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::cmp::Ordering;
  12 use std::borrow::Borrow;
  13 use std::mem::swap;
  14 use std::ops::Deref;
  15 use std::iter::ExactSizeIterator;
  16 use std::fmt::Write;
  17
  18 use {Indent, Spanned};
  19 use rewrite::{Rewrite, RewriteContext};
  20 use lists::{write_list, itemize_list, ListFormatting, SeparatorTactic, ListTactic,
  21             DefinitiveListTactic, definitive_tactic, ListItem, format_item_list};
  22 use string::{StringFormat, rewrite_string};
  23 use utils::{CodeMapSpanUtils, extra_offset, last_line_width, wrap_str, binary_search,
  24             first_line_width, semicolon_for_stmt};
  25 use visitor::FmtVisitor;
  26 use config::{Config, StructLitStyle, MultilineStyle};
  27 use comment::{FindUncommented, rewrite_comment, contains_comment, recover_comment_removed};
  28 use types::rewrite_path;
  29 use items::{span_lo_for_arg, span_hi_for_arg};
  30 use chains::rewrite_chain;
  31 use macros::rewrite_macro;
  32
  33 use syntax::{ast, ptr};
  34 use syntax::codemap::{CodeMap, Span, BytePos, mk_sp};
  35 use syntax::visit::Visitor;
  36
  37 impl Rewrite for ast::Expr {
  38     fn rewrite(&self, context: &RewriteContext, width: usize, offset: Indent) -> Option<String> {
  39         let result = match self.node {
  40             ast::ExprKind::Vec(ref expr_vec) => {
  41                 rewrite_array(expr_vec.iter().map(|e| &**e),
  42                               mk_sp(context.codemap.span_after(self.span, "["), self.span.hi),
  43                               context,
  44                               width,
  45                               offset)
  46             }
  47             ast::ExprKind::Lit(ref l) => {
  48                 match l.node {
  49                     ast::LitKind::Str(_, ast::StrStyle::Cooked) => {
  50                         rewrite_string_lit(context, l.span, width, offset)
  51                     }
  52                     _ => {
  53                         wrap_str(context.snippet(self.span),
  54                                  context.config.max_width,
  55                                  width,
  56                                  offset)
  57                     }
  58                 }
  59             }
  60             ast::ExprKind::Call(ref callee, ref args) => {
  61                 let inner_span = mk_sp(callee.span.hi, self.span.hi);
  62                 rewrite_call(context, &**callee, args, inner_span, width, offset)
  63             }
  64             ast::ExprKind::Paren(ref subexpr) => rewrite_paren(context, subexpr, width, offset),
  65             ast::ExprKind::Binary(ref op, ref lhs, ref rhs) => {
  66                 rewrite_binary_op(context, op, lhs, rhs, width, offset)
  67             }
  68             ast::ExprKind::Unary(ref op, ref subexpr) => {
  69                 rewrite_unary_op(context, op, subexpr, width, offset)
  70             }
  71             ast::ExprKind::Struct(ref path, ref fields, ref base) => {
  72                 rewrite_struct_lit(context,
  73                                    path,
  74                                    fields,
  75                                    base.as_ref().map(|e| &**e),
  76                                    self.span,
  77                                    width,
  78                                    offset)
  79             }
  80             ast::ExprKind::Tup(ref items) => {
  81                 rewrite_tuple(context,
  82                               items.iter().map(|x| &**x),
  83                               self.span,
  84                               width,
  85                               offset)
  86             }
  87             ast::ExprKind::While(ref cond, ref block, label) => {
  88                 Loop::new_while(None, cond, block, label).rewrite(context, width, offset)
  89             }
  90             ast::ExprKind::WhileLet(ref pat, ref cond, ref block, label) => {
  91                 Loop::new_while(Some(pat), cond, block, label).rewrite(context, width, offset)
  92             }
  93             ast::ExprKind::ForLoop(ref pat, ref cond, ref block, label) => {
  94                 Loop::new_for(pat, cond, block, label).rewrite(context, width, offset)
  95             }
  96             ast::ExprKind::Loop(ref block, label) => {
  97                 Loop::new_loop(block, label).rewrite(context, width, offset)
  98             }
  99             ast::ExprKind::Block(ref block) => block.rewrite(context, width, offset),
 100             ast::ExprKind::If(ref cond, ref if_block, ref else_block) => {
 101                 rewrite_if_else(context,
 102                                 cond,
 103                                 if_block,
 104                                 else_block.as_ref().map(|e| &**e),
 105                                 self.span,
 106                                 None,
 107                                 width,
 108                                 offset,
 109                                 true)
 110             }
 111             ast::ExprKind::IfLet(ref pat, ref cond, ref if_block, ref else_block) => {
 112                 rewrite_if_else(context,
 113                                 cond,
 114                                 if_block,
 115                                 else_block.as_ref().map(|e| &**e),
 116                                 self.span,
 117                                 Some(pat),
 118                                 width,
 119                                 offset,
 120                                 true)
 121             }
 122             ast::ExprKind::Match(ref cond, ref arms) => {
 123                 rewrite_match(context, cond, arms, width, offset, self.span)
 124             }
 125             ast::ExprKind::Path(ref qself, ref path) => {
 126                 rewrite_path(context, true, qself.as_ref(), path, width, offset)
 127             }
 128             ast::ExprKind::Assign(ref lhs, ref rhs) => {
 129                 rewrite_assignment(context, lhs, rhs, None, width, offset)
 130             }
 131             ast::ExprKind::AssignOp(ref op, ref lhs, ref rhs) => {
 132                 rewrite_assignment(context, lhs, rhs, Some(op), width, offset)
 133             }
 134             ast::ExprKind::Again(ref opt_ident) => {
 135                 let id_str = match *opt_ident {
 136                     Some(ident) => format!(" {}", ident.node),
 137                     None => String::new(),
 138                 };
 139                 Some(format!("continue{}", id_str))
 140             }
 141             ast::ExprKind::Break(ref opt_ident) => {
 142                 let id_str = match *opt_ident {
 143                     Some(ident) => format!(" {}", ident.node),
 144                     None => String::new(),
 145                 };
 146                 Some(format!("break{}", id_str))
 147             }
 148             ast::ExprKind::Closure(capture, ref fn_decl, ref body) => {
 149                 rewrite_closure(capture, fn_decl, body, self.span, context, width, offset)
 150             }
 151             ast::ExprKind::Field(..) |
 152             ast::ExprKind::TupField(..) |
 153             ast::ExprKind::MethodCall(..) => rewrite_chain(self, context, width, offset),
 154             ast::ExprKind::Mac(ref mac) => {
 155                 // Failure to rewrite a marco should not imply failure to
 156                 // rewrite the expression.
 157                 rewrite_macro(mac, None, context, width, offset).or_else(|| {
 158                     wrap_str(context.snippet(self.span),
 159                              context.config.max_width,
 160                              width,
 161                              offset)
 162                 })
 163             }
 164             ast::ExprKind::Ret(None) => {
 165                 wrap_str("return".to_owned(), context.config.max_width, width, offset)
 166             }
 167             ast::ExprKind::Ret(Some(ref expr)) => {
 168                 rewrite_unary_prefix(context, "return ", &**expr, width, offset)
 169             }
 170             ast::ExprKind::Box(ref expr) => {
 171                 rewrite_unary_prefix(context, "box ", &**expr, width, offset)
 172             }
 173             ast::ExprKind::AddrOf(mutability, ref expr) => {
 174                 rewrite_expr_addrof(context, mutability, expr, width, offset)
 175             }
 176             ast::ExprKind::Cast(ref expr, ref ty) => {
 177                 rewrite_pair(&**expr, &**ty, "", " as ", "", context, width, offset)
 178             }
 179             // TODO(#848): Handle type ascription; rust tracking issue
 180             //   https://github.com/rust-lang/rust/issues/23416
 181             ast::ExprKind::Type(_, _) => unimplemented!(),
 182             ast::ExprKind::Index(ref expr, ref index) => {
 183                 rewrite_pair(&**expr, &**index, "", "[", "]", context, width, offset)
 184             }
 185             ast::ExprKind::Repeat(ref expr, ref repeats) => {
 186                 rewrite_pair(&**expr, &**repeats, "[", "; ", "]", context, width, offset)
 187             }
 188             ast::ExprKind::Range(Some(ref lhs), Some(ref rhs)) => {
 189                 rewrite_pair(&**lhs, &**rhs, "", "..", "", context, width, offset)
 190             }
 191             ast::ExprKind::Range(None, Some(ref rhs)) => {
 192                 rewrite_unary_prefix(context, "..", &**rhs, width, offset)
 193             }
 194             ast::ExprKind::Range(Some(ref lhs), None) => {
 195                 Some(format!("{}..",
 196                              try_opt!(lhs.rewrite(context,
 197                                                   try_opt!(width.checked_sub(2)),
 198                                                   offset))))
 199             }
 200             ast::ExprKind::Range(None, None) => {
 201                 if width >= 2 {
 202                     Some("..".into())
 203                 } else {
 204                     None
 205                 }
 206             }
 207             // We do not format these expressions yet, but they should still
 208             // satisfy our width restrictions.
