src/patterns.rs

   1 use syntax::ast::{self, BindingMode, FieldPat, Pat, PatKind, RangeEnd, RangeSyntax};
   2 use syntax::ptr;
   3 use syntax::source_map::{self, BytePos, Span};
   4
   5 use crate::comment::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     itemize_list, shape_for_tactic, struct_lit_formatting, struct_lit_shape, struct_lit_tactic,
  10     write_list,
  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 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.node {
  40         ast::PatKind::Wild | ast::PatKind::Lit(_) => true,
  41         ast::PatKind::Ident(_, _, ref pat) => pat.is_none(),
  42         ast::PatKind::Struct(..)
  43         | ast::PatKind::Mac(..)
  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     }
  55 }
  56
  57 impl Rewrite for Pat {
  58     fn rewrite(&self, context: &RewriteContext<'_>, shape: Shape) -> Option<String> {
  59         match self.node {
  60             PatKind::Box(ref pat) => rewrite_unary_prefix(context, "box ", &**pat, shape),
  61             PatKind::Ident(binding_mode, ident, ref sub_pat) => {
  62                 let (prefix, mutability) = match binding_mode {
  63                     BindingMode::ByRef(mutability) => ("ref ", mutability),
  64                     BindingMode::ByValue(mutability) => ("", mutability),
  65                 };
  66                 let mut_infix = format_mutability(mutability);
  67                 let id_str = rewrite_ident(context, ident);
  68                 let sub_pat = match *sub_pat {
  69                     Some(ref p) => {
  70                         // 3 - ` @ `.
  71                         let width = shape
  72                             .width
  73                             .checked_sub(prefix.len() + mut_infix.len() + id_str.len() + 3)?;
  74                         format!(
  75                             " @ {}",
  76                             p.rewrite(context, Shape::legacy(width, shape.indent))?
  77                         )
  78                     }
  79                     None => "".to_owned(),
  80                 };
  81
  82                 Some(format!("{}{}{}{}", prefix, mut_infix, id_str, sub_pat))
  83             }
  84             PatKind::Wild => {
  85                 if 1 <= shape.width {
  86                     Some("_".to_owned())
  87                 } else {
  88                     None
  89                 }
  90             }
  91             PatKind::Range(ref lhs, ref rhs, ref end_kind) => {
  92                 let infix = match end_kind.node {
  93                     RangeEnd::Included(RangeSyntax::DotDotDot) => "...",
  94                     RangeEnd::Included(RangeSyntax::DotDotEq) => "..=",
  95                     RangeEnd::Excluded => "..",
  96                 };
  97                 let infix = if context.config.spaces_around_ranges() {
  98                     format!(" {} ", infix)
  99                 } else {
 100                     infix.to_owned()
 101                 };
 102                 rewrite_pair(
 103                     &**lhs,
 104                     &**rhs,
 105                     PairParts::infix(&infix),
 106                     context,
 107                     shape,
 108                     SeparatorPlace::Front,
 109                 )
 110             }
 111             PatKind::Ref(ref pat, mutability) => {
 112                 let prefix = format!("&{}", format_mutability(mutability));
 113                 rewrite_unary_prefix(context, &prefix, &**pat, shape)
 114             }
 115             PatKind::Tuple(ref items, dotdot_pos) => {
 116                 rewrite_tuple_pat(items, dotdot_pos, None, self.span, context, shape)
 117             }
 118             PatKind::Path(ref q_self, ref path) => {
 119                 rewrite_path(context, PathContext::Expr, q_self.as_ref(), path, shape)
 120             }
 121             PatKind::TupleStruct(ref path, ref pat_vec, dotdot_pos) => {
 122                 let path_str = rewrite_path(context, PathContext::Expr, None, path, shape)?;
 123                 rewrite_tuple_pat(
 124                     pat_vec,
 125                     dotdot_pos,
 126                     Some(path_str),
 127                     self.span,
 128                     context,
 129                     shape,
 130                 )
 131             }
 132             PatKind::Lit(ref expr) => expr.rewrite(context, shape),
 133             PatKind::Slice(ref prefix, ref slice_pat, ref suffix) => {
 134                 // Rewrite all the sub-patterns.
 135                 let prefix = prefix.iter().map(|p| p.rewrite(context, shape));
 136                 let slice_pat = slice_pat
 137                     .as_ref()
 138                     .and_then(|p| p.rewrite(context, shape))
 139                     .map(|rw| Some(format!("{}..", if rw == "_" { "" } else { &rw })));
 140                 let suffix = suffix.iter().map(|p| p.rewrite(context, shape));
 141
 142                 // Munge them together.
 143                 let pats: Option<Vec<String>> =
 144                     prefix.chain(slice_pat.into_iter()).chain(suffix).collect();
 145
 146                 // Check that all the rewrites succeeded, and if not return `None`.
 147                 let pats = pats?;
 148
 149                 // Unwrap all the sub-strings and join them with commas.
