src/overflow.rs

   1 //! Rewrite a list some items with overflow.
   2
   3 use std::cmp::min;
   4
   5 use itertools::Itertools;
   6 use syntax::parse::token::DelimToken;
   7 use syntax::source_map::Span;
   8 use syntax::{ast, ptr};
   9
  10 use crate::closures;
  11 use crate::config::lists::*;
  12 use crate::config::Version;
  13 use crate::expr::{
  14     can_be_overflowed_expr, is_every_expr_simple, is_method_call, is_nested_call, is_simple_expr,
  15     rewrite_cond,
  16 };
  17 use crate::lists::{
  18     definitive_tactic, itemize_list, write_list, ListFormatting, ListItem, Separator,
  19 };
  20 use crate::macros::MacroArg;
  21 use crate::patterns::{can_be_overflowed_pat, TuplePatField};
  22 use crate::rewrite::{Rewrite, RewriteContext};
  23 use crate::shape::Shape;
  24 use crate::source_map::SpanUtils;
  25 use crate::spanned::Spanned;
  26 use crate::types::{can_be_overflowed_type, SegmentParam};
  27 use crate::utils::{count_newlines, extra_offset, first_line_width, last_line_width, mk_sp};
  28
  29 const SHORT_ITEM_THRESHOLD: usize = 10;
  30
  31 /// A list of `format!`-like macros, that take a long format string and a list of arguments to
  32 /// format.
  33 ///
  34 /// Organized as a list of `(&str, usize)` tuples, giving the name of the macro and the number of
  35 /// arguments before the format string (none for `format!("format", ...)`, one for `assert!(result,
  36 /// "format", ...)`, two for `assert_eq!(left, right, "format", ...)`).
  37 const SPECIAL_MACRO_WHITELIST: &[(&str, usize)] = &[
  38     // format! like macros
  39     // From the Rust Standard Library.
  40     ("eprint!", 0),
  41     ("eprintln!", 0),
  42     ("format!", 0),
  43     ("format_args!", 0),
  44     ("print!", 0),
  45     ("println!", 0),
  46     ("panic!", 0),
  47     ("unreachable!", 0),
  48     // From the `log` crate.
  49     ("debug!", 0),
  50     ("error!", 0),
  51     ("info!", 0),
  52     ("warn!", 0),
  53     // write! like macros
  54     ("assert!", 1),
  55     ("debug_assert!", 1),
  56     ("write!", 1),
  57     ("writeln!", 1),
  58     // assert_eq! like macros
  59     ("assert_eq!", 2),
  60     ("assert_ne!", 2),
  61     ("debug_assert_eq!", 2),
  62     ("debug_assert_ne!", 2),
  63 ];
  64
  65 const SPECIAL_ATTR_WHITELIST: &[(&str, usize)] = &[
  66     // From the `failure` crate.
