src/patterns.rs

   1 use rustc_span::{BytePos, Span};
   2 use syntax::ast::{self, BindingMode, FieldPat, Pat, PatKind, RangeEnd, RangeSyntax};
   3 use syntax::ptr;
   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) => rewrite_macro(mac, None, context, shape, MacroPosition::Pat),
 235             PatKind::Paren(ref pat) => pat
 236                 .rewrite(context, shape.offset_left(1)?.sub_width(1)?)
 237                 .map(|inner_pat| format!("({})", inner_pat)),
 238         }
 239     }
 240 }
 241
 242 fn rewrite_struct_pat(
 243     path: &ast::Path,
 244     fields: &[ast::FieldPat],
 245     ellipsis: bool,
 246     span: Span,
 247     context: &RewriteContext<'_>,
 248     shape: Shape,
 249 ) -> Option<String> {
 250     // 2 =  ` {`
 251     let path_shape = shape.sub_width(2)?;
 252     let path_str = rewrite_path(context, PathContext::Expr, None, path, path_shape)?;
 253
 254     if fields.is_empty() && !ellipsis {
 255         return Some(format!("{} {{}}", path_str));
 256     }
 257
 258     let (ellipsis_str, terminator) = if ellipsis { (", ..", "..") } else { ("", "}") };
 259
 260     // 3 = ` { `, 2 = ` }`.
 261     let (h_shape, v_shape) =
 262         struct_lit_shape(shape, context, path_str.len() + 3, ellipsis_str.len() + 2)?;
 263
 264     let items = itemize_list(
 265         context.snippet_provider,
 266         fields.iter(),
 267         terminator,
 268         ",",
 269         |f| {
 270             if f.attrs.is_empty() {
 271                 f.span.lo()
 272             } else {
 273                 f.attrs.first().unwrap().span.lo()
 274             }
 275         },
 276         |f| f.span.hi(),
 277         |f| f.rewrite(context, v_shape),
 278         context.snippet_provider.span_after(span, "{"),
 279         span.hi(),
 280         false,
 281     );
 282     let item_vec = items.collect::<Vec<_>>();
 283
 284     let tactic = struct_lit_tactic(h_shape, context, &item_vec);
 285     let nested_shape = shape_for_tactic(tactic, h_shape, v_shape);
 286     let fmt = struct_lit_formatting(nested_shape, tactic, context, false);
 287
 288     let mut fields_str = write_list(&item_vec, &fmt)?;
 289     let one_line_width = h_shape.map_or(0, |shape| shape.width);
 290
 291     if ellipsis {
 292         if fields_str.contains('\n') || fields_str.len() > one_line_width {
 293             // Add a missing trailing comma.
 294             if context.config.trailing_comma() == SeparatorTactic::Never {
 295                 fields_str.push_str(",");
 296             }
 297             fields_str.push_str("\n");
 298             fields_str.push_str(&nested_shape.indent.to_string(context.config));
 299             fields_str.push_str("..");
 300         } else {
 301             if !fields_str.is_empty() {
 302                 // there are preceding struct fields being matched on
 303                 if tactic == DefinitiveListTactic::Vertical {
 304                     // if the tactic is Vertical, write_list already added a trailing ,
 305                     fields_str.push_str(" ");
 306                 } else {
 307                     fields_str.push_str(", ");
 308                 }
 309             }
 310             fields_str.push_str("..");
 311         }
 312     }
 313
 314     // ast::Pat doesn't have attrs so use &[]
 315     let fields_str = wrap_struct_field(context, &[], &fields_str, shape, v_shape, one_line_width)?;
 316     Some(format!("{} {{{}}}", path_str, fields_str))
 317 }
 318
 319 impl Rewrite for FieldPat {
 320     fn rewrite(&self, context: &RewriteContext<'_>, shape: Shape) -> Option<String> {
 321         let hi_pos = if let Some(last) = self.attrs.last() {
 322             last.span.hi()
 323         } else {
 324             self.pat.span.lo()
 325         };
 326
 327         let attrs_str = if self.attrs.is_empty() {
 328             String::from("")
 329         } else {
 330             self.attrs.rewrite(context, shape)?
 331         };
 332
 333         let pat_str = self.pat.rewrite(context, shape)?;
 334         if self.is_shorthand {
 335             combine_strs_with_missing_comments(
 336                 context,
 337                 &attrs_str,
 338                 &pat_str,
 339                 mk_sp(hi_pos, self.pat.span.lo()),
 340                 shape,
 341                 false,
 342             )
 343         } else {
 344             let nested_shape = shape.block_indent(context.config.tab_spaces());
 345             let id_str = rewrite_ident(context, self.ident);
 346             let one_line_width = id_str.len() + 2 + pat_str.len();
 347             let pat_and_id_str = if one_line_width <= shape.width {
 348                 format!("{}: {}", id_str, pat_str)
 349             } else {
 350                 format!(
 351                     "{}:\n{}{}",
 352                     id_str,
 353                     nested_shape.indent.to_string(context.config),
 354                     self.pat.rewrite(context, nested_shape)?
