src/overflow.rs

   1 // Copyright 2018 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 //! Rewrite a list some items with overflow.
  12
  13 use std::cmp::min;
  14
  15 use syntax::parse::token::DelimToken;
  16 use syntax::source_map::Span;
  17 use syntax::{ast, ptr};
  18
  19 use crate::closures;
  20 use crate::config::lists::*;
  21 use crate::config::Version;
  22 use crate::expr::{
  23     can_be_overflowed_expr, is_every_expr_simple, is_method_call, is_nested_call, is_simple_expr,
  24     rewrite_cond,
  25 };
  26 use crate::lists::{
  27     definitive_tactic, itemize_list, write_list, ListFormatting, ListItem, Separator,
  28 };
  29 use crate::macros::MacroArg;
  30 use crate::patterns::{can_be_overflowed_pat, TuplePatField};
  31 use crate::rewrite::{Rewrite, RewriteContext};
  32 use crate::shape::Shape;
  33 use crate::source_map::SpanUtils;
  34 use crate::spanned::Spanned;
  35 use crate::types::{can_be_overflowed_type, SegmentParam};
  36 use crate::utils::{count_newlines, extra_offset, first_line_width, last_line_width, mk_sp};
  37
  38 const SHORT_ITEM_THRESHOLD: usize = 10;
  39
  40 /// A list of `format!`-like macros, that take a long format string and a list of arguments to
  41 /// format.
  42 ///
  43 /// Organized as a list of `(&str, usize)` tuples, giving the name of the macro and the number of
  44 /// arguments before the format string (none for `format!("format", ...)`, one for `assert!(result,
  45 /// "format", ...)`, two for `assert_eq!(left, right, "format", ...)`).
  46 const SPECIAL_MACRO_WHITELIST: &[(&str, usize)] = &[
  47     // format! like macros
  48     // From the Rust Standard Library.
  49     ("eprint!", 0),
  50     ("eprintln!", 0),
  51     ("format!", 0),
  52     ("format_args!", 0),
  53     ("print!", 0),
  54     ("println!", 0),
  55     ("panic!", 0),
  56     ("unreachable!", 0),
  57     // From the `log` crate.
  58     ("debug!", 0),
  59     ("error!", 0),
  60     ("info!", 0),
  61     ("warn!", 0),
  62     // write! like macros
  63     ("assert!", 1),
  64     ("debug_assert!", 1),
  65     ("write!", 1),
  66     ("writeln!", 1),
  67     // assert_eq! like macros
  68     ("assert_eq!", 2),
  69     ("assert_ne!", 2),
  70     ("debug_assert_eq!", 2),
  71     ("debug_assert_ne!", 2),
  72 ];
  73
  74 const SPECIAL_ATTR_WHITELIST: &[(&str, usize)] = &[
  75     // From the `failure` crate.
  76     ("fail", 0),
  77 ];
  78
  79 #[derive(Debug)]
  80 pub enum OverflowableItem<'a> {
  81     Expr(&'a ast::Expr),
  82     GenericParam(&'a ast::GenericParam),
  83     MacroArg(&'a MacroArg),
  84     NestedMetaItem(&'a ast::NestedMetaItem),
  85     SegmentParam(&'a SegmentParam<'a>),
  86     StructField(&'a ast::StructField),
  87     TuplePatField(&'a TuplePatField<'a>),
  88     Ty(&'a ast::Ty),
  89 }
  90
  91 impl<'a> Rewrite for OverflowableItem<'a> {
  92     fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
  93         self.map(|item| item.rewrite(context, shape))
  94     }
  95 }
  96
  97 impl<'a> Spanned for OverflowableItem<'a> {
  98     fn span(&self) -> Span {
  99         self.map(|item| item.span())
 100     }
 101 }
 102
 103 impl<'a> OverflowableItem<'a> {
 104     pub fn map<F, T>(&self, f: F) -> T
 105     where
 106         F: Fn(&IntoOverflowableItem<'a>) -> T,
 107     {
 108         match self {
 109             OverflowableItem::Expr(expr) => f(*expr),
 110             OverflowableItem::GenericParam(gp) => f(*gp),
 111             OverflowableItem::MacroArg(macro_arg) => f(*macro_arg),
 112             OverflowableItem::NestedMetaItem(nmi) => f(*nmi),
 113             OverflowableItem::SegmentParam(sp) => f(*sp),
 114             OverflowableItem::StructField(sf) => f(*sf),
 115             OverflowableItem::TuplePatField(pat) => f(*pat),
 116             OverflowableItem::Ty(ty) => f(*ty),
 117         }
 118     }
 119
 120     pub fn is_simple(&self) -> bool {
 121         match self {
