rustfmt_nightly/
patterns.rs

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1use rustc_ast::ast::{self, BindingMode, ByRef, Pat, PatField, PatKind, RangeEnd, RangeSyntax};
2use rustc_ast::ptr;
3use rustc_span::{BytePos, Span};
4
5use crate::comment::{FindUncommented, combine_strs_with_missing_comments};
6use crate::config::StyleEdition;
7use crate::config::lists::*;
8use crate::expr::{can_be_overflowed_expr, rewrite_unary_prefix, wrap_struct_field};
9use crate::lists::{
10    ListFormatting, ListItem, Separator, definitive_tactic, itemize_list, shape_for_tactic,
11    struct_lit_formatting, struct_lit_shape, struct_lit_tactic, write_list,
12};
13use crate::macros::{MacroPosition, rewrite_macro};
14use crate::overflow;
15use crate::pairs::{PairParts, rewrite_pair};
16use crate::rewrite::{Rewrite, RewriteContext, RewriteError, RewriteErrorExt, RewriteResult};
17use crate::shape::Shape;
18use crate::source_map::SpanUtils;
19use crate::spanned::Spanned;
20use crate::types::{PathContext, rewrite_path};
21use crate::utils::{format_mutability, mk_sp, mk_sp_lo_plus_one, rewrite_ident};
22
23/// Returns `true` if the given pattern is "short".
24/// A short pattern is defined by the following grammar:
25///
26/// `[small, ntp]`:
27///     - single token
28///     - `&[single-line, ntp]`
29///
30/// `[small]`:
31///     - `[small, ntp]`
32///     - unary tuple constructor `([small, ntp])`
33///     - `&[small]`
34pub(crate) fn is_short_pattern(
35    context: &RewriteContext<'_>,
36    pat: &ast::Pat,
37    pat_str: &str,
38) -> bool {
39    // We also require that the pattern is reasonably 'small' with its literal width.
40    pat_str.len() <= 20 && !pat_str.contains('\n') && is_short_pattern_inner(context, pat)
41}
42
43fn is_short_pattern_inner(context: &RewriteContext<'_>, pat: &ast::Pat) -> bool {
44    match &pat.kind {
45        ast::PatKind::Rest | ast::PatKind::Never | ast::PatKind::Wild | ast::PatKind::Err(_) => {
46            true
47        }
48        ast::PatKind::Expr(expr) => match &expr.kind {
49            ast::ExprKind::Lit(_) => true,
50            ast::ExprKind::Unary(ast::UnOp::Neg, expr) => match &expr.kind {
51                ast::ExprKind::Lit(_) => true,
52                _ => unreachable!(),
53            },
54            ast::ExprKind::ConstBlock(_) | ast::ExprKind::Path(..) => {
55                context.config.style_edition() <= StyleEdition::Edition2024
56            }
57            _ => unreachable!(),
58        },
59        ast::PatKind::Ident(_, _, ref pat) => pat.is_none(),
60        ast::PatKind::Struct(..)
61        | ast::PatKind::MacCall(..)
62        | ast::PatKind::Slice(..)
63        | ast::PatKind::Path(..)
64        | ast::PatKind::Range(..)
