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};
  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                     "",
  69                     infix,
  70                     "",
  71                     context,
  72                     shape,
  73                     SeparatorPlace::Front,
  74                 )
  75             }
  76             PatKind::Ref(ref pat, mutability) => {
  77                 let prefix = format!("&{}", format_mutability(mutability));
  78                 rewrite_unary_prefix(context, &prefix, &**pat, shape)
  79             }
  80             PatKind::Tuple(ref items, dotdot_pos) => {
  81                 rewrite_tuple_pat(items, dotdot_pos, None, self.span, context, shape)
  82             }
  83             PatKind::Path(ref q_self, ref path) => {
  84                 rewrite_path(context, PathContext::Expr, q_self.as_ref(), path, shape)
  85             }
  86             PatKind::TupleStruct(ref path, ref pat_vec, dotdot_pos) => {
  87                 let path_str = rewrite_path(context, PathContext::Expr, None, path, shape)?;
  88                 rewrite_tuple_pat(
  89                     pat_vec,
  90                     dotdot_pos,
  91                     Some(path_str),
  92                     self.span,
  93                     context,
  94                     shape,
  95                 )
  96             }
  97             PatKind::Lit(ref expr) => expr.rewrite(context, shape),
  98             PatKind::Slice(ref prefix, ref slice_pat, ref suffix) => {
  99                 // Rewrite all the sub-patterns.
 100                 let prefix = prefix.iter().map(|p| p.rewrite(context, shape));
 101                 let slice_pat = slice_pat
 102                     .as_ref()
 103                     .map(|p| Some(format!("{}..", p.rewrite(context, shape)?)));
 104                 let suffix = suffix.iter().map(|p| p.rewrite(context, shape));
 105
 106                 // Munge them together.
 107                 let pats: Option<Vec<String>> =
 108                     prefix.chain(slice_pat.into_iter()).chain(suffix).collect();
 109
 110                 // Check that all the rewrites succeeded, and if not return None.
 111                 let pats = pats?;
 112
 113                 // Unwrap all the sub-strings and join them with commas.
 114                 let result = if context.config.spaces_within_square_brackets() {
 115                     format!("[ {} ]", pats.join(", "))
 116                 } else {
 117                     format!("[{}]", pats.join(", "))
 118                 };
 119                 Some(result)
 120             }
 121             PatKind::Struct(ref path, ref fields, elipses) => {
 122                 rewrite_struct_pat(path, fields, elipses, self.span, context, shape)
 123             }
 124             // FIXME(#819) format pattern macros.
 125             PatKind::Mac(..) => Some(context.snippet(self.span)),
 126         }
 127     }
 128 }
 129
 130 fn rewrite_struct_pat(
 131     path: &ast::Path,
 132     fields: &[codemap::Spanned<ast::FieldPat>],
 133     elipses: 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() && !elipses {
 143         return Some(format!("{} {{}}", path_str));
 144     }
 145
 146     let (elipses_str, terminator) = if elipses { (", ..", "..") } else { ("", "}") };
 147
 148     // 3 = ` { `, 2 = ` }`.
 149     let (h_shape, v_shape) =
 150         struct_lit_shape(shape, context, path_str.len() + 3, elipses_str.len() + 2)?;
 151
 152     let items = itemize_list(
 153         context.codemap,
 154         fields.iter(),
 155         terminator,
 156         |f| f.span.lo(),
 157         |f| f.span.hi(),
 158         |f| f.node.rewrite(context, v_shape),
 159         context.codemap.span_after(span, "{"),
 160         span.hi(),
 161         false,
 162     );
 163     let item_vec = items.collect::<Vec<_>>();
 164
 165     let tactic = struct_lit_tactic(h_shape, context, &item_vec);
 166     let nested_shape = shape_for_tactic(tactic, h_shape, v_shape);
 167     let fmt = struct_lit_formatting(nested_shape, tactic, context, false);
 168
 169     let mut fields_str = write_list(&item_vec, &fmt)?;
 170     let one_line_width = h_shape.map_or(0, |shape| shape.width);
 171
 172     if elipses {
 173         if fields_str.contains('\n') || fields_str.len() > one_line_width {
 174             // Add a missing trailing comma.
