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, RangeSyntax};
  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, PairParts};
  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 = shape
  42                             .width
  43                             .checked_sub(prefix.len() + mut_infix.len() + id_str.len() + 3)?;
  44                         format!(
  45                             " @ {}",
  46                             p.rewrite(context, Shape::legacy(width, shape.indent))?
  47                         )
  48                     }
  49                     None => "".to_owned(),
  50                 };
  51
  52                 Some(format!("{}{}{}{}", prefix, mut_infix, id_str, sub_pat))
  53             }
  54             PatKind::Wild => if 1 <= shape.width {
  55                 Some("_".to_owned())
  56             } else {
  57                 None
  58             },
  59             PatKind::Range(ref lhs, ref rhs, ref end_kind) => {
  60                 let infix = match *end_kind {
  61                     RangeEnd::Included(RangeSyntax::DotDotDot) => "...",
  62                     RangeEnd::Included(RangeSyntax::DotDotEq) => "..=",
  63                     RangeEnd::Excluded => "..",
  64                 };
  65                 rewrite_pair(
  66                     &**lhs,
  67                     &**rhs,
  68                     PairParts::new("", infix, ""),
  69                     context,
  70                     shape,
  71                     SeparatorPlace::Front,
  72                 )
  73             }
  74             PatKind::Ref(ref pat, mutability) => {
  75                 let prefix = format!("&{}", format_mutability(mutability));
  76                 rewrite_unary_prefix(context, &prefix, &**pat, shape)
  77             }
  78             PatKind::Tuple(ref items, dotdot_pos) => {
  79                 rewrite_tuple_pat(items, dotdot_pos, None, self.span, context, shape)
  80             }
  81             PatKind::Path(ref q_self, ref path) => {
  82                 rewrite_path(context, PathContext::Expr, q_self.as_ref(), path, shape)
  83             }
  84             PatKind::TupleStruct(ref path, ref pat_vec, dotdot_pos) => {
  85                 let path_str = rewrite_path(context, PathContext::Expr, None, path, shape)?;
  86                 rewrite_tuple_pat(
  87                     pat_vec,
  88                     dotdot_pos,
  89                     Some(path_str),
  90                     self.span,
  91                     context,
  92                     shape,
  93                 )
  94             }
  95             PatKind::Lit(ref expr) => expr.rewrite(context, shape),
  96             PatKind::Slice(ref prefix, ref slice_pat, ref suffix) => {
  97                 // Rewrite all the sub-patterns.
  98                 let prefix = prefix.iter().map(|p| p.rewrite(context, shape));
  99                 let slice_pat = slice_pat
 100                     .as_ref()
 101                     .map(|p| Some(format!("{}..", p.rewrite(context, shape)?)));
 102                 let suffix = suffix.iter().map(|p| p.rewrite(context, shape));
 103
 104                 // Munge them together.
 105                 let pats: Option<Vec<String>> =
 106                     prefix.chain(slice_pat.into_iter()).chain(suffix).collect();
 107
 108                 // Check that all the rewrites succeeded, and if not return None.
 109                 let pats = pats?;
 110
 111                 // Unwrap all the sub-strings and join them with commas.
 112                 let result = if context.config.spaces_within_square_brackets() {
 113                     format!("[ {} ]", pats.join(", "))
 114                 } else {
 115                     format!("[{}]", pats.join(", "))
 116                 };
 117                 Some(result)
 118             }
 119             PatKind::Struct(ref path, ref fields, ellipsis) => {
 120                 rewrite_struct_pat(path, fields, ellipsis, self.span, context, shape)
 121             }
 122             // FIXME(#819) format pattern macros.
 123             PatKind::Mac(..) => Some(context.snippet(self.span)),
 124         }
 125     }
 126 }
 127
 128 fn rewrite_struct_pat(
 129     path: &ast::Path,
 130     fields: &[codemap::Spanned<ast::FieldPat>],
 131     ellipsis: bool,
 132     span: Span,
 133     context: &RewriteContext,
 134     shape: Shape,
 135 ) -> Option<String> {
 136     // 2 =  ` {`
 137     let path_shape = shape.sub_width(2)?;
 138     let path_str = rewrite_path(context, PathContext::Expr, None, path, path_shape)?;
 139
 140     if fields.is_empty() && !ellipsis {
 141         return Some(format!("{} {{}}", path_str));
 142     }
 143
 144     let (ellipsis_str, terminator) = if ellipsis { (", ..", "..") } else { ("", "}") };
 145
 146     // 3 = ` { `, 2 = ` }`.
