
  25 use crate::pairs::{rewrite_all_pairs, rewrite_pair, PairParts};
  26 use crate::patterns::is_short_pattern;
  27 use crate::rewrite::{Rewrite, RewriteContext};
  28 use crate::shape::{Indent, Shape};
  29 use crate::source_map::{LineRangeUtils, SpanUtils};
  30 use crate::spanned::Spanned;
  31 use crate::string::{rewrite_string, StringFormat};
  32 use crate::types::{rewrite_path, PathContext};
  33 use crate::utils::{
  34     colon_spaces, contains_skip, count_newlines, first_line_ends_with, inner_attributes,
  35     last_line_extendable, last_line_width, mk_sp, outer_attributes, ptr_vec_to_ref_vec,
  36     semicolon_for_expr, unicode_str_width, wrap_str,
  37 };
  38 use crate::vertical::rewrite_with_alignment;
  39 use crate::visitor::FmtVisitor;
  40
  41 impl Rewrite for ast::Expr {
  42     fn rewrite(&self, context: &RewriteContext<'_>, shape: Shape) -> Option<String> {
  43         format_expr(self, ExprType::SubExpression, context, shape)
  44     }
  45 }
  46
  47 #[derive(Copy, Clone, PartialEq)]
  48 pub(crate) enum ExprType {
  49     Statement,
  50     SubExpression,
  51 }
  52
  53 pub(crate) fn format_expr(
  54     expr: &ast::Expr,
  55     expr_type: ExprType,
  56     context: &RewriteContext<'_>,
  57     shape: Shape,
  58 ) -> Option<String> {
  59     skip_out_of_file_lines_range!(context, expr.span);
  60
  61     if contains_skip(&*expr.attrs) {
  62         return Some(context.snippet(expr.span()).to_owned());
  63     }
  64     let shape = if expr_type == ExprType::Statement && semicolon_for_expr(context, expr) {
  65         shape.sub_width(1)?
  66     } else {
  67         shape
  68     };
  69
  70     let expr_rw = match expr.node {
  71         ast::ExprKind::Array(ref expr_vec) => rewrite_array(
  72             "",
  73             expr_vec.iter(),
  74             expr.span,
  75             context,
  76             shape,
  77             choose_separator_tactic(context, expr.span),
  78             None,
  79         ),
  80         ast::ExprKind::Lit(ref l) => rewrite_literal(context, l, shape),
  81         ast::ExprKind::Call(ref callee, ref args) => {
  82             let inner_span = mk_sp(callee.span.hi(), expr.span.hi());
  83             let callee_str = callee.rewrite(context, shape)?;
  84             rewrite_call(context, &callee_str, args, inner_span, shape)
  85         }
  86         ast::ExprKind::Paren(ref subexpr) => rewrite_paren(context, subexpr, shape, expr.span),
  87         ast::ExprKind::Binary(op, ref lhs, ref rhs) => {
  88             // FIXME: format comments between operands and operator
  89             rewrite_all_pairs(expr, shape, context).or_else(|| {
  90                 rewrite_pair(
  91                     &**lhs,
  92                     &**rhs,
  93                     PairParts::infix(&format!(" {} ", context.snippet(op.span))),
  94                     context,
  95                     shape,
  96                     context.config.binop_separator(),
  97                 )
  98             })
  99         }
 100         ast::ExprKind::Unary(op, ref subexpr) => rewrite_unary_op(context, op, subexpr, shape),
 101         ast::ExprKind::Struct(ref path, ref fields, ref base) => rewrite_struct_lit(
 102             context,
 103             path,
 104             fields,
 105             base.as_ref().map(|e| &**e),
 106             &expr.attrs,
 107             expr.span,
 108             shape,
 109         ),
 110         ast::ExprKind::Tup(ref items) => {
 111             rewrite_tuple(context, items.iter(), expr.span, shape, items.len() == 1)
 112         }
 113         ast::ExprKind::Let(..) => None,
 114         ast::ExprKind::If(..)
 115         | ast::ExprKind::ForLoop(..)
 116         | ast::ExprKind::Loop(..)
 117         | ast::ExprKind::While(..) => to_control_flow(expr, expr_type)
 118             .and_then(|control_flow| control_flow.rewrite(context, shape)),
 119         ast::ExprKind::Block(ref block, opt_label) => {
 120             match expr_type {
 121                 ExprType::Statement => {
 122                     if is_unsafe_block(block) {
 123                         rewrite_block(block, Some(&expr.attrs), opt_label, context, shape)
 124                     } else if let rw @ Some(_) =
 125                         rewrite_empty_block(context, block, Some(&expr.attrs), opt_label, "", shape)
 126                     {
 127                         // Rewrite block without trying to put it in a single line.
 128                         rw
 129                     } else {
 130                         let prefix = block_prefix(context, block, shape)?;
 131
 132                         rewrite_block_with_visitor(
 133                             context,
 134                             &prefix,
 135                             block,
 136                             Some(&expr.attrs),
 137                             opt_label,
 138                             shape,
 139                             true,
 140                         )
 141                     }
 142                 }
 143                 ExprType::SubExpression => {
 144                     rewrite_block(block, Some(&expr.attrs), opt_label, context, shape)
 145                 }
 146             }
 147         }
 148         ast::ExprKind::Match(ref cond, ref arms) => {
 149             rewrite_match(context, cond, arms, shape, expr.span, &expr.attrs)
 150         }
 151         ast::ExprKind::Path(ref qself, ref path) => {
 152             rewrite_path(context, PathContext::Expr, qself.as_ref(), path, shape)
 153         }
 154         ast::ExprKind::Assign(ref lhs, ref rhs) => {
 155             rewrite_assignment(context, lhs, rhs, None, shape)
 156         }
 157         ast::ExprKind::AssignOp(ref op, ref lhs, ref rhs) => {
 158             rewrite_assignment(context, lhs, rhs, Some(op), shape)
 159         }
 160         ast::ExprKind::Continue(ref opt_label) => {
 161             let id_str = match *opt_label {
 162                 Some(label) => format!(" {}", label.ident),
 163                 None => String::new(),
 164             };
 165             Some(format!("continue{}", id_str))
 166         }
 167         ast::ExprKind::Break(ref opt_label, ref opt_expr) => {
 168             let id_str = match *opt_label {
 169                 Some(label) => format!(" {}", label.ident),
 170                 None => String::new(),
 171             };
 172
 173             if let Some(ref expr) = *opt_expr {
 174                 rewrite_unary_prefix(context, &format!("break{} ", id_str), &**expr, shape)
 175             } else {
 176                 Some(format!("break{}", id_str))
 177             }
 178         }
 179         ast::ExprKind::Yield(ref opt_expr) => {
 180             if let Some(ref expr) = *opt_expr {
 181                 rewrite_unary_prefix(context, "yield ", &**expr, shape)
 182             } else {
 183                 Some("yield".to_string())
 184             }
 185         }
 186         ast::ExprKind::Closure(capture, ref is_async, movability, ref fn_decl, ref body, _) => {
 187             closures::rewrite_closure(
 188                 capture, is_async, movability, fn_decl, body, expr.span, context, shape,
 189             )
 190         }
 191         ast::ExprKind::Try(..) | ast::ExprKind::Field(..) | ast::ExprKind::MethodCall(..) => {
 192             rewrite_chain(expr, context, shape)
 193         }
 194         ast::ExprKind::Mac(ref mac) => {
 195             rewrite_macro(mac, None, context, shape, MacroPosition::Expression).or_else(|| {
 196                 wrap_str(
 197                     context.snippet(expr.span).to_owned(),
 198                     context.config.max_width(),
 199                     shape,
 200                 )
 201             })
 202         }
 203         ast::ExprKind::Ret(None) => Some("return".to_owned()),
 204         ast::ExprKind::Ret(Some(ref expr)) => {
 205             rewrite_unary_prefix(context, "return ", &**expr, shape)
 206         }
 207         ast::ExprKind::Box(ref expr) => rewrite_unary_prefix(context, "box ", &**expr, shape),
 208         ast::ExprKind::AddrOf(mutability, ref expr) => {
 209             rewrite_expr_addrof(context, mutability, expr, shape)
 210         }
 211         ast::ExprKind::Cast(ref expr, ref ty) => rewrite_pair(
 212             &**expr,
 213             &**ty,
 214             PairParts::infix(" as "),
 215             context,
 216             shape,
 217             SeparatorPlace::Front,
 218         ),
 219         ast::ExprKind::Type(ref expr, ref ty) => rewrite_pair(
 220             &**expr,
 221             &**ty,
 222             PairParts::infix(": "),
 223             context,
 224             shape,
 225             SeparatorPlace::Back,
 226         ),
 227         ast::ExprKind::Index(ref expr, ref index) => {
 228             rewrite_index(&**expr, &**index, context, shape)
 229         }
 230         ast::ExprKind::Repeat(ref expr, ref repeats) => rewrite_pair(
 231             &**expr,
 232             &*repeats.value,
 233             PairParts::new("[", "; ", "]"),
 234             context,
 235             shape,
 236             SeparatorPlace::Back,
 237         ),
 238         ast::ExprKind::Range(ref lhs, ref rhs, limits) => {
 239             let delim = match limits {
 240                 ast::RangeLimits::HalfOpen => "..",
 241                 ast::RangeLimits::Closed => "..=",
 242             };
 243
 244             fn needs_space_before_range(context: &RewriteContext<'_>, lhs: &ast::Expr) -> bool {
 245                 match lhs.node {
 246                     ast::ExprKind::Lit(ref lit) => match lit.node {
 247                         ast::LitKind::FloatUnsuffixed(..) => {
 248                             context.snippet(lit.span).ends_with('.')