65        | ast::PatKind::Guard(..) => false,
66        ast::PatKind::Tuple(ref subpats) => subpats.len() <= 1,
67        ast::PatKind::TupleStruct(_, ref path, ref subpats) => {
68            path.segments.len() <= 1 && subpats.len() <= 1
69        }
70        ast::PatKind::Box(ref p)
71        | PatKind::Deref(ref p)
72        | ast::PatKind::Ref(ref p, _)
73        | ast::PatKind::Paren(ref p) => is_short_pattern_inner(context, &*p),
74        PatKind::Or(ref pats) => pats.iter().all(|p| is_short_pattern_inner(context, p)),
75    }
76}
77
78pub(crate) struct RangeOperand<'a, T> {
79    pub operand: &'a Option<ptr::P<T>>,
80    pub span: Span,
81}
82
83impl<'a, T: Rewrite> Rewrite for RangeOperand<'a, T> {
84    fn rewrite(&self, context: &RewriteContext<'_>, shape: Shape) -> Option<String> {
85        self.rewrite_result(context, shape).ok()
86    }
87
88    fn rewrite_result(&self, context: &RewriteContext<'_>, shape: Shape) -> RewriteResult {
89        match &self.operand {
90            None => Ok("".to_owned()),
91            Some(ref exp) => exp.rewrite_result(context, shape),
92        }
93    }
94}
95
96impl Rewrite for Pat {
97    fn rewrite(&self, context: &RewriteContext<'_>, shape: Shape) -> Option<String> {
98        self.rewrite_result(context, shape).ok()
99    }
100
101    fn rewrite_result(&self, context: &RewriteContext<'_>, shape: Shape) -> RewriteResult {
102        match self.kind {
103            PatKind::Or(ref pats) => {
104                let pat_strs = pats
105                    .iter()
106                    .map(|p| p.rewrite_result(context, shape))
107                    .collect::<Result<Vec<_>, RewriteError>>()?;
108
109                let use_mixed_layout = pats
110                    .iter()
111                    .zip(pat_strs.iter())
112                    .all(|(pat, pat_str)| is_short_pattern(context, pat, pat_str));
113                let items: Vec<_> = pat_strs.into_iter().map(ListItem::from_str).collect();
114                let tactic = if use_mixed_layout {
115                    DefinitiveListTactic::Mixed
116                } else {
117                    definitive_tactic(
118                        &items,
119                        ListTactic::HorizontalVertical,
120                        Separator::VerticalBar,
121                        shape.width,
122                    )
123                };
124                let fmt = ListFormatting::new(shape, context.config)
125                    .tactic(tactic)
126                    .separator(" |")
127                    .separator_place(context.config.binop_separator())
128                    .ends_with_newline(false);
129                write_list(&items, &fmt)
130            }
131            PatKind::Box(ref pat) => rewrite_unary_prefix(context, "box ", &**pat, shape),
132            PatKind::Ident(BindingMode(by_ref, mutability), ident, ref sub_pat) => {
133                let mut_prefix = format_mutability(mutability).trim();
134
135                let (ref_kw, mut_infix) = match by_ref {
136                    ByRef::Yes(rmutbl) => ("ref", format_mutability(rmutbl).trim()),
137                    ByRef::No => ("", ""),
138                };
139                let id_str = rewrite_ident(context, ident);
140                let sub_pat = match *sub_pat {
141                    Some(ref p) => {
142                        // 2 - `@ `.
143                        let width = shape
144                            .width
145                            .checked_sub(
146                                mut_prefix.len()
147                                    + ref_kw.len()
148                                    + mut_infix.len()
149                                    + id_str.len()
150                                    + 2,
151                            )
152                            .max_width_error(shape.width, p.span())?;
153                        let lo = context.snippet_provider.span_after(self.span, "@");
154                        combine_strs_with_missing_comments(
155                            context,
156                            "@",
157                            &p.rewrite_result(context, Shape::legacy(width, shape.indent))?,
158                            mk_sp(lo, p.span.lo()),
159                            shape,
160                            true,
161                        )?
