src/patterns.rs

   1 use rustc_ast::ast::{
   2     self, BindingAnnotation, ByRef, Pat, PatField, PatKind, RangeEnd, RangeSyntax,
   3 };
   4 use rustc_ast::ptr;
   5 use rustc_span::{BytePos, Span};
   6
   7 use crate::comment::{combine_strs_with_missing_comments, FindUncommented};
   8 use crate::config::lists::*;
   9 use crate::config::Version;
  10 use crate::expr::{can_be_overflowed_expr, rewrite_unary_prefix, wrap_struct_field};
  11 use crate::lists::{
  12     definitive_tactic, itemize_list, shape_for_tactic, struct_lit_formatting, struct_lit_shape,
  13     struct_lit_tactic, write_list, ListFormatting, ListItem, Separator,
  14 };
  15 use crate::macros::{rewrite_macro, MacroPosition};
  16 use crate::overflow;
  17 use crate::pairs::{rewrite_pair, PairParts};
  18 use crate::rewrite::{Rewrite, RewriteContext};
  19 use crate::shape::Shape;
  20 use crate::source_map::SpanUtils;
  21 use crate::spanned::Spanned;
  22 use crate::types::{rewrite_path, PathContext};
  23 use crate::utils::{format_mutability, mk_sp, mk_sp_lo_plus_one, rewrite_ident};
  24
  25 /// Returns `true` if the given pattern is "short".
  26 /// A short pattern is defined by the following grammar:
  27 ///
  28 /// `[small, ntp]`:
  29 ///     - single token
  30 ///     - `&[single-line, ntp]`
  31 ///
  32 /// `[small]`:
  33 ///     - `[small, ntp]`
  34 ///     - unary tuple constructor `([small, ntp])`
  35 ///     - `&[small]`
  36 pub(crate) fn is_short_pattern(pat: &ast::Pat, pat_str: &str) -> bool {
  37     // We also require that the pattern is reasonably 'small' with its literal width.
  38     pat_str.len() <= 20 && !pat_str.contains('\n') && is_short_pattern_inner(pat)
  39 }
  40
  41 fn is_short_pattern_inner(pat: &ast::Pat) -> bool {
  42     match pat.kind {
  43         ast::PatKind::Rest | ast::PatKind::Wild | ast::PatKind::Lit(_) => true,
  44         ast::PatKind::Ident(_, _, ref pat) => pat.is_none(),
  45         ast::PatKind::Struct(..)
  46         | ast::PatKind::MacCall(..)
  47         | ast::PatKind::Slice(..)
  48         | ast::PatKind::Path(..)
  49         | ast::PatKind::Range(..) => false,
  50         ast::PatKind::Tuple(ref subpats) => subpats.len() <= 1,
  51         ast::PatKind::TupleStruct(_, ref path, ref subpats) => {
  52             path.segments.len() <= 1 && subpats.len() <= 1
  53         }
  54         ast::PatKind::Box(ref p) | ast::PatKind::Ref(ref p, _) | ast::PatKind::Paren(ref p) => {
  55             is_short_pattern_inner(&*p)
  56         }
  57         PatKind::Or(ref pats) => pats.iter().all(|p| is_short_pattern_inner(p)),
  58     }
  59 }
  60
  61 struct RangeOperand<'a>(&'a Option<ptr::P<ast::Expr>>);
  62
  63 impl<'a> Rewrite for RangeOperand<'a> {
  64     fn rewrite(&self, context: &RewriteContext<'_>, shape: Shape) -> Option<String> {
  65         match &self.0 {
  66             None => Some("".to_owned()),
  67             Some(ref exp) => exp.rewrite(context, shape),
  68         }
  69     }
  70 }
  71
  72 impl Rewrite for Pat {
  73     fn rewrite(&self, context: &RewriteContext<'_>, shape: Shape) -> Option<String> {
  74         match self.kind {
  75             PatKind::Or(ref pats) => {
  76                 let pat_strs = pats
  77                     .iter()
  78                     .map(|p| p.rewrite(context, shape))
  79                     .collect::<Option<Vec<_>>>()?;
  80
  81                 let use_mixed_layout = pats
  82                     .iter()
  83                     .zip(pat_strs.iter())
  84                     .all(|(pat, pat_str)| is_short_pattern(pat, pat_str));
  85                 let items: Vec<_> = pat_strs.into_iter().map(ListItem::from_str).collect();
  86                 let tactic = if use_mixed_layout {
  87                     DefinitiveListTactic::Mixed
  88                 } else {
  89                     definitive_tactic(
  90                         &items,
  91                         ListTactic::HorizontalVertical,
  92                         Separator::VerticalBar,
  93                         shape.width,
  94                     )
  95                 };
  96                 let fmt = ListFormatting::new(shape, context.config)
  97                     .tactic(tactic)
  98                     .separator(" |")
  99                     .separator_place(context.config.binop_separator())
 100                     .ends_with_newline(false);
 101                 write_list(&items, &fmt)
 102             }
 103             PatKind::Box(ref pat) => rewrite_unary_prefix(context, "box ", &**pat, shape),
 104             PatKind::Ident(BindingAnnotation(by_ref, mutability), ident, ref sub_pat) => {
 105                 let prefix = match by_ref {
 106                     ByRef::Yes => "ref",
 107                     ByRef::No => "",
 108                 };
 109                 let mut_infix = format_mutability(mutability).trim();
 110                 let id_str = rewrite_ident(context, ident);
 111                 let sub_pat = match *sub_pat {
 112                     Some(ref p) => {
 113                         // 2 - `@ `.
