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 syntax::ast::{self, BindingMode, FieldPat, Pat, PatKind, RangeEnd};
  12 use syntax::codemap::{self, BytePos, Span};
  13 use syntax::ptr;
  14
  15 use spanned::Spanned;
  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};
  20 use lists::{itemize_list, shape_for_tactic, struct_lit_formatting, struct_lit_shape,
  21             struct_lit_tactic, write_list, DefinitiveListTactic, SeparatorPlace, SeparatorTactic};
  22 use rewrite::{Rewrite, RewriteContext};
  23 use shape::Shape;
  24 use types::{rewrite_path, PathContext};
  25 use utils::{format_mutability, mk_sp};
  26
  27 impl Rewrite for Pat {
  28     fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
  29         match self.node {
  30             PatKind::Box(ref pat) => rewrite_unary_prefix(context, "box ", &**pat, shape),
  31             PatKind::Ident(binding_mode, ident, ref sub_pat) => {
  32                 let (prefix, mutability) = match binding_mode {
  33                     BindingMode::ByRef(mutability) => ("ref ", mutability),
  34                     BindingMode::ByValue(mutability) => ("", mutability),
  35                 };
  36                 let mut_infix = format_mutability(mutability);
  37                 let id_str = ident.node.to_string();
  38                 let sub_pat = match *sub_pat {
  39                     Some(ref p) => {
  40                         // 3 - ` @ `.
  41                         let width = try_opt!(
  42                             shape
  43                                 .width
  44                                 .checked_sub(prefix.len() + mut_infix.len() + id_str.len() + 3)
  45                         );
  46                         format!(
  47                             " @ {}",
  48                             try_opt!(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 => if 1 <= shape.width {
  57                 Some("_".to_owned())
  58             } else {
  59                 None
  60             },
  61             PatKind::Range(ref lhs, ref rhs, ref end_kind) => match *end_kind {
  62                 RangeEnd::Included => rewrite_pair(
  63                     &**lhs,
  64                     &**rhs,
  65                     "",
  66                     "...",
  67                     "",
  68                     context,
  69                     shape,
  70                     SeparatorPlace::Front,
  71                 ),
  72                 RangeEnd::Excluded => rewrite_pair(
  73                     &**lhs,
  74                     &**rhs,
  75                     "",
  76                     "..",
  77                     "",
  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 =
  95                     try_opt!(rewrite_path(context, PathContext::Expr, None, path, shape));
  96                 rewrite_tuple_pat(
  97                     pat_vec,
  98                     dotdot_pos,
  99                     Some(path_str),
 100                     self.span,
 101                     context,
 102                     shape,
 103                 )
 104             }
 105             PatKind::Lit(ref expr) => expr.rewrite(context, shape),
 106             PatKind::Slice(ref prefix, ref slice_pat, ref suffix) => {
 107                 // Rewrite all the sub-patterns.
 108                 let prefix = prefix.iter().map(|p| p.rewrite(context, shape));
 109                 let slice_pat = slice_pat.as_ref().map(|p| {
 110                     Some(format!("{}..", try_opt!(p.rewrite(context, shape))))
 111                 });
 112                 let suffix = suffix.iter().map(|p| p.rewrite(context, shape));
 113
 114                 // Munge them together.
 115                 let pats: Option<Vec<String>> =
 116                     prefix.chain(slice_pat.into_iter()).chain(suffix).collect();
 117
 118                 // Check that all the rewrites succeeded, and if not return None.
 119                 let pats = try_opt!(pats);
 120
 121                 // Unwrap all the sub-strings and join them with commas.
 122                 let result = if context.config.spaces_within_square_brackets() {
 123                     format!("[ {} ]", pats.join(", "))
 124                 } else {
 125                     format!("[{}]", pats.join(", "))
 126                 };
 127                 Some(result)
 128             }
 129             PatKind::Struct(ref path, ref fields, elipses) => {
 130                 rewrite_struct_pat(path, fields, elipses, self.span, context, shape)
 131             }
 132             // FIXME(#819) format pattern macros.
 133             PatKind::Mac(..) => Some(context.snippet(self.span)),
 134         }
 135     }
 136 }
 137
 138 fn rewrite_struct_pat(
 139     path: &ast::Path,
 140     fields: &[codemap::Spanned<ast::FieldPat>],
 141     elipses: bool,
 142     span: Span,
 143     context: &RewriteContext,
 144     shape: Shape,
 145 ) -> Option<String> {
 146     // 2 =  ` {`
 147     let path_shape = try_opt!(shape.sub_width(2));
 148     let path_str = try_opt!(rewrite_path(
 149         context,
 150         PathContext::Expr,
 151         None,
 152         path,
 153         path_shape,
 154     ));
 155
 156     if fields.is_empty() && !elipses {
 157         return Some(format!("{} {{}}", path_str));
 158     }
 159
 160     let (elipses_str, terminator) = if elipses { (", ..", "..") } else { ("", "}") };
 161
 162     // 3 = ` { `, 2 = ` }`.