 249                         }
 250                         _ => false,
 251                     },
 252                     _ => false,
 253                 }
 254             }
 255
 256             fn needs_space_after_range(rhs: &ast::Expr) -> bool {
 257                 match rhs.node {
 258                     // Don't format `.. ..` into `....`, which is invalid.
 259                     //
 260                     // This check is unnecessary for `lhs`, because a range
 261                     // starting from another range needs parentheses as `(x ..) ..`
 262                     // (`x .. ..` is a range from `x` to `..`).
 263                     ast::ExprKind::Range(None, _, _) => true,
 264                     _ => false,
 265                 }
 266             }
 267
 268             let default_sp_delim = |lhs: Option<&ast::Expr>, rhs: Option<&ast::Expr>| {
 269                 let space_if = |b: bool| if b { " " } else { "" };
 270
 271                 format!(
 272                     "{}{}{}",
 273                     lhs.map_or("", |lhs| space_if(needs_space_before_range(context, lhs))),
 274                     delim,
 275                     rhs.map_or("", |rhs| space_if(needs_space_after_range(rhs))),
 276                 )
 277             };
 278
 279             match (lhs.as_ref().map(|x| &**x), rhs.as_ref().map(|x| &**x)) {
 280                 (Some(lhs), Some(rhs)) => {
 281                     let sp_delim = if context.config.spaces_around_ranges() {
 282                         format!(" {} ", delim)
 283                     } else {
 284                         default_sp_delim(Some(lhs), Some(rhs))
 285                     };
 286                     rewrite_pair(
 287                         &*lhs,
 288                         &*rhs,
 289                         PairParts::infix(&sp_delim),
 290                         context,
 291                         shape,
 292                         context.config.binop_separator(),
 293                     )
 294                 }
 295                 (None, Some(rhs)) => {
 296                     let sp_delim = if context.config.spaces_around_ranges() {
 297                         format!("{} ", delim)
 298                     } else {
 299                         default_sp_delim(None, Some(rhs))
 300                     };
 301                     rewrite_unary_prefix(context, &sp_delim, &*rhs, shape)
 302                 }
 303                 (Some(lhs), None) => {
 304                     let sp_delim = if context.config.spaces_around_ranges() {
 305                         format!(" {}", delim)
 306                     } else {
 307                         default_sp_delim(Some(lhs), None)
 308                     };
 309                     rewrite_unary_suffix(context, &sp_delim, &*lhs, shape)
 310                 }
 311                 (None, None) => Some(delim.to_owned()),
 312             }
 313         }
 314         // We do not format these expressions yet, but they should still
 315         // satisfy our width restrictions.
 316         ast::ExprKind::InlineAsm(..) => Some(context.snippet(expr.span).to_owned()),
 317         ast::ExprKind::TryBlock(ref block) => {
 318             if let rw @ Some(_) =
 319                 rewrite_single_line_block(context, "try ", block, Some(&expr.attrs), None, shape)
 320             {
 321                 rw
 322             } else {
 323                 // 9 = `try `
 324                 let budget = shape.width.saturating_sub(9);
 325                 Some(format!(
 326                     "{}{}",
 327                     "try ",
 328                     rewrite_block(
 329                         block,
 330                         Some(&expr.attrs),
 331                         None,
 332                         context,
 333                         Shape::legacy(budget, shape.indent)
 334                     )?
 335                 ))
 336             }
 337         }
 338         ast::ExprKind::Async(capture_by, _node_id, ref block) => {
 339             let mover = if capture_by == ast::CaptureBy::Value {
 340                 "move "
 341             } else {
 342                 ""
 343             };
 344             if let rw @ Some(_) = rewrite_single_line_block(
 345                 context,
 346                 format!("{}{}", "async ", mover).as_str(),
 347                 block,
 348                 Some(&expr.attrs),
 349                 None,
 350                 shape,
 351             ) {
 352                 rw
 353             } else {
 354                 // 6 = `async `
 355                 let budget = shape.width.saturating_sub(6);
 356                 Some(format!(
 357                     "{}{}{}",
 358                     "async ",
 359                     mover,
 360                     rewrite_block(
 361                         block,
 362                         Some(&expr.attrs),
 363                         None,
 364                         context,
 365                         Shape::legacy(budget, shape.indent)
 366                     )?
 367                 ))
 368             }
 369         }
 370         ast::ExprKind::Await(ast::AwaitOrigin::FieldLike, _) => rewrite_chain(expr, context, shape),
 371         ast::ExprKind::Await(ast::AwaitOrigin::MacroLike, ref nested) => {
 372             overflow::rewrite_with_parens(
 373                 context,
 374                 "await!",
 375                 iter::once(nested),
 376                 shape,
 377                 expr.span,
 378                 context.config.max_width(),
 379                 None,
 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(crate) 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(crate) 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 // Rewrite condition if the given expression has one.
 571 pub(crate) fn rewrite_cond(
 572     context: &RewriteContext<'_>,
 573     expr: &ast::Expr,
 574     shape: Shape,
 575 ) -> Option<String> {
 576     match expr.node {
 577         ast::ExprKind::Match(ref cond, _) => {
 578             // `match `cond` {`
 579             let cond_shape = match context.config.indent_style() {
 580                 IndentStyle::Visual => shape.shrink_left(6).and_then(|s| s.sub_width(2))?,
 581                 IndentStyle::Block => shape.offset_left(8)?,
 582             };
 583             cond.rewrite(context, cond_shape)
 584         }
 585         _ => to_control_flow(expr, ExprType::SubExpression).and_then(|control_flow| {
 586             let alt_block_sep =
 587                 String::from("\n") + &shape.indent.block_only().to_string(context.config);
 588             control_flow
 589                 .rewrite_cond(context, shape, &alt_block_sep)
 590                 .and_then(|rw| Some(rw.0))
 591         }),
 592     }
 593 }
 594
 595 // Abstraction over control flow expressions
 596 #[derive(Debug)]
 597 struct ControlFlow<'a> {
 598     cond: Option<&'a ast::Expr>,
 599     block: &'a ast::Block,
 600     else_block: Option<&'a ast::Expr>,
 601     label: Option<ast::Label>,
 602     pats: Vec<&'a ast::Pat>,
 603     keyword: &'a str,
 604     matcher: &'a str,
 605     connector: &'a str,
 606     allow_single_line: bool,
 607     // HACK: `true` if this is an `if` expression in an `else if`.
 608     nested_if: bool,
 609     span: Span,
 610 }
 611
 612 fn extract_pats_and_cond(expr: &ast::Expr) -> (Vec<&ast::Pat>, &ast::Expr) {
 613     match expr.node {
 614         ast::ExprKind::Let(ref pats, ref cond) => (ptr_vec_to_ref_vec(pats), cond),
 615         _ => (vec![], expr),
 616     }
 617 }
 618
 619 // FIXME: Refactor this.