 122             OverflowableItem::Expr(expr) => is_simple_expr(expr),
 123             OverflowableItem::MacroArg(MacroArg::Expr(expr)) => is_simple_expr(expr),
 124             OverflowableItem::NestedMetaItem(nested_meta_item) => match nested_meta_item.node {
 125                 ast::NestedMetaItemKind::Literal(..) => true,
 126                 ast::NestedMetaItemKind::MetaItem(ref meta_item) => match meta_item.node {
 127                     ast::MetaItemKind::Word => true,
 128                     _ => false,
 129                 },
 130             },
 131             _ => false,
 132         }
 133     }
 134
 135     pub fn is_expr(&self) -> bool {
 136         match self {
 137             OverflowableItem::Expr(..) => true,
 138             OverflowableItem::MacroArg(MacroArg::Expr(..)) => true,
 139             _ => false,
 140         }
 141     }
 142
 143     pub fn is_nested_call(&self) -> bool {
 144         match self {
 145             OverflowableItem::Expr(expr) => is_nested_call(expr),
 146             OverflowableItem::MacroArg(MacroArg::Expr(expr)) => is_nested_call(expr),
 147             _ => false,
 148         }
 149     }
 150
 151     pub fn to_expr(&self) -> Option<&'a ast::Expr> {
 152         match self {
 153             OverflowableItem::Expr(expr) => Some(expr),
 154             OverflowableItem::MacroArg(macro_arg) => match macro_arg {
 155                 MacroArg::Expr(ref expr) => Some(expr),
 156                 _ => None,
 157             },
 158             _ => None,
 159         }
 160     }
 161
 162     pub fn can_be_overflowed(&self, context: &RewriteContext, len: usize) -> bool {
 163         match self {
 164             OverflowableItem::Expr(expr) => can_be_overflowed_expr(context, expr, len),
 165             OverflowableItem::MacroArg(macro_arg) => match macro_arg {
 166                 MacroArg::Expr(ref expr) => can_be_overflowed_expr(context, expr, len),
 167                 MacroArg::Ty(ref ty) => can_be_overflowed_type(context, ty, len),
 168                 MacroArg::Pat(..) => false,
 169                 MacroArg::Item(..) => len == 1,
 170             },
 171             OverflowableItem::NestedMetaItem(nested_meta_item) if len == 1 => {
 172                 match nested_meta_item.node {
 173                     ast::NestedMetaItemKind::Literal(..) => false,
 174                     ast::NestedMetaItemKind::MetaItem(..) => true,
 175                 }
 176             }
 177             OverflowableItem::SegmentParam(seg) => match seg {
 178                 SegmentParam::Type(ty) => can_be_overflowed_type(context, ty, len),
 179                 _ => false,
 180             },
 181             OverflowableItem::TuplePatField(pat) => can_be_overflowed_pat(context, pat, len),
 182             OverflowableItem::Ty(ty) => can_be_overflowed_type(context, ty, len),
 183             _ => false,
 184         }
 185     }
 186
 187     fn whitelist(&self) -> &'static [(&'static str, usize)] {
 188         match self {
 189             OverflowableItem::MacroArg(..) => SPECIAL_MACRO_WHITELIST,
 190             OverflowableItem::NestedMetaItem(..) => SPECIAL_ATTR_WHITELIST,
 191             _ => &[],
 192         }
 193     }
 194 }
 195
 196 pub trait IntoOverflowableItem<'a>: Rewrite + Spanned {
 197     fn into_overflowable_item(&'a self) -> OverflowableItem<'a>;
 198 }
 199
 200 impl<'a, T: 'a + IntoOverflowableItem<'a>> IntoOverflowableItem<'a> for ptr::P<T> {
 201     fn into_overflowable_item(&'a self) -> OverflowableItem<'a> {
 202         (**self).into_overflowable_item()
 203     }
 204 }
 205
 206 macro_rules! impl_into_overflowable_item_for_ast_node {
 207     ($($ast_node:ident),*) => {
 208         $(
 209             impl<'a> IntoOverflowableItem<'a> for ast::$ast_node {
 210                 fn into_overflowable_item(&'a self) -> OverflowableItem<'a> {
 211                     OverflowableItem::$ast_node(self)
 212                 }