 114                         let width = shape
 115                             .width
 116                             .checked_sub(prefix.len() + mut_infix.len() + id_str.len() + 2)?;
 117                         let lo = context.snippet_provider.span_after(self.span, "@");
 118                         combine_strs_with_missing_comments(
 119                             context,
 120                             "@",
 121                             &p.rewrite(context, Shape::legacy(width, shape.indent))?,
 122                             mk_sp(lo, p.span.lo()),
 123                             shape,
 124                             true,
 125                         )?
 126                     }
 127                     None => "".to_owned(),
 128                 };
 129
 130                 // combine prefix and mut
 131                 let (first_lo, first) = if !prefix.is_empty() && !mut_infix.is_empty() {
 132                     let hi = context.snippet_provider.span_before(self.span, "mut");
 133                     let lo = context.snippet_provider.span_after(self.span, "ref");
 134                     (
 135                         context.snippet_provider.span_after(self.span, "mut"),
 136                         combine_strs_with_missing_comments(
 137                             context,
 138                             prefix,
 139                             mut_infix,
 140                             mk_sp(lo, hi),
 141                             shape,
 142                             true,
 143                         )?,
 144                     )
 145                 } else if !prefix.is_empty() {
 146                     (
 147                         context.snippet_provider.span_after(self.span, "ref"),
 148                         prefix.to_owned(),
 149                     )
 150                 } else if !mut_infix.is_empty() {
 151                     (
 152                         context.snippet_provider.span_after(self.span, "mut"),
 153                         mut_infix.to_owned(),
 154                     )
 155                 } else {
 156                     (self.span.lo(), "".to_owned())
 157                 };
 158
 159                 let next = if !sub_pat.is_empty() {
 160                     let hi = context.snippet_provider.span_before(self.span, "@");
 161                     combine_strs_with_missing_comments(
 162                         context,
 163                         id_str,
 164                         &sub_pat,
 165                         mk_sp(ident.span.hi(), hi),
 166                         shape,
 167                         true,
 168                     )?