 175             if fmt.trailing_separator == SeparatorTactic::Never {
 176                 fields_str.push_str(",");
 177             }
 178             fields_str.push_str("\n");
 179             fields_str.push_str(&nested_shape.indent.to_string(context.config));
 180             fields_str.push_str("..");
 181         } else {
 182             if !fields_str.is_empty() {
 183                 // there are preceeding struct fields being matched on
 184                 if fmt.tactic == DefinitiveListTactic::Vertical {
 185                     // if the tactic is Vertical, write_list already added a trailing ,
 186                     fields_str.push_str(" ");
 187                 } else {
 188                     fields_str.push_str(", ");
 189                 }
 190             }
 191             fields_str.push_str("..");
 192         }
 193     }
 194
 195     let fields_str = wrap_struct_field(context, &fields_str, shape, v_shape, one_line_width);
 196     Some(format!("{} {{{}}}", path_str, fields_str))
 197 }
 198
 199 impl Rewrite for FieldPat {
 200     fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
 201         let pat = self.pat.rewrite(context, shape);
 202         if self.is_shorthand {
 203             pat
 204         } else {
 205             let pat_str = pat?;
 206             let id_str = self.ident.to_string();
 207             let one_line_width = id_str.len() + 2 + pat_str.len();
 208             if one_line_width <= shape.width {
 209                 Some(format!("{}: {}", id_str, pat_str))
 210             } else {
 211                 let nested_shape = shape.block_indent(context.config.tab_spaces());
 212                 let pat_str = self.pat.rewrite(context, nested_shape)?;
 213                 Some(format!(
 214                     "{}:\n{}{}",
 215                     id_str,
 216                     nested_shape.indent.to_string(context.config),
 217                     pat_str,
 218                 ))
 219             }
 220         }
 221     }
 222 }
 223
 224 pub enum TuplePatField<'a> {
 225     Pat(&'a ptr::P<ast::Pat>),
 226     Dotdot(Span),
 227 }
 228
 229 impl<'a> Rewrite for TuplePatField<'a> {
 230     fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
 231         match *self {
 232             TuplePatField::Pat(p) => p.rewrite(context, shape),
 233             TuplePatField::Dotdot(_) => Some("..".to_string()),
 234         }
 235     }
 236 }
 237
 238 impl<'a> Spanned for TuplePatField<'a> {
 239     fn span(&self) -> Span {
 240         match *self {
 241             TuplePatField::Pat(p) => p.span(),
 242             TuplePatField::Dotdot(span) => span,
 243         }
 244     }
 245 }
 246
 247 pub fn can_be_overflowed_pat(context: &RewriteContext, pat: &TuplePatField, len: usize) -> bool {
 248     match *pat {
 249         TuplePatField::Pat(pat) => match pat.node {
 250             ast::PatKind::Path(..) | ast::PatKind::Tuple(..) | ast::PatKind::Struct(..) => {
 251                 context.use_block_indent() && len == 1
 252             }
 253             ast::PatKind::Ref(ref p, _) | ast::PatKind::Box(ref p) => {
 254                 can_be_overflowed_pat(context, &TuplePatField::Pat(p), len)
 255             }
 256             ast::PatKind::Lit(ref expr) => can_be_overflowed_expr(context, expr, len),
 257             _ => false,
 258         },
 259         TuplePatField::Dotdot(..) => false,
 260     }
 261 }
 262
 263 fn rewrite_tuple_pat(
 264     pats: &[ptr::P<ast::Pat>],
 265     dotdot_pos: Option<usize>,
 266     path_str: Option<String>,