 213             }
 214         )*
 215     }
 216 }
 217
 218 macro_rules! impl_into_overflowable_item_for_rustfmt_types {
 219     ([$($ty:ident),*], [$($ty_with_lifetime:ident),*]) => {
 220         $(
 221             impl<'a> IntoOverflowableItem<'a> for $ty {
 222                 fn into_overflowable_item(&'a self) -> OverflowableItem<'a> {
 223                     OverflowableItem::$ty(self)
 224                 }
 225             }
 226         )*
 227         $(
 228             impl<'a> IntoOverflowableItem<'a> for $ty_with_lifetime<'a> {
 229                 fn into_overflowable_item(&'a self) -> OverflowableItem<'a> {
 230                     OverflowableItem::$ty_with_lifetime(self)
 231                 }
 232             }
 233         )*
 234     }
 235 }
 236
 237 impl_into_overflowable_item_for_ast_node!(Expr, GenericParam, NestedMetaItem, StructField, Ty);
 238 impl_into_overflowable_item_for_rustfmt_types!([MacroArg], [SegmentParam, TuplePatField]);
 239
 240 pub fn into_overflowable_list<'a, T>(
 241     iter: impl Iterator<Item = &'a T>,
 242 ) -> impl Iterator<Item = OverflowableItem<'a>>
 243 where
 244     T: 'a + IntoOverflowableItem<'a>,
 245 {
 246     iter.map(|x| IntoOverflowableItem::into_overflowable_item(x))
 247 }
 248
 249 pub fn rewrite_with_parens<'a, T: 'a + IntoOverflowableItem<'a>>(
 250     context: &'a RewriteContext,
 251     ident: &'a str,
 252     items: impl Iterator<Item = &'a T>,
 253     shape: Shape,
 254     span: Span,
 255     item_max_width: usize,
 256     force_separator_tactic: Option<SeparatorTactic>,
 257 ) -> Option<String> {
 258     Context::new(
 259         context,
 260         items,
 261         ident,
 262         shape,
 263         span,
 264         "(",
 265         ")",
 266         item_max_width,
 267         force_separator_tactic,
 268         None,
 269     )
 270     .rewrite(shape)
 271 }
 272
 273 pub fn rewrite_with_angle_brackets<'a, T: 'a + IntoOverflowableItem<'a>>(
 274     context: &'a RewriteContext,
 275     ident: &'a str,
 276     items: impl Iterator<Item = &'a T>,
 277     shape: Shape,
 278     span: Span,
 279 ) -> Option<String> {
 280     Context::new(
 281         context,
 282         items,
 283         ident,
 284         shape,
 285         span,
 286         "<",
 287         ">",
 288         context.config.max_width(),
 289         None,
 290         None,
 291     )
 292     .rewrite(shape)
 293 }
 294
 295 pub fn rewrite_with_square_brackets<'a, T: 'a + IntoOverflowableItem<'a>>(
 296     context: &'a RewriteContext,
 297     name: &'a str,
 298     items: impl Iterator<Item = &'a T>,
 299     shape: Shape,
 300     span: Span,
 301     force_separator_tactic: Option<SeparatorTactic>,
 302     delim_token: Option<DelimToken>,
 303 ) -> Option<String> {
 304     let (lhs, rhs) = match delim_token {
 305         Some(DelimToken::Paren) => ("(", ")"),
 306         Some(DelimToken::Brace) => ("{", "}"),
 307         _ => ("[", "]"),
 308     };
 309     Context::new(
 310         context,
 311         items,
 312         name,
 313         shape,
 314         span,
 315         lhs,
 316         rhs,
 317         context.config.width_heuristics().array_width,
 318         force_separator_tactic,
 319         Some(("[", "]")),
 320     )
 321     .rewrite(shape)
 322 }
 323
 324 struct Context<'a> {
 325     context: &'a RewriteContext<'a>,
 326     items: Vec<OverflowableItem<'a>>,
 327     ident: &'a str,
 328     prefix: &'static str,
 329     suffix: &'static str,
 330     one_line_shape: Shape,
 331     nested_shape: Shape,
 332     span: Span,
 333     item_max_width: usize,
 334     one_line_width: usize,
 335     force_separator_tactic: Option<SeparatorTactic>,
 336     custom_delims: Option<(&'a str, &'a str)>,
 337 }
 338
 339 impl<'a> Context<'a> {
 340     pub fn new<T: 'a + IntoOverflowableItem<'a>>(
 341         context: &'a RewriteContext,
 342         items: impl Iterator<Item = &'a T>,