162                    }
163                    None => "".to_owned(),
164                };
165
166                // combine prefix and ref
167                let (first_lo, first) = match (mut_prefix.is_empty(), ref_kw.is_empty()) {
168                    (false, false) => {
169                        let lo = context.snippet_provider.span_after(self.span, "mut");
170                        let hi = context.snippet_provider.span_before(self.span, "ref");
171                        (
172                            context.snippet_provider.span_after(self.span, "ref"),
173                            combine_strs_with_missing_comments(
174                                context,
175                                mut_prefix,
176                                ref_kw,
177                                mk_sp(lo, hi),
178                                shape,
179                                true,
180                            )?,
181                        )
182                    }
183                    (false, true) => (
184                        context.snippet_provider.span_after(self.span, "mut"),
185                        mut_prefix.to_owned(),
186                    ),
187                    (true, false) => (
188                        context.snippet_provider.span_after(self.span, "ref"),
189                        ref_kw.to_owned(),
190                    ),
191                    (true, true) => (self.span.lo(), "".to_owned()),
192                };
193
194                // combine result of above and mut
195                let (second_lo, second) = match (first.is_empty(), mut_infix.is_empty()) {
196                    (false, false) => {
197                        let lo = context.snippet_provider.span_after(self.span, "ref");
198                        let end_span = mk_sp(first_lo, self.span.hi());
199                        let hi = context.snippet_provider.span_before(end_span, "mut");
200                        (
201                            context.snippet_provider.span_after(end_span, "mut"),
202                            combine_strs_with_missing_comments(
203                                context,
204                                &first,
205                                mut_infix,
206                                mk_sp(lo, hi),
207                                shape,
208                                true,
209                            )?,
210                        )
211                    }
212                    (false, true) => (first_lo, first),
213                    (true, false) => unreachable!("mut_infix necessarily follows a ref"),
214                    (true, true) => (self.span.lo(), "".to_owned()),
215                };
216
217                let next = if !sub_pat.is_empty() {
218                    let hi = context.snippet_provider.span_before(self.span, "@");
219                    combine_strs_with_missing_comments(
220                        context,
221                        id_str,
222                        &sub_pat,
223                        mk_sp(ident.span.hi(), hi),
224                        shape,
225                        true,
226                    )?
227                } else {
228                    id_str.to_owned()
229                };
230
231                combine_strs_with_missing_comments(
232                    context,
233                    &second,
234                    &next,
235                    mk_sp(second_lo, ident.span.lo()),
236                    shape,
237                    true,
238                )
239            }
240            PatKind::Wild => {
241                if 1 <= shape.width {
242                    Ok("_".to_owned())
243                } else {
244                    Err(RewriteError::ExceedsMaxWidth {
245                        configured_width: 1,
246                        span: self.span,
247                    })
248                }
249            }
250            PatKind::Rest => {
251                if 1 <= shape.width {
252                    Ok("..".to_owned())
253                } else {
254                    Err(RewriteError::ExceedsMaxWidth {
255                        configured_width: 1,
256                        span: self.span,
257                    })
258                }
259            }
260            PatKind::Never => Err(RewriteError::Unknown),
261            PatKind::Range(ref lhs, ref rhs, ref end_kind) => {
262                rewrite_range_pat(context, shape, lhs, rhs, end_kind, self.span)
263            }
264            PatKind::Ref(ref pat, mutability) => {
265                let prefix = format!("&{}", format_mutability(mutability));
266                rewrite_unary_prefix(context, &prefix, &**pat, shape)
267            }
268            PatKind::Tuple(ref items) => rewrite_tuple_pat(items, None, self.span, context, shape),
269            PatKind::Path(ref q_self, ref path) => {
270                rewrite_path(context, PathContext::Expr, q_self, path, shape)
271            }
272            PatKind::TupleStruct(ref q_self, ref path, ref pat_vec) => {
273                let path_str = rewrite_path(context, PathContext::Expr, q_self, path, shape)?;
274                rewrite_tuple_pat(pat_vec, Some(path_str), self.span, context, shape)
275            }
276            PatKind::Expr(ref expr) => expr.rewrite_result(context, shape),
