src/patterns.rs

   1 // Copyright 2015 The Rust Project Developers. See the COPYRIGHT
   2 // file at the top-level directory of this distribution and at
   3 // http://rust-lang.org/COPYRIGHT.
   4 //
   5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
   6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
   7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
   8 // option. This file may not be copied, modified, or distributed
   9 // except according to those terms.
  10
  11 use config::lists::*;
  12 use syntax::ast::{self, BindingMode, FieldPat, Pat, PatKind, RangeEnd, RangeSyntax};
  13 use syntax::codemap::{self, BytePos, Span};
  14 use syntax::ptr;
  15
  16 use codemap::SpanUtils;
  17 use comment::FindUncommented;
  18 use expr::{can_be_overflowed_expr, rewrite_call_inner, rewrite_pair, rewrite_unary_prefix,
  19            wrap_struct_field, PairParts};
  20 use lists::{itemize_list, shape_for_tactic, struct_lit_formatting, struct_lit_shape,
  21             struct_lit_tactic, write_list};
  22 use macros::{rewrite_macro, MacroPosition};
  23 use rewrite::{Rewrite, RewriteContext};
  24 use shape::Shape;
  25 use spanned::Spanned;
  26 use types::{rewrite_path, PathContext};
  27 use utils::{format_mutability, mk_sp};
  28
  29 impl Rewrite for Pat {
  30     fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
  31         match self.node {
  32             PatKind::Box(ref pat) => rewrite_unary_prefix(context, "box ", &**pat, shape),
  33             PatKind::Ident(binding_mode, ident, ref sub_pat) => {
  34                 let (prefix, mutability) = match binding_mode {
  35                     BindingMode::ByRef(mutability) => ("ref ", mutability),
  36                     BindingMode::ByValue(mutability) => ("", mutability),
  37                 };
  38                 let mut_infix = format_mutability(mutability);
  39                 let id_str = ident.node.to_string();
  40                 let sub_pat = match *sub_pat {
  41                     Some(ref p) => {
  42                         // 3 - ` @ `.
  43                         let width = shape
  44                             .width
  45                             .checked_sub(prefix.len() + mut_infix.len() + id_str.len() + 3)?;
  46                         format!(
  47                             " @ {}",
  48                             p.rewrite(context, Shape::legacy(width, shape.indent))?
  49                         )
  50                     }
  51                     None => "".to_owned(),
  52                 };
  53
  54                 Some(format!("{}{}{}{}", prefix, mut_infix, id_str, sub_pat))
  55             }
  56             PatKind::Wild => {
  57                 if 1 <= shape.width {
  58                     Some("_".to_owned())
  59                 } else {
  60                     None
  61                 }
  62             }
  63             PatKind::Range(ref lhs, ref rhs, ref end_kind) => {
  64                 let infix = match *end_kind {
  65                     RangeEnd::Included(RangeSyntax::DotDotDot) => "...",
  66                     RangeEnd::Included(RangeSyntax::DotDotEq) => "..=",
  67                     RangeEnd::Excluded => "..",
  68                 };
  69                 let infix = if context.config.spaces_around_ranges() {
  70                     format!(" {} ", infix)
  71                 } else {
  72                     infix.to_owned()
  73                 };
  74                 rewrite_pair(
  75                     &**lhs,
  76                     &**rhs,
  77                     PairParts::new("", &infix, ""),
  78                     context,
  79                     shape,
  80                     SeparatorPlace::Front,
  81                 )
  82             }
  83             PatKind::Ref(ref pat, mutability) => {
  84                 let prefix = format!("&{}", format_mutability(mutability));
  85                 rewrite_unary_prefix(context, &prefix, &**pat, shape)
  86             }
  87             PatKind::Tuple(ref items, dotdot_pos) => {
  88                 rewrite_tuple_pat(items, dotdot_pos, None, self.span, context, shape)
  89             }
  90             PatKind::Path(ref q_self, ref path) => {
  91                 rewrite_path(context, PathContext::Expr, q_self.as_ref(), path, shape)
  92             }
  93             PatKind::TupleStruct(ref path, ref pat_vec, dotdot_pos) => {
  94                 let path_str = rewrite_path(context, PathContext::Expr, None, path, shape)?;
  95                 rewrite_tuple_pat(
  96                     pat_vec,
  97                     dotdot_pos,
  98                     Some(path_str),
  99                     self.span,
 100                     context,
 101                     shape,
 102                 )
 103             }
 104             PatKind::Lit(ref expr) => expr.rewrite(context, shape),
 105             PatKind::Slice(ref prefix, ref slice_pat, ref suffix) => {
 106                 // Rewrite all the sub-patterns.
