src/lists.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 //! Format list-like expressions and items.
  12
  13 use std::cmp;
  14 use std::iter::Peekable;
  15
  16 use config::lists::*;
  17 use syntax::codemap::BytePos;
  18
  19 use comment::{find_comment_end, rewrite_comment, FindUncommented};
  20 use config::{Config, IndentStyle};
  21 use rewrite::RewriteContext;
  22 use shape::{Indent, Shape};
  23 use utils::{count_newlines, first_line_width, last_line_width, mk_sp, starts_with_newline};
  24 use visitor::SnippetProvider;
  25
  26 pub struct ListFormatting<'a> {
  27     pub tactic: DefinitiveListTactic,
  28     pub separator: &'a str,
  29     pub trailing_separator: SeparatorTactic,
  30     pub separator_place: SeparatorPlace,
  31     pub shape: Shape,
  32     // Non-expressions, e.g. items, will have a new line at the end of the list.
  33     // Important for comment styles.
  34     pub ends_with_newline: bool,
  35     // Remove newlines between list elements for expressions.
  36     pub preserve_newline: bool,
  37     // Nested import lists get some special handling for the "Mixed" list type
  38     pub nested: bool,
  39     pub config: &'a Config,
  40 }
  41
  42 impl<'a> ListFormatting<'a> {
  43     pub fn needs_trailing_separator(&self) -> bool {
  44         match self.trailing_separator {
  45             // We always put separator in front.
  46             SeparatorTactic::Always => true,
  47             SeparatorTactic::Vertical => self.tactic == DefinitiveListTactic::Vertical,
  48             SeparatorTactic::Never => {
  49                 self.tactic == DefinitiveListTactic::Vertical && self.separator_place.is_front()
  50             }
  51         }
  52     }
  53 }
  54
  55 impl AsRef<ListItem> for ListItem {
  56     fn as_ref(&self) -> &ListItem {
  57         self
  58     }
  59 }
  60
  61 #[derive(PartialEq, Eq, Debug, Copy, Clone)]
  62 pub enum ListItemCommentStyle {
  63     // Try to keep the comment on the same line with the item.
  64     SameLine,
  65     // Put the comment on the previous or the next line of the item.
  66     DifferentLine,
  67     // No comment available.
  68     None,
  69 }
  70
  71 #[derive(Debug, Clone)]
  72 pub struct ListItem {
  73     // None for comments mean that they are not present.
  74     pub pre_comment: Option<String>,
  75     pub pre_comment_style: ListItemCommentStyle,
  76     // Item should include attributes and doc comments. None indicates a failed
  77     // rewrite.
  78     pub item: Option<String>,
  79     pub post_comment: Option<String>,
  80     // Whether there is extra whitespace before this item.
  81     pub new_lines: bool,
  82 }
  83
  84 impl ListItem {
  85     pub fn empty() -> ListItem {
  86         ListItem {
  87             pre_comment: None,
  88             pre_comment_style: ListItemCommentStyle::None,
  89             item: None,
  90             post_comment: None,
  91             new_lines: false,
  92         }
  93     }
  94
  95     pub fn inner_as_ref(&self) -> &str {
  96         self.item.as_ref().map_or("", |s| s)
  97     }
  98
  99     pub fn is_different_group(&self) -> bool {
 100         self.inner_as_ref().contains('\n') || self.pre_comment.is_some() || self
 101             .post_comment
 102             .as_ref()
 103             .map_or(false, |s| s.contains('\n'))
 104     }
 105
 106     pub fn is_multiline(&self) -> bool {
 107         self.inner_as_ref().contains('\n')
 108             || self
 109                 .pre_comment
 110                 .as_ref()
 111                 .map_or(false, |s| s.contains('\n'))
 112             || self
 113                 .post_comment
 114                 .as_ref()
 115                 .map_or(false, |s| s.contains('\n'))
 116     }
 117
 118     pub fn has_single_line_comment(&self) -> bool {
 119         self.pre_comment
 120             .as_ref()
 121             .map_or(false, |comment| comment.trim_left().starts_with("//"))
 122             || self
 123                 .post_comment
 124                 .as_ref()
 125                 .map_or(false, |comment| comment.trim_left().starts_with("//"))
 126     }
 127
 128     pub fn has_comment(&self) -> bool {
 129         self.pre_comment.is_some() || self.post_comment.is_some()
 130     }
 131
 132     pub fn from_str<S: Into<String>>(s: S) -> ListItem {
 133         ListItem {
 134             pre_comment: None,
 135             pre_comment_style: ListItemCommentStyle::None,
 136             item: Some(s.into()),
 137             post_comment: None,
 138             new_lines: false,
 139         }
 140     }
 141
 142     // true if the item causes something to be written.