 169                 } else {
 170                     id_str.to_owned()
 171                 };
 172
 173                 combine_strs_with_missing_comments(
 174                     context,
 175                     &first,
 176                     &next,
 177                     mk_sp(first_lo, ident.span.lo()),
 178                     shape,
 179                     true,
 180                 )
 181             }
 182             PatKind::Wild => {
 183                 if 1 <= shape.width {
 184                     Some("_".to_owned())
 185                 } else {
 186                     None
 187                 }
 188             }
 189             PatKind::Rest => {
 190                 if 1 <= shape.width {
 191                     Some("..".to_owned())
 192                 } else {
 193                     None
 194                 }
 195             }
 196             PatKind::Range(ref lhs, ref rhs, ref end_kind) => {
 197                 let infix = match end_kind.node {
 198                     RangeEnd::Included(RangeSyntax::DotDotDot) => "...",
 199                     RangeEnd::Included(RangeSyntax::DotDotEq) => "..=",
 200                     RangeEnd::Excluded => "..",
 201                 };
 202                 let infix = if context.config.spaces_around_ranges() {
 203                     let lhs_spacing = match lhs {
 204                         None => "",
 205                         Some(_) => " ",
 206                     };
 207                     let rhs_spacing = match rhs {
 208                         None => "",
 209                         Some(_) => " ",
 210                     };
 211                     format!("{}{}{}", lhs_spacing, infix, rhs_spacing)
 212                 } else {
 213                     infix.to_owned()
 214                 };
 215                 rewrite_pair(
 216                     &RangeOperand(lhs),
 217                     &RangeOperand(rhs),
 218                     PairParts::infix(&infix),
 219                     context,
 220                     shape,
 221                     SeparatorPlace::Front,
 222                 )
 223             }
 224             PatKind::Ref(ref pat, mutability) => {
 225                 let prefix = format!("&{}", format_mutability(mutability));
 226                 rewrite_unary_prefix(context, &prefix, &**pat, shape)
 227             }
 228             PatKind::Tuple(ref items) => rewrite_tuple_pat(items, None, self.span, context, shape),
 229             PatKind::Path(ref q_self, ref path) => {
 230                 rewrite_path(context, PathContext::Expr, q_self, path, shape)
 231             }
 232             PatKind::TupleStruct(ref q_self, ref path, ref pat_vec) => {
 233                 let path_str = rewrite_path(context, PathContext::Expr, q_self, path, shape)?;
 234                 rewrite_tuple_pat(pat_vec, Some(path_str), self.span, context, shape)
 235             }
 236             PatKind::Lit(ref expr) => expr.rewrite(context, shape),
 237             PatKind::Slice(ref slice_pat) if context.config.version() == Version::One => {
 238                 let rw: Vec<String> = slice_pat
 239                     .iter()
 240                     .map(|p| {
 241                         if let Some(rw) = p.rewrite(context, shape) {
 242                             rw
 243                         } else {
 244                             context.snippet(p.span).to_string()
 245                         }
 246                     })
 247                     .collect();
 248                 Some(format!("[{}]", rw.join(", ")))
 249             }
 250             PatKind::Slice(ref slice_pat) => overflow::rewrite_with_square_brackets(
 251                 context,
 252                 "",
 253                 slice_pat.iter(),
 254                 shape,
 255                 self.span,
 256                 None,
 257                 None,
 258             ),
 259             PatKind::Struct(ref qself, ref path, ref fields, ellipsis) => {
 260                 rewrite_struct_pat(qself, path, fields, ellipsis, self.span, context, shape)
 261             }
 262             PatKind::MacCall(ref mac) => {
 263                 rewrite_macro(mac, None, context, shape, MacroPosition::Pat)
 264             }
 265             PatKind::Paren(ref pat) => pat
 266                 .rewrite(context, shape.offset_left(1)?.sub_width(1)?)
 267                 .map(|inner_pat| format!("({})", inner_pat)),
 268         }
 269     }
 270 }
 271
 272 fn rewrite_struct_pat(
 273     qself: &Option<ptr::P<ast::QSelf>>,
 274     path: &ast::Path,
 275     fields: &[ast::PatField],
 276     ellipsis: bool,
 277     span: Span,
 278     context: &RewriteContext<'_>,
 279     shape: Shape,
 280 ) -> Option<String> {
 281     // 2 =  ` {`
 282     let path_shape = shape.sub_width(2)?;
 283     let path_str = rewrite_path(context, PathContext::Expr, qself, path, path_shape)?;
 284
 285     if fields.is_empty() && !ellipsis {
 286         return Some(format!("{} {{}}", path_str));
 287     }
 288
 289     let (ellipsis_str, terminator) = if ellipsis { (", ..", "..") } else { ("", "}") };
 290
 291     // 3 = ` { `, 2 = ` }`.