 107                 let prefix = prefix.iter().map(|p| p.rewrite(context, shape));
 108                 let slice_pat = slice_pat
 109                     .as_ref()
 110                     .map(|p| Some(format!("{}..", p.rewrite(context, shape)?)));
 111                 let suffix = suffix.iter().map(|p| p.rewrite(context, shape));
 112
 113                 // Munge them together.
 114                 let pats: Option<Vec<String>> =
 115                     prefix.chain(slice_pat.into_iter()).chain(suffix).collect();
 116
 117                 // Check that all the rewrites succeeded, and if not return None.
 118                 let pats = pats?;
 119
 120                 // Unwrap all the sub-strings and join them with commas.
 121                 let result = if context.config.spaces_within_parens_and_brackets() {
 122                     format!("[ {} ]", pats.join(", "))
 123                 } else {
 124                     format!("[{}]", pats.join(", "))
 125                 };
 126                 Some(result)
 127             }
 128             PatKind::Struct(ref path, ref fields, ellipsis) => {
 129                 rewrite_struct_pat(path, fields, ellipsis, self.span, context, shape)
 130             }
 131             PatKind::Mac(ref mac) => rewrite_macro(mac, None, context, shape, MacroPosition::Pat),
 132             PatKind::Paren(ref pat) => pat.rewrite(context, shape.offset_left(1)?.sub_width(1)?)
 133                 .map(|inner_pat| format!("({})", inner_pat)),
 134         }
 135     }
 136 }
 137
 138 fn rewrite_struct_pat(
 139     path: &ast::Path,
 140     fields: &[codemap::Spanned<ast::FieldPat>],
 141     ellipsis: bool,
 142     span: Span,
 143     context: &RewriteContext,
 144     shape: Shape,
 145 ) -> Option<String> {
 146     // 2 =  ` {`
 147     let path_shape = shape.sub_width(2)?;
 148     let path_str = rewrite_path(context, PathContext::Expr, None, path, path_shape)?;
 149
 150     if fields.is_empty() && !ellipsis {
 151         return Some(format!("{} {{}}", path_str));
 152     }
 153
 154     let (ellipsis_str, terminator) = if ellipsis { (", ..", "..") } else { ("", "}") };
 155
 156     // 3 = ` { `, 2 = ` }`.
 157     let (h_shape, v_shape) =
 158         struct_lit_shape(shape, context, path_str.len() + 3, ellipsis_str.len() + 2)?;
 159
 160     let items = itemize_list(
 161         context.snippet_provider,
 162         fields.iter(),
 163         terminator,
 164         ",",
 165         |f| f.span.lo(),
 166         |f| f.span.hi(),
 167         |f| f.node.rewrite(context, v_shape),
 168         context.snippet_provider.span_after(span, "{"),
 169         span.hi(),
 170         false,
 171     );
 172     let item_vec = items.collect::<Vec<_>>();
 173
 174     let tactic = struct_lit_tactic(h_shape, context, &item_vec);
 175     let nested_shape = shape_for_tactic(tactic, h_shape, v_shape);
 176     let fmt = struct_lit_formatting(nested_shape, tactic, context, false);
 177
 178     let mut fields_str = write_list(&item_vec, &fmt)?;
 179     let one_line_width = h_shape.map_or(0, |shape| shape.width);
 180
 181     if ellipsis {
 182         if fields_str.contains('\n') || fields_str.len() > one_line_width {
 183             // Add a missing trailing comma.