 343         ident: &'a str,
 344         shape: Shape,
 345         span: Span,
 346         prefix: &'static str,
 347         suffix: &'static str,
 348         item_max_width: usize,
 349         force_separator_tactic: Option<SeparatorTactic>,
 350         custom_delims: Option<(&'a str, &'a str)>,
 351     ) -> Context<'a> {
 352         let used_width = extra_offset(ident, shape);
 353         // 1 = `()`
 354         let one_line_width = shape.width.saturating_sub(used_width + 2);
 355
 356         // 1 = "(" or ")"
 357         let one_line_shape = shape
 358             .offset_left(last_line_width(ident) + 1)
 359             .and_then(|shape| shape.sub_width(1))
 360             .unwrap_or(Shape { width: 0, ..shape });
 361         let nested_shape = shape_from_indent_style(context, shape, used_width + 2, used_width + 1);
 362         Context {
 363             context,
 364             items: into_overflowable_list(items).collect(),
 365             ident,
 366             one_line_shape,
 367             nested_shape,
 368             span,
 369             prefix,
 370             suffix,
 371             item_max_width,
 372             one_line_width,
 373             force_separator_tactic,
 374             custom_delims,
 375         }
 376     }
 377
 378     fn last_item(&self) -> Option<&OverflowableItem> {
 379         self.items.last()
 380     }
 381
 382     fn items_span(&self) -> Span {
 383         let span_lo = self
 384             .context
 385             .snippet_provider
 386             .span_after(self.span, self.prefix);
 387         mk_sp(span_lo, self.span.hi())
 388     }
 389
 390     fn rewrite_last_item_with_overflow(
 391         &self,
 392         last_list_item: &mut ListItem,
 393         shape: Shape,
 394     ) -> Option<String> {
 395         let last_item = self.last_item()?;
 396         let rewrite = match last_item {
 397             OverflowableItem::Expr(ref expr) => {
 398                 match expr.node {
 399                     // When overflowing the closure which consists of a single control flow
 400                     // expression, force to use block if its condition uses multi line.
 401                     ast::ExprKind::Closure(..) => {
 402                         // If the argument consists of multiple closures, we do not overflow
 403                         // the last closure.
 404                         if closures::args_have_many_closure(&self.items) {
 405                             None
 406                         } else {
 407                             closures::rewrite_last_closure(self.context, expr, shape)
 408                         }
 409                     }
 410
 411                     // When overflowing the expressions which consists of a control flow
 412                     // expression, avoid condition to use multi line.
 413                     ast::ExprKind::If(..)
 414                     | ast::ExprKind::IfLet(..)
 415                     | ast::ExprKind::ForLoop(..)
 416                     | ast::ExprKind::Loop(..)
 417                     | ast::ExprKind::While(..)
 418                     | ast::ExprKind::WhileLet(..)
 419                     | ast::ExprKind::Match(..) => {
 420                         let multi_line = rewrite_cond(self.context, expr, shape)
 421                             .map_or(false, |cond| cond.contains('\n'));
 422
 423                         if multi_line {
 424                             None
 425                         } else {
 426                             expr.rewrite(self.context, shape)
 427                         }
 428                     }
 429
 430                     _ => expr.rewrite(self.context, shape),
 431                 }
 432             }
 433             item => item.rewrite(self.context, shape),
 434         };
 435
 436         if let Some(rewrite) = rewrite {
 437             // splitn(2, *).next().unwrap() is always safe.
