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 Shape;
  12 use codemap::SpanUtils;
  13 use config::{IndentStyle, MultilineStyle};
  14 use rewrite::{Rewrite, RewriteContext};
  15 use utils::{wrap_str, format_mutability};
  16 use lists::{DefinitiveListTactic, SeparatorTactic, format_item_list, itemize_list, ListItem,
  17             struct_lit_shape, struct_lit_tactic, shape_for_tactic, struct_lit_formatting,
  18             write_list};
  19 use expr::{rewrite_unary_prefix, rewrite_pair};
  20 use types::{rewrite_path, PathContext};
  21 use super::Spanned;
  22 use comment::FindUncommented;
  23
  24 use syntax::ast::{self, BindingMode, Pat, PatKind, FieldPat, RangeEnd};
  25 use syntax::ptr;
  26 use syntax::codemap::{self, BytePos, Span};
  27
  28 impl Rewrite for Pat {
  29     fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
  30         match self.node {
  31             PatKind::Box(ref pat) => rewrite_unary_prefix(context, "box ", &**pat, shape),
  32             PatKind::Ident(binding_mode, ident, ref sub_pat) => {
  33                 let (prefix, mutability) = match binding_mode {
  34                     BindingMode::ByRef(mutability) => ("ref ", mutability),
  35                     BindingMode::ByValue(mutability) => ("", mutability),
  36                 };
  37                 let mut_infix = format_mutability(mutability);
  38                 let id_str = ident.node.to_string();
  39                 let sub_pat = match *sub_pat {
  40                     Some(ref p) => {
  41                         // 3 - ` @ `.
  42                         let width = try_opt!(shape
  43                                                  .width
  44                                                  .checked_sub(prefix.len() + mut_infix.len() +
  45                                                               id_str.len() +
  46                                                               3));
  47                         format!(" @ {}",
  48                                 try_opt!(p.rewrite(context, Shape::legacy(width, shape.indent))))
  49                     }
  50                     None => "".to_owned(),
  51                 };
  52
  53                 let result = format!("{}{}{}{}", prefix, mut_infix, id_str, sub_pat);
  54                 wrap_str(result, context.config.max_width(), shape)
  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                 match *end_kind {
  65                     RangeEnd::Included => {
  66                         rewrite_pair(&**lhs, &**rhs, "", "...", "", context, shape)
  67                     }
  68                     RangeEnd::Excluded => {
  69                         rewrite_pair(&**lhs, &**rhs, "", "..", "", context, shape)
  70                     }
  71                 }
  72             }
  73             PatKind::Ref(ref pat, mutability) => {
  74                 let prefix = format!("&{}", format_mutability(mutability));
  75                 rewrite_unary_prefix(context, &prefix, &**pat, shape)
  76             }
  77             PatKind::Tuple(ref items, dotdot_pos) => {
  78                 rewrite_tuple_pat(items, dotdot_pos, None, self.span, context, shape)
  79             }
  80             PatKind::Path(ref q_self, ref path) => {
  81                 rewrite_path(context, PathContext::Expr, q_self.as_ref(), path, shape)
  82             }
  83             PatKind::TupleStruct(ref path, ref pat_vec, dotdot_pos) => {
  84                 let path_str =
  85                     try_opt!(rewrite_path(context, PathContext::Expr, None, path, shape));
  86                 rewrite_tuple_pat(pat_vec,
  87                                   dotdot_pos,
  88                                   Some(path_str),
  89                                   self.span,
  90                                   context,
  91                                   shape)
  92             }
  93             PatKind::Lit(ref expr) => expr.rewrite(context, shape),
  94             PatKind::Slice(ref prefix, ref slice_pat, ref suffix) => {
  95                 // Rewrite all the sub-patterns.
  96                 let prefix = prefix.iter().map(|p| p.rewrite(context, shape));
  97                 let slice_pat =
  98                     slice_pat
  99                         .as_ref()
 100                         .map(|p| Some(format!("{}..", try_opt!(p.rewrite(context, shape)))));
 101                 let suffix = suffix.iter().map(|p| p.rewrite(context, shape));
 102
 103                 // Munge them together.
 104                 let pats: Option<Vec<String>> =
 105                     prefix.chain(slice_pat.into_iter()).chain(suffix).collect();
 106
 107                 // Check that all the rewrites succeeded, and if not return None.
 108                 let pats = try_opt!(pats);
 109
 110                 // Unwrap all the sub-strings and join them with commas.