 150                 Some(format!("[{}]", pats.join(", ")))
 151             }
 152             PatKind::Struct(ref path, ref fields, ellipsis) => {
 153                 rewrite_struct_pat(path, fields, ellipsis, self.span, context, shape)
 154             }
 155             PatKind::Mac(ref mac) => rewrite_macro(mac, None, context, shape, MacroPosition::Pat),
 156             PatKind::Paren(ref pat) => pat
 157                 .rewrite(context, shape.offset_left(1)?.sub_width(1)?)
 158                 .map(|inner_pat| format!("({})", inner_pat)),
 159         }
 160     }
 161 }
 162
 163 fn rewrite_struct_pat(
 164     path: &ast::Path,
 165     fields: &[source_map::Spanned<ast::FieldPat>],
 166     ellipsis: bool,
 167     span: Span,
 168     context: &RewriteContext<'_>,
 169     shape: Shape,
 170 ) -> Option<String> {
 171     // 2 =  ` {`
 172     let path_shape = shape.sub_width(2)?;
 173     let path_str = rewrite_path(context, PathContext::Expr, None, path, path_shape)?;
 174
 175     if fields.is_empty() && !ellipsis {
 176         return Some(format!("{} {{}}", path_str));
 177     }
 178
 179     let (ellipsis_str, terminator) = if ellipsis { (", ..", "..") } else { ("", "}") };
 180
 181     // 3 = ` { `, 2 = ` }`.
 182     let (h_shape, v_shape) =
 183         struct_lit_shape(shape, context, path_str.len() + 3, ellipsis_str.len() + 2)?;
 184
 185     let items = itemize_list(
 186         context.snippet_provider,
 187         fields.iter(),
 188         terminator,
 189         ",",
 190         |f| f.span.lo(),
 191         |f| f.span.hi(),
 192         |f| f.node.rewrite(context, v_shape),
 193         context.snippet_provider.span_after(span, "{"),
 194         span.hi(),
 195         false,
 196     );
 197     let item_vec = items.collect::<Vec<_>>();
 198
 199     let tactic = struct_lit_tactic(h_shape, context, &item_vec);
 200     let nested_shape = shape_for_tactic(tactic, h_shape, v_shape);
 201     let fmt = struct_lit_formatting(nested_shape, tactic, context, false);
 202
 203     let mut fields_str = write_list(&item_vec, &fmt)?;
 204     let one_line_width = h_shape.map_or(0, |shape| shape.width);
 205
 206     if ellipsis {
 207         if fields_str.contains('\n') || fields_str.len() > one_line_width {
 208             // Add a missing trailing comma.
 209             if context.config.trailing_comma() == SeparatorTactic::Never {
 210                 fields_str.push_str(",");
 211             }
 212             fields_str.push_str("\n");
 213             fields_str.push_str(&nested_shape.indent.to_string(context.config));
 214             fields_str.push_str("..");
 215         } else {
 216             if !fields_str.is_empty() {
 217                 // there are preceding struct fields being matched on
 218                 if tactic == DefinitiveListTactic::Vertical {
 219                     // if the tactic is Vertical, write_list already added a trailing ,
 220                     fields_str.push_str(" ");
 221                 } else {
 222                     fields_str.push_str(", ");
 223                 }
 224             }
 225             fields_str.push_str("..");
 226         }
 227     }
 228
 229     let fields_str = wrap_struct_field(context, &fields_str, shape, v_shape, one_line_width);
 230     Some(format!("{} {{{}}}", path_str, fields_str))
 231 }
 232
 233 impl Rewrite for FieldPat {
 234     fn rewrite(&self, context: &RewriteContext<'_>, shape: Shape) -> Option<String> {
 235         let pat = self.pat.rewrite(context, shape);
 236         if self.is_shorthand {
 237             pat
 238         } else {
 239             let pat_str = pat?;
 240             let id_str = rewrite_ident(context, self.ident);
 241             let one_line_width = id_str.len() + 2 + pat_str.len();
 242             if one_line_width <= shape.width {
 243                 Some(format!("{}: {}", id_str, pat_str))
 244             } else {
 245                 let nested_shape = shape.block_indent(context.config.tab_spaces());
 246                 let pat_str = self.pat.rewrite(context, nested_shape)?;
 247                 Some(format!(
 248                     "{}:\n{}{}",
 249                     id_str,
 250                     nested_shape.indent.to_string(context.config),
 251                     pat_str,
 252                 ))
 253             }
 254         }
 255     }
 256 }
 257
 258 #[derive(Debug)]
 259 pub enum TuplePatField<'a> {
 260     Pat(&'a ptr::P<ast::Pat>),
 261     Dotdot(Span),
 262 }
 263
 264 impl<'a> Rewrite for TuplePatField<'a> {
 265     fn rewrite(&self, context: &RewriteContext<'_>, shape: Shape) -> Option<String> {
 266         match *self {
 267             TuplePatField::Pat(p) => p.rewrite(context, shape),
 268             TuplePatField::Dotdot(_) => Some("..".to_string()),
 269         }
 270     }
 271 }
 272
 273 impl<'a> Spanned for TuplePatField<'a> {
 274     fn span(&self) -> Span {
 275         match *self {
 276             TuplePatField::Pat(p) => p.span(),
 277             TuplePatField::Dotdot(span) => span,
 278         }
 279     }
 280 }
 281
 282 pub fn can_be_overflowed_pat(
 283     context: &RewriteContext<'_>,
 284     pat: &TuplePatField<'_>,
 285     len: usize,
 286 ) -> bool {
 287     match *pat {
 288         TuplePatField::Pat(pat) => match pat.node {
 289             ast::PatKind::Path(..)