 620 fn to_control_flow(expr: &ast::Expr, expr_type: ExprType) -> Option<ControlFlow<'_>> {
 621     match expr.node {
 622         ast::ExprKind::If(ref cond, ref if_block, ref else_block) => {
 623             let (pats, cond) = extract_pats_and_cond(cond);
 624             Some(ControlFlow::new_if(
 625                 cond,
 626                 pats,
 627                 if_block,
 628                 else_block.as_ref().map(|e| &**e),
 629                 expr_type == ExprType::SubExpression,
 630                 false,
 631                 expr.span,
 632             ))
 633         }
 634         ast::ExprKind::ForLoop(ref pat, ref cond, ref block, label) => {
 635             Some(ControlFlow::new_for(pat, cond, block, label, expr.span))
 636         }
 637         ast::ExprKind::Loop(ref block, label) => {
 638             Some(ControlFlow::new_loop(block, label, expr.span))
 639         }
 640         ast::ExprKind::While(ref cond, ref block, label) => {
 641             let (pats, cond) = extract_pats_and_cond(cond);
 642             Some(ControlFlow::new_while(pats, cond, block, label, expr.span))
 643         }
 644         _ => None,
 645     }
 646 }
 647
 648 fn choose_matcher(pats: &[&ast::Pat]) -> &'static str {
 649     if pats.is_empty() { "" } else { "let" }
 650 }
 651
 652 impl<'a> ControlFlow<'a> {
 653     fn new_if(
 654         cond: &'a ast::Expr,
 655         pats: Vec<&'a ast::Pat>,
 656         block: &'a ast::Block,
 657         else_block: Option<&'a ast::Expr>,
 658         allow_single_line: bool,
 659         nested_if: bool,
 660         span: Span,
 661     ) -> ControlFlow<'a> {
 662         let matcher = choose_matcher(&pats);
 663         ControlFlow {
 664             cond: Some(cond),
 665             block,
 666             else_block,
 667             label: None,
 668             pats,
 669             keyword: "if",
 670             matcher,
 671             connector: " =",
 672             allow_single_line,
 673             nested_if,
 674             span,
 675         }
 676     }
 677
 678     fn new_loop(block: &'a ast::Block, label: Option<ast::Label>, span: Span) -> ControlFlow<'a> {
 679         ControlFlow {
 680             cond: None,
 681             block,
 682             else_block: None,
 683             label,
 684             pats: vec![],
 685             keyword: "loop",
 686             matcher: "",
 687             connector: "",
 688             allow_single_line: false,
 689             nested_if: false,
 690             span,
 691         }
 692     }
 693
 694     fn new_while(
 695         pats: Vec<&'a ast::Pat>,
 696         cond: &'a ast::Expr,
 697         block: &'a ast::Block,
 698         label: Option<ast::Label>,
 699         span: Span,
 700     ) -> ControlFlow<'a> {
 701         let matcher = choose_matcher(&pats);
 702         ControlFlow {
 703             cond: Some(cond),
 704             block,
 705             else_block: None,
 706             label,
 707             pats,
 708             keyword: "while",
 709             matcher,
 710             connector: " =",
 711             allow_single_line: false,
 712             nested_if: false,
 713             span,
 714         }
 715     }
 716
 717     fn new_for(
 718         pat: &'a ast::Pat,
 719         cond: &'a ast::Expr,
 720         block: &'a ast::Block,
 721         label: Option<ast::Label>,
 722         span: Span,
 723     ) -> ControlFlow<'a> {
 724         ControlFlow {
 725             cond: Some(cond),
 726             block,
 727             else_block: None,
 728             label,
 729             pats: vec![pat],
 730             keyword: "for",
 731             matcher: "",
 732             connector: " in",
 733             allow_single_line: false,
 734             nested_if: false,
 735             span,
 736         }
 737     }
 738
 739     fn rewrite_single_line(
 740         &self,
 741         pat_expr_str: &str,
 742         context: &RewriteContext<'_>,
 743         width: usize,
 744     ) -> Option<String> {
 745         assert!(self.allow_single_line);
 746         let else_block = self.else_block?;
 747         let fixed_cost = self.keyword.len() + "  {  } else {  }".len();
 748
 749         if let ast::ExprKind::Block(ref else_node, _) = else_block.node {
 750             if !is_simple_block(self.block, None, context.source_map)
 751                 || !is_simple_block(else_node, None, context.source_map)
 752                 || pat_expr_str.contains('\n')
 753             {
 754                 return None;
 755             }
 756
 757             let new_width = width.checked_sub(pat_expr_str.len() + fixed_cost)?;
 758             let expr = &self.block.stmts[0];
 759             let if_str = expr.rewrite(context, Shape::legacy(new_width, Indent::empty()))?;
 760
 761             let new_width = new_width.checked_sub(if_str.len())?;
 762             let else_expr = &else_node.stmts[0];
 763             let else_str = else_expr.rewrite(context, Shape::legacy(new_width, Indent::empty()))?;
 764
 765             if if_str.contains('\n') || else_str.contains('\n') {
 766                 return None;
 767             }
 768
 769             let result = format!(
 770                 "{} {} {{ {} }} else {{ {} }}",
 771                 self.keyword, pat_expr_str, if_str, else_str
 772             );
 773
 774             if result.len() <= width {
 775                 return Some(result);
 776             }
 777         }
 778
 779         None
 780     }
 781 }
 782
 783 /// Returns `true` if the last line of pat_str has leading whitespace and it is wider than the
 784 /// shape's indent.
 785 fn last_line_offsetted(start_column: usize, pat_str: &str) -> bool {
 786     let mut leading_whitespaces = 0;
 787     for c in pat_str.chars().rev() {
 788         match c {
 789             '\n' => break,
 790             _ if c.is_whitespace() => leading_whitespaces += 1,
 791             _ => leading_whitespaces = 0,
 792         }
 793     }
 794     leading_whitespaces > start_column
 795 }
 796
 797 impl<'a> ControlFlow<'a> {
 798     fn rewrite_pat_expr(
 799         &self,
 800         context: &RewriteContext<'_>,
 801         expr: &ast::Expr,
 802         shape: Shape,
 803         offset: usize,
 804     ) -> Option<String> {
 805         debug!("rewrite_pat_expr {:?} {:?} {:?}", shape, self.pats, expr);
 806
 807         let cond_shape = shape.offset_left(offset)?;
 808         if !self.pats.is_empty() {
 809             let matcher = if self.matcher.is_empty() {
 810                 self.matcher.to_owned()
 811             } else {
 812                 format!("{} ", self.matcher)
 813             };
 814             let pat_shape = cond_shape
 815                 .offset_left(matcher.len())?
 816                 .sub_width(self.connector.len())?;
 817             let pat_string = rewrite_multiple_patterns(context, &self.pats, pat_shape)?;
 818             let result = format!("{}{}{}", matcher, pat_string, self.connector);
 819             return rewrite_assign_rhs(context, result, expr, cond_shape);
 820         }
 821
 822         let expr_rw = expr.rewrite(context, cond_shape);
 823         // The expression may (partially) fit on the current line.
 824         // We do not allow splitting between `if` and condition.
 825         if self.keyword == "if" || expr_rw.is_some() {
 826             return expr_rw;
 827         }
 828
 829         // The expression won't fit on the current line, jump to next.
 830         let nested_shape = shape
 831             .block_indent(context.config.tab_spaces())
 832             .with_max_width(context.config);
 833         let nested_indent_str = nested_shape.indent.to_string_with_newline(context.config);
 834         expr.rewrite(context, nested_shape)
 835             .map(|expr_rw| format!("{}{}", nested_indent_str, expr_rw))
 836     }
 837
 838     fn rewrite_cond(
 839         &self,
 840         context: &RewriteContext<'_>,
 841         shape: Shape,
 842         alt_block_sep: &str,
 843     ) -> Option<(String, usize)> {
 844         // Do not take the rhs overhead from the upper expressions into account
 845         // when rewriting pattern.
 846         let new_width = context.budget(shape.used_width());
 847         let fresh_shape = Shape {
 848             width: new_width,
 849             ..shape
 850         };
 851         let constr_shape = if self.nested_if {
 852             // We are part of an if-elseif-else chain. Our constraints are tightened.
 853             // 7 = "} else " .len()
 854             fresh_shape.offset_left(7)?
 855         } else {
 856             fresh_shape
 857         };
 858
 859         let label_string = rewrite_label(self.label);
 860         // 1 = space after keyword.
 861         let offset = self.keyword.len() + label_string.len() + 1;
 862
 863         let pat_expr_string = match self.cond {
 864             Some(cond) => self.rewrite_pat_expr(context, cond, constr_shape, offset)?,
 865             None => String::new(),
 866         };
 867
 868         let brace_overhead =
 869             if context.config.control_brace_style() != ControlBraceStyle::AlwaysNextLine {
 870                 // 2 = ` {`
 871                 2
 872             } else {
 873                 0
 874             };
 875         let one_line_budget = context
 876             .config
 877             .max_width()
 878             .saturating_sub(constr_shape.used_width() + offset + brace_overhead);
 879         let force_newline_brace = (pat_expr_string.contains('\n')
 880             || pat_expr_string.len() > one_line_budget)
 881             && (!last_line_extendable(&pat_expr_string)
 882                 || last_line_offsetted(shape.used_width(), &pat_expr_string));
 883
 884         // Try to format if-else on single line.
 885         if self.allow_single_line
 886             && context
 887                 .config
 888                 .width_heuristics()
 889                 .single_line_if_else_max_width
 890                 > 0
 891         {
 892             let trial = self.rewrite_single_line(&pat_expr_string, context, shape.width);
 893
 894             if let Some(cond_str) = trial {
 895                 if cond_str.len()
 896                     <= context
 897                         .config
 898                         .width_heuristics()
 899                         .single_line_if_else_max_width
 900                 {
 901                     return Some((cond_str, 0));
 902                 }
 903             }
 904         }
 905
 906         let cond_span = if let Some(cond) = self.cond {
 907             cond.span
 908         } else {
 909             mk_sp(self.block.span.lo(), self.block.span.lo())
 910         };
 911
 912         // `for event in event`
 913         // Do not include label in the span.