  67     ("fail", 0),
  68 ];
  69
  70 #[derive(Debug)]
  71 pub(crate) enum OverflowableItem<'a> {
  72     Expr(&'a ast::Expr),
  73     GenericParam(&'a ast::GenericParam),
  74     MacroArg(&'a MacroArg),
  75     NestedMetaItem(&'a ast::NestedMetaItem),
  76     SegmentParam(&'a SegmentParam<'a>),
  77     StructField(&'a ast::StructField),
  78     TuplePatField(&'a TuplePatField<'a>),
  79     Ty(&'a ast::Ty),
  80 }
  81
  82 impl<'a> Rewrite for OverflowableItem<'a> {
  83     fn rewrite(&self, context: &RewriteContext<'_>, shape: Shape) -> Option<String> {
  84         self.map(|item| item.rewrite(context, shape))
  85     }
  86 }
  87
  88 impl<'a> Spanned for OverflowableItem<'a> {
  89     fn span(&self) -> Span {
  90         self.map(|item| item.span())
  91     }
  92 }
  93
  94 impl<'a> OverflowableItem<'a> {
  95     fn has_attrs(&self) -> bool {
  96         match self {
  97             OverflowableItem::Expr(ast::Expr { attrs, .. })
  98             | OverflowableItem::GenericParam(ast::GenericParam { attrs, .. }) => !attrs.is_empty(),
  99             OverflowableItem::StructField(ast::StructField { attrs, .. }) => !attrs.is_empty(),
 100             OverflowableItem::MacroArg(MacroArg::Expr(expr)) => !expr.attrs.is_empty(),
 101             OverflowableItem::MacroArg(MacroArg::Item(item)) => !item.attrs.is_empty(),
 102             _ => false,
 103         }
 104     }
 105
 106     pub(crate) fn map<F, T>(&self, f: F) -> T
 107     where
 108         F: Fn(&dyn IntoOverflowableItem<'a>) -> T,
 109     {
 110         match self {
 111             OverflowableItem::Expr(expr) => f(*expr),
 112             OverflowableItem::GenericParam(gp) => f(*gp),
 113             OverflowableItem::MacroArg(macro_arg) => f(*macro_arg),
 114             OverflowableItem::NestedMetaItem(nmi) => f(*nmi),
 115             OverflowableItem::SegmentParam(sp) => f(*sp),
 116             OverflowableItem::StructField(sf) => f(*sf),
 117             OverflowableItem::TuplePatField(pat) => f(*pat),
 118             OverflowableItem::Ty(ty) => f(*ty),
 119         }
 120     }
 121
 122     pub(crate) fn is_simple(&self) -> bool {
 123         match self {
 124             OverflowableItem::Expr(expr) => is_simple_expr(expr),
 125             OverflowableItem::MacroArg(MacroArg::Expr(expr)) => is_simple_expr(expr),
 126             OverflowableItem::NestedMetaItem(nested_meta_item) => match nested_meta_item {
 127                 ast::NestedMetaItem::Literal(..) => true,
 128                 ast::NestedMetaItem::MetaItem(ref meta_item) => match meta_item.node {
 129                     ast::MetaItemKind::Word => true,
 130                     _ => false,
 131                 },
 132             },
 133             _ => false,
 134         }
 135     }
 136
 137     pub(crate) fn is_expr(&self) -> bool {
 138         match self {
 139             OverflowableItem::Expr(..) => true,
 140             OverflowableItem::MacroArg(MacroArg::Expr(..)) => true,
 141             _ => false,
 142         }
 143     }
 144
 145     pub(crate) fn is_nested_call(&self) -> bool {
 146         match self {
 147             OverflowableItem::Expr(expr) => is_nested_call(expr),
 148             OverflowableItem::MacroArg(MacroArg::Expr(expr)) => is_nested_call(expr),
 149             _ => false,
 150         }
 151     }
 152
 153     pub(crate) fn to_expr(&self) -> Option<&'a ast::Expr> {
 154         match self {
 155             OverflowableItem::Expr(expr) => Some(expr),
 156             OverflowableItem::MacroArg(macro_arg) => match macro_arg {
 157                 MacroArg::Expr(ref expr) => Some(expr),
 158                 _ => None,
 159             },
 160             _ => None,
 161         }
 162     }
 163
 164     pub(crate) fn can_be_overflowed(&self, context: &RewriteContext<'_>, len: usize) -> bool {
 165         match self {
 166             OverflowableItem::Expr(expr) => can_be_overflowed_expr(context, expr, len),
 167             OverflowableItem::MacroArg(macro_arg) => match macro_arg {
 168                 MacroArg::Expr(ref expr) => can_be_overflowed_expr(context, expr, len),