 292     let (h_shape, v_shape) =
 293         struct_lit_shape(shape, context, path_str.len() + 3, ellipsis_str.len() + 2)?;
 294
 295     let items = itemize_list(
 296         context.snippet_provider,
 297         fields.iter(),
 298         terminator,
 299         ",",
 300         |f| {
 301             if f.attrs.is_empty() {
 302                 f.span.lo()
 303             } else {
 304                 f.attrs.first().unwrap().span.lo()
 305             }
 306         },
 307         |f| f.span.hi(),
 308         |f| f.rewrite(context, v_shape),
 309         context.snippet_provider.span_after(span, "{"),
 310         span.hi(),
 311         false,
 312     );
 313     let item_vec = items.collect::<Vec<_>>();
 314
 315     let tactic = struct_lit_tactic(h_shape, context, &item_vec);
 316     let nested_shape = shape_for_tactic(tactic, h_shape, v_shape);
 317     let fmt = struct_lit_formatting(nested_shape, tactic, context, false);
 318
 319     let mut fields_str = write_list(&item_vec, &fmt)?;
 320     let one_line_width = h_shape.map_or(0, |shape| shape.width);
 321
 322     let has_trailing_comma = fmt.needs_trailing_separator();
 323
 324     if ellipsis {
 325         if fields_str.contains('\n') || fields_str.len() > one_line_width {
 326             // Add a missing trailing comma.
 327             if !has_trailing_comma {
 328                 fields_str.push(',');
 329             }
 330             fields_str.push('\n');
 331             fields_str.push_str(&nested_shape.indent.to_string(context.config));
 332         } else {
 333             if !fields_str.is_empty() {
 334                 // there are preceding struct fields being matched on
 335                 if has_trailing_comma {
 336                     fields_str.push(' ');
 337                 } else {
 338                     fields_str.push_str(", ");
 339                 }
 340             }
 341         }
 342         fields_str.push_str("..");
 343     }
 344
 345     // ast::Pat doesn't have attrs so use &[]
 346     let fields_str = wrap_struct_field(context, &[], &fields_str, shape, v_shape, one_line_width)?;
 347     Some(format!("{} {{{}}}", path_str, fields_str))
 348 }
 349
 350 impl Rewrite for PatField {
 351     fn rewrite(&self, context: &RewriteContext<'_>, shape: Shape) -> Option<String> {
 352         let hi_pos = if let Some(last) = self.attrs.last() {
 353             last.span.hi()
 354         } else {
 355             self.pat.span.lo()
 356         };
 357
 358         let attrs_str = if self.attrs.is_empty() {
 359             String::from("")
 360         } else {
 361             self.attrs.rewrite(context, shape)?
 362         };
 363
 364         let pat_str = self.pat.rewrite(context, shape)?;
 365         if self.is_shorthand {
 366             combine_strs_with_missing_comments(
 367                 context,
 368                 &attrs_str,
 369                 &pat_str,
 370                 mk_sp(hi_pos, self.pat.span.lo()),
 371                 shape,
 372                 false,
 373             )
 374         } else {
 375             let nested_shape = shape.block_indent(context.config.tab_spaces());
 376             let id_str = rewrite_ident(context, self.ident);
 377             let one_line_width = id_str.len() + 2 + pat_str.len();
 378             let pat_and_id_str = if one_line_width <= shape.width {
 379                 format!("{}: {}", id_str, pat_str)
 380             } else {
 381                 format!(
 382                     "{}:\n{}{}",
 383                     id_str,
 384                     nested_shape.indent.to_string(context.config),
 385                     self.pat.rewrite(context, nested_shape)?
 386                 )
 387             };
 388             combine_strs_with_missing_comments(
 389                 context,
 390                 &attrs_str,
 391                 &pat_and_id_str,
 392                 mk_sp(hi_pos, self.pat.span.lo()),
 393                 nested_shape,
 394                 false,
 395             )
 396         }
 397     }
 398 }
 399
 400 #[derive(Debug)]
 401 pub(crate) enum TuplePatField<'a> {
 402     Pat(&'a ptr::P<ast::Pat>),
 403     Dotdot(Span),
 404 }
 405
 406 impl<'a> Rewrite for TuplePatField<'a> {
 407     fn rewrite(&self, context: &RewriteContext<'_>, shape: Shape) -> Option<String> {
 408         match *self {
 409             TuplePatField::Pat(p) => p.rewrite(context, shape),
 410             TuplePatField::Dotdot(_) => Some("..".to_string()),
 411         }
 412     }
 413 }
 414
 415 impl<'a> Spanned for TuplePatField<'a> {
 416     fn span(&self) -> Span {
 417         match *self {
 418             TuplePatField::Pat(p) => p.span(),
 419             TuplePatField::Dotdot(span) => span,
 420         }
 421     }
 422 }
 423
 424 impl<'a> TuplePatField<'a> {
 425     fn is_dotdot(&self) -> bool {
 426         match self {
 427             TuplePatField::Pat(pat) => matches!(pat.kind, ast::PatKind::Rest),
 428             TuplePatField::Dotdot(_) => true,
 429         }
 430     }
 431 }
 432
 433 pub(crate) fn can_be_overflowed_pat(
 434     context: &RewriteContext<'_>,
 435     pat: &TuplePatField<'_>,
 436     len: usize,
 437 ) -> bool {
 438     match *pat {
 439         TuplePatField::Pat(pat) => match pat.kind {
 440             ast::PatKind::Path(..)