 184             if fmt.trailing_separator == SeparatorTactic::Never {
 185                 fields_str.push_str(",");
 186             }
 187             fields_str.push_str("\n");
 188             fields_str.push_str(&nested_shape.indent.to_string(context.config));
 189             fields_str.push_str("..");
 190         } else {
 191             if !fields_str.is_empty() {
 192                 // there are preceding struct fields being matched on
 193                 if fmt.tactic == DefinitiveListTactic::Vertical {
 194                     // if the tactic is Vertical, write_list already added a trailing ,
 195                     fields_str.push_str(" ");
 196                 } else {
 197                     fields_str.push_str(", ");
 198                 }
 199             }
 200             fields_str.push_str("..");
 201         }
 202     }
 203
 204     let fields_str = wrap_struct_field(context, &fields_str, shape, v_shape, one_line_width);
 205     Some(format!("{} {{{}}}", path_str, fields_str))
 206 }
 207
 208 impl Rewrite for FieldPat {
 209     fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
 210         let pat = self.pat.rewrite(context, shape);
 211         if self.is_shorthand {
 212             pat
 213         } else {
 214             let pat_str = pat?;
 215             let id_str = self.ident.to_string();
 216             let one_line_width = id_str.len() + 2 + pat_str.len();
 217             if one_line_width <= shape.width {
 218                 Some(format!("{}: {}", id_str, pat_str))
 219             } else {
 220                 let nested_shape = shape.block_indent(context.config.tab_spaces());
 221                 let pat_str = self.pat.rewrite(context, nested_shape)?;
 222                 Some(format!(
 223                     "{}:\n{}{}",
 224                     id_str,
 225                     nested_shape.indent.to_string(context.config),
 226                     pat_str,
 227                 ))
 228             }
 229         }
 230     }
 231 }
 232
 233 pub enum TuplePatField<'a> {
 234     Pat(&'a ptr::P<ast::Pat>),
 235     Dotdot(Span),
 236 }
 237
 238 impl<'a> Rewrite for TuplePatField<'a> {
 239     fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
 240         match *self {
 241             TuplePatField::Pat(p) => p.rewrite(context, shape),
 242             TuplePatField::Dotdot(_) => Some("..".to_string()),
 243         }
 244     }
 245 }
 246
 247 impl<'a> Spanned for TuplePatField<'a> {
 248     fn span(&self) -> Span {
 249         match *self {
 250             TuplePatField::Pat(p) => p.span(),
 251             TuplePatField::Dotdot(span) => span,
 252         }
 253     }
 254 }
 255
 256 pub fn can_be_overflowed_pat(context: &RewriteContext, pat: &TuplePatField, len: usize) -> bool {
 257     match *pat {
 258         TuplePatField::Pat(pat) => match pat.node {
 259             ast::PatKind::Path(..)
 260             | ast::PatKind::Tuple(..)
 261             | ast::PatKind::Struct(..)