 209             ast::ExprKind::InPlace(..) |
 210             ast::ExprKind::InlineAsm(..) => {
 211                 wrap_str(context.snippet(self.span),
 212                          context.config.max_width,
 213                          width,
 214                          offset)
 215             }
 216         };
 217         result.and_then(|res| recover_comment_removed(res, self.span, context, width, offset))
 218     }
 219 }
 220
 221 pub fn rewrite_pair<LHS, RHS>(lhs: &LHS,
 222                               rhs: &RHS,
 223                               prefix: &str,
 224                               infix: &str,
 225                               suffix: &str,
 226                               context: &RewriteContext,
 227                               width: usize,
 228                               offset: Indent)
 229                               -> Option<String>
 230     where LHS: Rewrite,
 231           RHS: Rewrite
 232 {
 233     let max_width = try_opt!(width.checked_sub(prefix.len() + infix.len() + suffix.len()));
 234
 235     binary_search(1, max_width, |lhs_budget| {
 236         let lhs_offset = offset + prefix.len();
 237         let lhs_str = match lhs.rewrite(context, lhs_budget, lhs_offset) {
 238             Some(result) => result,
 239             None => return Err(Ordering::Greater),
 240         };
 241
 242         let last_line_width = last_line_width(&lhs_str);
 243         let rhs_budget = match max_width.checked_sub(last_line_width) {
 244             Some(b) => b,
 245             None => return Err(Ordering::Less),
 246         };
 247         let rhs_indent = offset + last_line_width + prefix.len() + infix.len();
 248
 249         let rhs_str = match rhs.rewrite(context, rhs_budget, rhs_indent) {
 250             Some(result) => result,
 251             None => return Err(Ordering::Less),
 252         };
 253
 254         Ok(format!("{}{}{}{}{}", prefix, lhs_str, infix, rhs_str, suffix))
 255     })
 256 }
 257
 258 pub fn rewrite_array<'a, I>(expr_iter: I,
 259                             span: Span,
 260                             context: &RewriteContext,
 261                             width: usize,
 262                             offset: Indent)
 263                             -> Option<String>
 264     where I: Iterator<Item = &'a ast::Expr>
 265 {
 266     // 2 for brackets;
 267     let offset = offset + 1;
 268     let inner_context = &RewriteContext { block_indent: offset, ..*context };
 269     let max_item_width = try_opt!(width.checked_sub(2));
 270     let items = itemize_list(context.codemap,
 271                              expr_iter,
 272                              "]",
 273                              |item| item.span.lo,
 274                              |item| item.span.hi,
 275                              // 1 = [
 276                              |item| item.rewrite(&inner_context, max_item_width, offset),
 277                              span.lo,
 278                              span.hi)
 279                     .collect::<Vec<_>>();
 280
 281     let has_long_item = try_opt!(items.iter()
 282                                       .map(|li| li.item.as_ref().map(|s| s.len() > 10))
 283                                       .fold(Some(false),
 284                                             |acc, x| acc.and_then(|y| x.map(|x| x || y))));
 285
 286     let tactic = if has_long_item || items.iter().any(ListItem::is_multiline) {
 287         definitive_tactic(&items, ListTactic::HorizontalVertical, max_item_width)
 288     } else {
 289         DefinitiveListTactic::Mixed
 290     };
 291
 292     let fmt = ListFormatting {
 293         tactic: tactic,
 294         separator: ",",
 295         trailing_separator: SeparatorTactic::Never,
 296         indent: offset,
 297         width: max_item_width,
 298         ends_with_newline: false,
 299         config: context.config,
 300     };
 301     let list_str = try_opt!(write_list(&items, &fmt));
 302
 303     Some(format!("[{}]", list_str))
 304 }
 305
 306 // This functions is pretty messy because of the wrapping and unwrapping of
 307 // expressions into and from blocks. See rust issue #27872.
 308 fn rewrite_closure(capture: ast::CaptureBy,
 309                    fn_decl: &ast::FnDecl,
 310                    body: &ast::Block,
 311                    span: Span,
 312                    context: &RewriteContext,
 313                    width: usize,
 314                    offset: Indent)
 315                    -> Option<String> {
 316     let mover = if capture == ast::CaptureBy::Value {
 317         "move "
 318     } else {
 319         ""
 320     };
 321     let offset = offset + mover.len();
 322
 323     // 4 = "|| {".len(), which is overconservative when the closure consists of
 324     // a single expression.
 325     let budget = try_opt!(width.checked_sub(4 + mover.len()));
 326     // 1 = |
 327     let argument_offset = offset + 1;
 328     let ret_str = try_opt!(fn_decl.output.rewrite(context, budget, argument_offset));
 329     // 1 = space between arguments and return type.
 330     let horizontal_budget = budget.checked_sub(ret_str.len() + 1).unwrap_or(0);
 331
 332     let arg_items = itemize_list(context.codemap,
 333                                  fn_decl.inputs.iter(),
 334                                  "|",
 335                                  |arg| span_lo_for_arg(arg),
 336                                  |arg| span_hi_for_arg(arg),
 337                                  |arg| arg.rewrite(context, budget, argument_offset),
 338                                  context.codemap.span_after(span, "|"),
 339                                  body.span.lo);
 340     let item_vec = arg_items.collect::<Vec<_>>();
 341     let tactic = definitive_tactic(&item_vec, ListTactic::HorizontalVertical, horizontal_budget);
 342     let budget = match tactic {
 343         DefinitiveListTactic::Horizontal => horizontal_budget,
 344         _ => budget,
 345     };
 346
 347     let fmt = ListFormatting {
 348         tactic: tactic,
 349         separator: ",",
 350         trailing_separator: SeparatorTactic::Never,
 351         indent: argument_offset,
 352         width: budget,
 353         ends_with_newline: false,
 354         config: context.config,
 355     };
 356     let list_str = try_opt!(write_list(&item_vec, &fmt));
 357     let mut prefix = format!("{}|{}|", mover, list_str);
 358
 359     if !ret_str.is_empty() {
 360         if prefix.contains('\n') {
 361             prefix.push('\n');
 362             prefix.push_str(&argument_offset.to_string(context.config));
 363         } else {
 364             prefix.push(' ');
 365         }
 366         prefix.push_str(&ret_str);
 367     }
 368
 369     // Try to format closure body as a single line expression without braces.
 370     if is_simple_block(body, context.codemap) && !prefix.contains('\n') {
 371         let (spacer, closer) = if ret_str.is_empty() {
 372             (" ", "")
 373         } else {
 374             (" { ", " }")
 375         };
 376         let expr = body.expr.as_ref().unwrap();
 377         // All closure bodies are blocks in the eyes of the AST, but we may not
 378         // want to unwrap them when they only contain a single expression.
 379         let inner_expr = match expr.node {
 380             ast::ExprKind::Block(ref inner) if inner.stmts.is_empty() && inner.expr.is_some() &&
 381                                                inner.rules == ast::BlockCheckMode::Default => {
 382                 inner.expr.as_ref().unwrap()
 383             }
 384             _ => expr,
 385         };
 386         let extra_offset = extra_offset(&prefix, offset) + spacer.len();
 387         let budget = try_opt!(width.checked_sub(extra_offset + closer.len()));
 388         let rewrite = inner_expr.rewrite(context, budget, offset + extra_offset);
 389
 390         // Checks if rewrite succeeded and fits on a single line.
 391         let accept_rewrite = rewrite.as_ref().map_or(false, |result| !result.contains('\n'));
 392
 393         if accept_rewrite {
 394             return Some(format!("{}{}{}{}", prefix, spacer, rewrite.unwrap(), closer));
 395         }
 396     }
 397
 398     // We couldn't format the closure body as a single line expression; fall
 399     // back to block formatting.