 147     let (h_shape, v_shape) =
 148         struct_lit_shape(shape, context, path_str.len() + 3, ellipsis_str.len() + 2)?;
 149
 150     let items = itemize_list(
 151         context.codemap,
 152         fields.iter(),
 153         terminator,
 154         |f| f.span.lo(),
 155         |f| f.span.hi(),
 156         |f| f.node.rewrite(context, v_shape),
 157         context.codemap.span_after(span, "{"),
 158         span.hi(),
 159         false,
 160     );
 161     let item_vec = items.collect::<Vec<_>>();
 162
 163     let tactic = struct_lit_tactic(h_shape, context, &item_vec);
 164     let nested_shape = shape_for_tactic(tactic, h_shape, v_shape);
 165     let fmt = struct_lit_formatting(nested_shape, tactic, context, false);
 166
 167     let mut fields_str = write_list(&item_vec, &fmt)?;
 168     let one_line_width = h_shape.map_or(0, |shape| shape.width);
 169
 170     if ellipsis {
 171         if fields_str.contains('\n') || fields_str.len() > one_line_width {
 172             // Add a missing trailing comma.
 173             if fmt.trailing_separator == SeparatorTactic::Never {
 174                 fields_str.push_str(",");
 175             }
 176             fields_str.push_str("\n");
 177             fields_str.push_str(&nested_shape.indent.to_string(context.config));
 178             fields_str.push_str("..");
 179         } else {
 180             if !fields_str.is_empty() {
 181                 // there are preceding struct fields being matched on
 182                 if fmt.tactic == DefinitiveListTactic::Vertical {
 183                     // if the tactic is Vertical, write_list already added a trailing ,
 184                     fields_str.push_str(" ");
 185                 } else {
 186                     fields_str.push_str(", ");
 187                 }
 188             }
 189             fields_str.push_str("..");
 190         }
 191     }
 192
 193     let fields_str = wrap_struct_field(context, &fields_str, shape, v_shape, one_line_width);
 194     Some(format!("{} {{{}}}", path_str, fields_str))
 195 }
 196
 197 impl Rewrite for FieldPat {
 198     fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
 199         let pat = self.pat.rewrite(context, shape);
 200         if self.is_shorthand {
 201             pat
 202         } else {
 203             let pat_str = pat?;
 204             let id_str = self.ident.to_string();
 205             let one_line_width = id_str.len() + 2 + pat_str.len();
 206             if one_line_width <= shape.width {
 207                 Some(format!("{}: {}", id_str, pat_str))
 208             } else {
 209                 let nested_shape = shape.block_indent(context.config.tab_spaces());
 210                 let pat_str = self.pat.rewrite(context, nested_shape)?;
 211                 Some(format!(
 212                     "{}:\n{}{}",
 213                     id_str,
 214                     nested_shape.indent.to_string(context.config),
 215                     pat_str,
 216                 ))
 217             }
 218         }
 219     }
 220 }
 221
 222 pub 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(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(p) => p.span(),
 240             TuplePatField::Dotdot(span) => span,
 241         }
 242     }
 243 }
 244
 245 pub fn can_be_overflowed_pat(context: &RewriteContext, pat: &TuplePatField, len: usize) -> bool {
 246     match *pat {
 247         TuplePatField::Pat(pat) => match pat.node {
 248             ast::PatKind::Path(..) |
 249             ast::PatKind::Tuple(..) |
 250             ast::PatKind::Struct(..) |
 251             ast::PatKind::TupleStruct(..) => context.use_block_indent() && len == 1,
 252             ast::PatKind::Ref(ref p, _) | ast::PatKind::Box(ref p) => {
 253                 can_be_overflowed_pat(context, &TuplePatField::Pat(p), len)
 254             }