 914         let lo = self
 915             .label
 916             .map_or(self.span.lo(), |label| label.ident.span.hi());
 917         let between_kwd_cond = mk_sp(
 918             context
 919                 .snippet_provider
 920                 .span_after(mk_sp(lo, self.span.hi()), self.keyword.trim()),
 921             if self.pats.is_empty() {
 922                 cond_span.lo()
 923             } else if self.matcher.is_empty() {
 924                 self.pats[0].span.lo()
 925             } else {
 926                 context
 927                     .snippet_provider
 928                     .span_before(self.span, self.matcher.trim())
 929             },
 930         );
 931
 932         let between_kwd_cond_comment = extract_comment(between_kwd_cond, context, shape);
 933
 934         let after_cond_comment =
 935             extract_comment(mk_sp(cond_span.hi(), self.block.span.lo()), context, shape);
 936
 937         let block_sep = if self.cond.is_none() && between_kwd_cond_comment.is_some() {
 938             ""
 939         } else if context.config.control_brace_style() == ControlBraceStyle::AlwaysNextLine
 940             || force_newline_brace
 941         {
 942             alt_block_sep
 943         } else {
 944             " "
 945         };
 946
 947         let used_width = if pat_expr_string.contains('\n') {
 948             last_line_width(&pat_expr_string)
 949         } else {
 950             // 2 = spaces after keyword and condition.
 951             label_string.len() + self.keyword.len() + pat_expr_string.len() + 2
 952         };
 953
 954         Some((
 955             format!(
 956                 "{}{}{}{}{}",
 957                 label_string,
 958                 self.keyword,
 959                 between_kwd_cond_comment.as_ref().map_or(
 960                     if pat_expr_string.is_empty() || pat_expr_string.starts_with('\n') {
 961                         ""
 962                     } else {
 963                         " "
 964                     },
 965                     |s| &**s,
 966                 ),
 967                 pat_expr_string,
 968                 after_cond_comment.as_ref().map_or(block_sep, |s| &**s)
 969             ),
 970             used_width,
 971         ))
 972     }
 973 }
 974
 975 impl<'a> Rewrite for ControlFlow<'a> {
 976     fn rewrite(&self, context: &RewriteContext<'_>, shape: Shape) -> Option<String> {
 977         debug!("ControlFlow::rewrite {:?} {:?}", self, shape);
 978
 979         let alt_block_sep = &shape.indent.to_string_with_newline(context.config);
 980         let (cond_str, used_width) = self.rewrite_cond(context, shape, alt_block_sep)?;
 981         // If `used_width` is 0, it indicates that whole control flow is written in a single line.
 982         if used_width == 0 {
 983             return Some(cond_str);
 984         }
 985
 986         let block_width = shape.width.saturating_sub(used_width);
 987         // This is used only for the empty block case: `{}`. So, we use 1 if we know
 988         // we should avoid the single line case.
 989         let block_width = if self.else_block.is_some() || self.nested_if {
 990             min(1, block_width)
 991         } else {
 992             block_width
 993         };
 994         let block_shape = Shape {
 995             width: block_width,
 996             ..shape
 997         };
 998         let block_str = {
 999             let old_val = context.is_if_else_block.replace(self.else_block.is_some());
1000             let result =
1001                 rewrite_block_with_visitor(context, "", self.block, None, None, block_shape, true);
1002             context.is_if_else_block.replace(old_val);
1003             result?
1004         };
1005
1006         let mut result = format!("{}{}", cond_str, block_str);
1007
1008         if let Some(else_block) = self.else_block {
1009             let shape = Shape::indented(shape.indent, context.config);
1010             let mut last_in_chain = false;
1011             let rewrite = match else_block.node {
1012                 // If the else expression is another if-else expression, prevent it
1013                 // from being formatted on a single line.
1014                 // Note how we're passing the original shape, as the
1015                 // cost of "else" should not cascade.
1016                 ast::ExprKind::If(ref cond, ref if_block, ref next_else_block) => {
1017                     let (pats, cond) = extract_pats_and_cond(cond);
1018                     ControlFlow::new_if(
1019                         cond,
1020                         pats,
1021                         if_block,
1022                         next_else_block.as_ref().map(|e| &**e),
1023                         false,
1024                         true,
1025                         mk_sp(else_block.span.lo(), self.span.hi()),
1026                     )
1027                     .rewrite(context, shape)
1028                 }
1029                 _ => {
1030                     last_in_chain = true;
1031                     // When rewriting a block, the width is only used for single line
1032                     // blocks, passing 1 lets us avoid that.
1033                     let else_shape = Shape {
1034                         width: min(1, shape.width),
1035                         ..shape
1036                     };
1037                     format_expr(else_block, ExprType::Statement, context, else_shape)
1038                 }
1039             };
1040
1041             let between_kwd_else_block = mk_sp(
1042                 self.block.span.hi(),
1043                 context
1044                     .snippet_provider
1045                     .span_before(mk_sp(self.block.span.hi(), else_block.span.lo()), "else"),
1046             );
1047             let between_kwd_else_block_comment =
1048                 extract_comment(between_kwd_else_block, context, shape);
1049
1050             let after_else = mk_sp(
1051                 context
1052                     .snippet_provider
1053                     .span_after(mk_sp(self.block.span.hi(), else_block.span.lo()), "else"),
1054                 else_block.span.lo(),
1055             );
1056             let after_else_comment = extract_comment(after_else, context, shape);
1057
1058             let between_sep = match context.config.control_brace_style() {
1059                 ControlBraceStyle::AlwaysNextLine | ControlBraceStyle::ClosingNextLine => {
1060                     &*alt_block_sep
1061                 }
1062                 ControlBraceStyle::AlwaysSameLine => " ",
1063             };
1064             let after_sep = match context.config.control_brace_style() {
1065                 ControlBraceStyle::AlwaysNextLine if last_in_chain => &*alt_block_sep,
1066                 _ => " ",
1067             };
1068
1069             result.push_str(&format!(
1070                 "{}else{}",
1071                 between_kwd_else_block_comment
1072                     .as_ref()
1073                     .map_or(between_sep, |s| &**s),
1074                 after_else_comment.as_ref().map_or(after_sep, |s| &**s),
1075             ));
1076             result.push_str(&rewrite?);
1077         }
1078
1079         Some(result)
1080     }
1081 }
1082
1083 fn rewrite_label(opt_label: Option<ast::Label>) -> Cow<'static, str> {
1084     match opt_label {
1085         Some(label) => Cow::from(format!("{}: ", label.ident)),
1086         None => Cow::from(""),
1087     }
1088 }
1089
1090 fn extract_comment(span: Span, context: &RewriteContext<'_>, shape: Shape) -> Option<String> {
1091     match rewrite_missing_comment(span, shape, context) {
1092         Some(ref comment) if !comment.is_empty() => Some(format!(
1093             "{indent}{}{indent}",
1094             comment,
1095             indent = shape.indent.to_string_with_newline(context.config)
1096         )),
1097         _ => None,
1098     }
1099 }
1100
1101 pub(crate) fn block_contains_comment(block: &ast::Block, source_map: &SourceMap) -> bool {
1102     let snippet = source_map.span_to_snippet(block.span).unwrap();
1103     contains_comment(&snippet)
1104 }
1105
1106 // Checks that a block contains no statements, an expression and no comments or
1107 // attributes.
1108 // FIXME: incorrectly returns false when comment is contained completely within
1109 // the expression.
1110 pub(crate) fn is_simple_block(
1111     block: &ast::Block,
1112     attrs: Option<&[ast::Attribute]>,
1113     source_map: &SourceMap,
1114 ) -> bool {
1115     (block.stmts.len() == 1
1116         && stmt_is_expr(&block.stmts[0])
1117         && !block_contains_comment(block, source_map)
1118         && attrs.map_or(true, |a| a.is_empty()))
1119 }
1120
1121 /// Checks whether a block contains at most one statement or expression, and no
1122 /// comments or attributes.
1123 pub(crate) fn is_simple_block_stmt(
1124     block: &ast::Block,
1125     attrs: Option<&[ast::Attribute]>,
1126     source_map: &SourceMap,
1127 ) -> bool {
1128     block.stmts.len() <= 1
1129         && !block_contains_comment(block, source_map)
1130         && attrs.map_or(true, |a| a.is_empty())
1131 }
1132
1133 /// Checks whether a block contains no statements, expressions, comments, or
1134 /// inner attributes.