 400     let body_rewrite = body.expr
 401                            .as_ref()
 402                            .and_then(|body_expr| {
 403                                if let ast::ExprKind::Block(ref inner) = body_expr.node {
 404                                    Some(inner.rewrite(&context, 2, Indent::empty()))
 405                                } else {
 406                                    None
 407                                }
 408                            })
 409                            .unwrap_or_else(|| body.rewrite(&context, 2, Indent::empty()));
 410
 411     Some(format!("{} {}", prefix, try_opt!(body_rewrite)))
 412 }
 413
 414 fn nop_block_collapse(block_str: Option<String>, budget: usize) -> Option<String> {
 415     block_str.map(|block_str| {
 416         if block_str.starts_with("{") && budget >= 2 &&
 417            (block_str[1..].find(|c: char| !c.is_whitespace()).unwrap() == block_str.len() - 2) {
 418             "{}".to_owned()
 419         } else {
 420             block_str.to_owned()
 421         }
 422     })
 423 }
 424
 425 impl Rewrite for ast::Block {
 426     fn rewrite(&self, context: &RewriteContext, width: usize, offset: Indent) -> Option<String> {
 427         let user_str = context.snippet(self.span);
 428         if user_str == "{}" && width >= 2 {
 429             return Some(user_str);
 430         }
 431
 432         let mut visitor = FmtVisitor::from_codemap(context.parse_session, context.config);
 433         visitor.block_indent = context.block_indent;
 434
 435         let prefix = match self.rules {
 436             ast::BlockCheckMode::Unsafe(..) => {
 437                 let snippet = context.snippet(self.span);
 438                 let open_pos = try_opt!(snippet.find_uncommented("{"));
 439                 visitor.last_pos = self.span.lo + BytePos(open_pos as u32);
 440
 441                 // Extract comment between unsafe and block start.
 442                 let trimmed = &snippet[6..open_pos].trim();
 443
 444                 let prefix = if !trimmed.is_empty() {
 445                     // 9 = "unsafe  {".len(), 7 = "unsafe ".len()
 446                     let budget = try_opt!(width.checked_sub(9));
 447                     format!("unsafe {} ",
 448                             try_opt!(rewrite_comment(trimmed,
 449                                                      true,
 450                                                      budget,
 451                                                      offset + 7,
 452                                                      context.config)))
 453                 } else {
 454                     "unsafe ".to_owned()
 455                 };
 456
 457                 if is_simple_block(self, context.codemap) && prefix.len() < width {
 458                     let body = self.expr
 459                                    .as_ref()
 460                                    .unwrap()
 461                                    .rewrite(context, width - prefix.len(), offset);
 462                     if let Some(ref expr_str) = body {
 463                         let result = format!("{}{{ {} }}", prefix, expr_str);
 464                         if result.len() <= width && !result.contains('\n') {
 465                             return Some(result);
 466                         }
 467                     }
 468                 }
 469
 470                 prefix
 471             }
 472             ast::BlockCheckMode::Default => {
 473                 visitor.last_pos = self.span.lo;
 474
 475                 String::new()
 476             }
 477         };
 478
 479         visitor.visit_block(self);
 480
 481         Some(format!("{}{}", prefix, visitor.buffer))
 482     }
 483 }
 484
 485 impl Rewrite for ast::Stmt {
 486     fn rewrite(&self, context: &RewriteContext, _width: usize, offset: Indent) -> Option<String> {
 487         let result = match self.node {
 488             ast::StmtKind::Decl(ref decl, _) => {
 489                 if let ast::DeclKind::Local(ref local) = decl.node {
 490                     local.rewrite(context, context.config.max_width, offset)
 491                 } else {
 492                     None
 493                 }
 494             }
 495             ast::StmtKind::Expr(ref ex, _) | ast::StmtKind::Semi(ref ex, _) => {
 496                 let suffix = if semicolon_for_stmt(self) {
 497                     ";"
 498                 } else {
 499                     ""
 500                 };
 501
 502                 ex.rewrite(context,
 503                            context.config.max_width - offset.width() - suffix.len(),
 504                            offset)
 505                   .map(|s| s + suffix)
 506             }
 507             ast::StmtKind::Mac(..) => None,
 508         };
 509         result.and_then(|res| recover_comment_removed(res, self.span, context, _width, offset))
 510     }
 511 }
 512
 513 // Abstraction over for, while and loop expressions
 514 struct Loop<'a> {
 515     cond: Option<&'a ast::Expr>,
 516     block: &'a ast::Block,
 517     label: Option<ast::Ident>,
 518     pat: Option<&'a ast::Pat>,
 519     keyword: &'a str,
 520     matcher: &'a str,
 521     connector: &'a str,
 522 }
 523
 524 impl<'a> Loop<'a> {
 525     fn new_loop(block: &'a ast::Block, label: Option<ast::Ident>) -> Loop<'a> {
 526         Loop {
 527             cond: None,
 528             block: block,
 529             label: label,
 530             pat: None,
 531             keyword: "loop",
 532             matcher: "",
 533             connector: "",
 534         }
 535     }
 536
 537     fn new_while(pat: Option<&'a ast::Pat>,
 538                  cond: &'a ast::Expr,
 539                  block: &'a ast::Block,
 540                  label: Option<ast::Ident>)
 541                  -> Loop<'a> {
 542         Loop {
 543             cond: Some(cond),
 544             block: block,
 545             label: label,
 546             pat: pat,
 547             keyword: "while ",
 548             matcher: match pat {
 549                 Some(..) => "let ",
 550                 None => "",
 551             },
 552             connector: " =",
 553         }
 554     }
 555
 556     fn new_for(pat: &'a ast::Pat,
 557                cond: &'a ast::Expr,
 558                block: &'a ast::Block,
 559                label: Option<ast::Ident>)
 560                -> Loop<'a> {
 561         Loop {
 562             cond: Some(cond),
 563             block: block,
 564             label: label,
 565             pat: Some(pat),
 566             keyword: "for ",
 567             matcher: "",
 568             connector: " in",
 569         }
 570     }
 571 }
 572
 573 impl<'a> Rewrite for Loop<'a> {
 574     fn rewrite(&self, context: &RewriteContext, width: usize, offset: Indent) -> Option<String> {
 575         let label_string = rewrite_label(self.label);
 576         // 2 = " {".len()
 577         let inner_width = try_opt!(width.checked_sub(self.keyword.len() + 2 + label_string.len()));
 578         let inner_offset = offset + self.keyword.len() + label_string.len();
 579
 580         let pat_expr_string = match self.cond {
 581             Some(cond) => {
 582                 try_opt!(rewrite_pat_expr(context,
 583                                           self.pat,
 584                                           cond,
 585                                           self.matcher,
 586                                           self.connector,
 587                                           inner_width,
 588                                           inner_offset))
 589             }
 590             None => String::new(),
 591         };
 592
 593         // FIXME: this drops any comment between "loop" and the block.
 594         self.block
 595             .rewrite(context, width, offset)
 596             .map(|result| {
 597                 format!("{}{}{} {}",
 598                         label_string,
 599                         self.keyword,
 600                         pat_expr_string,
 601                         result)
 602             })
 603     }
 604 }
 605
 606 fn rewrite_label(label: Option<ast::Ident>) -> String {
 607     match label {
 608         Some(ident) => format!("{}: ", ident),
 609         None => "".to_owned(),
 610     }
 611 }
 612
 613 fn extract_comment(span: Span,
 614                    context: &RewriteContext,
 615                    offset: Indent,
 616                    width: usize)
 617                    -> Option<String> {
 618     let comment_str = context.snippet(span);
 619     if contains_comment(&comment_str) {
 620         let comment = try_opt!(rewrite_comment(comment_str.trim(),
 621                                                false,
 622                                                width,
 623                                                offset,
 624                                                context.config));
 625         Some(format!("\n{indent}{}\n{indent}",
 626                      comment,
 627                      indent = offset.to_string(context.config)))
 628     } else {
 629         None
 630     }
 631 }
 632
 633 // Rewrites if-else blocks. If let Some(_) = pat, the expression is
 634 // treated as an if-let-else expression.
 635 fn rewrite_if_else(context: &RewriteContext,
 636                    cond: &ast::Expr,
 637                    if_block: &ast::Block,
 638                    else_block_opt: Option<&ast::Expr>,
 639                    span: Span,
 640                    pat: Option<&ast::Pat>,
 641                    width: usize,
 642                    offset: Indent,
 643                    allow_single_line: bool)
 644                    -> Option<String> {
 645     // 3 = "if ", 2 = " {"
 646     let pat_expr_string = try_opt!(rewrite_pat_expr(context,
 647                                                     pat,
 648                                                     cond,
 649                                                     "let ",
 650                                                     " =",
 651                                                     try_opt!(width.checked_sub(3 + 2)),
 652                                                     offset + 3));
 653
 654     // Try to format if-else on single line.