 143     fn is_substantial(&self) -> bool {
 144         fn empty(s: &Option<String>) -> bool {
 145             match *s {
 146                 Some(ref s) if !s.is_empty() => false,
 147                 _ => true,
 148             }
 149         }
 150
 151         !(empty(&self.pre_comment) && empty(&self.item) && empty(&self.post_comment))
 152     }
 153 }
 154
 155 /// The type of separator for lists.
 156 #[derive(Copy, Clone, Eq, PartialEq, Debug)]
 157 pub enum Separator {
 158     Comma,
 159     VerticalBar,
 160 }
 161
 162 impl Separator {
 163     pub fn len(&self) -> usize {
 164         match *self {
 165             // 2 = `, `
 166             Separator::Comma => 2,
 167             // 3 = ` | `
 168             Separator::VerticalBar => 3,
 169         }
 170     }
 171 }
 172
 173 pub fn definitive_tactic<I, T>(
 174     items: I,
 175     tactic: ListTactic,
 176     sep: Separator,
 177     width: usize,
 178 ) -> DefinitiveListTactic
 179 where
 180     I: IntoIterator<Item = T> + Clone,
 181     T: AsRef<ListItem>,
 182 {
 183     let pre_line_comments = items
 184         .clone()
 185         .into_iter()
 186         .any(|item| item.as_ref().has_single_line_comment());
 187
 188     let limit = match tactic {
 189         _ if pre_line_comments => return DefinitiveListTactic::Vertical,
 190         ListTactic::Horizontal => return DefinitiveListTactic::Horizontal,
 191         ListTactic::Vertical => return DefinitiveListTactic::Vertical,
 192         ListTactic::LimitedHorizontalVertical(limit) => ::std::cmp::min(width, limit),
 193         ListTactic::Mixed | ListTactic::HorizontalVertical => width,
 194     };
 195
 196     let (sep_count, total_width) = calculate_width(items.clone());
 197     let total_sep_len = sep.len() * sep_count.saturating_sub(1);
 198     let real_total = total_width + total_sep_len;
 199
 200     if real_total <= limit
 201         && !pre_line_comments
 202         && !items.into_iter().any(|item| item.as_ref().is_multiline())
 203     {
 204         DefinitiveListTactic::Horizontal
 205     } else {
 206         match tactic {
 207             ListTactic::Mixed => DefinitiveListTactic::Mixed,
 208             _ => DefinitiveListTactic::Vertical,
 209         }
 210     }
 211 }
 212
 213 // Format a list of commented items into a string.
 214 pub fn write_list<I, T>(items: I, formatting: &ListFormatting) -> Option<String>
 215 where
 216     I: IntoIterator<Item = T> + Clone,
 217     T: AsRef<ListItem>,
 218 {
 219     let tactic = formatting.tactic;
 220     let sep_len = formatting.separator.len();
 221
 222     // Now that we know how we will layout, we can decide for sure if there
 223     // will be a trailing separator.
 224     let mut trailing_separator = formatting.needs_trailing_separator();
 225     let mut result = String::with_capacity(128);
 226     let cloned_items = items.clone();
 227     let mut iter = items.into_iter().enumerate().peekable();
 228     let mut item_max_width: Option<usize> = None;
 229     let sep_place =
 230         SeparatorPlace::from_tactic(formatting.separator_place, tactic, formatting.separator);
 231     let mut prev_item_had_post_comment = false;
 232     let mut prev_item_is_nested_import = false;
 233
 234     let mut line_len = 0;
 235     let indent_str = &formatting.shape.indent.to_string(formatting.config);
 236     while let Some((i, item)) = iter.next() {
 237         let item = item.as_ref();
 238         let inner_item = item.item.as_ref()?;
 239         let first = i == 0;
 240         let last = iter.peek().is_none();
 241         let mut separate = match sep_place {
 242             SeparatorPlace::Front => !first,
 243             SeparatorPlace::Back => !last || trailing_separator,
 244         };
 245         let item_sep_len = if separate { sep_len } else { 0 };
 246
 247         // Item string may be multi-line. Its length (used for block comment alignment)
 248         // should be only the length of the last line.