 163     let (h_shape, v_shape) = try_opt!(struct_lit_shape(
 164         shape,
 165         context,
 166         path_str.len() + 3,
 167         elipses_str.len() + 2,
 168     ));
 169
 170     let items = itemize_list(
 171         context.codemap,
 172         fields.iter(),
 173         terminator,
 174         |f| f.span.lo(),
 175         |f| f.span.hi(),
 176         |f| f.node.rewrite(context, v_shape),
 177         context.codemap.span_after(span, "{"),
 178         span.hi(),
 179         false,
 180     );
 181     let item_vec = items.collect::<Vec<_>>();
 182
 183     let tactic = struct_lit_tactic(h_shape, context, &item_vec);
 184     let nested_shape = shape_for_tactic(tactic, h_shape, v_shape);
 185     let fmt = struct_lit_formatting(nested_shape, tactic, context, false);
 186
 187     let mut fields_str = try_opt!(write_list(&item_vec, &fmt));
 188     let one_line_width = h_shape.map_or(0, |shape| shape.width);
 189
 190     if elipses {
 191         if fields_str.contains('\n') || fields_str.len() > one_line_width {
 192             // Add a missing trailing comma.
 193             if fmt.trailing_separator == SeparatorTactic::Never {
 194                 fields_str.push_str(",");
 195             }
 196             fields_str.push_str("\n");
 197             fields_str.push_str(&nested_shape.indent.to_string(context.config));
 198             fields_str.push_str("..");
 199         } else {
 200             if !fields_str.is_empty() {
 201                 // there are preceeding struct fields being matched on
 202                 if fmt.tactic == DefinitiveListTactic::Vertical {
 203                     // if the tactic is Vertical, write_list already added a trailing ,
 204                     fields_str.push_str(" ");
 205                 } else {
 206                     fields_str.push_str(", ");
 207                 }
 208             }
 209             fields_str.push_str("..");
 210         }
 211     }
 212
 213     let fields_str = wrap_struct_field(context, &fields_str, shape, v_shape, one_line_width);
 214     Some(format!("{} {{{}}}", path_str, fields_str))
 215 }
 216
 217 impl Rewrite for FieldPat {
 218     fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
 219         let pat = self.pat.rewrite(context, shape);
 220         if self.is_shorthand {
 221             pat
 222         } else {
 223             let pat_str = try_opt!(pat);
 224             let id_str = self.ident.to_string();
 225             let one_line_width = id_str.len() + 2 + pat_str.len();
 226             if one_line_width <= shape.width {
 227                 Some(format!("{}: {}", id_str, pat_str))
 228             } else {
 229                 let nested_shape = shape.block_indent(context.config.tab_spaces());
 230                 let pat_str = try_opt!(self.pat.rewrite(context, nested_shape));
 231                 Some(format!(
 232                     "{}:\n{}{}",
 233                     id_str,
 234                     nested_shape.indent.to_string(context.config),
 235                     pat_str,
 236                 ))
 237             }
 238         }
 239     }
 240 }
 241
 242 pub enum TuplePatField<'a> {
 243     Pat(&'a ptr::P<ast::Pat>),
 244     Dotdot(Span),
 245 }
 246
 247 impl<'a> Rewrite for TuplePatField<'a> {
 248     fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
 249         match *self {
 250             TuplePatField::Pat(p) => p.rewrite(context, shape),
 251             TuplePatField::Dotdot(_) => Some("..".to_string()),
 252         }
 253     }
 254 }
 255
 256 impl<'a> Spanned for TuplePatField<'a> {
 257     fn span(&self) -> Span {
 258         match *self {
 259             TuplePatField::Pat(p) => p.span(),
 260             TuplePatField::Dotdot(span) => span,
 261         }
 262     }
 263 }
 264
 265 pub fn can_be_overflowed_pat(context: &RewriteContext, pat: &TuplePatField, len: usize) -> bool {
 266     match *pat {
 267         TuplePatField::Pat(pat) => match pat.node {
 268             ast::PatKind::Path(..) | ast::PatKind::Tuple(..) | ast::PatKind::Struct(..) => {
 269                 context.use_block_indent() && len == 1