 655     if allow_single_line && context.config.single_line_if_else {
 656         let trial = single_line_if_else(context, &pat_expr_string, if_block, else_block_opt, width);
 657
 658         if trial.is_some() {
 659             return trial;
 660         }
 661     }
 662
 663     let if_block_string = try_opt!(if_block.rewrite(context, width, offset));
 664
 665     let between_if_cond = mk_sp(context.codemap.span_after(span, "if"),
 666                                 pat.map_or(cond.span.lo,
 667                                            |_| context.codemap.span_before(span, "let")));
 668
 669     let between_if_cond_comment = extract_comment(between_if_cond, &context, offset, width);
 670
 671     let after_cond_comment = extract_comment(mk_sp(cond.span.hi, if_block.span.lo),
 672                                              context,
 673                                              offset,
 674                                              width);
 675
 676     let mut result = format!("if{}{}{}{}",
 677                              between_if_cond_comment.as_ref().map_or(" ", |str| &**str),
 678                              pat_expr_string,
 679                              after_cond_comment.as_ref().map_or(" ", |str| &**str),
 680                              if_block_string);
 681
 682     if let Some(else_block) = else_block_opt {
 683         let rewrite = match else_block.node {
 684             // If the else expression is another if-else expression, prevent it
 685             // from being formatted on a single line.
 686             ast::ExprKind::IfLet(ref pat, ref cond, ref if_block, ref next_else_block) => {
 687                 rewrite_if_else(context,
 688                                 cond,
 689                                 if_block,
 690                                 next_else_block.as_ref().map(|e| &**e),
 691                                 mk_sp(else_block.span.lo, span.hi),
 692                                 Some(pat),
 693                                 width,
 694                                 offset,
 695                                 false)
 696             }
 697             ast::ExprKind::If(ref cond, ref if_block, ref next_else_block) => {
 698                 rewrite_if_else(context,
 699                                 cond,
 700                                 if_block,
 701                                 next_else_block.as_ref().map(|e| &**e),
 702                                 mk_sp(else_block.span.lo, span.hi),
 703                                 None,
 704                                 width,
 705                                 offset,
 706                                 false)
 707             }
 708             _ => else_block.rewrite(context, width, offset),
 709         };
 710
 711         let between_if_else_block = mk_sp(if_block.span.hi,
 712                                           context.codemap.span_before(mk_sp(if_block.span.hi,
 713                                                                             else_block.span.lo),
 714                                                                       "else"));
 715         let between_if_else_block_comment = extract_comment(between_if_else_block,
 716                                                             &context,
 717                                                             offset,
 718                                                             width);
 719
 720         let after_else = mk_sp(context.codemap
 721                                       .span_after(mk_sp(if_block.span.hi, else_block.span.lo),
 722                                                   "else"),
 723                                else_block.span.lo);
 724         let after_else_comment = extract_comment(after_else, &context, offset, width);
 725
 726         try_opt!(write!(&mut result,
 727                         "{}else{}",
 728                         between_if_else_block_comment.as_ref().map_or(" ", |str| &**str),
 729                         after_else_comment.as_ref().map_or(" ", |str| &**str))
 730                      .ok());
 731         result.push_str(&&try_opt!(rewrite));
 732     }
 733
 734     Some(result)
 735 }
 736
 737 fn single_line_if_else(context: &RewriteContext,
 738                        pat_expr_str: &str,
 739                        if_node: &ast::Block,
 740                        else_block_opt: Option<&ast::Expr>,
 741                        width: usize)
 742                        -> Option<String> {
 743     let else_block = try_opt!(else_block_opt);
 744     let fixed_cost = "if  {  } else {  }".len();
 745
 746     if let ast::ExprKind::Block(ref else_node) = else_block.node {
 747         if !is_simple_block(if_node, context.codemap) ||
 748            !is_simple_block(else_node, context.codemap) || pat_expr_str.contains('\n') {
 749             return None;
 750         }
 751
 752         let new_width = try_opt!(width.checked_sub(pat_expr_str.len() + fixed_cost));
 753         let if_expr = if_node.expr.as_ref().unwrap();
 754         let if_str = try_opt!(if_expr.rewrite(context, new_width, Indent::empty()));
 755
 756         let new_width = try_opt!(new_width.checked_sub(if_str.len()));
 757         let else_expr = else_node.expr.as_ref().unwrap();
 758         let else_str = try_opt!(else_expr.rewrite(context, new_width, Indent::empty()));
 759
 760         // FIXME: this check shouldn't be necessary. Rewrites should either fail
 761         // or wrap to a newline when the object does not fit the width.
 762         let fits_line = fixed_cost + pat_expr_str.len() + if_str.len() + else_str.len() <= width;
 763
 764         if fits_line && !if_str.contains('\n') && !else_str.contains('\n') {
 765             return Some(format!("if {} {{ {} }} else {{ {} }}",
 766                                 pat_expr_str,
 767                                 if_str,
 768                                 else_str));
 769         }
 770     }
 771
 772     None
 773 }
 774
 775 fn block_contains_comment(block: &ast::Block, codemap: &CodeMap) -> bool {
 776     let snippet = codemap.span_to_snippet(block.span).unwrap();
 777     contains_comment(&snippet)
 778 }
 779
 780 // Checks that a block contains no statements, an expression and no comments.
 781 // FIXME: incorrectly returns false when comment is contained completely within
 782 // the expression.
 783 pub fn is_simple_block(block: &ast::Block, codemap: &CodeMap) -> bool {
 784     block.stmts.is_empty() && block.expr.is_some() && !block_contains_comment(block, codemap)
 785 }
 786
 787 /// Checks whether a block contains at most one statement or expression, and no comments.
 788 pub fn is_simple_block_stmt(block: &ast::Block, codemap: &CodeMap) -> bool {
 789     (block.stmts.is_empty() || (block.stmts.len() == 1 && block.expr.is_none())) &&
 790     !block_contains_comment(block, codemap)
 791 }
 792
 793 /// Checks whether a block contains no statements, expressions, or comments.
 794 pub fn is_empty_block(block: &ast::Block, codemap: &CodeMap) -> bool {
 795     block.stmts.is_empty() && block.expr.is_none() && !block_contains_comment(block, codemap)
 796 }
 797
 798 fn is_unsafe_block(block: &ast::Block) -> bool {
 799     if let ast::BlockCheckMode::Unsafe(..) = block.rules {
 800         true
 801     } else {
 802         false
 803     }
 804 }
 805
 806 // inter-match-arm-comment-rules:
 807 //  - all comments following a match arm before the start of the next arm
 808 //    are about the second arm
 809 fn rewrite_match_arm_comment(context: &RewriteContext,
 810                              missed_str: &str,
 811                              width: usize,
 812                              arm_indent: Indent,
 813                              arm_indent_str: &str)
 814                              -> Option<String> {
 815     // The leading "," is not part of the arm-comment
 816     let missed_str = match missed_str.find_uncommented(",") {
 817         Some(n) => &missed_str[n + 1..],
 818         None => &missed_str[..],
 819     };
 820
 821     let mut result = String::new();
 822     // any text not preceeded by a newline is pushed unmodified to the block
 823     let first_brk = missed_str.find(|c: char| c == '\n').unwrap_or(0);
 824     result.push_str(&missed_str[..first_brk]);
 825     let missed_str = &missed_str[first_brk..]; // If missed_str had one newline, it starts with it
 826
 827     let first = missed_str.find(|c: char| !c.is_whitespace()).unwrap_or(missed_str.len());
 828     if missed_str[..first].chars().filter(|c| c == &'\n').count() >= 2 {
 829         // Excessive vertical whitespace before comment should be preserved
 830         // TODO handle vertical whitespace better
 831         result.push('\n');
 832     }
 833     let missed_str = missed_str[first..].trim();
 834     if !missed_str.is_empty() {
 835         let comment = try_opt!(rewrite_comment(&missed_str,
 836                                                false,
 837                                                width,
 838                                                arm_indent,
 839                                                context.config));
 840         result.push('\n');
 841         result.push_str(arm_indent_str);
 842         result.push_str(&comment);
 843     }
 844
 845     Some(result)
 846 }
 847
 848 fn rewrite_match(context: &RewriteContext,
 849                  cond: &ast::Expr,
 850                  arms: &[ast::Arm],
 851                  width: usize,
 852                  offset: Indent,
 853                  span: Span)
 854                  -> Option<String> {
 855     if arms.is_empty() {
 856         return None;
 857     }
 858
 859     // `match `cond` {`
 860     let cond_budget = try_opt!(width.checked_sub(8));
 861     let cond_str = try_opt!(cond.rewrite(context, cond_budget, offset + 6));
 862     let mut result = format!("match {} {{", cond_str);
 863
 864     let nested_context = context.nested_context();
 865     let arm_indent = nested_context.block_indent;
 866     let arm_indent_str = arm_indent.to_string(context.config);
 867
 868     let open_brace_pos = context.codemap
 869                                 .span_after(mk_sp(cond.span.hi, arm_start_pos(&arms[0])), "{");
 870
 871     for (i, arm) in arms.iter().enumerate() {
 872         // Make sure we get the stuff between arms.
