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.width.checked_sub(prefix.len() +
  43                                                                      mut_infix.len() +
  44                                                                      id_str.len() +
  45                                                                      3));
  46                         format!(" @ {}",
  47                                 try_opt!(p.rewrite(context, Shape::legacy(width, shape.indent))))
  48                     }
  49                     None => "".to_owned(),
  50                 };
  51
  52                 let result = format!("{}{}{}{}", prefix, mut_infix, id_str, sub_pat);
  53                 wrap_str(result, context.config.max_width, shape)
  54             }
  55             PatKind::Wild => {
  56                 if 1 <= shape.width {
  57                     Some("_".to_owned())
  58                 } else {
  59                     None
  60                 }
  61             }
  62             PatKind::Range(ref lhs, ref rhs, ref end_kind) => {
  63                 match *end_kind {
  64                     RangeEnd::Included => {
  65                         rewrite_pair(&**lhs, &**rhs, "", "...", "", context, shape)
  66                     }
  67                     RangeEnd::Excluded => {
  68                         rewrite_pair(&**lhs, &**rhs, "", "..", "", context, shape)
  69                     }
  70                 }
  71             }
  72             PatKind::Ref(ref pat, mutability) => {
  73                 let prefix = format!("&{}", format_mutability(mutability));
  74                 rewrite_unary_prefix(context, &prefix, &**pat, shape)
  75             }
  76             PatKind::Tuple(ref items, dotdot_pos) => {
  77                 rewrite_tuple_pat(items, dotdot_pos, None, self.span, context, shape)
  78             }
  79             PatKind::Path(ref q_self, ref path) => {
  80                 rewrite_path(context, PathContext::Expr, q_self.as_ref(), path, shape)
  81             }
  82             PatKind::TupleStruct(ref path, ref pat_vec, dotdot_pos) => {
  83                 let path_str =
  84                     try_opt!(rewrite_path(context, PathContext::Expr, None, path, shape));
  85                 rewrite_tuple_pat(pat_vec,
  86                                   dotdot_pos,
  87                                   Some(path_str),
  88                                   self.span,
  89                                   context,
  90                                   shape)
  91             }
  92             PatKind::Lit(ref expr) => expr.rewrite(context, shape),
  93             PatKind::Slice(ref prefix, ref slice_pat, ref suffix) => {
  94                 // Rewrite all the sub-patterns.
  95                 let prefix = prefix.iter().map(|p| p.rewrite(context, shape));
  96                 let slice_pat =
  97                     slice_pat
  98                         .as_ref()
  99                         .map(|p| Some(format!("{}..", try_opt!(p.rewrite(context, shape)))));
 100                 let suffix = suffix.iter().map(|p| p.rewrite(context, shape));
 101
 102                 // Munge them together.
 103                 let pats: Option<Vec<String>> =
 104                     prefix.chain(slice_pat.into_iter()).chain(suffix).collect();
 105
 106                 // Check that all the rewrites succeeded, and if not return None.
 107                 let pats = try_opt!(pats);
 108
 109                 // Unwrap all the sub-strings and join them with commas.
 110                 let result = if context.config.spaces_within_square_brackets {
 111                     format!("[ {} ]", pats.join(", "))
 112                 } else {
 113                     format!("[{}]", pats.join(", "))
 114                 };
 115                 wrap_str(result, context.config.max_width, shape)
 116             }
 117             PatKind::Struct(ref path, ref fields, elipses) => {
 118                 rewrite_struct_pat(path, fields, elipses, self.span, context, shape)
 119             }
 120             // FIXME(#819) format pattern macros.
 121             PatKind::Mac(..) => {
 122                 wrap_str(context.snippet(self.span), context.config.max_width, shape)
 123             }
 124         }
 125     }
 126 }
 127
 128 fn rewrite_struct_pat(path: &ast::Path,
 129                       fields: &[codemap::Spanned<ast::FieldPat>],
 130                       elipses: bool,
 131                       span: Span,
 132                       context: &RewriteContext,
 133                       shape: Shape)
 134                       -> Option<String> {
 135     // 2 =  ` {`
 136     let path_shape = try_opt!(shape.sub_width(2));
 137     let path_str = try_opt!(rewrite_path(context, PathContext::Expr, None, path, path_shape));
 138
 139     if fields.len() == 0 && !elipses {
 140         return Some(format!("{} {{}}", path_str));
 141     }
 142
 143     let (elipses_str, terminator) = if elipses { (", ..", "..") } else { ("", "}") };
 144
 145     // 3 = ` { `, 2 = ` }`.