 249         let item_last_line = if item.is_multiline() {
 250             inner_item.lines().last().unwrap_or("")
 251         } else {
 252             inner_item.as_ref()
 253         };
 254         let mut item_last_line_width = item_last_line.len() + item_sep_len;
 255         if item_last_line.starts_with(&**indent_str) {
 256             item_last_line_width -= indent_str.len();
 257         }
 258
 259         if !item.is_substantial() {
 260             continue;
 261         }
 262
 263         match tactic {
 264             DefinitiveListTactic::Horizontal if !first => {
 265                 result.push(' ');
 266             }
 267             DefinitiveListTactic::SpecialMacro(num_args_before) => {
 268                 if i == 0 {
 269                     // Nothing
 270                 } else if i < num_args_before {
 271                     result.push(' ');
 272                 } else if i <= num_args_before + 1 {
 273                     result.push('\n');
 274                     result.push_str(indent_str);
 275                 } else {
 276                     result.push(' ');
 277                 }
 278             }
 279             DefinitiveListTactic::Vertical
 280                 if !first && !inner_item.is_empty() && !result.is_empty() =>
 281             {
 282                 result.push('\n');
 283                 result.push_str(indent_str);
 284             }
 285             DefinitiveListTactic::Mixed => {
 286                 let total_width = total_item_width(item) + item_sep_len;
 287
 288                 // 1 is space between separator and item.
 289                 if (line_len > 0 && line_len + 1 + total_width > formatting.shape.width)
 290                     || prev_item_had_post_comment
 291                     || (formatting.nested
 292                         && (prev_item_is_nested_import || (!first && inner_item.contains("::"))))
 293                 {
 294                     result.push('\n');
 295                     result.push_str(indent_str);
 296                     line_len = 0;
 297                     if formatting.ends_with_newline {
 298                         trailing_separator = true;
 299                     }
 300                 } else if line_len > 0 {
 301                     result.push(' ');
 302                     line_len += 1;
 303                 }
 304
 305                 if last && formatting.ends_with_newline {
 306                     separate = formatting.trailing_separator != SeparatorTactic::Never;
 307                 }
 308
 309                 line_len += total_width;
 310             }
 311             _ => {}
 312         }
 313
 314         // Pre-comments
 315         if let Some(ref comment) = item.pre_comment {
 316             // Block style in non-vertical mode.
 317             let block_mode = tactic == DefinitiveListTactic::Horizontal;
 318             // Width restriction is only relevant in vertical mode.
 319             let comment =
 320                 rewrite_comment(comment, block_mode, formatting.shape, formatting.config)?;
 321             result.push_str(&comment);
 322
 323             if !inner_item.is_empty() {
 324                 if tactic == DefinitiveListTactic::Vertical || tactic == DefinitiveListTactic::Mixed
 325                 {
 326                     // We cannot keep pre-comments on the same line if the comment if normalized.
 327                     let keep_comment = if formatting.config.normalize_comments()
 328                         || item.pre_comment_style == ListItemCommentStyle::DifferentLine
 329                     {
 330                         false
 331                     } else {
 332                         // We will try to keep the comment on the same line with the item here.
 333                         // 1 = ` `
 334                         let total_width = total_item_width(item) + item_sep_len + 1;
 335                         total_width <= formatting.shape.width
 336                     };
 337                     if keep_comment {
 338                         result.push(' ');
 339                     } else {
 340                         result.push('\n');
 341                         result.push_str(indent_str);
 342                         // This is the width of the item (without comments).