 873         let missed_str = if i == 0 {
 874             context.snippet(mk_sp(open_brace_pos, arm_start_pos(arm)))
 875         } else {
 876             context.snippet(mk_sp(arm_end_pos(&arms[i - 1]), arm_start_pos(arm)))
 877         };
 878         let comment = try_opt!(rewrite_match_arm_comment(context,
 879                                                          &missed_str,
 880                                                          width,
 881                                                          arm_indent,
 882                                                          &arm_indent_str));
 883         result.push_str(&comment);
 884         result.push('\n');
 885         result.push_str(&arm_indent_str);
 886
 887         let arm_str = arm.rewrite(&nested_context,
 888                                   context.config.max_width - arm_indent.width(),
 889                                   arm_indent);
 890         if let Some(ref arm_str) = arm_str {
 891             result.push_str(arm_str);
 892         } else {
 893             // We couldn't format the arm, just reproduce the source.
 894             let snippet = context.snippet(mk_sp(arm_start_pos(arm), arm_end_pos(arm)));
 895             result.push_str(&snippet);
 896             result.push_str(arm_comma(&context.config, &arm, &arm.body));
 897         }
 898     }
 899     // BytePos(1) = closing match brace.
 900     let last_span = mk_sp(arm_end_pos(&arms[arms.len() - 1]), span.hi - BytePos(1));
 901     let last_comment = context.snippet(last_span);
 902     let comment = try_opt!(rewrite_match_arm_comment(context,
 903                                                      &last_comment,
 904                                                      width,
 905                                                      arm_indent,
 906                                                      &arm_indent_str));
 907     result.push_str(&comment);
 908     result.push('\n');
 909     result.push_str(&context.block_indent.to_string(context.config));
 910     result.push('}');
 911     Some(result)
 912 }
 913
 914 fn arm_start_pos(arm: &ast::Arm) -> BytePos {
 915     let &ast::Arm { ref attrs, ref pats, .. } = arm;
 916     if !attrs.is_empty() {
 917         return attrs[0].span.lo;
 918     }
 919
 920     pats[0].span.lo
 921 }
 922
 923 fn arm_end_pos(arm: &ast::Arm) -> BytePos {
 924     arm.body.span.hi
 925 }
 926
 927 fn arm_comma(config: &Config, arm: &ast::Arm, body: &ast::Expr) -> &'static str {
 928     if !config.match_wildcard_trailing_comma {
 929         if arm.pats.len() == 1 && arm.pats[0].node == ast::PatKind::Wild && arm.guard.is_none() {
 930             return "";
 931         }
 932     }
 933
 934     if config.match_block_trailing_comma {
 935         ","
 936     } else if let ast::ExprKind::Block(ref block) = body.node {
 937         if let ast::BlockCheckMode::Default = block.rules {
 938             ""
 939         } else {
 940             ","
 941         }
 942     } else {
 943         ","
 944     }
 945 }
 946
 947 // Match arms.
 948 impl Rewrite for ast::Arm {
 949     fn rewrite(&self, context: &RewriteContext, width: usize, offset: Indent) -> Option<String> {
 950         let &ast::Arm { ref attrs, ref pats, ref guard, ref body } = self;
 951         let indent_str = offset.to_string(context.config);
 952
 953         // FIXME this is all a bit grotty, would be nice to abstract out the
 954         // treatment of attributes.
 955         let attr_str = if !attrs.is_empty() {
 956             // We only use this visitor for the attributes, should we use it for
 957             // more?
 958             let mut attr_visitor = FmtVisitor::from_codemap(context.parse_session, context.config);
 959             attr_visitor.block_indent = context.block_indent;
 960             attr_visitor.last_pos = attrs[0].span.lo;
 961             if attr_visitor.visit_attrs(attrs) {
 962                 // Attributes included a skip instruction.
 963                 return None;
 964             }
 965             attr_visitor.format_missing(pats[0].span.lo);
 966             attr_visitor.buffer.to_string()
 967         } else {
 968             String::new()
 969         };
 970
 971         // Patterns
 972         // 5 = ` => {`
 973         let pat_budget = try_opt!(width.checked_sub(5));
 974         let pat_strs = try_opt!(pats.iter()
 975                                     .map(|p| p.rewrite(context, pat_budget, offset))
 976                                     .collect::<Option<Vec<_>>>());
 977
 978         let mut total_width = pat_strs.iter().fold(0, |a, p| a + p.len());
 979         // Add ` | `.len().
 980         total_width += (pat_strs.len() - 1) * 3;
 981
 982         let mut vertical = total_width > pat_budget || pat_strs.iter().any(|p| p.contains('\n'));
 983         if !vertical && context.config.take_source_hints {
 984             // If the patterns were previously stacked, keep them stacked.
 985             let pat_span = mk_sp(pats[0].span.lo, pats[pats.len() - 1].span.hi);
 986             let pat_str = context.snippet(pat_span);
 987             vertical = pat_str.contains('\n');
 988         }
 989
 990         let pats_width = if vertical {
 991             pat_strs.last().unwrap().len()
 992         } else {
 993             total_width
 994         };
 995
 996         let mut pats_str = String::new();
 997         for p in pat_strs {
 998             if !pats_str.is_empty() {
 999                 if vertical {
1000                     pats_str.push_str(" |\n");
1001                     pats_str.push_str(&indent_str);
1002                 } else {
1003                     pats_str.push_str(" | ");
1004                 }
1005             }
1006             pats_str.push_str(&p);
1007         }
1008
1009         let guard_str = try_opt!(rewrite_guard(context, guard, width, offset, pats_width));
1010
1011         let pats_str = format!("{}{}", pats_str, guard_str);
1012         // Where the next text can start.
1013         let mut line_start = last_line_width(&pats_str);
1014         if !pats_str.contains('\n') {
1015             line_start += offset.width();
1016         }
1017
1018         let body = match **body {
1019             ast::Expr { node: ast::ExprKind::Block(ref block), .. }
1020                 if !is_unsafe_block(block) && is_simple_block(block, context.codemap) &&
1021                 context.config.wrap_match_arms => block.expr.as_ref().map(|e| &**e).unwrap(),
1022             ref x => x,
1023         };
1024
1025         let comma = arm_comma(&context.config, self, body);
1026
1027         // Let's try and get the arm body on the same line as the condition.
1028         // 4 = ` => `.len()
1029         if context.config.max_width > line_start + comma.len() + 4 {
1030             let budget = context.config.max_width - line_start - comma.len() - 4;
1031             let offset = Indent::new(offset.block_indent, line_start + 4 - offset.block_indent);
1032             let rewrite = nop_block_collapse(body.rewrite(context, budget, offset), budget);
1033             let is_block = if let ast::ExprKind::Block(..) = body.node {
1034                 true
1035             } else {
1036                 false
1037             };
1038
1039             match rewrite {
1040                 Some(ref body_str) if !body_str.contains('\n') || !context.config.wrap_match_arms ||
1041                                       is_block => {
1042                     return Some(format!("{}{} => {}{}",
1043                                         attr_str.trim_left(),
1044                                         pats_str,
1045                                         body_str,
1046                                         comma));
1047                 }
1048                 _ => {}
1049             }
1050         }
1051
1052         // FIXME: we're doing a second rewrite of the expr; This may not be
1053         // necessary.
