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 macros::{rewrite_macro, MacroPosition};
  23 use rewrite::{Rewrite, RewriteContext};
  24 use shape::Shape;
  25 use types::{rewrite_path, PathContext};
  26 use utils::{format_mutability, mk_sp};
  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 = shape
  43                             .width
  44                             .checked_sub(prefix.len() + mut_infix.len() + id_str.len() + 3)?;
  45                         format!(
  46                             " @ {}",
  47                             p.rewrite(context, Shape::legacy(width, shape.indent))?
  48                         )
  49                     }
  50                     None => "".to_owned(),
  51                 };
  52
  53                 Some(format!("{}{}{}{}", prefix, mut_infix, id_str, sub_pat))
  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                 let infix = match *end_kind {
  64                     RangeEnd::Included(RangeSyntax::DotDotDot) => "...",
  65                     RangeEnd::Included(RangeSyntax::DotDotEq) => "..=",
  66                     RangeEnd::Excluded => "..",
  67                 };
  68                 rewrite_pair(
  69                     &**lhs,
  70                     &**rhs,
  71                     PairParts::new("", infix, ""),
  72                     context,
  73                     shape,
  74                     SeparatorPlace::Front,
  75                 )
  76             }
  77             PatKind::Ref(ref pat, mutability) => {
  78                 let prefix = format!("&{}", format_mutability(mutability));
  79                 rewrite_unary_prefix(context, &prefix, &**pat, shape)
  80             }
  81             PatKind::Tuple(ref items, dotdot_pos) => {
  82                 rewrite_tuple_pat(items, dotdot_pos, None, self.span, context, shape)
  83             }
  84             PatKind::Path(ref q_self, ref path) => {
  85                 rewrite_path(context, PathContext::Expr, q_self.as_ref(), path, shape)
  86             }
  87             PatKind::TupleStruct(ref path, ref pat_vec, dotdot_pos) => {
  88                 let path_str = rewrite_path(context, PathContext::Expr, None, path, shape)?;
  89                 rewrite_tuple_pat(
  90                     pat_vec,
  91                     dotdot_pos,
  92                     Some(path_str),
  93                     self.span,
  94                     context,
  95                     shape,
  96                 )
  97             }
  98             PatKind::Lit(ref expr) => expr.rewrite(context, shape),
  99             PatKind::Slice(ref prefix, ref slice_pat, ref suffix) => {
 100                 // Rewrite all the sub-patterns.
 101                 let prefix = prefix.iter().map(|p| p.rewrite(context, shape));
 102                 let slice_pat = slice_pat
 103                     .as_ref()
 104                     .map(|p| Some(format!("{}..", p.rewrite(context, shape)?)));
 105                 let suffix = suffix.iter().map(|p| p.rewrite(context, shape));
 106
 107                 // Munge them together.
 108                 let pats: Option<Vec<String>> =
 109                     prefix.chain(slice_pat.into_iter()).chain(suffix).collect();
 110
 111                 // Check that all the rewrites succeeded, and if not return None.
 112                 let pats = pats?;
 113
 114                 // Unwrap all the sub-strings and join them with commas.
 115                 let result = if context.config.spaces_within_parens_and_brackets() {
 116                     format!("[ {} ]", pats.join(", "))
 117                 } else {
 118                     format!("[{}]", pats.join(", "))
 119                 };
 120                 Some(result)
 121             }
 122             PatKind::Struct(ref path, ref fields, ellipsis) => {
 123                 rewrite_struct_pat(path, fields, ellipsis, self.span, context, shape)
 124             }
 125             PatKind::Mac(ref mac) => rewrite_macro(mac, None, context, shape, MacroPosition::Pat),
 126         }
 127     }
 128 }
 129
 130 fn rewrite_struct_pat(
 131     path: &ast::Path,
 132     fields: &[codemap::Spanned<ast::FieldPat>],
 133     ellipsis: bool,
 134     span: Span,
 135     context: &RewriteContext,
 136     shape: Shape,
 137 ) -> Option<String> {
 138     // 2 =  ` {`
 139     let path_shape = shape.sub_width(2)?;
 140     let path_str = rewrite_path(context, PathContext::Expr, None, path, path_shape)?;
 141
 142     if fields.is_empty() && !ellipsis {
 143         return Some(format!("{} {{}}", path_str));
 144     }
 145
 146     let (ellipsis_str, terminator) = if ellipsis { (", ..", "..") } else { ("", "}") };
 147
 148     // 3 = ` { `, 2 = ` }`.