 441             | ast::PatKind::Tuple(..)
 442             | ast::PatKind::Struct(..)
 443             | ast::PatKind::TupleStruct(..) => context.use_block_indent() && len == 1,
 444             ast::PatKind::Ref(ref p, _) | ast::PatKind::Box(ref p) => {
 445                 can_be_overflowed_pat(context, &TuplePatField::Pat(p), len)
 446             }
 447             ast::PatKind::Lit(ref expr) => can_be_overflowed_expr(context, expr, len),
 448             _ => false,
 449         },
 450         TuplePatField::Dotdot(..) => false,
 451     }
 452 }
 453
 454 fn rewrite_tuple_pat(
 455     pats: &[ptr::P<ast::Pat>],
 456     path_str: Option<String>,
 457     span: Span,
 458     context: &RewriteContext<'_>,
 459     shape: Shape,
 460 ) -> Option<String> {
 461     if pats.is_empty() {
 462         return Some(format!("{}()", path_str.unwrap_or_default()));
 463     }
 464     let mut pat_vec: Vec<_> = pats.iter().map(TuplePatField::Pat).collect();
 465
 466     let wildcard_suffix_len = count_wildcard_suffix_len(context, &pat_vec, span, shape);
 467     let (pat_vec, span) = if context.config.condense_wildcard_suffixes() && wildcard_suffix_len >= 2
 468     {
 469         let new_item_count = 1 + pat_vec.len() - wildcard_suffix_len;
 470         let sp = pat_vec[new_item_count - 1].span();
 471         let snippet = context.snippet(sp);
 472         let lo = sp.lo() + BytePos(snippet.find_uncommented("_").unwrap() as u32);
 473         pat_vec[new_item_count - 1] = TuplePatField::Dotdot(mk_sp_lo_plus_one(lo));
 474         (
 475             &pat_vec[..new_item_count],
 476             mk_sp(span.lo(), lo + BytePos(1)),
 477         )
 478     } else {
 479         (&pat_vec[..], span)
 480     };
 481
 482     let is_last_pat_dotdot = pat_vec.last().map_or(false, |p| p.is_dotdot());
 483     let add_comma = path_str.is_none() && pat_vec.len() == 1 && !is_last_pat_dotdot;
 484     let path_str = path_str.unwrap_or_default();
 485
 486     overflow::rewrite_with_parens(
 487         context,
 488         &path_str,
 489         pat_vec.iter(),
 490         shape,
 491         span,
 492         context.config.max_width(),
 493         if add_comma {
 494             Some(SeparatorTactic::Always)
 495         } else {
 496             None
 497         },
 498     )
 499 }
 500
 501 fn count_wildcard_suffix_len(
 502     context: &RewriteContext<'_>,
 503     patterns: &[TuplePatField<'_>],
 504     span: Span,
 505     shape: Shape,
 506 ) -> usize {
 507     let mut suffix_len = 0;
 508
 509     let items: Vec<_> = itemize_list(
 510         context.snippet_provider,
 511         patterns.iter(),
 512         ")",
 513         ",",
 514         |item| item.span().lo(),
 515         |item| item.span().hi(),
 516         |item| item.rewrite(context, shape),
 517         context.snippet_provider.span_after(span, "("),
 518         span.hi() - BytePos(1),
 519         false,
 520     )
 521     .collect();
 522
 523     for item in items
 524         .iter()
 525         .rev()
 526         .take_while(|i| matches!(i.item, Some(ref internal_string) if internal_string == "_"))
 527     {
 528         suffix_len += 1;
 529
 530         if item.has_comment() {
 531             break;
 532         }
 533     }
 534
 535     suffix_len
 536 }