 169                 MacroArg::Ty(ref ty) => can_be_overflowed_type(context, ty, len),
 170                 MacroArg::Pat(..) => false,
 171                 MacroArg::Item(..) => len == 1,
 172                 MacroArg::Keyword(..) => false,
 173             },
 174             OverflowableItem::NestedMetaItem(nested_meta_item) if len == 1 => {
 175                 match nested_meta_item {
 176                     ast::NestedMetaItem::Literal(..) => false,
 177                     ast::NestedMetaItem::MetaItem(..) => true,
 178                 }
 179             }
 180             OverflowableItem::SegmentParam(seg) => match seg {
 181                 SegmentParam::Type(ty) => can_be_overflowed_type(context, ty, len),
 182                 _ => false,
 183             },
 184             OverflowableItem::TuplePatField(pat) => can_be_overflowed_pat(context, pat, len),
 185             OverflowableItem::Ty(ty) => can_be_overflowed_type(context, ty, len),
 186             _ => false,
 187         }
 188     }
 189
 190     fn whitelist(&self) -> &'static [(&'static str, usize)] {
 191         match self {
 192             OverflowableItem::MacroArg(..) => SPECIAL_MACRO_WHITELIST,
 193             OverflowableItem::NestedMetaItem(..) => SPECIAL_ATTR_WHITELIST,
 194             _ => &[],
 195         }
 196     }
 197 }
 198
 199 pub(crate) trait IntoOverflowableItem<'a>: Rewrite + Spanned {
 200     fn into_overflowable_item(&'a self) -> OverflowableItem<'a>;
 201 }
 202
 203 impl<'a, T: 'a + IntoOverflowableItem<'a>> IntoOverflowableItem<'a> for ptr::P<T> {
 204     fn into_overflowable_item(&'a self) -> OverflowableItem<'a> {
 205         (**self).into_overflowable_item()
 206     }
 207 }
 208
 209 macro_rules! impl_into_overflowable_item_for_ast_node {
 210     ($($ast_node:ident),*) => {
 211         $(
 212             impl<'a> IntoOverflowableItem<'a> for ast::$ast_node {
 213                 fn into_overflowable_item(&'a self) -> OverflowableItem<'a> {
 214                     OverflowableItem::$ast_node(self)
 215                 }
 216             }
 217         )*
 218     }
 219 }
 220
 221 macro_rules! impl_into_overflowable_item_for_rustfmt_types {
 222     ([$($ty:ident),*], [$($ty_with_lifetime:ident),*]) => {
 223         $(
 224             impl<'a> IntoOverflowableItem<'a> for $ty {
 225                 fn into_overflowable_item(&'a self) -> OverflowableItem<'a> {
 226                     OverflowableItem::$ty(self)
 227                 }
 228             }
 229         )*
 230         $(
 231             impl<'a> IntoOverflowableItem<'a> for $ty_with_lifetime<'a> {
 232                 fn into_overflowable_item(&'a self) -> OverflowableItem<'a> {
 233                     OverflowableItem::$ty_with_lifetime(self)
 234                 }
 235             }
 236         )*
 237     }
 238 }
 239
 240 impl_into_overflowable_item_for_ast_node!(Expr, GenericParam, NestedMetaItem, StructField, Ty);
 241 impl_into_overflowable_item_for_rustfmt_types!([MacroArg], [SegmentParam, TuplePatField]);
 242
 243 pub(crate) fn into_overflowable_list<'a, T>(
 244     iter: impl Iterator<Item = &'a T>,
 245 ) -> impl Iterator<Item = OverflowableItem<'a>>
 246 where
 247     T: 'a + IntoOverflowableItem<'a>,
 248 {
 249     iter.map(|x| IntoOverflowableItem::into_overflowable_item(x))
 250 }
 251
 252 pub(crate) fn rewrite_with_parens<'a, T: 'a + IntoOverflowableItem<'a>>(
 253     context: &'a RewriteContext<'_>,
 254     ident: &'a str,
 255     items: impl Iterator<Item = &'a T>,
 256     shape: Shape,
 257     span: Span,
 258     item_max_width: usize,
 259     force_separator_tactic: Option<SeparatorTactic>,
 260 ) -> Option<String> {
 261     Context::new(
 262         context,
 263         items,
 264         ident,
 265         shape,
 266         span,
 267         "(",
 268         ")",
 269         item_max_width,
 270         force_separator_tactic,
 271         None,
 272     )
 273     .rewrite(shape)
 274 }
 275
 276 pub(crate) fn rewrite_with_angle_brackets<'a, T: 'a + IntoOverflowableItem<'a>>(
 277     context: &'a RewriteContext<'_>,