 438             let rewrite_first_line = Some(rewrite.splitn(2, '\n').next().unwrap().to_owned());
 439             last_list_item.item = rewrite_first_line;
 440             Some(rewrite)
 441         } else {
 442             None
 443         }
 444     }
 445
 446     fn default_tactic(&self, list_items: &[ListItem]) -> DefinitiveListTactic {
 447         definitive_tactic(
 448             list_items,
 449             ListTactic::LimitedHorizontalVertical(self.item_max_width),
 450             Separator::Comma,
 451             self.one_line_width,
 452         )
 453     }
 454
 455     fn try_overflow_last_item(&self, list_items: &mut Vec<ListItem>) -> DefinitiveListTactic {
 456         // 1 = "("
 457         let combine_arg_with_callee = self.items.len() == 1
 458             && self.items[0].is_expr()
 459             && self.ident.len() < self.context.config.tab_spaces();
 460         let overflow_last = combine_arg_with_callee || can_be_overflowed(self.context, &self.items);
 461
 462         // Replace the last item with its first line to see if it fits with
 463         // first arguments.
 464         let placeholder = if overflow_last {
 465             let old_value = *self.context.force_one_line_chain.borrow();
 466             match self.last_item() {
 467                 Some(OverflowableItem::Expr(expr))
 468                     if !combine_arg_with_callee && is_method_call(expr) =>
 469                 {
 470                     self.context.force_one_line_chain.replace(true);
 471                 }
 472                 Some(OverflowableItem::MacroArg(MacroArg::Expr(expr)))
 473                     if !combine_arg_with_callee
 474                         && is_method_call(expr)
 475                         && self.context.config.version() == Version::Two =>
 476                 {
 477                     self.context.force_one_line_chain.replace(true);
 478                 }
 479                 _ => (),
 480             }
 481             let result = last_item_shape(
 482                 &self.items,
 483                 list_items,
 484                 self.one_line_shape,
 485                 self.item_max_width,
 486             )
 487             .and_then(|arg_shape| {
 488                 self.rewrite_last_item_with_overflow(
 489                     &mut list_items[self.items.len() - 1],
 490                     arg_shape,
 491                 )
 492             });
 493             self.context.force_one_line_chain.replace(old_value);
 494             result
 495         } else {
 496             None
 497         };
 498
 499         let mut tactic = definitive_tactic(
 500             &*list_items,
 501             ListTactic::LimitedHorizontalVertical(self.item_max_width),
 502             Separator::Comma,
 503             self.one_line_width,
 504         );
 505
 506         // Replace the stub with the full overflowing last argument if the rewrite
 507         // succeeded and its first line fits with the other arguments.
 508         match (overflow_last, tactic, placeholder) {
 509             (true, DefinitiveListTactic::Horizontal, Some(ref overflowed))
 510                 if self.items.len() == 1 =>
 511             {
 512                 // When we are rewriting a nested function call, we restrict the
 513                 // budget for the inner function to avoid them being deeply nested.
 514                 // However, when the inner function has a prefix or a suffix
 515                 // (e.g. `foo() as u32`), this budget reduction may produce poorly
 516                 // formatted code, where a prefix or a suffix being left on its own
 517                 // line. Here we explicitlly check those cases.
 518                 if count_newlines(overflowed) == 1 {
 519                     let rw = self
 520                         .items
 521                         .last()
 522                         .and_then(|last_item| last_item.rewrite(self.context, self.nested_shape));
 523                     let no_newline = rw.as_ref().map_or(false, |s| !s.contains('\n'));
 524                     if no_newline {
 525                         list_items[self.items.len() - 1].item = rw;
 526                     } else {
 527                         list_items[self.items.len() - 1].item = Some(overflowed.to_owned());
 528                     }
 529                 } else {
 530                     list_items[self.items.len() - 1].item = Some(overflowed.to_owned());
 531                 }
 532             }
 533             (true, DefinitiveListTactic::Horizontal, placeholder @ Some(..)) => {
 534                 list_items[self.items.len() - 1].item = placeholder;
 535             }
 536             _ if !self.items.is_empty() => {
 537                 list_items[self.items.len() - 1].item = self
 538                     .items
 539                     .last()
 540                     .and_then(|last_item| last_item.rewrite(self.context, self.nested_shape));
 541
 542                 // Use horizontal layout for a function with a single argument as long as
 543                 // everything fits in a single line.
 544                 // `self.one_line_width == 0` means vertical layout is forced.