 111                 let result = if context.config.spaces_within_square_brackets() {
 112                     format!("[ {} ]", pats.join(", "))
 113                 } else {
 114                     format!("[{}]", pats.join(", "))
 115                 };
 116                 wrap_str(result, context.config.max_width(), shape)
 117             }
 118             PatKind::Struct(ref path, ref fields, elipses) => {
 119                 rewrite_struct_pat(path, fields, elipses, self.span, context, shape)
 120             }
 121             // FIXME(#819) format pattern macros.
 122             PatKind::Mac(..) => {
 123                 wrap_str(context.snippet(self.span),
 124                          context.config.max_width(),
 125                          shape)
 126             }
 127         }
 128     }
 129 }
 130
 131 fn rewrite_struct_pat(path: &ast::Path,
 132                       fields: &[codemap::Spanned<ast::FieldPat>],
 133                       elipses: bool,
 134                       span: Span,
 135                       context: &RewriteContext,
 136                       shape: Shape)
 137                       -> Option<String> {
 138     // 2 =  ` {`
 139     let path_shape = try_opt!(shape.sub_width(2));
 140     let path_str = try_opt!(rewrite_path(context, PathContext::Expr, None, path, path_shape));
 141
 142     if fields.len() == 0 && !elipses {
 143         return Some(format!("{} {{}}", path_str));
 144     }
 145
 146     let (elipses_str, terminator) = if elipses { (", ..", "..") } else { ("", "}") };
 147
 148     // 3 = ` { `, 2 = ` }`.
 149     let (h_shape, v_shape) =
 150         try_opt!(struct_lit_shape(shape, context, path_str.len() + 3, elipses_str.len() + 2));
 151
 152     let items = itemize_list(context.codemap,
 153                              fields.iter(),
 154                              terminator,
 155                              |f| f.span.lo,
 156                              |f| f.span.hi,
 157                              |f| f.node.rewrite(context, v_shape),
 158                              context.codemap.span_after(span, "{"),
 159                              span.hi);
 160     let item_vec = items.collect::<Vec<_>>();
 161
 162     let tactic = struct_lit_tactic(h_shape, context, &item_vec);
 163     let nested_shape = shape_for_tactic(tactic, h_shape, v_shape);
 164     let fmt = struct_lit_formatting(nested_shape, tactic, context, false);
 165
 166     let mut fields_str = try_opt!(write_list(&item_vec, &fmt));
 167
 168     if elipses {
 169         if fields_str.contains('\n') {
 170             // Add a missing trailing comma.
 171             if fmt.trailing_separator == SeparatorTactic::Never {
 172                 fields_str.push_str(",");
 173             }
 174             fields_str.push_str("\n");
 175             fields_str.push_str(&nested_shape.indent.to_string(context.config));
 176             fields_str.push_str("..");
 177         } else {
 178             if !fields_str.is_empty() {
 179                 // there are preceeding struct fields being matched on
 180                 if fmt.tactic == DefinitiveListTactic::Vertical {
 181                     // if the tactic is Vertical, write_list already added a trailing ,
 182                     fields_str.push_str(" ");
 183                 } else {
 184                     fields_str.push_str(", ");
 185                 }
 186             }
 187             fields_str.push_str("..");
 188         }
 189     }
 190
 191
 192     let fields_str = if context.config.struct_lit_style() == IndentStyle::Block &&
 193                         (fields_str.contains('\n') ||
 194                          context.config.struct_lit_multiline_style() ==
 195                          MultilineStyle::ForceMulti ||
 196                          fields_str.len() > h_shape.map(|s| s.width).unwrap_or(0)) {
 197         format!("\n{}{}\n{}",
 198                 v_shape.indent.to_string(context.config),
 199                 fields_str,
 200                 shape.indent.to_string(context.config))
 201     } else {
 202         // One liner or visual indent.