 278     ident: &'a str,
 279     items: impl Iterator<Item = &'a T>,
 280     shape: Shape,
 281     span: Span,
 282 ) -> Option<String> {
 283     Context::new(
 284         context,
 285         items,
 286         ident,
 287         shape,
 288         span,
 289         "<",
 290         ">",
 291         context.config.max_width(),
 292         None,
 293         None,
 294     )
 295     .rewrite(shape)
 296 }
 297
 298 pub(crate) fn rewrite_with_square_brackets<'a, T: 'a + IntoOverflowableItem<'a>>(
 299     context: &'a RewriteContext<'_>,
 300     name: &'a str,
 301     items: impl Iterator<Item = &'a T>,
 302     shape: Shape,
 303     span: Span,
 304     force_separator_tactic: Option<SeparatorTactic>,
 305     delim_token: Option<DelimToken>,
 306 ) -> Option<String> {
 307     let (lhs, rhs) = match delim_token {
 308         Some(DelimToken::Paren) => ("(", ")"),
 309         Some(DelimToken::Brace) => ("{", "}"),
 310         _ => ("[", "]"),
 311     };
 312     Context::new(
 313         context,
 314         items,
 315         name,
 316         shape,
 317         span,
 318         lhs,
 319         rhs,
 320         context.config.width_heuristics().array_width,
 321         force_separator_tactic,
 322         Some(("[", "]")),
 323     )
 324     .rewrite(shape)
 325 }
 326
 327 struct Context<'a> {
 328     context: &'a RewriteContext<'a>,
 329     items: Vec<OverflowableItem<'a>>,
 330     ident: &'a str,
 331     prefix: &'static str,
 332     suffix: &'static str,
 333     one_line_shape: Shape,
 334     nested_shape: Shape,
 335     span: Span,
 336     item_max_width: usize,
 337     one_line_width: usize,
 338     force_separator_tactic: Option<SeparatorTactic>,
 339     custom_delims: Option<(&'a str, &'a str)>,
 340 }
 341
 342 impl<'a> Context<'a> {
 343     fn new<T: 'a + IntoOverflowableItem<'a>>(
 344         context: &'a RewriteContext<'_>,
 345         items: impl Iterator<Item = &'a T>,
 346         ident: &'a str,
 347         shape: Shape,
 348         span: Span,
 349         prefix: &'static str,
 350         suffix: &'static str,
 351         item_max_width: usize,
 352         force_separator_tactic: Option<SeparatorTactic>,
 353         custom_delims: Option<(&'a str, &'a str)>,
 354     ) -> Context<'a> {
 355         let used_width = extra_offset(ident, shape);
 356         // 1 = `()`
 357         let one_line_width = shape.width.saturating_sub(used_width + 2);
 358
 359         // 1 = "(" or ")"
 360         let one_line_shape = shape
 361             .offset_left(last_line_width(ident) + 1)
 362             .and_then(|shape| shape.sub_width(1))
 363             .unwrap_or(Shape { width: 0, ..shape });
 364         let nested_shape = shape_from_indent_style(context, shape, used_width + 2, used_width + 1);
 365         Context {
 366             context,
 367             items: into_overflowable_list(items).collect(),
 368             ident,
 369             one_line_shape,
 370             nested_shape,
 371             span,
 372             prefix,
 373             suffix,
 374             item_max_width,
 375             one_line_width,
 376             force_separator_tactic,
 377             custom_delims,
 378         }
 379     }
 380
 381     fn last_item(&self) -> Option<&OverflowableItem<'_>> {
 382         self.items.last()
 383     }
 384
 385     fn items_span(&self) -> Span {
 386         let span_lo = self
 387             .context
 388             .snippet_provider
 389             .span_after(self.span, self.prefix);
 390         mk_sp(span_lo, self.span.hi())
 391     }
 392
 393     fn rewrite_last_item_with_overflow(
 394         &self,
 395         last_list_item: &mut ListItem,
 396         shape: Shape,
 397     ) -> Option<String> {
 398         let last_item = self.last_item()?;
 399         let rewrite = match last_item {
 400             OverflowableItem::Expr(ref expr) => {
 401                 match expr.node {
 402                     // When overflowing the closure which consists of a single control flow
 403                     // expression, force to use block if its condition uses multi line.
