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