 255             ast::PatKind::Lit(ref expr) => can_be_overflowed_expr(context, expr, len),
 256             _ => false,
 257         },
 258         TuplePatField::Dotdot(..) => false,
 259     }
 260 }
 261
 262 fn rewrite_tuple_pat(
 263     pats: &[ptr::P<ast::Pat>],
 264     dotdot_pos: Option<usize>,
 265     path_str: Option<String>,
 266     span: Span,
 267     context: &RewriteContext,
 268     shape: Shape,
 269 ) -> Option<String> {
 270     let mut pat_vec: Vec<_> = pats.into_iter().map(|x| TuplePatField::Pat(x)).collect();
 271
 272     if let Some(pos) = dotdot_pos {
 273         let prev = if pos == 0 {
 274             span.lo()
 275         } else {
 276             pats[pos - 1].span().hi()
 277         };
 278         let next = if pos + 1 >= pats.len() {
 279             span.hi()
 280         } else {
 281             pats[pos + 1].span().lo()
 282         };
 283         let dot_span = mk_sp(prev, next);
 284         let snippet = context.snippet(dot_span);
 285         let lo = dot_span.lo() + BytePos(snippet.find_uncommented("..").unwrap() as u32);
 286         let dotdot = TuplePatField::Dotdot(Span::new(
 287             lo,
 288             // 2 == "..".len()
 289             lo + BytePos(2),
 290             codemap::NO_EXPANSION,
 291         ));
 292         pat_vec.insert(pos, dotdot);
 293     }
 294
 295     if pat_vec.is_empty() {
 296         return Some(format!("{}()", path_str.unwrap_or_default()));
 297     }
 298
 299     let wildcard_suffix_len = count_wildcard_suffix_len(context, &pat_vec, span, shape);
 300     let (pat_vec, span) = if context.config.condense_wildcard_suffixes() && wildcard_suffix_len >= 2
 301     {
 302         let new_item_count = 1 + pat_vec.len() - wildcard_suffix_len;
 303         let sp = pat_vec[new_item_count - 1].span();
 304         let snippet = context.snippet(sp);
 305         let lo = sp.lo() + BytePos(snippet.find_uncommented("_").unwrap() as u32);
 306         pat_vec[new_item_count - 1] = TuplePatField::Dotdot(mk_sp(lo, lo + BytePos(1)));
 307         (
 308             &pat_vec[..new_item_count],
 309             mk_sp(span.lo(), lo + BytePos(1)),
 310         )
 311     } else {
 312         (&pat_vec[..], span)
 313     };
 314
 315     // add comma if `(x,)`
 316     let add_comma = path_str.is_none() && pat_vec.len() == 1 && dotdot_pos.is_none();
 317     let mut context = context.clone();
 318     if let Some(&TuplePatField::Dotdot(..)) = pat_vec.last() {
 319         context.inside_macro = true;
 320     }
 321     let path_str = path_str.unwrap_or_default();
 322     let mut pat_ref_vec = Vec::with_capacity(pat_vec.len());
 323     for pat in pat_vec {
 324         pat_ref_vec.push(pat);
 325     }
 326
 327     rewrite_call_inner(
 328         &context,
 329         &path_str,
 330         &pat_ref_vec[..],
 331         span,
 332         shape,
 333         shape.width,
 334         add_comma,
 335     )
 336 }
 337
 338 fn count_wildcard_suffix_len(
 339     context: &RewriteContext,
 340     patterns: &[TuplePatField],
 341     span: Span,
 342     shape: Shape,
 343 ) -> usize {
 344     let mut suffix_len = 0;
 345
 346     let items: Vec<_> = itemize_list(
 347         context.codemap,
 348         patterns.iter(),
 349         ")",
 350         |item| item.span().lo(),
 351         |item| item.span().hi(),
 352         |item| item.rewrite(context, shape),
 353         context.codemap.span_after(span, "("),
 354         span.hi() - BytePos(1),
 355         false,
 356     ).collect();
 357
 358     for item in items.iter().rev().take_while(|i| match i.item {
 359         Some(ref internal_string) if internal_string == "_" => true,
 360         _ => false,
 361     }) {
 362         suffix_len += 1;
 363
 364         if item.pre_comment.is_some() || item.post_comment.is_some() {
 365             break;
 366         }
 367     }
 368
 369     suffix_len
 370 }