1135 pub(crate) fn is_empty_block(
1136     block: &ast::Block,
1137     attrs: Option<&[ast::Attribute]>,
1138     source_map: &SourceMap,
1139 ) -> bool {
1140     block.stmts.is_empty()
1141         && !block_contains_comment(block, source_map)
1142         && attrs.map_or(true, |a| inner_attributes(a).is_empty())
1143 }
1144
1145 pub(crate) fn stmt_is_expr(stmt: &ast::Stmt) -> bool {
1146     match stmt.node {
1147         ast::StmtKind::Expr(..) => true,
1148         _ => false,
1149     }
1150 }
1151
1152 pub(crate) fn is_unsafe_block(block: &ast::Block) -> bool {
1153     if let ast::BlockCheckMode::Unsafe(..) = block.rules {
1154         true
1155     } else {
1156         false
1157     }
1158 }
1159
1160 pub(crate) fn rewrite_multiple_patterns(
1161     context: &RewriteContext<'_>,
1162     pats: &[&ast::Pat],
1163     shape: Shape,
1164 ) -> Option<String> {
1165     let pat_strs = pats
1166         .iter()
1167         .map(|p| p.rewrite(context, shape))
1168         .collect::<Option<Vec<_>>>()?;
1169
1170     let use_mixed_layout = pats
1171         .iter()
1172         .zip(pat_strs.iter())
1173         .all(|(pat, pat_str)| is_short_pattern(pat, pat_str));
1174     let items: Vec<_> = pat_strs.into_iter().map(ListItem::from_str).collect();
1175     let tactic = if use_mixed_layout {
1176         DefinitiveListTactic::Mixed
1177     } else {
1178         definitive_tactic(
1179             &items,
1180             ListTactic::HorizontalVertical,
1181             Separator::VerticalBar,
1182             shape.width,
1183         )
1184     };
1185     let fmt = ListFormatting::new(shape, context.config)
1186         .tactic(tactic)
1187         .separator(" |")
1188         .separator_place(context.config.binop_separator())
1189         .ends_with_newline(false);
1190     write_list(&items, &fmt)
1191 }
1192
1193 pub(crate) fn rewrite_literal(
1194     context: &RewriteContext<'_>,
1195     l: &ast::Lit,
1196     shape: Shape,
1197 ) -> Option<String> {
1198     match l.node {
1199         ast::LitKind::Str(_, ast::StrStyle::Cooked) => rewrite_string_lit(context, l.span, shape),
1200         _ => wrap_str(
1201             context.snippet(l.span).to_owned(),
1202             context.config.max_width(),
1203             shape,
1204         ),
1205     }
1206 }
1207
1208 fn rewrite_string_lit(context: &RewriteContext<'_>, span: Span, shape: Shape) -> Option<String> {
1209     let string_lit = context.snippet(span);
1210
1211     if !context.config.format_strings() {
1212         if string_lit
1213             .lines()
1214             .dropping_back(1)
1215             .all(|line| line.ends_with('\\'))
1216         {
1217             let new_indent = shape.visual_indent(1).indent;
1218             let indented_string_lit = String::from(
1219                 string_lit
1220                     .lines()
1221                     .map(|line| {
1222                         format!(
1223                             "{}{}",
1224                             new_indent.to_string(context.config),
1225                             line.trim_start()
1226                         )
1227                     })
1228                     .collect::<Vec<_>>()
1229                     .join("\n")
1230                     .trim_start(),
1231             );
1232             return if context.config.version() == Version::Two {
1233                 Some(indented_string_lit)
1234             } else {
1235                 wrap_str(indented_string_lit, context.config.max_width(), shape)
1236             };
1237         } else {
1238             return wrap_str(string_lit.to_owned(), context.config.max_width(), shape);
1239         }
1240     }
1241
1242     // Remove the quote characters.
1243     let str_lit = &string_lit[1..string_lit.len() - 1];
1244
1245     rewrite_string(
1246         str_lit,
1247         &StringFormat::new(shape.visual_indent(0), context.config),
1248         shape.width.saturating_sub(2),
1249     )
1250 }
1251
1252 fn choose_separator_tactic(context: &RewriteContext<'_>, span: Span) -> Option<SeparatorTactic> {
1253     if context.inside_macro() {
1254         if span_ends_with_comma(context, span) {
1255             Some(SeparatorTactic::Always)
1256         } else {
1257             Some(SeparatorTactic::Never)
1258         }
1259     } else {
1260         None
1261     }
1262 }
1263
1264 pub(crate) fn rewrite_call(
1265     context: &RewriteContext<'_>,
1266     callee: &str,
1267     args: &[ptr::P<ast::Expr>],
1268     span: Span,
1269     shape: Shape,
1270 ) -> Option<String> {
1271     overflow::rewrite_with_parens(
1272         context,
1273         callee,
1274         args.iter(),
1275         shape,
1276         span,
1277         context.config.width_heuristics().fn_call_width,
1278         choose_separator_tactic(context, span),
1279     )
1280 }
1281
1282 pub(crate) fn is_simple_expr(expr: &ast::Expr) -> bool {
1283     match expr.node {
1284         ast::ExprKind::Lit(..) => true,
1285         ast::ExprKind::Path(ref qself, ref path) => qself.is_none() && path.segments.len() <= 1,
1286         ast::ExprKind::AddrOf(_, ref expr)
1287         | ast::ExprKind::Box(ref expr)
1288         | ast::ExprKind::Cast(ref expr, _)
1289         | ast::ExprKind::Field(ref expr, _)
1290         | ast::ExprKind::Try(ref expr)
1291         | ast::ExprKind::Unary(_, ref expr) => is_simple_expr(expr),
1292         ast::ExprKind::Index(ref lhs, ref rhs) => is_simple_expr(lhs) && is_simple_expr(rhs),
1293         ast::ExprKind::Repeat(ref lhs, ref rhs) => {
1294             is_simple_expr(lhs) && is_simple_expr(&*rhs.value)
1295         }
1296         _ => false,
1297     }
1298 }
1299
1300 pub(crate) fn is_every_expr_simple(lists: &[OverflowableItem<'_>]) -> bool {
1301     lists.iter().all(OverflowableItem::is_simple)
1302 }
1303
1304 pub(crate) fn can_be_overflowed_expr(
1305     context: &RewriteContext<'_>,
1306     expr: &ast::Expr,
1307     args_len: usize,
1308 ) -> bool {
1309     match expr.node {
1310         _ if !expr.attrs.is_empty() => false,
1311         ast::ExprKind::Match(..) => {
1312             (context.use_block_indent() && args_len == 1)
1313                 || (context.config.indent_style() == IndentStyle::Visual && args_len > 1)
1314                 || context.config.overflow_delimited_expr()
1315         }
1316         ast::ExprKind::If(..)
1317         | ast::ExprKind::ForLoop(..)
1318         | ast::ExprKind::Loop(..)
1319         | ast::ExprKind::While(..) => {
1320             context.config.combine_control_expr() && context.use_block_indent() && args_len == 1
1321         }
1322
1323         // Handle always block-like expressions
1324         ast::ExprKind::Async(..) | ast::ExprKind::Block(..) | ast::ExprKind::Closure(..) => true,
1325
1326         // Handle `[]` and `{}`-like expressions
1327         ast::ExprKind::Array(..) | ast::ExprKind::Struct(..) => {
1328             context.config.overflow_delimited_expr()
1329                 || (context.use_block_indent() && args_len == 1)
1330         }
1331         ast::ExprKind::Mac(ref macro_) => {
1332             match (macro_.node.delim, context.config.overflow_delimited_expr()) {
1333                 (ast::MacDelimiter::Bracket, true) | (ast::MacDelimiter::Brace, true) => true,
1334                 _ => context.use_block_indent() && args_len == 1,
1335             }
1336         }
1337
1338         // Handle parenthetical expressions
1339         ast::ExprKind::Call(..) | ast::ExprKind::MethodCall(..) | ast::ExprKind::Tup(..) => {
1340             context.use_block_indent() && args_len == 1
1341         }
1342
1343         // Handle unary-like expressions
1344         ast::ExprKind::AddrOf(_, ref expr)
1345         | ast::ExprKind::Box(ref expr)
1346         | ast::ExprKind::Try(ref expr)
1347         | ast::ExprKind::Unary(_, ref expr)
1348         | ast::ExprKind::Cast(ref expr, _) => can_be_overflowed_expr(context, expr, args_len),
1349         _ => false,
1350     }
1351 }
1352
1353 pub(crate) fn is_nested_call(expr: &ast::Expr) -> bool {
1354     match expr.node {
1355         ast::ExprKind::Call(..) | ast::ExprKind::Mac(..) => true,
1356         ast::ExprKind::AddrOf(_, ref expr)
1357         | ast::ExprKind::Box(ref expr)
1358         | ast::ExprKind::Try(ref expr)
1359         | ast::ExprKind::Unary(_, ref expr)
1360         | ast::ExprKind::Cast(ref expr, _) => is_nested_call(expr),
1361         _ => false,
1362     }
1363 }
1364
1365 /// Returns `true` if a function call or a method call represented by the given span ends with a
1366 /// trailing comma. This function is used when rewriting macro, as adding or removing a trailing
1367 /// comma from macro can potentially break the code.