 149     let (h_shape, v_shape) =
 150         struct_lit_shape(shape, context, path_str.len() + 3, ellipsis_str.len() + 2)?;
 151
 152     let items = itemize_list(
 153         context.codemap,
 154         fields.iter(),
 155         terminator,
 156         ",",
 157         |f| f.span.lo(),
 158         |f| f.span.hi(),
 159         |f| f.node.rewrite(context, v_shape),
 160         context.codemap.span_after(span, "{"),
 161         span.hi(),
 162         false,
 163     );
 164     let item_vec = items.collect::<Vec<_>>();
 165
 166     let tactic = struct_lit_tactic(h_shape, context, &item_vec);
 167     let nested_shape = shape_for_tactic(tactic, h_shape, v_shape);
 168     let fmt = struct_lit_formatting(nested_shape, tactic, context, false);
 169
 170     let mut fields_str = write_list(&item_vec, &fmt)?;
 171     let one_line_width = h_shape.map_or(0, |shape| shape.width);
 172
 173     if ellipsis {
 174         if fields_str.contains('\n') || fields_str.len() > one_line_width {
 175             // Add a missing trailing comma.
 176             if fmt.trailing_separator == SeparatorTactic::Never {
 177                 fields_str.push_str(",");
 178             }
 179             fields_str.push_str("\n");
 180             fields_str.push_str(&nested_shape.indent.to_string(context.config));
 181             fields_str.push_str("..");
 182         } else {
 183             if !fields_str.is_empty() {
 184                 // there are preceding struct fields being matched on
 185                 if fmt.tactic == DefinitiveListTactic::Vertical {
 186                     // if the tactic is Vertical, write_list already added a trailing ,
 187                     fields_str.push_str(" ");
 188                 } else {
 189                     fields_str.push_str(", ");
 190                 }
 191             }
 192             fields_str.push_str("..");
 193         }
 194     }
 195
 196     let fields_str = wrap_struct_field(context, &fields_str, shape, v_shape, one_line_width);
 197     Some(format!("{} {{{}}}", path_str, fields_str))
 198 }
 199
 200 impl Rewrite for FieldPat {
 201     fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
 202         let pat = self.pat.rewrite(context, shape);
 203         if self.is_shorthand {
 204             pat
 205         } else {
 206             let pat_str = pat?;
 207             let id_str = self.ident.to_string();
 208             let one_line_width = id_str.len() + 2 + pat_str.len();
 209             if one_line_width <= shape.width {
 210                 Some(format!("{}: {}", id_str, pat_str))
 211             } else {
 212                 let nested_shape = shape.block_indent(context.config.tab_spaces());
 213                 let pat_str = self.pat.rewrite(context, nested_shape)?;
 214                 Some(format!(
 215                     "{}:\n{}{}",
 216                     id_str,
 217                     nested_shape.indent.to_string(context.config),
 218                     pat_str,
 219                 ))
 220             }
 221         }
 222     }
 223 }
 224
 225 pub enum TuplePatField<'a> {
 226     Pat(&'a ptr::P<ast::Pat>),
 227     Dotdot(Span),
 228 }
 229
 230 impl<'a> Rewrite for TuplePatField<'a> {
 231     fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
 232         match *self {
 233             TuplePatField::Pat(p) => p.rewrite(context, shape),
 234             TuplePatField::Dotdot(_) => Some("..".to_string()),
 235         }
 236     }
 237 }
 238
 239 impl<'a> Spanned for TuplePatField<'a> {
 240     fn span(&self) -> Span {
 241         match *self {
 242             TuplePatField::Pat(p) => p.span(),
 243             TuplePatField::Dotdot(span) => span,
 244         }
 245     }
 246 }
 247
 248 pub fn can_be_overflowed_pat(context: &RewriteContext, pat: &TuplePatField, len: usize) -> bool {
 249     match *pat {
 250         TuplePatField::Pat(pat) => match pat.node {
 251             ast::PatKind::Path(..)
 252             | ast::PatKind::Tuple(..)
 253             | ast::PatKind::Struct(..)