 343                         line_len = item.item.as_ref().map_or(0, |str| str.len());
 344                     }
 345                 } else {
 346                     result.push(' ');
 347                 }
 348             }
 349             item_max_width = None;
 350         }
 351
 352         if separate && sep_place.is_front() && !first {
 353             result.push_str(formatting.separator.trim());
 354             result.push(' ');
 355         }
 356         result.push_str(inner_item);
 357
 358         // Post-comments
 359         if tactic == DefinitiveListTactic::Horizontal && item.post_comment.is_some() {
 360             let comment = item.post_comment.as_ref().unwrap();
 361             let formatted_comment = rewrite_comment(
 362                 comment,
 363                 true,
 364                 Shape::legacy(formatting.shape.width, Indent::empty()),
 365                 formatting.config,
 366             )?;
 367
 368             result.push(' ');
 369             result.push_str(&formatted_comment);
 370         }
 371
 372         if separate && sep_place.is_back() {
 373             result.push_str(formatting.separator);
 374         }
 375
 376         if tactic != DefinitiveListTactic::Horizontal && item.post_comment.is_some() {
 377             let comment = item.post_comment.as_ref().unwrap();
 378             let overhead = last_line_width(&result) + first_line_width(comment.trim());
 379
 380             let rewrite_post_comment = |item_max_width: &mut Option<usize>| {
 381                 if item_max_width.is_none() && !last && !inner_item.contains('\n') {
 382                     *item_max_width = Some(max_width_of_item_with_post_comment(
 383                         &cloned_items,
 384                         i,
 385                         overhead,
 386                         formatting.config.max_width(),
 387                     ));
 388                 }
 389                 let overhead = if starts_with_newline(comment) {
 390                     0
 391                 } else if let Some(max_width) = *item_max_width {
 392                     max_width + 2
 393                 } else {
 394                     // 1 = space between item and comment.
 395                     item_last_line_width + 1
 396                 };
 397                 let width = formatting.shape.width.checked_sub(overhead).unwrap_or(1);
 398                 let offset = formatting.shape.indent + overhead;
 399                 let comment_shape = Shape::legacy(width, offset);
 400
 401                 // Use block-style only for the last item or multiline comments.
 402                 let block_style = !formatting.ends_with_newline && last
 403                     || comment.trim().contains('\n')
 404                     || comment.trim().len() > width;
 405
 406                 rewrite_comment(
 407                     comment.trim_left(),
 408                     block_style,
 409                     comment_shape,
 410                     formatting.config,
 411                 )
 412             };
 413
 414             let mut formatted_comment = rewrite_post_comment(&mut item_max_width)?;
 415
 416             if !starts_with_newline(comment) {
 417                 let mut comment_alignment =
 418                     post_comment_alignment(item_max_width, inner_item.len());
 419                 if first_line_width(&formatted_comment)
 420                     + last_line_width(&result)
 421                     + comment_alignment
 422                     + 1
 423                     > formatting.config.max_width()
 424                 {
 425                     item_max_width = None;
 426                     formatted_comment = rewrite_post_comment(&mut item_max_width)?;
 427                     comment_alignment = post_comment_alignment(item_max_width, inner_item.len());
 428                 }
 429                 for _ in 0..(comment_alignment + 1) {
 430                     result.push(' ');
 431                 }
 432                 // An additional space for the missing trailing separator.
 433                 if last && item_max_width.is_some() && !separate && !formatting.separator.is_empty()
 434                 {
 435                     result.push(' ');
 436                 }
 437             } else {
 438                 result.push('\n');
 439                 result.push_str(indent_str);
 440             }
 441             if formatted_comment.contains('\n') {
 442                 item_max_width = None;
 443             }
 444             result.push_str(&formatted_comment);
 445         } else {
 446             item_max_width = None;
 447         }
 448
 449         if formatting.preserve_newline
 450             && !last
 451             && tactic == DefinitiveListTactic::Vertical
 452             && item.new_lines
 453         {
 454             item_max_width = None;
 455             result.push('\n');
 456         }
 457
 458         prev_item_had_post_comment = item.post_comment.is_some();
 459         prev_item_is_nested_import = inner_item.contains("::");
 460     }
 461
 462     Some(result)
 463 }
 464
 465 fn max_width_of_item_with_post_comment<I, T>(
 466     items: &I,
 467     i: usize,
 468     overhead: usize,
 469     max_budget: usize,
 470 ) -> usize
 471 where
 472     I: IntoIterator<Item = T> + Clone,
 473     T: AsRef<ListItem>,
 474 {
 475     let mut max_width = 0;
 476     let mut first = true;
 477     for item in items.clone().into_iter().skip(i) {
 478         let item = item.as_ref();