1054         let body_budget = try_opt!(width.checked_sub(context.config.tab_spaces));
1055         let indent = context.block_indent.block_indent(context.config);
1056         let inner_context = &RewriteContext { block_indent: indent, ..*context };
1057         let next_line_body = try_opt!(nop_block_collapse(body.rewrite(inner_context,
1058                                                                       body_budget,
1059                                                                       indent),
1060                                                          body_budget));
1061         let indent_str = offset.block_indent(context.config).to_string(context.config);
1062         let (body_prefix, body_suffix) = if context.config.wrap_match_arms {
1063             if context.config.match_block_trailing_comma {
1064                 (" {", "},")
1065             } else {
1066                 (" {", "}")
1067             }
1068         } else {
1069             ("", "")
1070         };
1071
1072         Some(format!("{}{} =>{}\n{}{}\n{}{}",
1073                      attr_str.trim_left(),
1074                      pats_str,
1075                      body_prefix,
1076                      indent_str,
1077                      next_line_body,
1078                      offset.to_string(context.config),
1079                      body_suffix))
1080     }
1081 }
1082
1083 // The `if ...` guard on a match arm.
1084 fn rewrite_guard(context: &RewriteContext,
1085                  guard: &Option<ptr::P<ast::Expr>>,
1086                  width: usize,
1087                  offset: Indent,
1088                  // The amount of space used up on this line for the pattern in
1089                  // the arm (excludes offset).
1090                  pattern_width: usize)
1091                  -> Option<String> {
1092     if let Some(ref guard) = *guard {
1093         // First try to fit the guard string on the same line as the pattern.
1094         // 4 = ` if `, 5 = ` => {`
1095         let overhead = pattern_width + 4 + 5;
1096         if overhead < width {
1097             let cond_str = guard.rewrite(context, width - overhead, offset + pattern_width + 4);
1098             if let Some(cond_str) = cond_str {
1099                 return Some(format!(" if {}", cond_str));
1100             }
1101         }
1102
1103         // Not enough space to put the guard after the pattern, try a newline.
1104         let overhead = context.config.tab_spaces + 4 + 5;
1105         if overhead < width {
1106             let cond_str = guard.rewrite(context,
1107                                          width - overhead,
1108                                          offset.block_indent(context.config));
1109             if let Some(cond_str) = cond_str {
1110                 return Some(format!("\n{}if {}",
1111                                     offset.block_indent(context.config).to_string(context.config),
1112                                     cond_str));
1113             }
1114         }
1115
1116         None
1117     } else {
1118         Some(String::new())
1119     }
1120 }
1121
1122 fn rewrite_pat_expr(context: &RewriteContext,
1123                     pat: Option<&ast::Pat>,
1124                     expr: &ast::Expr,
1125                     matcher: &str,
1126                     // Connecting piece between pattern and expression,
1127                     // *without* trailing space.
1128                     connector: &str,
1129                     width: usize,
1130                     offset: Indent)
1131                     -> Option<String> {
1132     let pat_offset = offset + matcher.len();
1133     let mut result = match pat {
1134         Some(pat) => {
1135             let pat_budget = try_opt!(width.checked_sub(connector.len() + matcher.len()));
1136             let pat_string = try_opt!(pat.rewrite(context, pat_budget, pat_offset));
1137             format!("{}{}{}", matcher, pat_string, connector)
1138         }
1139         None => String::new(),
1140     };
1141
1142     // Consider only the last line of the pat string.
1143     let extra_offset = extra_offset(&result, offset);
1144
1145     // The expression may (partionally) fit on the current line.
1146     if width > extra_offset + 1 {
1147         let spacer = if pat.is_some() {
1148             " "
1149         } else {
1150             ""
1151         };
1152
1153         let expr_rewrite = expr.rewrite(context,
1154                                         width - extra_offset - spacer.len(),
1155                                         offset + extra_offset + spacer.len());
1156
1157         if let Some(expr_string) = expr_rewrite {
1158             result.push_str(spacer);
1159             result.push_str(&expr_string);
1160             return Some(result);
1161         }
1162     }
1163
1164     // The expression won't fit on the current line, jump to next.
1165     result.push('\n');
1166     result.push_str(&pat_offset.to_string(context.config));
1167
1168     let expr_rewrite = expr.rewrite(context,
1169                                     context.config.max_width - pat_offset.width(),
1170                                     pat_offset);
1171     result.push_str(&&try_opt!(expr_rewrite));
1172
1173     Some(result)
1174 }
1175
1176 fn rewrite_string_lit(context: &RewriteContext,
1177                       span: Span,
1178                       width: usize,
1179                       offset: Indent)
1180                       -> Option<String> {
1181     let string_lit = context.snippet(span);
1182
1183     if !context.config.format_strings && !context.config.force_format_strings {
1184         return Some(string_lit);
1185     }
1186
1187     if !context.config.force_format_strings &&
1188        !string_requires_rewrite(context, span, &string_lit, width, offset) {
1189         return Some(string_lit);
1190     }
1191
1192     let fmt = StringFormat {
1193         opener: "\"",
1194         closer: "\"",
1195         line_start: " ",
1196         line_end: "\\",
1197         width: width,
1198         offset: offset,
1199         trim_end: false,
1200         config: context.config,
1201     };
1202
1203     // Remove the quote characters.
1204     let str_lit = &string_lit[1..string_lit.len() - 1];
1205
1206     rewrite_string(str_lit, &fmt)
1207 }
1208
1209 fn string_requires_rewrite(context: &RewriteContext,
1210                            span: Span,
1211                            string: &str,
1212                            width: usize,
1213                            offset: Indent)
1214                            -> bool {
1215     if context.codemap.lookup_char_pos(span.lo).col.0 != offset.width() {
1216         return true;
1217     }
1218
1219     for (i, line) in string.lines().enumerate() {
1220         if i == 0 {
1221             if line.len() > width {
1222                 return true;
1223             }
1224         } else {
1225             if line.len() > width + offset.width() {
1226                 return true;
1227             }
1228         }
1229     }
1230
1231     false
1232 }
1233
1234 pub fn rewrite_call<R>(context: &RewriteContext,
1235                        callee: &R,
1236                        args: &[ptr::P<ast::Expr>],
1237                        span: Span,
1238                        width: usize,
1239                        offset: Indent)
1240                        -> Option<String>
1241     where R: Rewrite
1242 {
1243     let closure = |callee_max_width| {
1244         rewrite_call_inner(context, callee, callee_max_width, args, span, width, offset)
1245     };
1246
1247     // 2 is for parens
1248     let max_width = try_opt!(width.checked_sub(2));
1249     binary_search(1, max_width, closure)
1250 }
1251
1252 fn rewrite_call_inner<R>(context: &RewriteContext,
1253                          callee: &R,
1254                          max_callee_width: usize,
1255                          args: &[ptr::P<ast::Expr>],
1256                          span: Span,
1257                          width: usize,
1258                          offset: Indent)
1259                          -> Result<String, Ordering>
1260     where R: Rewrite
1261 {
1262     let callee = callee.borrow();
1263     // FIXME using byte lens instead of char lens (and probably all over the
1264     // place too)
1265     let callee_str = match callee.rewrite(context, max_callee_width, offset) {
1266         Some(string) => {
1267             if !string.contains('\n') && string.len() > max_callee_width {
1268                 panic!("{:?} {}", string, max_callee_width);
1269             } else {
1270                 string
1271             }
1272         }
1273         None => return Err(Ordering::Greater),
1274     };
1275
1276     let span_lo = context.codemap.span_after(span, "(");
1277     let span = mk_sp(span_lo, span.hi);
1278
1279     let extra_offset = extra_offset(&callee_str, offset);
1280     // 2 is for parens.
1281     let remaining_width = match width.checked_sub(extra_offset + 2) {
1282         Some(str) => str,
1283         None => return Err(Ordering::Greater),
1284     };
1285     let offset = offset + extra_offset + 1;
1286     let arg_count = args.len();
1287     let block_indent = if arg_count == 1 {
1288         context.block_indent
1289     } else {
1290         offset
1291     };
1292     let inner_context = &RewriteContext { block_indent: block_indent, ..*context };
1293
1294     let items = itemize_list(context.codemap,
1295                              args.iter(),
1296                              ")",
1297                              |item| item.span.lo,
1298                              |item| item.span.hi,
1299                              |item| item.rewrite(&inner_context, remaining_width, offset),
1300                              span.lo,
1301                              span.hi);
1302     let mut item_vec: Vec<_> = items.collect();
1303
1304     // Try letting the last argument overflow to the next line with block
1305     // indentation. If its first line fits on one line with the other arguments,
1306     // we format the function arguments horizontally.
1307     let overflow_last = match args.last().map(|x| &x.node) {
1308         Some(&ast::ExprKind::Closure(..)) |
1309         Some(&ast::ExprKind::Block(..)) if arg_count > 1 => true,
1310         _ => false,
1311     } && context.config.chains_overflow_last;
1312
1313     let mut orig_last = None;
1314     let mut placeholder = None;
1315
1316     // Replace the last item with its first line to see if it fits with
1317     // first arguments.