1368 pub(crate) fn span_ends_with_comma(context: &RewriteContext<'_>, span: Span) -> bool {
1369     let mut result: bool = Default::default();
1370     let mut prev_char: char = Default::default();
1371     let closing_delimiters = &[')', '}', ']'];
1372
1373     for (kind, c) in CharClasses::new(context.snippet(span).chars()) {
1374         match c {
1375             _ if kind.is_comment() || c.is_whitespace() => continue,
1376             c if closing_delimiters.contains(&c) => {
1377                 result &= !closing_delimiters.contains(&prev_char);
1378             }
1379             ',' => result = true,
1380             _ => result = false,
1381         }
1382         prev_char = c;
1383     }
1384
1385     result
1386 }
1387
1388 fn rewrite_paren(
1389     context: &RewriteContext<'_>,
1390     mut subexpr: &ast::Expr,
1391     shape: Shape,
1392     mut span: Span,
1393 ) -> Option<String> {
1394     debug!("rewrite_paren, shape: {:?}", shape);
1395
1396     // Extract comments within parens.
1397     let mut pre_span;
1398     let mut post_span;
1399     let mut pre_comment;
1400     let mut post_comment;
1401     let remove_nested_parens = context.config.remove_nested_parens();
1402     loop {
1403         // 1 = "(" or ")"
1404         pre_span = mk_sp(span.lo() + BytePos(1), subexpr.span.lo());
1405         post_span = mk_sp(subexpr.span.hi(), span.hi() - BytePos(1));
1406         pre_comment = rewrite_missing_comment(pre_span, shape, context)?;
1407         post_comment = rewrite_missing_comment(post_span, shape, context)?;
1408
1409         // Remove nested parens if there are no comments.
1410         if let ast::ExprKind::Paren(ref subsubexpr) = subexpr.node {
1411             if remove_nested_parens && pre_comment.is_empty() && post_comment.is_empty() {
1412                 span = subexpr.span;
1413                 subexpr = subsubexpr;
1414                 continue;
1415             }
1416         }
1417
1418         break;
1419     }
1420
1421     // 1 = `(` and `)`
1422     let sub_shape = shape.offset_left(1)?.sub_width(1)?;
1423     let subexpr_str = subexpr.rewrite(context, sub_shape)?;
1424     let fits_single_line = !pre_comment.contains("//") && !post_comment.contains("//");
1425     if fits_single_line {
1426         Some(format!("({}{}{})", pre_comment, subexpr_str, post_comment))
1427     } else {
1428         rewrite_paren_in_multi_line(context, subexpr, shape, pre_span, post_span)
1429     }
1430 }
1431
1432 fn rewrite_paren_in_multi_line(
1433     context: &RewriteContext<'_>,
1434     subexpr: &ast::Expr,
1435     shape: Shape,
1436     pre_span: Span,
1437     post_span: Span,
1438 ) -> Option<String> {
1439     let nested_indent = shape.indent.block_indent(context.config);
1440     let nested_shape = Shape::indented(nested_indent, context.config);
1441     let pre_comment = rewrite_missing_comment(pre_span, nested_shape, context)?;
1442     let post_comment = rewrite_missing_comment(post_span, nested_shape, context)?;
1443     let subexpr_str = subexpr.rewrite(context, nested_shape)?;
1444
1445     let mut result = String::with_capacity(subexpr_str.len() * 2);
1446     result.push('(');
1447     if !pre_comment.is_empty() {
1448         result.push_str(&nested_indent.to_string_with_newline(context.config));
1449         result.push_str(&pre_comment);
1450     }
1451     result.push_str(&nested_indent.to_string_with_newline(context.config));
1452     result.push_str(&subexpr_str);
1453     if !post_comment.is_empty() {
1454         result.push_str(&nested_indent.to_string_with_newline(context.config));
1455         result.push_str(&post_comment);
1456     }
1457     result.push_str(&shape.indent.to_string_with_newline(context.config));
1458     result.push(')');
1459
1460     Some(result)
1461 }
1462
1463 fn rewrite_index(
1464     expr: &ast::Expr,
1465     index: &ast::Expr,
1466     context: &RewriteContext<'_>,
1467     shape: Shape,
1468 ) -> Option<String> {
1469     let expr_str = expr.rewrite(context, shape)?;
1470
1471     let offset = last_line_width(&expr_str) + 1;
1472     let rhs_overhead = shape.rhs_overhead(context.config);
1473     let index_shape = if expr_str.contains('\n') {
1474         Shape::legacy(context.config.max_width(), shape.indent)
1475             .offset_left(offset)
1476             .and_then(|shape| shape.sub_width(1 + rhs_overhead))
1477     } else {
1478         match context.config.indent_style() {
1479             IndentStyle::Block => shape
1480                 .offset_left(offset)
1481                 .and_then(|shape| shape.sub_width(1)),
1482             IndentStyle::Visual => shape.visual_indent(offset).sub_width(offset + 1),
1483         }
1484     };
1485     let orig_index_rw = index_shape.and_then(|s| index.rewrite(context, s));
1486
1487     // Return if index fits in a single line.
1488     match orig_index_rw {
1489         Some(ref index_str) if !index_str.contains('\n') => {
1490             return Some(format!("{}[{}]", expr_str, index_str));
1491         }
1492         _ => (),
1493     }
1494
1495     // Try putting index on the next line and see if it fits in a single line.
1496     let indent = shape.indent.block_indent(context.config);
1497     let index_shape = Shape::indented(indent, context.config).offset_left(1)?;
1498     let index_shape = index_shape.sub_width(1 + rhs_overhead)?;
1499     let new_index_rw = index.rewrite(context, index_shape);
1500     match (orig_index_rw, new_index_rw) {
1501         (_, Some(ref new_index_str)) if !new_index_str.contains('\n') => Some(format!(
1502             "{}{}[{}]",
1503             expr_str,
1504             indent.to_string_with_newline(context.config),
1505             new_index_str,
1506         )),
1507         (None, Some(ref new_index_str)) => Some(format!(
1508             "{}{}[{}]",
1509             expr_str,
1510             indent.to_string_with_newline(context.config),
1511             new_index_str,
1512         )),
1513         (Some(ref index_str), _) => Some(format!("{}[{}]", expr_str, index_str)),
1514         _ => None,
1515     }
1516 }
1517
1518 fn struct_lit_can_be_aligned(fields: &[ast::Field], base: Option<&ast::Expr>) -> bool {
1519     if base.is_some() {
1520         return false;
1521     }
1522
1523     fields.iter().all(|field| !field.is_shorthand)
1524 }
1525
1526 fn rewrite_struct_lit<'a>(
1527     context: &RewriteContext<'_>,
1528     path: &ast::Path,
1529     fields: &'a [ast::Field],
1530     base: Option<&'a ast::Expr>,
1531     attrs: &[ast::Attribute],
1532     span: Span,
1533     shape: Shape,
1534 ) -> Option<String> {
1535     debug!("rewrite_struct_lit: shape {:?}", shape);
1536
1537     enum StructLitField<'a> {
1538         Regular(&'a ast::Field),
1539         Base(&'a ast::Expr),
1540     }
1541
1542     // 2 = " {".len()
1543     let path_shape = shape.sub_width(2)?;
1544     let path_str = rewrite_path(context, PathContext::Expr, None, path, path_shape)?;
1545
1546     if fields.is_empty() && base.is_none() {
1547         return Some(format!("{} {{}}", path_str));
1548     }
1549
1550     // Foo { a: Foo } - indent is +3, width is -5.
1551     let (h_shape, v_shape) = struct_lit_shape(shape, context, path_str.len() + 3, 2)?;
1552
1553     let one_line_width = h_shape.map_or(0, |shape| shape.width);
1554     let body_lo = context.snippet_provider.span_after(span, "{");
1555     let fields_str = if struct_lit_can_be_aligned(fields, base)
1556         && context.config.struct_field_align_threshold() > 0
1557     {
1558         rewrite_with_alignment(
1559             fields,
1560             context,
1561             v_shape,
1562             mk_sp(body_lo, span.hi()),
1563             one_line_width,
1564         )?
1565     } else {
1566         let field_iter = fields
1567             .iter()
1568             .map(StructLitField::Regular)
1569             .chain(base.into_iter().map(StructLitField::Base));
1570
1571         let span_lo = |item: &StructLitField<'_>| match *item {
1572             StructLitField::Regular(field) => field.span().lo(),
1573             StructLitField::Base(expr) => {
1574                 let last_field_hi = fields.last().map_or(span.lo(), |field| field.span.hi());
1575                 let snippet = context.snippet(mk_sp(last_field_hi, expr.span.lo()));
1576                 let pos = snippet.find_uncommented("..").unwrap();
1577                 last_field_hi + BytePos(pos as u32)
1578             }
1579         };
1580         let span_hi = |item: &StructLitField<'_>| match *item {
1581             StructLitField::Regular(field) => field.span().hi(),
1582             StructLitField::Base(expr) => expr.span.hi(),
1583         };
1584         let rewrite = |item: &StructLitField<'_>| match *item {
1585             StructLitField::Regular(field) => {
1586                 // The 1 taken from the v_budget is for the comma.
1587                 rewrite_field(context, field, v_shape.sub_width(1)?, 0)
1588             }
1589             StructLitField::Base(expr) => {
1590                 // 2 = ..