277            PatKind::Slice(ref slice_pat)
278                if context.config.style_edition() <= StyleEdition::Edition2021 =>
279            {
280                let rw: Vec<String> = slice_pat
281                    .iter()
282                    .map(|p| {
283                        if let Ok(rw) = p.rewrite_result(context, shape) {
284                            rw
285                        } else {
286                            context.snippet(p.span).to_string()
287                        }
288                    })
289                    .collect();
290                Ok(format!("[{}]", rw.join(", ")))
291            }
292            PatKind::Slice(ref slice_pat) => overflow::rewrite_with_square_brackets(
293                context,
294                "",
295                slice_pat.iter(),
296                shape,
297                self.span,
298                None,
299                None,
300            ),
301            PatKind::Struct(ref qself, ref path, ref fields, rest) => rewrite_struct_pat(
302                qself,
303                path,
304                fields,
305                rest == ast::PatFieldsRest::Rest,
306                self.span,
307                context,
308                shape,
309            ),
310            PatKind::MacCall(ref mac) => {
311                rewrite_macro(mac, None, context, shape, MacroPosition::Pat)
312            }
313            PatKind::Paren(ref pat) => pat
314                .rewrite_result(
315                    context,
316                    shape
317                        .offset_left(1)
318                        .and_then(|s| s.sub_width(1))
319                        .max_width_error(shape.width, self.span)?,
320                )
321                .map(|inner_pat| format!("({})", inner_pat)),
322            PatKind::Guard(..) => Ok(context.snippet(self.span).to_string()),
323            PatKind::Deref(_) => Err(RewriteError::Unknown),
324            PatKind::Err(_) => Err(RewriteError::Unknown),
325        }
326    }
327}
328
329pub fn rewrite_range_pat<T: Rewrite>(
330    context: &RewriteContext<'_>,
331    shape: Shape,
332    lhs: &Option<ptr::P<T>>,
333    rhs: &Option<ptr::P<T>>,
334    end_kind: &rustc_span::source_map::Spanned<RangeEnd>,
335    span: Span,
336) -> RewriteResult {
337    let infix = match end_kind.node {
338        RangeEnd::Included(RangeSyntax::DotDotDot) => "...",
339        RangeEnd::Included(RangeSyntax::DotDotEq) => "..=",
340        RangeEnd::Excluded => "..",
341    };
342    let infix = if context.config.spaces_around_ranges() {
343        let lhs_spacing = match lhs {
344            None => "",
345            Some(_) => " ",
346        };
347        let rhs_spacing = match rhs {
348            None => "",
349            Some(_) => " ",
350        };
351        format!("{lhs_spacing}{infix}{rhs_spacing}")
352    } else {
353        infix.to_owned()
354    };
355    let lspan = span.with_hi(end_kind.span.lo());
356    let rspan = span.with_lo(end_kind.span.hi());
357    rewrite_pair(
358        &RangeOperand {
359            operand: lhs,
360            span: lspan,
361        },
362        &RangeOperand {
363            operand: rhs,
364            span: rspan,
365        },
366        PairParts::infix(&infix),
367        context,
368        shape,
369        SeparatorPlace::Front,
370    )
371}
372
373fn rewrite_struct_pat(
374    qself: &Option<ptr::P<ast::QSelf>>,
375    path: &ast::Path,
376    fields: &[ast::PatField],
377    ellipsis: bool,
378    span: Span,
379    context: &RewriteContext<'_>,
380    shape: Shape,
381) -> RewriteResult {
382    // 2 =  ` {`
383    let path_shape = shape.sub_width(2).max_width_error(shape.width, span)?;
384    let path_str = rewrite_path(context, PathContext::Expr, qself, path, path_shape)?;
385
386    if fields.is_empty() && !ellipsis {
387        return Ok(format!("{path_str} {{}}"));
388    }
389
390    let (ellipsis_str, terminator) = if ellipsis { (", ..", "..") } else { ("", "}") };
391
392    // 3 = ` { `, 2 = ` }`.
393    let (h_shape, v_shape) =
394        struct_lit_shape(shape, context, path_str.len() + 3, ellipsis_str.len() + 2)
395            .max_width_error(shape.width, span)?;
396
397    let items = itemize_list(
398        context.snippet_provider,
399        fields.iter(),
400        terminator,
401        ",",
402        |f| {
403            if f.attrs.is_empty() {
404                f.span.lo()
405            } else {
406                f.attrs.first().unwrap().span.lo()
407            }
408        },
409        |f| f.span.hi(),
410        |f| f.rewrite_result(context, v_shape),
411        context.snippet_provider.span_after(span, "{"),
412        span.hi(),
413        false,
414    );
415    let item_vec = items.collect::<Vec<_>>();
416
417    let tactic = struct_lit_tactic(h_shape, context, &item_vec);
418    let nested_shape = shape_for_tactic(tactic, h_shape, v_shape);
419    let fmt = struct_lit_formatting(nested_shape, tactic, context, false);
420
421    let mut fields_str = write_list(&item_vec, &fmt)?;
422    let one_line_width = h_shape.map_or(0, |shape| shape.width);
423
424    let has_trailing_comma = fmt.needs_trailing_separator();
425
426    if ellipsis {
427        if fields_str.contains('\n') || fields_str.len() > one_line_width {
428            // Add a missing trailing comma.