 545                 if self.items.len() == 1
 546                     && self.one_line_width != 0
 547                     && !list_items[0].has_comment()
 548                     && !list_items[0].inner_as_ref().contains('\n')
 549                     && crate::lists::total_item_width(&list_items[0]) <= self.one_line_width
 550                 {
 551                     tactic = DefinitiveListTactic::Horizontal;
 552                 } else {
 553                     tactic = self.default_tactic(list_items);
 554
 555                     if tactic == DefinitiveListTactic::Vertical {
 556                         if let Some((all_simple, num_args_before)) =
 557                             maybe_get_args_offset(self.ident, &self.items)
 558                         {
 559                             let one_line = all_simple
 560                                 && definitive_tactic(
 561                                     &list_items[..num_args_before],
 562                                     ListTactic::HorizontalVertical,
 563                                     Separator::Comma,
 564                                     self.nested_shape.width,
 565                                 ) == DefinitiveListTactic::Horizontal
 566                                 && definitive_tactic(
 567                                     &list_items[num_args_before + 1..],
 568                                     ListTactic::HorizontalVertical,
 569                                     Separator::Comma,
 570                                     self.nested_shape.width,
 571                                 ) == DefinitiveListTactic::Horizontal;
 572
 573                             if one_line {
 574                                 tactic = DefinitiveListTactic::SpecialMacro(num_args_before);
 575                             };
 576                         } else if is_every_expr_simple(&self.items) && no_long_items(list_items) {
 577                             tactic = DefinitiveListTactic::Mixed;
 578                         }
 579                     }
 580                 }
 581             }
 582             _ => (),
 583         }
 584
 585         tactic
 586     }
 587
 588     fn rewrite_items(&self) -> Option<(bool, String)> {
 589         let span = self.items_span();
 590         let items = itemize_list(
 591             self.context.snippet_provider,
 592             self.items.iter(),
 593             self.suffix,
 594             ",",
 595             |item| item.span().lo(),
 596             |item| item.span().hi(),
 597             |item| item.rewrite(self.context, self.nested_shape),
 598             span.lo(),
 599             span.hi(),
 600             true,
 601         );
 602         let mut list_items: Vec<_> = items.collect();
 603
 604         // Try letting the last argument overflow to the next line with block
 605         // indentation. If its first line fits on one line with the other arguments,
 606         // we format the function arguments horizontally.
 607         let tactic = self.try_overflow_last_item(&mut list_items);
 608         let trailing_separator = if let Some(tactic) = self.force_separator_tactic {
 609             tactic
 610         } else if !self.context.use_block_indent() {
 611             SeparatorTactic::Never
 612         } else {
 613             self.context.config.trailing_comma()
 614         };
 615         let ends_with_newline = match tactic {
 616             DefinitiveListTactic::Vertical | DefinitiveListTactic::Mixed => {
 617                 self.context.use_block_indent()
 618             }
 619             _ => false,
 620         };
 621
 622         let fmt = ListFormatting::new(self.nested_shape, self.context.config)
 623             .tactic(tactic)
 624             .trailing_separator(trailing_separator)
 625             .ends_with_newline(ends_with_newline);
 626
 627         write_list(&list_items, &fmt)
 628             .map(|items_str| (tactic == DefinitiveListTactic::Horizontal, items_str))
 629     }
 630
 631     fn wrap_items(&self, items_str: &str, shape: Shape, is_extendable: bool) -> String {
 632         let shape = Shape {
 633             width: shape.width.saturating_sub(last_line_width(self.ident)),
 634             ..shape
 635         };
 636
 637         let (prefix, suffix) = match self.custom_delims {
 638             Some((lhs, rhs)) => (lhs, rhs),
 639             _ => (self.prefix, self.suffix),
 640         };
 641
 642         let extend_width = if items_str.is_empty() {
 643             2
 644         } else {
 645             first_line_width(items_str) + 1
 646         };
 647         let nested_indent_str = self
 648             .nested_shape
 649             .indent
 650             .to_string_with_newline(self.context.config);
 651         let indent_str = shape
 652             .block()
 653             .indent
 654             .to_string_with_newline(self.context.config);
 655         let mut result = String::with_capacity(
 656             self.ident.len() + items_str.len() + 2 + indent_str.len() + nested_indent_str.len(),
 657         );
 658         result.push_str(self.ident);
 659         result.push_str(prefix);
 660         let force_single_line = if self.context.config.version() == Version::Two {
 661             !self.context.use_block_indent() || (is_extendable && extend_width <= shape.width)
 662         } else {
 663             // 2 = `()`
 664             let fits_one_line = items_str.len() + 2 <= shape.width;
 665             !self.context.use_block_indent()
 666                 || (self.context.inside_macro() && !items_str.contains('\n') && fits_one_line)
 667                 || (is_extendable && extend_width <= shape.width)
 668         };
 669         if force_single_line {
 670             result.push_str(items_str);
 671         } else {
 672             if !items_str.is_empty() {
 673                 result.push_str(&nested_indent_str);
 674                 result.push_str(items_str);
 675             }
 676             result.push_str(&indent_str);
 677         }
 678         result.push_str(suffix);
 679         result
 680     }
 681
 682     fn rewrite(&self, shape: Shape) -> Option<String> {
 683         let (extendable, items_str) = self.rewrite_items()?;
 684
 685         // If we are using visual indent style and failed to format, retry with block indent.