 270             }
 271             ast::PatKind::Ref(ref p, _) | ast::PatKind::Box(ref p) => {
 272                 can_be_overflowed_pat(context, &TuplePatField::Pat(p), len)
 273             }
 274             ast::PatKind::Lit(ref expr) => can_be_overflowed_expr(context, expr, len),
 275             _ => false,
 276         },
 277         TuplePatField::Dotdot(..) => false,
 278     }
 279 }
 280
 281 fn rewrite_tuple_pat(
 282     pats: &[ptr::P<ast::Pat>],
 283     dotdot_pos: Option<usize>,
 284     path_str: Option<String>,
 285     span: Span,
 286     context: &RewriteContext,
 287     shape: Shape,
 288 ) -> Option<String> {
 289     let mut pat_vec: Vec<_> = pats.into_iter().map(|x| TuplePatField::Pat(x)).collect();
 290
 291     if let Some(pos) = dotdot_pos {
 292         let prev = if pos == 0 {
 293             span.lo()
 294         } else {
 295             pats[pos - 1].span().hi()
 296         };
 297         let next = if pos + 1 >= pats.len() {
 298             span.hi()
 299         } else {
 300             pats[pos + 1].span().lo()
 301         };
 302         let dot_span = mk_sp(prev, next);
 303         let snippet = context.snippet(dot_span);
 304         let lo = dot_span.lo() + BytePos(snippet.find_uncommented("..").unwrap() as u32);
 305         let dotdot = TuplePatField::Dotdot(Span::new(
 306             lo,
 307             // 2 == "..".len()
 308             lo + BytePos(2),
 309             codemap::NO_EXPANSION,
 310         ));
 311         pat_vec.insert(pos, dotdot);
 312     }
 313
 314     if pat_vec.is_empty() {
 315         return Some(format!("{}()", path_str.unwrap_or_default()));
 316     }
 317
 318     let wildcard_suffix_len = count_wildcard_suffix_len(context, &pat_vec, span, shape);
 319     let (pat_vec, span) = if context.config.condense_wildcard_suffixes() && wildcard_suffix_len >= 2
 320     {
 321         let new_item_count = 1 + pat_vec.len() - wildcard_suffix_len;
 322         let sp = pat_vec[new_item_count - 1].span();
 323         let snippet = context.snippet(sp);
 324         let lo = sp.lo() + BytePos(snippet.find_uncommented("_").unwrap() as u32);
 325         pat_vec[new_item_count - 1] = TuplePatField::Dotdot(mk_sp(lo, lo + BytePos(1)));
 326         (
 327             &pat_vec[..new_item_count],
 328             mk_sp(span.lo(), lo + BytePos(1)),
 329         )
 330     } else {
 331         (&pat_vec[..], span)
 332     };
 333
 334     // add comma if `(x,)`
 335     let add_comma = path_str.is_none() && pat_vec.len() == 1 && dotdot_pos.is_none();
 336     let mut context = context.clone();
 337     if let Some(&TuplePatField::Dotdot(..)) = pat_vec.last() {
 338         context.inside_macro = true;
 339     }
 340     let path_str = path_str.unwrap_or_default();
 341     let mut pat_ref_vec = Vec::with_capacity(pat_vec.len());
 342     for pat in pat_vec {
 343         pat_ref_vec.push(pat);
 344     }
 345
 346     rewrite_call_inner(
 347         &context,
 348         &path_str,
 349         &pat_ref_vec[..],
 350         span,
 351         shape,
 352         shape.width,
 353         add_comma,
 354     ).ok()
 355 }
 356
 357 fn count_wildcard_suffix_len(
 358     context: &RewriteContext,
 359     patterns: &[TuplePatField],
 360     span: Span,
 361     shape: Shape,
 362 ) -> usize {
 363     let mut suffix_len = 0;
 364
 365     let items: Vec<_> = itemize_list(
 366         context.codemap,
 367         patterns.iter(),
 368         ")",
 369         |item| item.span().lo(),
 370         |item| item.span().hi(),
 371         |item| item.rewrite(context, shape),
 372         context.codemap.span_after(span, "("),
 373         span.hi() - BytePos(1),
 374         false,
 375     ).collect();
 376
 377     for item in items.iter().rev().take_while(|i| match i.item {
 378         Some(ref internal_string) if internal_string == "_" => true,
 379         _ => false,
 380     }) {
 381         suffix_len += 1;
 382
 383         if item.pre_comment.is_some() || item.post_comment.is_some() {
 384             break;
 385         }
 386     }
 387
 388     suffix_len
 389 }