429            if !has_trailing_comma {
430                fields_str.push(',');
431            }
432            fields_str.push('\n');
433            fields_str.push_str(&nested_shape.indent.to_string(context.config));
434        } else {
435            if !fields_str.is_empty() {
436                // there are preceding struct fields being matched on
437                if has_trailing_comma {
438                    fields_str.push(' ');
439                } else {
440                    fields_str.push_str(", ");
441                }
442            }
443        }
444        fields_str.push_str("..");
445    }
446
447    // ast::Pat doesn't have attrs so use &[]
448    let fields_str = wrap_struct_field(context, &[], &fields_str, shape, v_shape, one_line_width)?;
449    Ok(format!("{path_str} {{{fields_str}}}"))
450}
451
452impl Rewrite for PatField {
453    fn rewrite(&self, context: &RewriteContext<'_>, shape: Shape) -> Option<String> {
454        self.rewrite_result(context, shape).ok()
455    }
456
457    fn rewrite_result(&self, context: &RewriteContext<'_>, shape: Shape) -> RewriteResult {
458        let hi_pos = if let Some(last) = self.attrs.last() {
459            last.span.hi()
460        } else {
461            self.pat.span.lo()
462        };
463
464        let attrs_str = if self.attrs.is_empty() {
465            String::from("")
466        } else {
467            self.attrs.rewrite_result(context, shape)?
468        };
469
470        let pat_str = self.pat.rewrite_result(context, shape)?;
471        if self.is_shorthand {
472            combine_strs_with_missing_comments(
473                context,
474                &attrs_str,
475                &pat_str,
476                mk_sp(hi_pos, self.pat.span.lo()),
477                shape,
478                false,
479            )
480        } else {
481            let nested_shape = shape.block_indent(context.config.tab_spaces());
482            let id_str = rewrite_ident(context, self.ident);
483            let one_line_width = id_str.len() + 2 + pat_str.len();
484            let pat_and_id_str = if one_line_width <= shape.width {
485                format!("{id_str}: {pat_str}")
486            } else {
487                format!(
488                    "{}:\n{}{}",
489                    id_str,
490                    nested_shape.indent.to_string(context.config),
491                    self.pat.rewrite_result(context, nested_shape)?
492                )
493            };
494            combine_strs_with_missing_comments(
495                context,
496                &attrs_str,
497                &pat_and_id_str,
498                mk_sp(hi_pos, self.pat.span.lo()),
499                nested_shape,
500                false,
501            )
502        }
503    }
504}
505
506#[derive(Debug)]
507pub(crate) enum TuplePatField<'a> {
508    Pat(&'a ptr::P<ast::Pat>),
509    Dotdot(Span),
510}
511
512impl<'a> Rewrite for TuplePatField<'a> {
513    fn rewrite(&self, context: &RewriteContext<'_>, shape: Shape) -> Option<String> {
514        self.rewrite_result(context, shape).ok()
515    }
516
517    fn rewrite_result(&self, context: &RewriteContext<'_>, shape: Shape) -> RewriteResult {
518        match *self {
519            TuplePatField::Pat(p) => p.rewrite_result(context, shape),
520            TuplePatField::Dotdot(_) => Ok("..".to_string()),
521        }
522    }
523}
524
525impl<'a> Spanned for TuplePatField<'a> {
526    fn span(&self) -> Span {
527        match *self {
528            TuplePatField::Pat(p) => p.span(),
529            TuplePatField::Dotdot(span) => span,
530        }
531    }
532}
533
534impl<'a> TuplePatField<'a> {
535    fn is_dotdot(&self) -> bool {
536        match self {
537            TuplePatField::Pat(pat) => matches!(pat.kind, ast::PatKind::Rest),
538            TuplePatField::Dotdot(_) => true,
539        }
540    }
541}
542
543pub(crate) fn can_be_overflowed_pat(
544    context: &RewriteContext<'_>,
545    pat: &TuplePatField<'_>,
546    len: usize,
547) -> bool {
548    match *pat {
549        TuplePatField::Pat(pat) => match pat.kind {
550            ast::PatKind::Path(..)