 404                     ast::ExprKind::Closure(..) => {
 405                         // If the argument consists of multiple closures, we do not overflow
 406                         // the last closure.
 407                         if closures::args_have_many_closure(&self.items) {
 408                             None
 409                         } else {
 410                             closures::rewrite_last_closure(self.context, expr, shape)
 411                         }
 412                     }
 413
 414                     // When overflowing the expressions which consists of a control flow
 415                     // expression, avoid condition to use multi line.
 416                     ast::ExprKind::If(..)
 417                     | ast::ExprKind::ForLoop(..)
 418                     | ast::ExprKind::Loop(..)
 419                     | ast::ExprKind::While(..)
 420                     | ast::ExprKind::Match(..) => {
 421                         let multi_line = rewrite_cond(self.context, expr, shape)
 422                             .map_or(false, |cond| cond.contains('\n'));
 423
 424                         if multi_line {
 425                             None
 426                         } else {
 427                             expr.rewrite(self.context, shape)
 428                         }
 429                     }
 430
 431                     _ => expr.rewrite(self.context, shape),
 432                 }
 433             }
 434             item => item.rewrite(self.context, shape),
 435         };
 436
 437         if let Some(rewrite) = rewrite {
 438             // splitn(2, *).next().unwrap() is always safe.
 439             let rewrite_first_line = Some(rewrite.splitn(2, '\n').next().unwrap().to_owned());
 440             last_list_item.item = rewrite_first_line;
 441             Some(rewrite)
 442         } else {
 443             None
 444         }
 445     }
 446
 447     fn default_tactic(&self, list_items: &[ListItem]) -> DefinitiveListTactic {
 448         definitive_tactic(
 449             list_items,
 450             ListTactic::LimitedHorizontalVertical(self.item_max_width),
 451             Separator::Comma,
 452             self.one_line_width,
 453         )
 454     }
 455
 456     fn try_overflow_last_item(&self, list_items: &mut Vec<ListItem>) -> DefinitiveListTactic {
 457         // 1 = "("
 458         let combine_arg_with_callee = self.items.len() == 1
 459             && self.items[0].is_expr()
 460             && !self.items[0].has_attrs()
 461             && self.ident.len() < self.context.config.tab_spaces();
 462         let overflow_last = combine_arg_with_callee || can_be_overflowed(self.context, &self.items);
 463
 464         // Replace the last item with its first line to see if it fits with
 465         // first arguments.