 262             | ast::PatKind::TupleStruct(..) => context.use_block_indent() && len == 1,
 263             ast::PatKind::Ref(ref p, _) | ast::PatKind::Box(ref p) => {
 264                 can_be_overflowed_pat(context, &TuplePatField::Pat(p), len)
 265             }
 266             ast::PatKind::Lit(ref expr) => can_be_overflowed_expr(context, expr, len),
 267             _ => false,
 268         },
 269         TuplePatField::Dotdot(..) => false,
 270     }
 271 }
 272
 273 fn rewrite_tuple_pat(
 274     pats: &[ptr::P<ast::Pat>],
 275     dotdot_pos: Option<usize>,
 276     path_str: Option<String>,
 277     span: Span,
 278     context: &RewriteContext,
 279     shape: Shape,
 280 ) -> Option<String> {
 281     let mut pat_vec: Vec<_> = pats.into_iter().map(|x| TuplePatField::Pat(x)).collect();
 282
 283     if let Some(pos) = dotdot_pos {
 284         let prev = if pos == 0 {
 285             span.lo()
 286         } else {
 287             pats[pos - 1].span().hi()
 288         };
 289         let next = if pos + 1 >= pats.len() {
 290             span.hi()
 291         } else {
 292             pats[pos + 1].span().lo()
 293         };
 294         let dot_span = mk_sp(prev, next);
 295         let snippet = context.snippet(dot_span);
 296         let lo = dot_span.lo() + BytePos(snippet.find_uncommented("..").unwrap() as u32);
 297         let dotdot = TuplePatField::Dotdot(Span::new(
 298             lo,
 299             // 2 == "..".len()
 300             lo + BytePos(2),
 301             codemap::NO_EXPANSION,
 302         ));
 303         pat_vec.insert(pos, dotdot);
 304     }
 305
 306     if pat_vec.is_empty() {
 307         return Some(format!("{}()", path_str.unwrap_or_default()));
 308     }
 309
 310     let wildcard_suffix_len = count_wildcard_suffix_len(context, &pat_vec, span, shape);
 311     let (pat_vec, span) = if context.config.condense_wildcard_suffixes() && wildcard_suffix_len >= 2
 312     {
 313         let new_item_count = 1 + pat_vec.len() - wildcard_suffix_len;
 314         let sp = pat_vec[new_item_count - 1].span();
 315         let snippet = context.snippet(sp);
 316         let lo = sp.lo() + BytePos(snippet.find_uncommented("_").unwrap() as u32);
 317         pat_vec[new_item_count - 1] = TuplePatField::Dotdot(mk_sp(lo, lo + BytePos(1)));
 318         (
 319             &pat_vec[..new_item_count],
 320             mk_sp(span.lo(), lo + BytePos(1)),
 321         )
 322     } else {
 323         (&pat_vec[..], span)
 324     };
 325
 326     // add comma if `(x,)`
 327     let add_comma = path_str.is_none() && pat_vec.len() == 1 && dotdot_pos.is_none();
 328     let mut context = context.clone();
 329     if let Some(&TuplePatField::Dotdot(..)) = pat_vec.last() {
 330         context.inside_macro = true;
 331     }
 332     let path_str = path_str.unwrap_or_default();
 333     let mut pat_ref_vec = Vec::with_capacity(pat_vec.len());
 334     for pat in pat_vec {
 335         pat_ref_vec.push(pat);
 336     }
 337
 338     rewrite_call_inner(
 339         &context,
 340         &path_str,
 341         &pat_ref_vec[..],
 342         span,
 343         shape,
 344         shape.width,
 345         add_comma,
 346     )
 347 }
 348
 349 fn count_wildcard_suffix_len(
 350     context: &RewriteContext,
 351     patterns: &[TuplePatField],
 352     span: Span,
 353     shape: Shape,
 354 ) -> usize {
 355     let mut suffix_len = 0;
 356
 357     let items: Vec<_> = itemize_list(
 358         context.snippet_provider,
 359         patterns.iter(),
 360         ")",
 361         ",",
 362         |item| item.span().lo(),
 363         |item| item.span().hi(),
 364         |item| item.rewrite(context, shape),
 365         context.snippet_provider.span_after(span, "("),
 366         span.hi() - BytePos(1),
 367         false,
 368     ).collect();
 369
 370     for item in items.iter().rev().take_while(|i| match i.item {
 371         Some(ref internal_string) if internal_string == "_" => true,
 372         _ => false,
 373     }) {
 374         suffix_len += 1;
 375
 376         if item.pre_comment.is_some() || item.post_comment.is_some() {
 377             break;
 378         }
 379     }
 380
 381     suffix_len
 382 }