 479         let inner_item_width = item.inner_as_ref().len();
 480         if !first
 481             && (item.is_different_group()
 482                 || item.post_comment.is_none()
 483                 || inner_item_width + overhead > max_budget)
 484         {
 485             return max_width;
 486         }
 487         if max_width < inner_item_width {
 488             max_width = inner_item_width;
 489         }
 490         if item.new_lines {
 491             return max_width;
 492         }
 493         first = false;
 494     }
 495     max_width
 496 }
 497
 498 fn post_comment_alignment(item_max_width: Option<usize>, inner_item_len: usize) -> usize {
 499     item_max_width.unwrap_or(0).saturating_sub(inner_item_len)
 500 }
 501
 502 pub struct ListItems<'a, I, F1, F2, F3>
 503 where
 504     I: Iterator,
 505 {
 506     snippet_provider: &'a SnippetProvider<'a>,
 507     inner: Peekable<I>,
 508     get_lo: F1,
 509     get_hi: F2,
 510     get_item_string: F3,
 511     prev_span_end: BytePos,
 512     next_span_start: BytePos,
 513     terminator: &'a str,
 514     separator: &'a str,
 515     leave_last: bool,
 516 }
 517
 518 impl<'a, T, I, F1, F2, F3> Iterator for ListItems<'a, I, F1, F2, F3>
 519 where
 520     I: Iterator<Item = T>,
 521     F1: Fn(&T) -> BytePos,
 522     F2: Fn(&T) -> BytePos,
 523     F3: Fn(&T) -> Option<String>,
 524 {
 525     type Item = ListItem;
 526
 527     fn next(&mut self) -> Option<Self::Item> {
 528         let white_space: &[_] = &[' ', '\t'];
 529
 530         self.inner.next().map(|item| {
 531             let mut new_lines = false;
 532             // Pre-comment
 533             let pre_snippet = self
 534                 .snippet_provider
 535                 .span_to_snippet(mk_sp(self.prev_span_end, (self.get_lo)(&item)))
 536                 .unwrap_or("");
 537             let trimmed_pre_snippet = pre_snippet.trim();
 538             let has_single_line_comment = trimmed_pre_snippet.starts_with("//");
 539             let has_block_comment = trimmed_pre_snippet.starts_with("/*");
 540             let (pre_comment, pre_comment_style) = if has_single_line_comment {
 541                 (
 542                     Some(trimmed_pre_snippet.to_owned()),
 543                     ListItemCommentStyle::DifferentLine,
 544                 )
 545             } else if has_block_comment {
 546                 let comment_end = pre_snippet.chars().rev().position(|c| c == '/').unwrap();
 547                 if pre_snippet
 548                     .chars()
 549                     .rev()
 550                     .take(comment_end + 1)
 551                     .any(|c| c == '\n')
 552                 {
 553                     (
 554                         Some(trimmed_pre_snippet.to_owned()),
 555                         ListItemCommentStyle::DifferentLine,
 556                     )
 557                 } else {
 558                     (
 559                         Some(trimmed_pre_snippet.to_owned()),
 560                         ListItemCommentStyle::SameLine,
 561                     )
 562                 }
 563             } else {
 564                 (None, ListItemCommentStyle::None)
 565             };
 566
 567             // Post-comment
 568             let next_start = match self.inner.peek() {
 569                 Some(next_item) => (self.get_lo)(next_item),
 570                 None => self.next_span_start,
 571             };
 572             let post_snippet = self
 573                 .snippet_provider
 574                 .span_to_snippet(mk_sp((self.get_hi)(&item), next_start))
 575                 .unwrap_or("");
 576
 577             let comment_end = match self.inner.peek() {
 578                 Some(..) => {
 579                     let mut block_open_index = post_snippet.find("/*");
 580                     // check if it really is a block comment (and not `//*` or a nested comment)
 581                     if let Some(i) = block_open_index {
 582                         match post_snippet.find('/') {
 583                             Some(j) if j < i => block_open_index = None,
 584                             _ if i > 0 && &post_snippet[i - 1..i] == "/" => block_open_index = None,
 585                             _ => (),
 586                         }
 587                     }
 588                     let newline_index = post_snippet.find('\n');
 589                     if let Some(separator_index) = post_snippet.find_uncommented(self.separator) {
 590                         match (block_open_index, newline_index) {
 591                             // Separator before comment, with the next item on same line.
 592                             // Comment belongs to next item.
 593                             (Some(i), None) if i > separator_index => separator_index + 1,
 594                             // Block-style post-comment before the separator.
 595                             (Some(i), None) => cmp::max(
 596                                 find_comment_end(&post_snippet[i..]).unwrap() + i,
 597                                 separator_index + 1,
 598                             ),
 599                             // Block-style post-comment. Either before or after the separator.
 600                             (Some(i), Some(j)) if i < j => cmp::max(
 601                                 find_comment_end(&post_snippet[i..]).unwrap() + i,
 602                                 separator_index + 1,
 603                             ),
 604                             // Potential *single* line comment.