 254             | ast::PatKind::TupleStruct(..) => context.use_block_indent() && len == 1,
 255             ast::PatKind::Ref(ref p, _) | ast::PatKind::Box(ref p) => {
 256                 can_be_overflowed_pat(context, &TuplePatField::Pat(p), len)
 257             }
 258             ast::PatKind::Lit(ref expr) => can_be_overflowed_expr(context, expr, len),
 259             _ => false,
 260         },
 261         TuplePatField::Dotdot(..) => false,
 262     }
 263 }
 264
 265 fn rewrite_tuple_pat(
 266     pats: &[ptr::P<ast::Pat>],
 267     dotdot_pos: Option<usize>,
 268     path_str: Option<String>,
 269     span: Span,
 270     context: &RewriteContext,
 271     shape: Shape,
 272 ) -> Option<String> {
 273     let mut pat_vec: Vec<_> = pats.into_iter().map(|x| TuplePatField::Pat(x)).collect();
 274
 275     if let Some(pos) = dotdot_pos {
 276         let prev = if pos == 0 {
 277             span.lo()
 278         } else {
 279             pats[pos - 1].span().hi()
 280         };
 281         let next = if pos + 1 >= pats.len() {
 282             span.hi()
 283         } else {
 284             pats[pos + 1].span().lo()
 285         };
 286         let dot_span = mk_sp(prev, next);
 287         let snippet = context.snippet(dot_span);
 288         let lo = dot_span.lo() + BytePos(snippet.find_uncommented("..").unwrap() as u32);
 289         let dotdot = TuplePatField::Dotdot(Span::new(
 290             lo,
 291             // 2 == "..".len()
 292             lo + BytePos(2),
 293             codemap::NO_EXPANSION,
 294         ));
 295         pat_vec.insert(pos, dotdot);
 296     }
 297
 298     if pat_vec.is_empty() {
 299         return Some(format!("{}()", path_str.unwrap_or_default()));
 300     }
 301
 302     let wildcard_suffix_len = count_wildcard_suffix_len(context, &pat_vec, span, shape);
 303     let (pat_vec, span) = if context.config.condense_wildcard_suffixes() && wildcard_suffix_len >= 2
 304     {
 305         let new_item_count = 1 + pat_vec.len() - wildcard_suffix_len;
 306         let sp = pat_vec[new_item_count - 1].span();
 307         let snippet = context.snippet(sp);
 308         let lo = sp.lo() + BytePos(snippet.find_uncommented("_").unwrap() as u32);
 309         pat_vec[new_item_count - 1] = TuplePatField::Dotdot(mk_sp(lo, lo + BytePos(1)));
 310         (
 311             &pat_vec[..new_item_count],
 312             mk_sp(span.lo(), lo + BytePos(1)),
 313         )
 314     } else {
 315         (&pat_vec[..], span)
 316     };
 317
 318     // add comma if `(x,)`
 319     let add_comma = path_str.is_none() && pat_vec.len() == 1 && dotdot_pos.is_none();
 320     let mut context = context.clone();
 321     if let Some(&TuplePatField::Dotdot(..)) = pat_vec.last() {
 322         context.inside_macro = true;
 323     }
 324     let path_str = path_str.unwrap_or_default();
 325     let mut pat_ref_vec = Vec::with_capacity(pat_vec.len());
 326     for pat in pat_vec {
 327         pat_ref_vec.push(pat);
 328     }
 329
 330     rewrite_call_inner(
 331         &context,
 332         &path_str,
 333         &pat_ref_vec[..],
 334         span,
 335         shape,
 336         shape.width,
 337         add_comma,
 338     )
 339 }
 340
 341 fn count_wildcard_suffix_len(
 342     context: &RewriteContext,
 343     patterns: &[TuplePatField],
 344     span: Span,
 345     shape: Shape,
 346 ) -> usize {
 347     let mut suffix_len = 0;
 348
 349     let items: Vec<_> = itemize_list(
 350         context.codemap,
 351         patterns.iter(),
 352         ")",
 353         ",",
 354         |item| item.span().lo(),
 355         |item| item.span().hi(),
 356         |item| item.rewrite(context, shape),
 357         context.codemap.span_after(span, "("),
 358         span.hi() - BytePos(1),
 359         false,
 360     ).collect();
 361
 362     for item in items.iter().rev().take_while(|i| match i.item {
 363         Some(ref internal_string) if internal_string == "_" => true,
 364         _ => false,
 365     }) {
 366         suffix_len += 1;
 367
 368         if item.pre_comment.is_some() || item.post_comment.is_some() {
 369             break;
 370         }
 371     }
 372
 373     suffix_len
 374 }