 146     let (h_shape, v_shape) =
 147         try_opt!(struct_lit_shape(shape, context, path_str.len() + 3, elipses_str.len() + 2));
 148
 149     let items = itemize_list(context.codemap,
 150                              fields.iter(),
 151                              terminator,
 152                              |f| f.span.lo,
 153                              |f| f.span.hi,
 154                              |f| f.node.rewrite(context, v_shape),
 155                              context.codemap.span_after(span, "{"),
 156                              span.hi);
 157     let item_vec = items.collect::<Vec<_>>();
 158
 159     let tactic = struct_lit_tactic(h_shape, context, &item_vec);
 160     let nested_shape = shape_for_tactic(tactic, h_shape, v_shape);
 161     let fmt = struct_lit_formatting(nested_shape, tactic, context, false);
 162
 163     let mut fields_str = try_opt!(write_list(&item_vec, &fmt));
 164
 165     if elipses {
 166         if fields_str.contains('\n') {
 167             // Add a missing trailing comma.
 168             if fmt.trailing_separator == SeparatorTactic::Never {
 169                 fields_str.push_str(",");
 170             }
 171             fields_str.push_str("\n");
 172             fields_str.push_str(&nested_shape.indent.to_string(context.config));
 173             fields_str.push_str("..");
 174         } else {
 175             if !fields_str.is_empty() {
 176                 // there are preceeding struct fields being matched on
 177                 if fmt.tactic == DefinitiveListTactic::Vertical {
 178                     // if the tactic is Vertical, write_list already added a trailing ,
 179                     fields_str.push_str(" ");
 180                 } else {
 181                     fields_str.push_str(", ");
 182                 }
 183             }
 184             fields_str.push_str("..");
 185         }
 186     }
 187
 188
 189     let fields_str = if context.config.struct_lit_style == IndentStyle::Block &&
 190                         (fields_str.contains('\n') ||
 191                          context.config.struct_lit_multiline_style == MultilineStyle::ForceMulti ||
 192                          fields_str.len() > h_shape.map(|s| s.width).unwrap_or(0)) {
 193         format!("\n{}{}\n{}",
 194                 v_shape.indent.to_string(context.config),
 195                 fields_str,
 196                 shape.indent.to_string(context.config))
 197     } else {
 198         // One liner or visual indent.
 199         format!(" {} ", fields_str)
 200     };
 201
 202     Some(format!("{} {{{}}}", path_str, fields_str))
 203 }
 204
 205 impl Rewrite for FieldPat {
 206     fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
 207         let pat = self.pat.rewrite(context, shape);
 208         if self.is_shorthand {
 209             pat
 210         } else {
 211             wrap_str(format!("{}: {}", self.ident.to_string(), try_opt!(pat)),
 212                      context.config.max_width,
 213                      shape)
 214         }
 215     }
 216 }
 217
 218 enum TuplePatField<'a> {
 219     Pat(&'a ptr::P<ast::Pat>),
 220     Dotdot(Span),
 221 }
 222
 223 impl<'a> Rewrite for TuplePatField<'a> {
 224     fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
 225         match *self {
 226             TuplePatField::Pat(ref p) => p.rewrite(context, shape),
 227             TuplePatField::Dotdot(_) => Some("..".to_string()),
 228         }
 229     }
 230 }
 231
 232 impl<'a> Spanned for TuplePatField<'a> {
 233     fn span(&self) -> Span {
 234         match *self {
 235             TuplePatField::Pat(ref p) => p.span(),
 236             TuplePatField::Dotdot(span) => span,
 237         }
 238     }
 239 }
 240
 241 fn rewrite_tuple_pat(pats: &[ptr::P<ast::Pat>],
 242                      dotdot_pos: Option<usize>,
 243                      path_str: Option<String>,
 244                      span: Span,
 245                      context: &RewriteContext,
 246                      shape: Shape)
 247                      -> Option<String> {