 466         let placeholder = if overflow_last {
 467             let old_value = *self.context.force_one_line_chain.borrow();
 468             match self.last_item() {
 469                 Some(OverflowableItem::Expr(expr))
 470                     if !combine_arg_with_callee && is_method_call(expr) =>
 471                 {
 472                     self.context.force_one_line_chain.replace(true);
 473                 }
 474                 Some(OverflowableItem::MacroArg(MacroArg::Expr(expr)))
 475                     if !combine_arg_with_callee
 476                         && is_method_call(expr)
 477                         && self.context.config.version() == Version::Two =>
 478                 {
 479                     self.context.force_one_line_chain.replace(true);
 480                 }
 481                 _ => (),
 482             }
 483             let result = last_item_shape(
 484                 &self.items,
 485                 list_items,
 486                 self.one_line_shape,
 487                 self.item_max_width,
 488             )
 489             .and_then(|arg_shape| {
 490                 self.rewrite_last_item_with_overflow(
 491                     &mut list_items[self.items.len() - 1],
 492                     arg_shape,
 493                 )
 494             });
 495             self.context.force_one_line_chain.replace(old_value);
 496             result
 497         } else {
 498             None
 499         };
 500
 501         let mut tactic = definitive_tactic(
 502             &*list_items,
 503             ListTactic::LimitedHorizontalVertical(self.item_max_width),
 504             Separator::Comma,
 505             self.one_line_width,
 506         );
 507
 508         // Replace the stub with the full overflowing last argument if the rewrite
 509         // succeeded and its first line fits with the other arguments.
 510         match (overflow_last, tactic, placeholder) {
 511             (true, DefinitiveListTactic::Horizontal, Some(ref overflowed))
 512                 if self.items.len() == 1 =>
 513             {
 514                 // When we are rewriting a nested function call, we restrict the
 515                 // budget for the inner function to avoid them being deeply nested.
 516                 // However, when the inner function has a prefix or a suffix
 517                 // (e.g., `foo() as u32`), this budget reduction may produce poorly
 518                 // formatted code, where a prefix or a suffix being left on its own
 519                 // line. Here we explicitlly check those cases.
 520                 if count_newlines(overflowed) == 1 {
 521                     let rw = self
 522                         .items
 523                         .last()
 524                         .and_then(|last_item| last_item.rewrite(self.context, self.nested_shape));
 525                     let no_newline = rw.as_ref().map_or(false, |s| !s.contains('\n'));
 526                     if no_newline {
 527                         list_items[self.items.len() - 1].item = rw;
 528                     } else {
 529                         list_items[self.items.len() - 1].item = Some(overflowed.to_owned());
 530                     }
 531                 } else {
 532                     list_items[self.items.len() - 1].item = Some(overflowed.to_owned());
 533                 }
 534             }
 535             (true, DefinitiveListTactic::Horizontal, placeholder @ Some(..)) => {
 536                 list_items[self.items.len() - 1].item = placeholder;
 537             }
 538             _ if !self.items.is_empty() => {
 539                 list_items[self.items.len() - 1].item = self
 540                     .items
 541                     .last()
 542                     .and_then(|last_item| last_item.rewrite(self.context, self.nested_shape));
 543
 544                 // Use horizontal layout for a function with a single argument as long as
 545                 // everything fits in a single line.
 546                 // `self.one_line_width == 0` means vertical layout is forced.