1591                 expr.rewrite(context, v_shape.offset_left(2)?)
1592                     .map(|s| format!("..{}", s))
1593             }
1594         };
1595
1596         let items = itemize_list(
1597             context.snippet_provider,
1598             field_iter,
1599             "}",
1600             ",",
1601             span_lo,
1602             span_hi,
1603             rewrite,
1604             body_lo,
1605             span.hi(),
1606             false,
1607         );
1608         let item_vec = items.collect::<Vec<_>>();
1609
1610         let tactic = struct_lit_tactic(h_shape, context, &item_vec);
1611         let nested_shape = shape_for_tactic(tactic, h_shape, v_shape);
1612
1613         let ends_with_comma = span_ends_with_comma(context, span);
1614         let force_no_trailing_comma = context.inside_macro() && !ends_with_comma;
1615
1616         let fmt = struct_lit_formatting(
1617             nested_shape,
1618             tactic,
1619             context,
1620             force_no_trailing_comma || base.is_some() || !context.use_block_indent(),
1621         );
1622
1623         write_list(&item_vec, &fmt)?
1624     };
1625
1626     let fields_str =
1627         wrap_struct_field(context, &attrs, &fields_str, shape, v_shape, one_line_width)?;
1628     Some(format!("{} {{{}}}", path_str, fields_str))
1629
1630     // FIXME if context.config.indent_style() == Visual, but we run out
1631     // of space, we should fall back to BlockIndent.
1632 }
1633
1634 pub(crate) fn wrap_struct_field(
1635     context: &RewriteContext<'_>,
1636     attrs: &[ast::Attribute],
1637     fields_str: &str,
1638     shape: Shape,
1639     nested_shape: Shape,
1640     one_line_width: usize,
1641 ) -> Option<String> {
1642     let should_vertical = context.config.indent_style() == IndentStyle::Block
1643         && (fields_str.contains('\n')
1644             || !context.config.struct_lit_single_line()
1645             || fields_str.len() > one_line_width);
1646
1647     let inner_attrs = &inner_attributes(attrs);
1648     if inner_attrs.is_empty() {
1649         if should_vertical {
1650             Some(format!(
1651                 "{}{}{}",
1652                 nested_shape.indent.to_string_with_newline(context.config),
1653                 fields_str,
1654                 shape.indent.to_string_with_newline(context.config)
1655             ))
1656         } else {
1657             // One liner or visual indent.
1658             Some(format!(" {} ", fields_str))
1659         }
1660     } else {
1661         Some(format!(
1662             "{}{}{}{}{}",
1663             nested_shape.indent.to_string_with_newline(context.config),
1664             inner_attrs.rewrite(context, shape)?,
1665             nested_shape.indent.to_string_with_newline(context.config),
1666             fields_str,
1667             shape.indent.to_string_with_newline(context.config)
1668         ))
1669     }
1670 }
1671
1672 pub(crate) fn struct_lit_field_separator(config: &Config) -> &str {
1673     colon_spaces(config)
1674 }
1675
1676 pub(crate) fn rewrite_field(
1677     context: &RewriteContext<'_>,
1678     field: &ast::Field,
1679     shape: Shape,
1680     prefix_max_width: usize,
1681 ) -> Option<String> {
1682     if contains_skip(&field.attrs) {
1683         return Some(context.snippet(field.span()).to_owned());
1684     }
1685     let mut attrs_str = field.attrs.rewrite(context, shape)?;
1686     if !attrs_str.is_empty() {
1687         attrs_str.push_str(&shape.indent.to_string_with_newline(context.config));
1688     };
1689     let name = context.snippet(field.ident.span);
1690     if field.is_shorthand {
1691         Some(attrs_str + name)
1692     } else {
1693         let mut separator = String::from(struct_lit_field_separator(context.config));
1694         for _ in 0..prefix_max_width.saturating_sub(name.len()) {
1695             separator.push(' ');
1696         }
1697         let overhead = name.len() + separator.len();
1698         let expr_shape = shape.offset_left(overhead)?;
1699         let expr = field.expr.rewrite(context, expr_shape);
1700
1701         match expr {
1702             Some(ref e) if e.as_str() == name && context.config.use_field_init_shorthand() => {
1703                 Some(attrs_str + name)
1704             }
1705             Some(e) => Some(format!("{}{}{}{}", attrs_str, name, separator, e)),
1706             None => {
1707                 let expr_offset = shape.indent.block_indent(context.config);
1708                 let expr = field
1709                     .expr
1710                     .rewrite(context, Shape::indented(expr_offset, context.config));
1711                 expr.map(|s| {
1712                     format!(
1713                         "{}{}:\n{}{}",
1714                         attrs_str,
1715                         name,
1716                         expr_offset.to_string(context.config),
1717                         s
1718                     )
1719                 })
1720             }
1721         }
1722     }
1723 }
1724
1725 fn rewrite_tuple_in_visual_indent_style<'a, T: 'a + IntoOverflowableItem<'a>>(
1726     context: &RewriteContext<'_>,
1727     mut items: impl Iterator<Item = &'a T>,
1728     span: Span,
1729     shape: Shape,
1730     is_singleton_tuple: bool,
1731 ) -> Option<String> {
1732     // In case of length 1, need a trailing comma
1733     debug!("rewrite_tuple_in_visual_indent_style {:?}", shape);
1734     if is_singleton_tuple {
1735         // 3 = "(" + ",)"
1736         let nested_shape = shape.sub_width(3)?.visual_indent(1);
1737         return items
1738             .next()
1739             .unwrap()
1740             .rewrite(context, nested_shape)
1741             .map(|s| format!("({},)", s));
1742     }
1743
1744     let list_lo = context.snippet_provider.span_after(span, "(");
1745     let nested_shape = shape.sub_width(2)?.visual_indent(1);
1746     let items = itemize_list(
1747         context.snippet_provider,
1748         items,
1749         ")",
1750         ",",
1751         |item| item.span().lo(),
1752         |item| item.span().hi(),
1753         |item| item.rewrite(context, nested_shape),
1754         list_lo,
1755         span.hi() - BytePos(1),
1756         false,
1757     );
1758     let item_vec: Vec<_> = items.collect();
1759     let tactic = definitive_tactic(
1760         &item_vec,
1761         ListTactic::HorizontalVertical,
1762         Separator::Comma,
1763         nested_shape.width,
1764     );
1765     let fmt = ListFormatting::new(nested_shape, context.config)
1766         .tactic(tactic)
1767         .ends_with_newline(false);
1768     let list_str = write_list(&item_vec, &fmt)?;
1769
1770     Some(format!("({})", list_str))
1771 }
1772
1773 pub(crate) fn rewrite_tuple<'a, T: 'a + IntoOverflowableItem<'a>>(
1774     context: &'a RewriteContext<'_>,
1775     items: impl Iterator<Item = &'a T>,
1776     span: Span,
1777     shape: Shape,
1778     is_singleton_tuple: bool,
1779 ) -> Option<String> {
1780     debug!("rewrite_tuple {:?}", shape);
1781     if context.use_block_indent() {
1782         // We use the same rule as function calls for rewriting tuples.
1783         let force_tactic = if context.inside_macro() {
1784             if span_ends_with_comma(context, span) {
1785                 Some(SeparatorTactic::Always)
1786             } else {
1787                 Some(SeparatorTactic::Never)
1788             }
1789         } else if is_singleton_tuple {
1790             Some(SeparatorTactic::Always)
1791         } else {
1792             None
1793         };
1794         overflow::rewrite_with_parens(
1795             context,
1796             "",
1797             items,
1798             shape,
1799             span,
1800             context.config.width_heuristics().fn_call_width,
1801             force_tactic,
1802         )
1803     } else {
1804         rewrite_tuple_in_visual_indent_style(context, items, span, shape, is_singleton_tuple)
1805     }
1806 }
1807
1808 pub(crate) fn rewrite_unary_prefix<R: Rewrite>(
1809     context: &RewriteContext<'_>,
1810     prefix: &str,
1811     rewrite: &R,
1812     shape: Shape,
1813 ) -> Option<String> {
1814     rewrite
1815         .rewrite(context, shape.offset_left(prefix.len())?)
1816         .map(|r| format!("{}{}", prefix, r))
1817 }
1818
1819 // FIXME: this is probably not correct for multi-line Rewrites. we should
1820 // subtract suffix.len() from the last line budget, not the first!
1821 pub(crate) fn rewrite_unary_suffix<R: Rewrite>(
1822     context: &RewriteContext<'_>,
1823     suffix: &str,
1824     rewrite: &R,
1825     shape: Shape,
1826 ) -> Option<String> {
1827     rewrite
1828         .rewrite(context, shape.sub_width(suffix.len())?)
1829         .map(|mut r| {
1830             r.push_str(suffix);
1831             r
1832         })
1833 }
1834
1835 fn rewrite_unary_op(
1836     context: &RewriteContext<'_>,
1837     op: ast::UnOp,
1838     expr: &ast::Expr,
1839     shape: Shape,
1840 ) -> Option<String> {
1841     // For some reason, an UnOp is not spanned like BinOp!