 267     span: Span,
 268     context: &RewriteContext,
 269     shape: Shape,
 270 ) -> Option<String> {
 271     let mut pat_vec: Vec<_> = pats.into_iter().map(|x| TuplePatField::Pat(x)).collect();
 272
 273     if let Some(pos) = dotdot_pos {
 274         let prev = if pos == 0 {
 275             span.lo()
 276         } else {
 277             pats[pos - 1].span().hi()
 278         };
 279         let next = if pos + 1 >= pats.len() {
 280             span.hi()
 281         } else {
 282             pats[pos + 1].span().lo()
 283         };
 284         let dot_span = mk_sp(prev, next);
 285         let snippet = context.snippet(dot_span);
 286         let lo = dot_span.lo() + BytePos(snippet.find_uncommented("..").unwrap() as u32);
 287         let dotdot = TuplePatField::Dotdot(Span::new(
 288             lo,
 289             // 2 == "..".len()
 290             lo + BytePos(2),
 291             codemap::NO_EXPANSION,
 292         ));
 293         pat_vec.insert(pos, dotdot);
 294     }
 295
 296     if pat_vec.is_empty() {
 297         return Some(format!("{}()", path_str.unwrap_or_default()));
 298     }
 299
 300     let wildcard_suffix_len = count_wildcard_suffix_len(context, &pat_vec, span, shape);
 301     let (pat_vec, span) = if context.config.condense_wildcard_suffixes() && wildcard_suffix_len >= 2
 302     {
 303         let new_item_count = 1 + pat_vec.len() - wildcard_suffix_len;
 304         let sp = pat_vec[new_item_count - 1].span();
 305         let snippet = context.snippet(sp);
 306         let lo = sp.lo() + BytePos(snippet.find_uncommented("_").unwrap() as u32);
 307         pat_vec[new_item_count - 1] = TuplePatField::Dotdot(mk_sp(lo, lo + BytePos(1)));
 308         (
 309             &pat_vec[..new_item_count],
 310             mk_sp(span.lo(), lo + BytePos(1)),
 311         )
 312     } else {
 313         (&pat_vec[..], span)
 314     };
 315
 316     // add comma if `(x,)`
 317     let add_comma = path_str.is_none() && pat_vec.len() == 1 && dotdot_pos.is_none();
 318     let mut context = context.clone();
 319     if let Some(&TuplePatField::Dotdot(..)) = pat_vec.last() {
 320         context.inside_macro = true;
 321     }
 322     let path_str = path_str.unwrap_or_default();
 323     let mut pat_ref_vec = Vec::with_capacity(pat_vec.len());
 324     for pat in pat_vec {
 325         pat_ref_vec.push(pat);
 326     }
 327
 328     rewrite_call_inner(
 329         &context,
 330         &path_str,
 331         &pat_ref_vec[..],
 332         span,
 333         shape,
 334         shape.width,
 335         add_comma,
 336     )
 337 }
 338
 339 fn count_wildcard_suffix_len(
 340     context: &RewriteContext,
 341     patterns: &[TuplePatField],
 342     span: Span,
 343     shape: Shape,
 344 ) -> usize {
 345     let mut suffix_len = 0;
 346
 347     let items: Vec<_> = itemize_list(
 348         context.codemap,
 349         patterns.iter(),
 350         ")",
 351         |item| item.span().lo(),
 352         |item| item.span().hi(),
 353         |item| item.rewrite(context, shape),
 354         context.codemap.span_after(span, "("),
 355         span.hi() - BytePos(1),
 356         false,
 357     ).collect();
 358
 359     for item in items.iter().rev().take_while(|i| match i.item {
 360         Some(ref internal_string) if internal_string == "_" => true,
 361         _ => false,
 362     }) {
 363         suffix_len += 1;
 364
 365         if item.pre_comment.is_some() || item.post_comment.is_some() {
 366             break;
 367         }
 368     }
 369
 370     suffix_len
 371 }