1318     if overflow_last {
1319         let inner_context = &RewriteContext { block_indent: context.block_indent, ..*context };
1320         let rewrite = args.last().unwrap().rewrite(&inner_context, remaining_width, offset);
1321
1322         if let Some(rewrite) = rewrite {
1323             let rewrite_first_line = Some(rewrite[..first_line_width(&rewrite)].to_owned());
1324             placeholder = Some(rewrite);
1325
1326             swap(&mut item_vec[arg_count - 1].item, &mut orig_last);
1327             item_vec[arg_count - 1].item = rewrite_first_line;
1328         }
1329     }
1330
1331     let tactic = definitive_tactic(&item_vec,
1332                                    ListTactic::LimitedHorizontalVertical(context.config
1333                                                                                 .fn_call_width),
1334                                    remaining_width);
1335
1336     // Replace the stub with the full overflowing last argument if the rewrite
1337     // succeeded and its first line fits with the other arguments.
1338     match (overflow_last, tactic, placeholder) {
1339         (true, DefinitiveListTactic::Horizontal, placeholder @ Some(..)) => {
1340             item_vec[arg_count - 1].item = placeholder;
1341         }
1342         (true, _, _) => {
1343             item_vec[arg_count - 1].item = orig_last;
1344         }
1345         (false, _, _) => {}
1346     }
1347
1348     let fmt = ListFormatting {
1349         tactic: tactic,
1350         separator: ",",
1351         trailing_separator: SeparatorTactic::Never,
1352         indent: offset,
1353         width: width,
1354         ends_with_newline: false,
1355         config: context.config,
1356     };
1357
1358     let list_str = match write_list(&item_vec, &fmt) {
1359         Some(str) => str,
1360         None => return Err(Ordering::Less),
1361     };
1362
1363     Ok(format!("{}({})", callee_str, list_str))
1364 }
1365
1366 fn rewrite_paren(context: &RewriteContext,
1367                  subexpr: &ast::Expr,
1368                  width: usize,
1369                  offset: Indent)
1370                  -> Option<String> {
1371     debug!("rewrite_paren, width: {}, offset: {:?}", width, offset);
1372     // 1 is for opening paren, 2 is for opening+closing, we want to keep the closing
1373     // paren on the same line as the subexpr.
1374     let subexpr_str = subexpr.rewrite(context, try_opt!(width.checked_sub(2)), offset + 1);
1375     debug!("rewrite_paren, subexpr_str: `{:?}`", subexpr_str);
1376     subexpr_str.map(|s| format!("({})", s))
1377 }
1378
1379 fn rewrite_struct_lit<'a>(context: &RewriteContext,
1380                           path: &ast::Path,
1381                           fields: &'a [ast::Field],
1382                           base: Option<&'a ast::Expr>,
1383                           span: Span,
1384                           width: usize,
1385                           offset: Indent)
1386                           -> Option<String> {
1387     debug!("rewrite_struct_lit: width {}, offset {:?}", width, offset);
1388     assert!(!fields.is_empty() || base.is_some());
1389
1390     enum StructLitField<'a> {
1391         Regular(&'a ast::Field),
1392         Base(&'a ast::Expr),
1393     }
1394
1395     // 2 = " {".len()
1396     let path_budget = try_opt!(width.checked_sub(2));
1397     let path_str = try_opt!(rewrite_path(context, true, None, path, path_budget, offset));
1398
1399     // Foo { a: Foo } - indent is +3, width is -5.
1400     let h_budget = width.checked_sub(path_str.len() + 5).unwrap_or(0);
1401     // The 1 taken from the v_budget is for the comma.
1402     let (indent, v_budget) = match context.config.struct_lit_style {
1403         StructLitStyle::Visual => (offset + path_str.len() + 3, h_budget),
1404         StructLitStyle::Block => {
1405             // If we are all on one line, then we'll ignore the indent, and we
1406             // have a smaller budget.
1407             let indent = context.block_indent.block_indent(context.config);
1408             let v_budget = context.config.max_width.checked_sub(indent.width()).unwrap_or(0);
1409             (indent, v_budget)
1410         }
1411     };
1412
1413     let field_iter = fields.into_iter()
1414                            .map(StructLitField::Regular)
1415                            .chain(base.into_iter().map(StructLitField::Base));
1416
1417     let inner_context = &RewriteContext { block_indent: indent, ..*context };
1418
1419     let items = itemize_list(context.codemap,
1420                              field_iter,
1421                              "}",
1422                              |item| {
1423                                  match *item {
1424                                      StructLitField::Regular(ref field) => field.span.lo,
1425                                      StructLitField::Base(ref expr) => {
1426                                          let last_field_hi = fields.last().map_or(span.lo,
1427                                                                                   |field| {
1428                                                                                       field.span.hi
1429                                                                                   });
1430                                          let snippet = context.snippet(mk_sp(last_field_hi,
1431                                                                              expr.span.lo));
1432                                          let pos = snippet.find_uncommented("..").unwrap();
1433                                          last_field_hi + BytePos(pos as u32)
1434                                      }
1435                                  }
1436                              },
1437                              |item| {
1438                                  match *item {
1439                                      StructLitField::Regular(ref field) => field.span.hi,
1440                                      StructLitField::Base(ref expr) => expr.span.hi,
1441                                  }
1442                              },
1443                              |item| {
1444                                  match *item {
1445                                      StructLitField::Regular(ref field) => {
1446                                          rewrite_field(inner_context,
1447                                                        &field,
1448                                                        v_budget.checked_sub(1).unwrap_or(0),
1449                                                        indent)
1450                                      }
1451                                      StructLitField::Base(ref expr) => {
1452                                          // 2 = ..
1453                                          expr.rewrite(inner_context,
1454                                                       try_opt!(v_budget.checked_sub(2)),
1455                                                       indent + 2)
1456                                              .map(|s| format!("..{}", s))
1457                                      }
1458                                  }
1459                              },
1460                              context.codemap.span_after(span, "{"),
1461                              span.hi);
1462     let item_vec = items.collect::<Vec<_>>();
1463
1464     let tactic = {
1465         let mut prelim_tactic = match (context.config.struct_lit_style, fields.len()) {
1466             (StructLitStyle::Visual, 1) => ListTactic::HorizontalVertical,
1467             _ => context.config.struct_lit_multiline_style.to_list_tactic(),
1468         };
1469
1470         if prelim_tactic == ListTactic::HorizontalVertical && fields.len() > 1 {
1471             prelim_tactic = ListTactic::LimitedHorizontalVertical(context.config.struct_lit_width);
1472         }
1473
1474         definitive_tactic(&item_vec, prelim_tactic, h_budget)
1475     };
1476
1477     let budget = match tactic {
1478         DefinitiveListTactic::Horizontal => h_budget,
1479         _ => v_budget,
1480     };
1481
1482     let ends_with_newline = context.config.struct_lit_style != StructLitStyle::Visual &&
1483                             tactic == DefinitiveListTactic::Vertical;
1484
1485     let fmt = ListFormatting {
1486         tactic: tactic,
1487         separator: ",",
1488         trailing_separator: if base.is_some() {
1489             SeparatorTactic::Never
1490         } else {
1491             context.config.struct_lit_trailing_comma
1492         },
1493         indent: indent,
1494         width: budget,
1495         ends_with_newline: ends_with_newline,
1496         config: context.config,
1497     };
1498     let fields_str = try_opt!(write_list(&item_vec, &fmt));
1499
1500     let format_on_newline = || {
1501         let inner_indent = context.block_indent
1502                                   .block_indent(context.config)
1503                                   .to_string(context.config);
1504         let outer_indent = context.block_indent.to_string(context.config);
1505         Some(format!("{} {{\n{}{}\n{}}}",
1506                      path_str,
1507                      inner_indent,
1508                      fields_str,
1509                      outer_indent))
1510     };
1511
1512     match (context.config.struct_lit_style, context.config.struct_lit_multiline_style) {
1513         (StructLitStyle::Block, _) if fields_str.contains('\n') || fields_str.len() > h_budget => {
1514             format_on_newline()
1515         }
1516         (StructLitStyle::Block, MultilineStyle::ForceMulti) => format_on_newline(),
1517         _ => Some(format!("{} {{ {} }}", path_str, fields_str)),
1518     }
1519
1520     // FIXME if context.config.struct_lit_style == Visual, but we run out
1521     // of space, we should fall back to BlockIndent.