 547                 if self.items.len() == 1
 548                     && self.one_line_width != 0
 549                     && !list_items[0].has_comment()
 550                     && !list_items[0].inner_as_ref().contains('\n')
 551                     && crate::lists::total_item_width(&list_items[0]) <= self.one_line_width
 552                 {
 553                     tactic = DefinitiveListTactic::Horizontal;
 554                 } else {
 555                     tactic = self.default_tactic(list_items);
 556
 557                     if tactic == DefinitiveListTactic::Vertical {
 558                         if let Some((all_simple, num_args_before)) =
 559                             maybe_get_args_offset(self.ident, &self.items)
 560                         {
 561                             let one_line = all_simple
 562                                 && definitive_tactic(
 563                                     &list_items[..num_args_before],
 564                                     ListTactic::HorizontalVertical,
 565                                     Separator::Comma,
 566                                     self.nested_shape.width,
 567                                 ) == DefinitiveListTactic::Horizontal
 568                                 && definitive_tactic(
 569                                     &list_items[num_args_before + 1..],
 570                                     ListTactic::HorizontalVertical,
 571                                     Separator::Comma,
 572                                     self.nested_shape.width,
 573                                 ) == DefinitiveListTactic::Horizontal;
 574
 575                             if one_line {
 576                                 tactic = DefinitiveListTactic::SpecialMacro(num_args_before);
 577                             };
 578                         } else if is_every_expr_simple(&self.items) && no_long_items(list_items) {
 579                             tactic = DefinitiveListTactic::Mixed;
 580                         }
 581                     }
 582                 }
 583             }
 584             _ => (),
 585         }
 586
 587         tactic
 588     }
 589
 590     fn rewrite_items(&self) -> Option<(bool, String)> {
 591         let span = self.items_span();
 592         let items = itemize_list(
 593             self.context.snippet_provider,
 594             self.items.iter(),
 595             self.suffix,
 596             ",",
 597             |item| item.span().lo(),
 598             |item| item.span().hi(),
 599             |item| item.rewrite(self.context, self.nested_shape),
 600             span.lo(),
 601             span.hi(),
 602             true,
 603         );
 604         let mut list_items: Vec<_> = items.collect();
 605
 606         // Try letting the last argument overflow to the next line with block
 607         // indentation. If its first line fits on one line with the other arguments,
 608         // we format the function arguments horizontally.
 609         let tactic = self.try_overflow_last_item(&mut list_items);
 610         let trailing_separator = if let Some(tactic) = self.force_separator_tactic {
 611             tactic
 612         } else if !self.context.use_block_indent() {
 613             SeparatorTactic::Never
 614         } else {
 615             self.context.config.trailing_comma()
 616         };
 617         let ends_with_newline = match tactic {
 618             DefinitiveListTactic::Vertical | DefinitiveListTactic::Mixed => {
 619                 self.context.use_block_indent()
 620             }
 621             _ => false,
 622         };
 623
 624         let fmt = ListFormatting::new(self.nested_shape, self.context.config)
 625             .tactic(tactic)
 626             .trailing_separator(trailing_separator)
 627             .ends_with_newline(ends_with_newline);
 628
 629         write_list(&list_items, &fmt)
 630             .map(|items_str| (tactic == DefinitiveListTactic::Horizontal, items_str))
 631     }
 632
 633     fn wrap_items(&self, items_str: &str, shape: Shape, is_extendable: bool) -> String {
 634         let shape = Shape {
 635             width: shape.width.saturating_sub(last_line_width(self.ident)),
 636             ..shape
 637         };
 638
 639         let (prefix, suffix) = match self.custom_delims {
 640             Some((lhs, rhs)) => (lhs, rhs),
 641             _ => (self.prefix, self.suffix),
 642         };
 643
 644         let extend_width = if items_str.is_empty() {
 645             2
 646         } else {
 647             first_line_width(items_str) + 1
 648         };
 649         let nested_indent_str = self
 650             .nested_shape
 651             .indent
 652             .to_string_with_newline(self.context.config);
 653         let indent_str = shape
 654             .block()
 655             .indent
 656             .to_string_with_newline(self.context.config);
 657         let mut result = String::with_capacity(
 658             self.ident.len() + items_str.len() + 2 + indent_str.len() + nested_indent_str.len(),
 659         );
 660         result.push_str(self.ident);
 661         result.push_str(prefix);
 662         let force_single_line = if self.context.config.version() == Version::Two {
 663             !self.context.use_block_indent() || (is_extendable && extend_width <= shape.width)
 664         } else {
 665             // 2 = `()`
 666             let fits_one_line = items_str.len() + 2 <= shape.width;
 667             !self.context.use_block_indent()
 668                 || (self.context.inside_macro() && !items_str.contains('\n') && fits_one_line)
 669                 || (is_extendable && extend_width <= shape.width)
 670         };
 671         if force_single_line {
 672             result.push_str(items_str);
 673         } else {
 674             if !items_str.is_empty() {
 675                 result.push_str(&nested_indent_str);
 676                 result.push_str(items_str);
 677             }
 678             result.push_str(&indent_str);
 679         }
 680         result.push_str(suffix);
 681         result
 682     }
 683
 684     fn rewrite(&self, shape: Shape) -> Option<String> {
 685         let (extendable, items_str) = self.rewrite_items()?;
 686
 687         // If we are using visual indent style and failed to format, retry with block indent.