551            | ast::PatKind::Tuple(..)
552            | ast::PatKind::Struct(..)
553            | ast::PatKind::TupleStruct(..) => context.use_block_indent() && len == 1,
554            ast::PatKind::Ref(ref p, _) | ast::PatKind::Box(ref p) => {
555                can_be_overflowed_pat(context, &TuplePatField::Pat(p), len)
556            }
557            ast::PatKind::Expr(ref expr) => can_be_overflowed_expr(context, expr, len),
558            _ => false,
559        },
560        TuplePatField::Dotdot(..) => false,
561    }
562}
563
564fn rewrite_tuple_pat(
565    pats: &[ptr::P<ast::Pat>],
566    path_str: Option<String>,
567    span: Span,
568    context: &RewriteContext<'_>,
569    shape: Shape,
570) -> RewriteResult {
571    if pats.is_empty() {
572        return Ok(format!("{}()", path_str.unwrap_or_default()));
573    }
574    let mut pat_vec: Vec<_> = pats.iter().map(TuplePatField::Pat).collect();
575
576    let wildcard_suffix_len = count_wildcard_suffix_len(context, &pat_vec, span, shape);
577    let (pat_vec, span) = if context.config.condense_wildcard_suffixes() && wildcard_suffix_len >= 2
578    {
579        let new_item_count = 1 + pat_vec.len() - wildcard_suffix_len;
580        let sp = pat_vec[new_item_count - 1].span();
581        let snippet = context.snippet(sp);
582        let lo = sp.lo() + BytePos(snippet.find_uncommented("_").unwrap() as u32);
583        pat_vec[new_item_count - 1] = TuplePatField::Dotdot(mk_sp_lo_plus_one(lo));
584        (
585            &pat_vec[..new_item_count],
586            mk_sp(span.lo(), lo + BytePos(1)),
587        )
588    } else {
589        (&pat_vec[..], span)
590    };
591
592    let is_last_pat_dotdot = pat_vec.last().map_or(false, |p| p.is_dotdot());
593    let add_comma = path_str.is_none() && pat_vec.len() == 1 && !is_last_pat_dotdot;
594    let path_str = path_str.unwrap_or_default();
595
596    overflow::rewrite_with_parens(
597        context,
598        &path_str,
599        pat_vec.iter(),
600        shape,
601        span,
602        context.config.max_width(),
603        if add_comma {
604            Some(SeparatorTactic::Always)
605        } else {
606            None
607        },
608    )
609}
610
611fn count_wildcard_suffix_len(
612    context: &RewriteContext<'_>,
613    patterns: &[TuplePatField<'_>],
614    span: Span,
615    shape: Shape,
616) -> usize {
617    let mut suffix_len = 0;
618
619    let items: Vec<_> = itemize_list(
620        context.snippet_provider,
621        patterns.iter(),
622        ")",
623        ",",
624        |item| item.span().lo(),
625        |item| item.span().hi(),
626        |item| item.rewrite_result(context, shape),
627        context.snippet_provider.span_after(span, "("),
628        span.hi() - BytePos(1),
629        false,
630    )
631    .collect();
632
633    for item in items
634        .iter()
635        .rev()
636        .take_while(|i| matches!(i.item, Ok(ref internal_string) if internal_string == "_"))
637    {
638        suffix_len += 1;
639
640        if item.has_comment() {
641            break;
642        }
643    }
644
645    suffix_len
646}
rustfmt_nightly/patterns.rs

rustfmt_nightly/
patterns.rs