 248     let mut pat_vec: Vec<_> = pats.into_iter().map(|x| TuplePatField::Pat(x)).collect();
 249
 250     if let Some(pos) = dotdot_pos {
 251         let prev = if pos == 0 {
 252             span.lo
 253         } else {
 254             pats[pos - 1].span().hi
 255         };
 256         let next = if pos + 1 >= pats.len() {
 257             span.hi
 258         } else {
 259             pats[pos + 1].span().lo
 260         };
 261         let dot_span = codemap::mk_sp(prev, next);
 262         let snippet = context.snippet(dot_span);
 263         let lo = dot_span.lo + BytePos(snippet.find_uncommented("..").unwrap() as u32);
 264         let span = Span {
 265             lo: lo,
 266             // 2 == "..".len()
 267             hi: lo + BytePos(2),
 268             expn_id: codemap::NO_EXPANSION,
 269         };
 270         let dotdot = TuplePatField::Dotdot(span);
 271         pat_vec.insert(pos, dotdot);
 272     }
 273
 274     if pat_vec.is_empty() {
 275         return Some(format!("{}()", try_opt!(path_str)));
 276     }
 277     // add comma if `(x,)`
 278     let add_comma = path_str.is_none() && pat_vec.len() == 1 && dotdot_pos.is_none();
 279
 280     let path_len = path_str.as_ref().map(|p| p.len()).unwrap_or(0);
 281     // 2 = "()".len(), 3 = "(,)".len()
 282     let nested_shape = try_opt!(shape.sub_width(path_len + if add_comma { 3 } else { 2 }));
 283     // 1 = "(".len()
 284     let nested_shape = nested_shape.visual_indent(path_len + 1);
 285     let mut items: Vec<_> = itemize_list(context.codemap,
 286                                          pat_vec.iter(),
 287                                          if add_comma { ",)" } else { ")" },
 288                                          |item| item.span().lo,
 289                                          |item| item.span().hi,
 290                                          |item| item.rewrite(context, nested_shape),
 291                                          context.codemap.span_after(span, "("),
 292                                          span.hi - BytePos(1))
 293             .collect();
 294
 295     // Condense wildcard string suffix into a single ..
 296     let wildcard_suffix_len = count_wildcard_suffix_len(&items);
 297
 298     let list = if context.config.condense_wildcard_suffixes && wildcard_suffix_len >= 2 {
 299         let new_item_count = 1 + pats.len() - wildcard_suffix_len;
 300         items[new_item_count - 1].item = Some("..".to_owned());
 301
 302         let da_iter = items.into_iter().take(new_item_count);
 303         try_opt!(format_item_list(da_iter, nested_shape, context.config))
 304     } else {
 305         try_opt!(format_item_list(items.into_iter(), nested_shape, context.config))
 306     };
 307
 308     match path_str {
 309         Some(path_str) => {
 310             Some(if context.config.spaces_within_parens {
 311                      format!("{}( {} )", path_str, list)
 312                  } else {
 313                      format!("{}({})", path_str, list)
 314                  })
 315         }
 316         None => {
 317             let comma = if add_comma { "," } else { "" };
 318             Some(if context.config.spaces_within_parens {
 319                      format!("( {}{} )", list, comma)
 320                  } else {
 321                      format!("({}{})", list, comma)
 322                  })
 323         }
 324     }
 325 }
 326
 327 fn count_wildcard_suffix_len(items: &[ListItem]) -> usize {
 328     let mut suffix_len = 0;
 329
 330     for item in items.iter().rev().take_while(|i| match i.item {
 331                                                   Some(ref internal_string) if internal_string ==
 332                                                                                "_" => true,
 333                                                   _ => false,
 334                                               }) {
 335         suffix_len += 1;
 336
 337         if item.pre_comment.is_some() || item.post_comment.is_some() {
 338             break;
 339         }
 340     }
 341
 342     suffix_len
 343 }