 290             | ast::PatKind::Tuple(..)
 291             | ast::PatKind::Struct(..)
 292             | ast::PatKind::TupleStruct(..) => context.use_block_indent() && len == 1,
 293             ast::PatKind::Ref(ref p, _) | ast::PatKind::Box(ref p) => {
 294                 can_be_overflowed_pat(context, &TuplePatField::Pat(p), len)
 295             }
 296             ast::PatKind::Lit(ref expr) => can_be_overflowed_expr(context, expr, len),
 297             _ => false,
 298         },
 299         TuplePatField::Dotdot(..) => false,
 300     }
 301 }
 302
 303 fn rewrite_tuple_pat(
 304     pats: &[ptr::P<ast::Pat>],
 305     dotdot_pos: Option<usize>,
 306     path_str: Option<String>,
 307     span: Span,
 308     context: &RewriteContext<'_>,
 309     shape: Shape,
 310 ) -> Option<String> {
 311     let mut pat_vec: Vec<_> = pats.iter().map(|x| TuplePatField::Pat(x)).collect();
 312
 313     if let Some(pos) = dotdot_pos {
 314         let prev = if pos == 0 {
 315             span.lo()
 316         } else {
 317             pats[pos - 1].span().hi()
 318         };
 319         let next = if pos + 1 >= pats.len() {
 320             span.hi()
 321         } else {
 322             pats[pos + 1].span().lo()
 323         };
 324         let dot_span = mk_sp(prev, next);
 325         let snippet = context.snippet(dot_span);
 326         let lo = dot_span.lo() + BytePos(snippet.find_uncommented("..").unwrap() as u32);
 327         let dotdot = TuplePatField::Dotdot(Span::new(
 328             lo,
 329             // 2 == "..".len()
 330             lo + BytePos(2),
 331             source_map::NO_EXPANSION,
 332         ));
 333         pat_vec.insert(pos, dotdot);
 334     }
 335     if pat_vec.is_empty() {
 336         return Some(format!("{}()", path_str.unwrap_or_default()));
 337     }
 338     let wildcard_suffix_len = count_wildcard_suffix_len(context, &pat_vec, span, shape);
 339     let (pat_vec, span, condensed) =
 340         if context.config.condense_wildcard_suffixes() && wildcard_suffix_len >= 2 {
 341             let new_item_count = 1 + pat_vec.len() - wildcard_suffix_len;
 342             let sp = pat_vec[new_item_count - 1].span();
 343             let snippet = context.snippet(sp);
 344             let lo = sp.lo() + BytePos(snippet.find_uncommented("_").unwrap() as u32);
 345             pat_vec[new_item_count - 1] = TuplePatField::Dotdot(mk_sp(lo, lo + BytePos(1)));
 346             (
 347                 &pat_vec[..new_item_count],
 348                 mk_sp(span.lo(), lo + BytePos(1)),
 349                 true,
 350             )
 351         } else {
 352             (&pat_vec[..], span, false)
 353         };
 354
 355     // add comma if `(x,)`
 356     let add_comma = path_str.is_none() && pat_vec.len() == 1 && dotdot_pos.is_none() && !condensed;
 357     let path_str = path_str.unwrap_or_default();
 358
 359     overflow::rewrite_with_parens(
 360         &context,
 361         &path_str,
 362         pat_vec.iter(),
 363         shape,
 364         span,
 365         context.config.max_width(),
 366         if dotdot_pos.is_some() {
 367             Some(SeparatorTactic::Never)
 368         } else if add_comma {
 369             Some(SeparatorTactic::Always)
 370         } else {
 371             None
 372         },
 373     )
 374 }
 375
 376 fn count_wildcard_suffix_len(
 377     context: &RewriteContext<'_>,
 378     patterns: &[TuplePatField<'_>],
 379     span: Span,
 380     shape: Shape,
 381 ) -> usize {
 382     let mut suffix_len = 0;
 383
 384     let items: Vec<_> = itemize_list(
 385         context.snippet_provider,
 386         patterns.iter(),
 387         ")",
 388         ",",
 389         |item| item.span().lo(),
 390         |item| item.span().hi(),
 391         |item| item.rewrite(context, shape),
 392         context.snippet_provider.span_after(span, "("),
 393         span.hi() - BytePos(1),
 394         false,
 395     )
 396     .collect();
 397
 398     for item in items.iter().rev().take_while(|i| match i.item {
 399         Some(ref internal_string) if internal_string == "_" => true,
 400         _ => false,
 401     }) {
 402         suffix_len += 1;
 403
 404         if item.has_comment() {
 405             break;
 406         }
 407     }
 408
 409     suffix_len
 410 }