1522 }
1523
1524 fn rewrite_field(context: &RewriteContext,
1525                  field: &ast::Field,
1526                  width: usize,
1527                  offset: Indent)
1528                  -> Option<String> {
1529     let name = &field.ident.node.to_string();
1530     let overhead = name.len() + 2;
1531     let expr = field.expr.rewrite(context,
1532                                   try_opt!(width.checked_sub(overhead)),
1533                                   offset + overhead);
1534
1535     match expr {
1536         Some(e) => Some(format!("{}: {}", name, e)),
1537         None => {
1538             let expr_offset = offset.block_indent(&context.config);
1539             let expr = field.expr.rewrite(context,
1540                                           try_opt!(context.config
1541                                                           .max_width
1542                                                           .checked_sub(expr_offset.width())),
1543                                           expr_offset);
1544             expr.map(|s| format!("{}:\n{}{}", name, expr_offset.to_string(&context.config), s))
1545         }
1546     }
1547 }
1548
1549 pub fn rewrite_tuple<'a, I>(context: &RewriteContext,
1550                             mut items: I,
1551                             span: Span,
1552                             width: usize,
1553                             offset: Indent)
1554                             -> Option<String>
1555     where I: ExactSizeIterator,
1556           <I as Iterator>::Item: Deref,
1557           <I::Item as Deref>::Target: Rewrite + Spanned + 'a
1558 {
1559     let indent = offset + 1;
1560     // In case of length 1, need a trailing comma
1561     if items.len() == 1 {
1562         // 3 = "(" + ",)"
1563         let budget = try_opt!(width.checked_sub(3));
1564         return items.next().unwrap().rewrite(context, budget, indent).map(|s| format!("({},)", s));
1565     }
1566
1567     let list_lo = context.codemap.span_after(span, "(");
1568     let items = itemize_list(context.codemap,
1569                              items,
1570                              ")",
1571                              |item| item.span().lo,
1572                              |item| item.span().hi,
1573                              |item| {
1574                                  let inner_width = try_opt!(context.config
1575                                                                    .max_width
1576                                                                    .checked_sub(indent.width() +
1577                                                                                 1));
1578                                  item.rewrite(context, inner_width, indent)
1579                              },
1580                              list_lo,
1581                              span.hi - BytePos(1));
1582     let budget = try_opt!(width.checked_sub(2));
1583     let list_str = try_opt!(format_item_list(items, budget, indent, context.config));
1584
1585     Some(format!("({})", list_str))
1586 }
1587
1588 fn rewrite_binary_op(context: &RewriteContext,
1589                      op: &ast::BinOp,
1590                      lhs: &ast::Expr,
1591                      rhs: &ast::Expr,
1592                      width: usize,
1593                      offset: Indent)
1594                      -> Option<String> {
1595     // FIXME: format comments between operands and operator
1596
1597     let operator_str = context.snippet(op.span);
1598
1599     // Get "full width" rhs and see if it fits on the current line. This
1600     // usually works fairly well since it tends to place operands of
1601     // operations with high precendence close together.
1602     let rhs_result = try_opt!(rhs.rewrite(context, width, offset));
1603
1604     // Second condition is needed in case of line break not caused by a
1605     // shortage of space, but by end-of-line comments, for example.
1606     // Note that this is non-conservative, but its just to see if it's even
1607     // worth trying to put everything on one line.
1608     if rhs_result.len() + 2 + operator_str.len() < width && !rhs_result.contains('\n') {
1609         // 1 = space between lhs expr and operator
1610         if let Some(mut result) = lhs.rewrite(context, width - 1 - operator_str.len(), offset) {
1611             result.push(' ');
1612             result.push_str(&operator_str);
1613             result.push(' ');
1614
1615             let remaining_width = width.checked_sub(last_line_width(&result)).unwrap_or(0);
1616
1617             if rhs_result.len() <= remaining_width {
1618                 result.push_str(&rhs_result);
1619                 return Some(result);
1620             }
1621
1622             if let Some(rhs_result) = rhs.rewrite(context, remaining_width, offset + result.len()) {
1623                 if rhs_result.len() <= remaining_width {
1624                     result.push_str(&rhs_result);
1625                     return Some(result);
1626                 }
1627             }
1628         }
1629     }
1630
1631     // We have to use multiple lines.
1632
1633     // Re-evaluate the lhs because we have more space now:
1634     let budget = try_opt!(context.config
1635                                  .max_width
1636                                  .checked_sub(offset.width() + 1 + operator_str.len()));
1637     Some(format!("{} {}\n{}{}",
1638                  try_opt!(lhs.rewrite(context, budget, offset)),
1639                  operator_str,
1640                  offset.to_string(context.config),
1641                  rhs_result))
1642 }
1643
1644 pub fn rewrite_unary_prefix<R: Rewrite>(context: &RewriteContext,
1645                                         prefix: &str,
1646                                         rewrite: &R,
1647                                         width: usize,
1648                                         offset: Indent)
1649                                         -> Option<String> {
1650     rewrite.rewrite(context,
1651                     try_opt!(width.checked_sub(prefix.len())),
1652                     offset + prefix.len())
1653            .map(|r| format!("{}{}", prefix, r))
1654 }
1655
1656 fn rewrite_unary_op(context: &RewriteContext,
1657                     op: &ast::UnOp,
1658                     expr: &ast::Expr,
1659                     width: usize,
1660                     offset: Indent)
1661                     -> Option<String> {
1662     // For some reason, an UnOp is not spanned like BinOp!
1663     let operator_str = match *op {
1664         ast::UnOp::Deref => "*",
1665         ast::UnOp::Not => "!",
1666         ast::UnOp::Neg => "-",
1667     };
1668     rewrite_unary_prefix(context, operator_str, expr, width, offset)
1669 }
1670
1671 fn rewrite_assignment(context: &RewriteContext,
1672                       lhs: &ast::Expr,
1673                       rhs: &ast::Expr,
1674                       op: Option<&ast::BinOp>,
1675                       width: usize,
1676                       offset: Indent)
1677                       -> Option<String> {
1678     let operator_str = match op {
1679         Some(op) => context.snippet(op.span),
1680         None => "=".to_owned(),
1681     };
1682
1683     // 1 = space between lhs and operator.
1684     let max_width = try_opt!(width.checked_sub(operator_str.len() + 1));
1685     let lhs_str = format!("{} {}",
1686                           try_opt!(lhs.rewrite(context, max_width, offset)),
1687                           operator_str);
1688
1689     rewrite_assign_rhs(&context, lhs_str, rhs, width, offset)
1690 }
1691
1692 // The left hand side must contain everything up to, and including, the
1693 // assignment operator.
1694 pub fn rewrite_assign_rhs<S: Into<String>>(context: &RewriteContext,
1695                                            lhs: S,
1696                                            ex: &ast::Expr,
1697                                            width: usize,
1698                                            offset: Indent)
1699                                            -> Option<String> {
1700     let mut result = lhs.into();
1701     let last_line_width = last_line_width(&result) -
1702                           if result.contains('\n') {
1703         offset.width()
1704     } else {
1705         0
1706     };
1707     // 1 = space between operator and rhs.
1708     let max_width = try_opt!(width.checked_sub(last_line_width + 1));
1709     let rhs = ex.rewrite(&context, max_width, offset + last_line_width + 1);
1710
1711     match rhs {
1712         Some(new_str) => {
1713             result.push(' ');
1714             result.push_str(&new_str)
1715         }
1716         None => {
1717             // Expression did not fit on the same line as the identifier. Retry
1718             // on the next line.
1719             let new_offset = offset.block_indent(context.config);
1720             result.push_str(&format!("\n{}", new_offset.to_string(context.config)));
1721
1722             // FIXME: we probably should related max_width to width instead of
1723             // config.max_width where is the 1 coming from anyway?
1724             let max_width = try_opt!(context.config.max_width.checked_sub(new_offset.width() + 1));
1725             let inner_context = context.nested_context();
1726             let rhs = ex.rewrite(&inner_context, max_width, new_offset);
1727
1728             result.push_str(&&try_opt!(rhs));
1729         }
1730     }
1731
1732     Some(result)
1733 }
1734
1735 fn rewrite_expr_addrof(context: &RewriteContext,
1736                        mutability: ast::Mutability,
1737                        expr: &ast::Expr,
1738                        width: usize,
1739                        offset: Indent)
1740                        -> Option<String> {
1741     let operator_str = match mutability {
1742         ast::Mutability::Immutable => "&",
1743         ast::Mutability::Mutable => "&mut ",
1744     };
1745     rewrite_unary_prefix(context, operator_str, expr, width, offset)
1746 }