1842     rewrite_unary_prefix(context, ast::UnOp::to_string(op), expr, shape)
1843 }
1844
1845 fn rewrite_assignment(
1846     context: &RewriteContext<'_>,
1847     lhs: &ast::Expr,
1848     rhs: &ast::Expr,
1849     op: Option<&ast::BinOp>,
1850     shape: Shape,
1851 ) -> Option<String> {
1852     let operator_str = match op {
1853         Some(op) => context.snippet(op.span),
1854         None => "=",
1855     };
1856
1857     // 1 = space between lhs and operator.
1858     let lhs_shape = shape.sub_width(operator_str.len() + 1)?;
1859     let lhs_str = format!("{} {}", lhs.rewrite(context, lhs_shape)?, operator_str);
1860
1861     rewrite_assign_rhs(context, lhs_str, rhs, shape)
1862 }
1863
1864 /// Controls where to put the rhs.
1865 #[derive(Debug, Copy, Clone, PartialEq, Eq)]
1866 pub(crate) enum RhsTactics {
1867     /// Use heuristics.
1868     Default,
1869     /// Put the rhs on the next line if it uses multiple line, without extra indentation.
1870     ForceNextLineWithoutIndent,
1871     /// Allow overflowing max width if neither `Default` nor `ForceNextLineWithoutIndent`
1872     /// did not work.
1873     AllowOverflow,
1874 }
1875
1876 // The left hand side must contain everything up to, and including, the
1877 // assignment operator.
1878 pub(crate) fn rewrite_assign_rhs<S: Into<String>, R: Rewrite>(
1879     context: &RewriteContext<'_>,
1880     lhs: S,
1881     ex: &R,
1882     shape: Shape,
1883 ) -> Option<String> {
1884     rewrite_assign_rhs_with(context, lhs, ex, shape, RhsTactics::Default)
1885 }
1886
1887 pub(crate) fn rewrite_assign_rhs_with<S: Into<String>, R: Rewrite>(
1888     context: &RewriteContext<'_>,
1889     lhs: S,
1890     ex: &R,
1891     shape: Shape,
1892     rhs_tactics: RhsTactics,
1893 ) -> Option<String> {
1894     let lhs = lhs.into();
1895     let last_line_width = last_line_width(&lhs).saturating_sub(if lhs.contains('\n') {
1896         shape.indent.width()
1897     } else {
1898         0
1899     });
1900     // 1 = space between operator and rhs.
1901     let orig_shape = shape.offset_left(last_line_width + 1).unwrap_or(Shape {
1902         width: 0,
1903         offset: shape.offset + last_line_width + 1,
1904         ..shape
1905     });
1906     let rhs = choose_rhs(
1907         context,
1908         ex,
1909         orig_shape,
1910         ex.rewrite(context, orig_shape),
1911         rhs_tactics,
1912     )?;
1913     Some(lhs + &rhs)
1914 }
1915
1916 fn choose_rhs<R: Rewrite>(
1917     context: &RewriteContext<'_>,
1918     expr: &R,
1919     shape: Shape,
1920     orig_rhs: Option<String>,
1921     rhs_tactics: RhsTactics,
1922 ) -> Option<String> {
1923     match orig_rhs {
1924         Some(ref new_str)
1925             if !new_str.contains('\n') && unicode_str_width(new_str) <= shape.width =>
1926         {
1927             Some(format!(" {}", new_str))
1928         }
1929         _ => {
1930             // Expression did not fit on the same line as the identifier.
1931             // Try splitting the line and see if that works better.
1932             let new_shape = shape_from_rhs_tactic(context, shape, rhs_tactics)?;
1933             let new_rhs = expr.rewrite(context, new_shape);
1934             let new_indent_str = &shape
1935                 .indent
1936                 .block_indent(context.config)
1937                 .to_string_with_newline(context.config);
1938
1939             match (orig_rhs, new_rhs) {
1940                 (Some(ref orig_rhs), Some(ref new_rhs))
1941                     if wrap_str(new_rhs.clone(), context.config.max_width(), new_shape)
1942                         .is_none() =>
1943                 {
1944                     Some(format!(" {}", orig_rhs))
1945                 }
1946                 (Some(ref orig_rhs), Some(ref new_rhs))
1947                     if prefer_next_line(orig_rhs, new_rhs, rhs_tactics) =>
1948                 {
1949                     Some(format!("{}{}", new_indent_str, new_rhs))
1950                 }
1951                 (None, Some(ref new_rhs)) => Some(format!("{}{}", new_indent_str, new_rhs)),
1952                 (None, None) if rhs_tactics == RhsTactics::AllowOverflow => {
1953                     let shape = shape.infinite_width();
1954                     expr.rewrite(context, shape).map(|s| format!(" {}", s))
1955                 }
1956                 (None, None) => None,
1957                 (Some(orig_rhs), _) => Some(format!(" {}", orig_rhs)),
1958             }
1959         }
1960     }
1961 }
1962
1963 fn shape_from_rhs_tactic(
1964     context: &RewriteContext<'_>,
1965     shape: Shape,
1966     rhs_tactic: RhsTactics,
1967 ) -> Option<Shape> {
1968     match rhs_tactic {
1969         RhsTactics::ForceNextLineWithoutIndent => shape
1970             .with_max_width(context.config)
1971             .sub_width(shape.indent.width()),
1972         RhsTactics::Default | RhsTactics::AllowOverflow => {
1973             Shape::indented(shape.indent.block_indent(context.config), context.config)
1974                 .sub_width(shape.rhs_overhead(context.config))
1975         }
1976     }
1977 }
1978
1979 /// Returns true if formatting next_line_rhs is better on a new line when compared to the
1980 /// original's line formatting.
1981 ///
1982 /// It is considered better if:
1983 /// 1. the tactic is ForceNextLineWithoutIndent
1984 /// 2. next_line_rhs doesn't have newlines
1985 /// 3. the original line has more newlines than next_line_rhs
1986 /// 4. the original formatting of the first line ends with `(`, `{`, or `[` and next_line_rhs
1987 ///    doesn't
1988 pub(crate) fn prefer_next_line(
1989     orig_rhs: &str,
1990     next_line_rhs: &str,
1991     rhs_tactics: RhsTactics,
1992 ) -> bool {
1993     rhs_tactics == RhsTactics::ForceNextLineWithoutIndent
1994         || !next_line_rhs.contains('\n')
1995         || count_newlines(orig_rhs) > count_newlines(next_line_rhs) + 1
1996         || first_line_ends_with(orig_rhs, '(') && !first_line_ends_with(next_line_rhs, '(')
1997         || first_line_ends_with(orig_rhs, '{') && !first_line_ends_with(next_line_rhs, '{')
1998         || first_line_ends_with(orig_rhs, '[') && !first_line_ends_with(next_line_rhs, '[')
1999 }
2000
2001 fn rewrite_expr_addrof(
2002     context: &RewriteContext<'_>,
2003     mutability: ast::Mutability,
2004     expr: &ast::Expr,
2005     shape: Shape,
2006 ) -> Option<String> {
2007     let operator_str = match mutability {
2008         ast::Mutability::Immutable => "&",
2009         ast::Mutability::Mutable => "&mut ",
2010     };
2011     rewrite_unary_prefix(context, operator_str, expr, shape)
2012 }
2013
2014 pub(crate) fn is_method_call(expr: &ast::Expr) -> bool {
2015     match expr.node {
2016         ast::ExprKind::MethodCall(..) => true,
2017         ast::ExprKind::AddrOf(_, ref expr)
2018         | ast::ExprKind::Box(ref expr)
2019         | ast::ExprKind::Cast(ref expr, _)
2020         | ast::ExprKind::Try(ref expr)
2021         | ast::ExprKind::Unary(_, ref expr) => is_method_call(expr),
2022         _ => false,
2023     }
2024 }
2025
2026 #[cfg(test)]
2027 mod test {
2028     use super::last_line_offsetted;
2029
2030     #[test]
2031     fn test_last_line_offsetted() {
2032         let lines = "one\n    two";
2033         assert_eq!(last_line_offsetted(2, lines), true);
2034         assert_eq!(last_line_offsetted(4, lines), false);
2035         assert_eq!(last_line_offsetted(6, lines), false);
2036
2037         let lines = "one    two";
2038         assert_eq!(last_line_offsetted(2, lines), false);
2039         assert_eq!(last_line_offsetted(0, lines), false);
2040
2041         let lines = "\ntwo";
2042         assert_eq!(last_line_offsetted(2, lines), false);
2043         assert_eq!(last_line_offsetted(0, lines), false);
2044
2045         let lines = "one\n    two      three";
2046         assert_eq!(last_line_offsetted(2, lines), true);
2047         let lines = "one\n two      three";
2048         assert_eq!(last_line_offsetted(2, lines), false);
2049     }
2050 }