 605                             (_, Some(j)) if j > separator_index => j + 1,
 606                             _ => post_snippet.len(),
 607                         }
 608                     } else if let Some(newline_index) = newline_index {
 609                         // Match arms may not have trailing comma. In any case, for match arms,
 610                         // we will assume that the post comment belongs to the next arm if they
 611                         // do not end with trailing comma.
 612                         newline_index + 1
 613                     } else {
 614                         0
 615                     }
 616                 }
 617                 None => post_snippet
 618                     .find_uncommented(self.terminator)
 619                     .unwrap_or_else(|| post_snippet.len()),
 620             };
 621
 622             if !post_snippet.is_empty() && comment_end > 0 {
 623                 // Account for extra whitespace between items. This is fiddly
 624                 // because of the way we divide pre- and post- comments.
 625
 626                 // Everything from the separator to the next item.
 627                 let test_snippet = &post_snippet[comment_end - 1..];
 628                 let first_newline = test_snippet
 629                     .find('\n')
 630                     .unwrap_or_else(|| test_snippet.len());
 631                 // From the end of the first line of comments.
 632                 let test_snippet = &test_snippet[first_newline..];
 633                 let first = test_snippet
 634                     .find(|c: char| !c.is_whitespace())
 635                     .unwrap_or_else(|| test_snippet.len());
 636                 // From the end of the first line of comments to the next non-whitespace char.
 637                 let test_snippet = &test_snippet[..first];
 638
 639                 if count_newlines(test_snippet) > 1 {
 640                     // There were multiple line breaks which got trimmed to nothing.
 641                     new_lines = true;
 642                 }
 643             }
 644
 645             // Cleanup post-comment: strip separators and whitespace.
 646             self.prev_span_end = (self.get_hi)(&item) + BytePos(comment_end as u32);
 647             let post_snippet = post_snippet[..comment_end].trim();
 648
 649             let post_snippet_trimmed = if post_snippet.starts_with(|c| c == ',' || c == ':') {
 650                 post_snippet[1..].trim_matches(white_space)
 651             } else if post_snippet.starts_with(self.separator) {
 652                 post_snippet[self.separator.len()..].trim_matches(white_space)
 653             } else if post_snippet.ends_with(',') {
 654                 post_snippet[..(post_snippet.len() - 1)].trim_matches(white_space)
 655             } else {
 656                 post_snippet
 657             };
 658
 659             let post_comment = if !post_snippet_trimmed.is_empty() {
 660                 Some(post_snippet_trimmed.to_owned())
 661             } else {
 662                 None
 663             };
 664
 665             ListItem {
 666                 pre_comment,
 667                 pre_comment_style,
 668                 item: if self.inner.peek().is_none() && self.leave_last {
 669                     None
 670                 } else {
 671                     (self.get_item_string)(&item)
 672                 },
 673                 post_comment,
 674                 new_lines,
 675             }
 676         })
 677     }
 678 }
 679
 680 #[cfg_attr(feature = "cargo-clippy", allow(too_many_arguments))]
 681 // Creates an iterator over a list's items with associated comments.
 682 pub fn itemize_list<'a, T, I, F1, F2, F3>(
 683     snippet_provider: &'a SnippetProvider,
 684     inner: I,
 685     terminator: &'a str,
 686     separator: &'a str,
 687     get_lo: F1,
 688     get_hi: F2,
 689     get_item_string: F3,
 690     prev_span_end: BytePos,
 691     next_span_start: BytePos,
 692     leave_last: bool,
 693 ) -> ListItems<'a, I, F1, F2, F3>
 694 where
 695     I: Iterator<Item = T>,
 696     F1: Fn(&T) -> BytePos,
 697     F2: Fn(&T) -> BytePos,
 698     F3: Fn(&T) -> Option<String>,
 699 {
 700     ListItems {
 701         snippet_provider,
 702         inner: inner.peekable(),
 703         get_lo,
 704         get_hi,
 705         get_item_string,
 706         prev_span_end,
 707         next_span_start,
 708         terminator,
 709         separator,
 710         leave_last,
 711     }
 712 }
 713
 714 /// Returns the count and total width of the list items.