 688         if !self.context.use_block_indent()
 689             && need_block_indent(&items_str, self.nested_shape)
 690             && !extendable
 691         {
 692             self.context.use_block.replace(true);
 693             let result = self.rewrite(shape);
 694             self.context.use_block.replace(false);
 695             return result;
 696         }
 697
 698         Some(self.wrap_items(&items_str, shape, extendable))
 699     }
 700 }
 701
 702 fn need_block_indent(s: &str, shape: Shape) -> bool {
 703     s.lines().skip(1).any(|s| {
 704         s.find(|c| !char::is_whitespace(c))
 705             .map_or(false, |w| w + 1 < shape.indent.width())
 706     })
 707 }
 708
 709 fn can_be_overflowed(context: &RewriteContext<'_>, items: &[OverflowableItem<'_>]) -> bool {
 710     items
 711         .last()
 712         .map_or(false, |x| x.can_be_overflowed(context, items.len()))
 713 }
 714
 715 /// Returns a shape for the last argument which is going to be overflowed.
 716 fn last_item_shape(
 717     lists: &[OverflowableItem<'_>],
 718     items: &[ListItem],
 719     shape: Shape,
 720     args_max_width: usize,
 721 ) -> Option<Shape> {
 722     if items.len() == 1 && !lists.get(0)?.is_nested_call() {
 723         return Some(shape);
 724     }
 725     let offset = items
 726         .iter()
 727         .dropping_back(1)
 728         .map(|i| {
 729             // 2 = ", "
 730             2 + i.inner_as_ref().len()
 731         })
 732         .sum();
 733     Shape {
 734         width: min(args_max_width, shape.width),
 735         ..shape
 736     }
 737     .offset_left(offset)
 738 }
 739
 740 fn shape_from_indent_style(
 741     context: &RewriteContext<'_>,
 742     shape: Shape,
 743     overhead: usize,
 744     offset: usize,
 745 ) -> Shape {
 746     let (shape, overhead) = if context.use_block_indent() {
 747         let shape = shape
 748             .block()
 749             .block_indent(context.config.tab_spaces())
 750             .with_max_width(context.config);
 751         (shape, 1) // 1 = ","
 752     } else {
 753         (shape.visual_indent(offset), overhead)
 754     };
 755     Shape {
 756         width: shape.width.saturating_sub(overhead),
 757         ..shape
 758     }
 759 }
 760
 761 fn no_long_items(list: &[ListItem]) -> bool {
 762     list.iter()
 763         .all(|item| item.inner_as_ref().len() <= SHORT_ITEM_THRESHOLD)
 764 }
 765
 766 /// In case special-case style is required, returns an offset from which we start horizontal layout.
 767 pub(crate) fn maybe_get_args_offset(
 768     callee_str: &str,
 769     args: &[OverflowableItem<'_>],
 770 ) -> Option<(bool, usize)> {
 771     if let Some(&(_, num_args_before)) = args
 772         .get(0)?
 773         .whitelist()
 774         .iter()
 775         .find(|&&(s, _)| s == callee_str)
 776     {
 777         let all_simple = args.len() > num_args_before
 778             && is_every_expr_simple(&args[0..num_args_before])
 779             && is_every_expr_simple(&args[num_args_before + 1..]);
 780
 781         Some((all_simple, num_args_before))
 782     } else {
 783         None
 784     }
 785 }