src/patterns.rs

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