 355                 )
 356             };
 357             combine_strs_with_missing_comments(
 358                 context,
 359                 &attrs_str,
 360                 &pat_and_id_str,
 361                 mk_sp(hi_pos, self.pat.span.lo()),
 362                 nested_shape,
 363                 false,
 364             )
 365         }
 366     }
 367 }
 368
 369 #[derive(Debug)]
 370 pub(crate) enum TuplePatField<'a> {
 371     Pat(&'a ptr::P<ast::Pat>),
 372     Dotdot(Span),
 373 }
 374
 375 impl<'a> Rewrite for TuplePatField<'a> {
 376     fn rewrite(&self, context: &RewriteContext<'_>, shape: Shape) -> Option<String> {
 377         match *self {
 378             TuplePatField::Pat(p) => p.rewrite(context, shape),
 379             TuplePatField::Dotdot(_) => Some("..".to_string()),
 380         }
 381     }
 382 }
 383
 384 impl<'a> Spanned for TuplePatField<'a> {
 385     fn span(&self) -> Span {
 386         match *self {
 387             TuplePatField::Pat(p) => p.span(),
 388             TuplePatField::Dotdot(span) => span,
 389         }
 390     }
 391 }
 392
 393 impl<'a> TuplePatField<'a> {
 394     fn is_dotdot(&self) -> bool {
 395         match self {
 396             TuplePatField::Pat(pat) => match pat.kind {
 397                 ast::PatKind::Rest => true,
 398                 _ => false,
 399             },
 400             TuplePatField::Dotdot(_) => true,
 401         }
 402     }
 403 }
 404
 405 pub(crate) fn can_be_overflowed_pat(
 406     context: &RewriteContext<'_>,
 407     pat: &TuplePatField<'_>,
 408     len: usize,
 409 ) -> bool {
 410     match *pat {
 411         TuplePatField::Pat(pat) => match pat.kind {
 412             ast::PatKind::Path(..)
 413             | ast::PatKind::Tuple(..)
 414             | ast::PatKind::Struct(..)
 415             | ast::PatKind::TupleStruct(..) => context.use_block_indent() && len == 1,
 416             ast::PatKind::Ref(ref p, _) | ast::PatKind::Box(ref p) => {
 417                 can_be_overflowed_pat(context, &TuplePatField::Pat(p), len)
 418             }
 419             ast::PatKind::Lit(ref expr) => can_be_overflowed_expr(context, expr, len),
 420             _ => false,
 421         },
 422         TuplePatField::Dotdot(..) => false,
 423     }
 424 }
 425
 426 fn rewrite_tuple_pat(
 427     pats: &[ptr::P<ast::Pat>],
 428     path_str: Option<String>,
 429     span: Span,
 430     context: &RewriteContext<'_>,
 431     shape: Shape,
 432 ) -> Option<String> {
 433     let mut pat_vec: Vec<_> = pats.iter().map(|x| TuplePatField::Pat(x)).collect();
 434
 435     if pat_vec.is_empty() {
 436         return Some(format!("{}()", path_str.unwrap_or_default()));
 437     }
 438     let wildcard_suffix_len = count_wildcard_suffix_len(context, &pat_vec, span, shape);
 439     let (pat_vec, span) = if context.config.condense_wildcard_suffixes() && wildcard_suffix_len >= 2
 440     {
 441         let new_item_count = 1 + pat_vec.len() - wildcard_suffix_len;
 442         let sp = pat_vec[new_item_count - 1].span();
 443         let snippet = context.snippet(sp);
 444         let lo = sp.lo() + BytePos(snippet.find_uncommented("_").unwrap() as u32);
 445         pat_vec[new_item_count - 1] = TuplePatField::Dotdot(mk_sp(lo, lo + BytePos(1)));
 446         (
 447             &pat_vec[..new_item_count],
 448             mk_sp(span.lo(), lo + BytePos(1)),
 449         )
 450     } else {
 451         (&pat_vec[..], span)
 452     };
 453
 454     let is_last_pat_dotdot = pat_vec.last().map_or(false, |p| p.is_dotdot());
 455     let add_comma = path_str.is_none() && pat_vec.len() == 1 && !is_last_pat_dotdot;
 456     let path_str = path_str.unwrap_or_default();
 457
 458     overflow::rewrite_with_parens(
 459         &context,
 460         &path_str,
 461         pat_vec.iter(),
 462         shape,
 463         span,
 464         context.config.max_width(),
 465         if add_comma {
 466             Some(SeparatorTactic::Always)
 467         } else {
 468             None
 469         },
 470     )
 471 }
 472
 473 fn count_wildcard_suffix_len(
 474     context: &RewriteContext<'_>,
 475     patterns: &[TuplePatField<'_>],
 476     span: Span,
 477     shape: Shape,
 478 ) -> usize {
 479     let mut suffix_len = 0;
 480
 481     let items: Vec<_> = itemize_list(
 482         context.snippet_provider,
 483         patterns.iter(),
 484         ")",
 485         ",",
 486         |item| item.span().lo(),
 487         |item| item.span().hi(),
 488         |item| item.rewrite(context, shape),
 489         context.snippet_provider.span_after(span, "("),
 490         span.hi() - BytePos(1),
 491         false,
 492     )
 493     .collect();
 494
 495     for item in items.iter().rev().take_while(|i| match i.item {
 496         Some(ref internal_string) if internal_string == "_" => true,
 497         _ => false,
 498     }) {
 499         suffix_len += 1;
 500
 501         if item.has_comment() {
 502             break;
 503         }
 504     }
 505
 506     suffix_len
 507 }