 203         format!(" {} ", fields_str)
 204     };
 205
 206     Some(format!("{} {{{}}}", path_str, fields_str))
 207 }
 208
 209 impl Rewrite for FieldPat {
 210     fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
 211         let pat = self.pat.rewrite(context, shape);
 212         if self.is_shorthand {
 213             pat
 214         } else {
 215             wrap_str(format!("{}: {}", self.ident.to_string(), try_opt!(pat)),
 216                      context.config.max_width(),
 217                      shape)
 218         }
 219     }
 220 }
 221
 222 enum TuplePatField<'a> {
 223     Pat(&'a ptr::P<ast::Pat>),
 224     Dotdot(Span),
 225 }
 226
 227 impl<'a> Rewrite for TuplePatField<'a> {
 228     fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
 229         match *self {
 230             TuplePatField::Pat(ref p) => p.rewrite(context, shape),
 231             TuplePatField::Dotdot(_) => Some("..".to_string()),
 232         }
 233     }
 234 }
 235
 236 impl<'a> Spanned for TuplePatField<'a> {
 237     fn span(&self) -> Span {
 238         match *self {
 239             TuplePatField::Pat(ref p) => p.span(),
 240             TuplePatField::Dotdot(span) => span,
 241         }
 242     }
 243 }
 244
 245 fn rewrite_tuple_pat(pats: &[ptr::P<ast::Pat>],
 246                      dotdot_pos: Option<usize>,
 247                      path_str: Option<String>,
 248                      span: Span,
 249                      context: &RewriteContext,
 250                      shape: Shape)
 251                      -> Option<String> {
 252     let mut pat_vec: Vec<_> = pats.into_iter().map(|x| TuplePatField::Pat(x)).collect();
 253
 254     if let Some(pos) = dotdot_pos {
 255         let prev = if pos == 0 {
 256             span.lo
 257         } else {
 258             pats[pos - 1].span().hi
 259         };
 260         let next = if pos + 1 >= pats.len() {
 261             span.hi
 262         } else {
 263             pats[pos + 1].span().lo
 264         };
 265         let dot_span = codemap::mk_sp(prev, next);
 266         let snippet = context.snippet(dot_span);
 267         let lo = dot_span.lo + BytePos(snippet.find_uncommented("..").unwrap() as u32);
 268         let span = Span {
 269             lo: lo,
 270             // 2 == "..".len()
 271             hi: lo + BytePos(2),
 272             expn_id: codemap::NO_EXPANSION,
 273         };
 274         let dotdot = TuplePatField::Dotdot(span);
 275         pat_vec.insert(pos, dotdot);
 276     }
 277
 278     if pat_vec.is_empty() {
 279         return Some(format!("{}()", try_opt!(path_str)));
 280     }
 281     // add comma if `(x,)`
 282     let add_comma = path_str.is_none() && pat_vec.len() == 1 && dotdot_pos.is_none();
 283
 284     let path_len = path_str.as_ref().map(|p| p.len()).unwrap_or(0);
 285     // 2 = "()".len(), 3 = "(,)".len()
 286     let nested_shape = try_opt!(shape.sub_width(path_len + if add_comma { 3 } else { 2 }));
 287     // 1 = "(".len()
 288     let nested_shape = nested_shape.visual_indent(path_len + 1);
 289     let mut items: Vec<_> = itemize_list(context.codemap,
 290                                          pat_vec.iter(),
 291                                          if add_comma { ",)" } else { ")" },
 292                                          |item| item.span().lo,
 293                                          |item| item.span().hi,
 294                                          |item| item.rewrite(context, nested_shape),
 295                                          context.codemap.span_after(span, "("),
 296                                          span.hi - BytePos(1))
 297             .collect();
 298
 299     // Condense wildcard string suffix into a single ..
 300     let wildcard_suffix_len = count_wildcard_suffix_len(&items);
 301
 302     let list = if context.config.condense_wildcard_suffices() && wildcard_suffix_len >= 2 {
 303         let new_item_count = 1 + pats.len() - wildcard_suffix_len;
 304         items[new_item_count - 1].item = Some("..".to_owned());
 305
 306         let da_iter = items.into_iter().take(new_item_count);
 307         try_opt!(format_item_list(da_iter, nested_shape, context.config))
 308     } else {
 309         try_opt!(format_item_list(items.into_iter(), nested_shape, context.config))
 310     };
 311
 312     match path_str {
 313         Some(path_str) => {
 314             Some(if context.config.spaces_within_parens() {
 315                      format!("{}( {} )", path_str, list)
 316                  } else {
 317                      format!("{}({})", path_str, list)
 318                  })
 319         }
 320         None => {
 321             let comma = if add_comma { "," } else { "" };
 322             Some(if context.config.spaces_within_parens() {
 323                      format!("( {}{} )", list, comma)
 324                  } else {
 325                      format!("({}{})", list, comma)
 326                  })
 327         }
 328     }
 329 }
 330
 331 fn count_wildcard_suffix_len(items: &[ListItem]) -> usize {
 332     let mut suffix_len = 0;
 333
 334     for item in items
 335             .iter()
 336             .rev()
 337             .take_while(|i| match i.item {
 338                             Some(ref internal_string) if internal_string == "_" => true,
 339                             _ => false,
 340                         }) {
 341         suffix_len += 1;
 342
 343         if item.pre_comment.is_some() || item.post_comment.is_some() {
 344             break;
 345         }
 346     }
 347
 348     suffix_len
 349 }