 686         if !self.context.use_block_indent()
 687             && need_block_indent(&items_str, self.nested_shape)
 688             && !extendable
 689         {
 690             self.context.use_block.replace(true);
 691             let result = self.rewrite(shape);
 692             self.context.use_block.replace(false);
 693             return result;
 694         }
 695
 696         Some(self.wrap_items(&items_str, shape, extendable))
 697     }
 698 }
 699
 700 fn need_block_indent(s: &str, shape: Shape) -> bool {
 701     s.lines().skip(1).any(|s| {
 702         s.find(|c| !char::is_whitespace(c))
 703             .map_or(false, |w| w + 1 < shape.indent.width())
 704     })
 705 }
 706
 707 fn can_be_overflowed(context: &RewriteContext, items: &[OverflowableItem]) -> bool {
 708     items
 709         .last()
 710         .map_or(false, |x| x.can_be_overflowed(context, items.len()))
 711 }
 712
 713 /// Returns a shape for the last argument which is going to be overflowed.
 714 fn last_item_shape(
 715     lists: &[OverflowableItem],
 716     items: &[ListItem],
 717     shape: Shape,
 718     args_max_width: usize,
 719 ) -> Option<Shape> {
 720     if items.len() == 1 && !lists.get(0)?.is_nested_call() {
 721         return Some(shape);
 722     }
 723     let offset = items.iter().rev().skip(1).fold(0, |acc, i| {
 724         // 2 = ", "
 725         acc + 2 + i.inner_as_ref().len()
 726     });
 727     Shape {
 728         width: min(args_max_width, shape.width),
 729         ..shape
 730     }
 731     .offset_left(offset)
 732 }
 733
 734 fn shape_from_indent_style(
 735     context: &RewriteContext,
 736     shape: Shape,
 737     overhead: usize,
 738     offset: usize,
 739 ) -> Shape {
 740     let (shape, overhead) = if context.use_block_indent() {
 741         let shape = shape
 742             .block()
 743             .block_indent(context.config.tab_spaces())
 744             .with_max_width(context.config);
 745         (shape, 1) // 1 = ","
 746     } else {
 747         (shape.visual_indent(offset), overhead)
 748     };
 749     Shape {
 750         width: shape.width.saturating_sub(overhead),
 751         ..shape
 752     }
 753 }
 754
 755 fn no_long_items(list: &[ListItem]) -> bool {
 756     list.iter()
 757         .all(|item| item.inner_as_ref().len() <= SHORT_ITEM_THRESHOLD)
 758 }
 759
 760 /// In case special-case style is required, returns an offset from which we start horizontal layout.
 761 pub fn maybe_get_args_offset(callee_str: &str, args: &[OverflowableItem]) -> Option<(bool, usize)> {
 762     if let Some(&(_, num_args_before)) = args
 763         .get(0)?
 764         .whitelist()
 765         .iter()
 766         .find(|&&(s, _)| s == callee_str)
 767     {
 768         let all_simple = args.len() > num_args_before
 769             && is_every_expr_simple(&args[0..num_args_before])
 770             && is_every_expr_simple(&args[num_args_before + 1..]);
 771
 772         Some((all_simple, num_args_before))
 773     } else {
 774         None
 775     }
 776 }