 715 fn calculate_width<I, T>(items: I) -> (usize, usize)
 716 where
 717     I: IntoIterator<Item = T>,
 718     T: AsRef<ListItem>,
 719 {
 720     items
 721         .into_iter()
 722         .map(|item| total_item_width(item.as_ref()))
 723         .fold((0, 0), |acc, l| (acc.0 + 1, acc.1 + l))
 724 }
 725
 726 pub fn total_item_width(item: &ListItem) -> usize {
 727     comment_len(item.pre_comment.as_ref().map(|x| &(*x)[..]))
 728         + comment_len(item.post_comment.as_ref().map(|x| &(*x)[..]))
 729         + item.item.as_ref().map_or(0, |str| str.len())
 730 }
 731
 732 fn comment_len(comment: Option<&str>) -> usize {
 733     match comment {
 734         Some(s) => {
 735             let text_len = s.trim().len();
 736             if text_len > 0 {
 737                 // We'll put " /*" before and " */" after inline comments.
 738                 text_len + 6
 739             } else {
 740                 text_len
 741             }
 742         }
 743         None => 0,
 744     }
 745 }
 746
 747 // Compute horizontal and vertical shapes for a struct-lit-like thing.
 748 pub fn struct_lit_shape(
 749     shape: Shape,
 750     context: &RewriteContext,
 751     prefix_width: usize,
 752     suffix_width: usize,
 753 ) -> Option<(Option<Shape>, Shape)> {
 754     let v_shape = match context.config.indent_style() {
 755         IndentStyle::Visual => shape
 756             .visual_indent(0)
 757             .shrink_left(prefix_width)?
 758             .sub_width(suffix_width)?,
 759         IndentStyle::Block => {
 760             let shape = shape.block_indent(context.config.tab_spaces());
 761             Shape {
 762                 width: context.budget(shape.indent.width()),
 763                 ..shape
 764             }
 765         }
 766     };
 767     let shape_width = shape.width.checked_sub(prefix_width + suffix_width);
 768     if let Some(w) = shape_width {
 769         let shape_width = cmp::min(w, context.config.width_heuristics().struct_lit_width);
 770         Some((Some(Shape::legacy(shape_width, shape.indent)), v_shape))
 771     } else {
 772         Some((None, v_shape))
 773     }
 774 }
 775
 776 // Compute the tactic for the internals of a struct-lit-like thing.
 777 pub fn struct_lit_tactic(
 778     h_shape: Option<Shape>,
 779     context: &RewriteContext,
 780     items: &[ListItem],
 781 ) -> DefinitiveListTactic {
 782     if let Some(h_shape) = h_shape {
 783         let prelim_tactic = match (context.config.indent_style(), items.len()) {
 784             (IndentStyle::Visual, 1) => ListTactic::HorizontalVertical,
 785             _ if context.config.struct_lit_single_line() => ListTactic::HorizontalVertical,
 786             _ => ListTactic::Vertical,
 787         };
 788         definitive_tactic(items, prelim_tactic, Separator::Comma, h_shape.width)
 789     } else {
 790         DefinitiveListTactic::Vertical
 791     }
 792 }
 793
 794 // Given a tactic and possible shapes for horizontal and vertical layout,
 795 // come up with the actual shape to use.
 796 pub fn shape_for_tactic(
 797     tactic: DefinitiveListTactic,
 798     h_shape: Option<Shape>,
 799     v_shape: Shape,
 800 ) -> Shape {
 801     match tactic {
 802         DefinitiveListTactic::Horizontal => h_shape.unwrap(),
 803         _ => v_shape,
 804     }
 805 }
 806
 807 // Create a ListFormatting object for formatting the internals of a
 808 // struct-lit-like thing, that is a series of fields.
 809 pub fn struct_lit_formatting<'a>(
 810     shape: Shape,
 811     tactic: DefinitiveListTactic,
 812     context: &'a RewriteContext,
 813     force_no_trailing_comma: bool,
 814 ) -> ListFormatting<'a> {
 815     let ends_with_newline = context.config.indent_style() != IndentStyle::Visual
 816         && tactic == DefinitiveListTactic::Vertical;
 817     ListFormatting {
 818         tactic,
 819         separator: ",",
 820         trailing_separator: if force_no_trailing_comma {
 821             SeparatorTactic::Never
 822         } else {
 823             context.config.trailing_comma()
 824         },
 825         separator_place: SeparatorPlace::Back,
 826         shape,
 827         ends_with_newline,
 828         preserve_newline: true,
 829         nested: false,
 830         config: context.config,
 831     }
 832 }