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 = 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) => {
  62                 let infix = match *end_kind {
  63                     RangeEnd::Included(RangeSyntax::DotDotDot) => "...",
  64                     RangeEnd::Included(RangeSyntax::DotDotEq) => "..=",
  65                     RangeEnd::Excluded => "..",
  66                 };
  67                 rewrite_pair(
  68                     &**lhs,
  69                     &**rhs,
  70                     "",
  71                     infix,
  72                     "",
  73                     context,
  74                     shape,
  75                     SeparatorPlace::Front,
  76                 )
  77             }
  78             PatKind::Ref(ref pat, mutability) => {
  79                 let prefix = format!("&{}", format_mutability(mutability));
  80                 rewrite_unary_prefix(context, &prefix, &**pat, shape)
  81             }
  82             PatKind::Tuple(ref items, dotdot_pos) => {
  83                 rewrite_tuple_pat(items, dotdot_pos, None, self.span, context, shape)
  84             }
  85             PatKind::Path(ref q_self, ref path) => {
  86                 rewrite_path(context, PathContext::Expr, q_self.as_ref(), path, shape)
  87             }
  88             PatKind::TupleStruct(ref path, ref pat_vec, dotdot_pos) => {
  89                 let path_str =
  90                     try_opt!(rewrite_path(context, PathContext::Expr, None, path, shape));
  91                 rewrite_tuple_pat(
  92                     pat_vec,
  93                     dotdot_pos,
  94                     Some(path_str),
  95                     self.span,
  96                     context,
  97                     shape,
  98                 )
  99             }
 100             PatKind::Lit(ref expr) => expr.rewrite(context, shape),
 101             PatKind::Slice(ref prefix, ref slice_pat, ref suffix) => {
 102                 // Rewrite all the sub-patterns.
 103                 let prefix = prefix.iter().map(|p| p.rewrite(context, shape));
 104                 let slice_pat = slice_pat.as_ref().map(|p| {
 105                     Some(format!("{}..", try_opt!(p.rewrite(context, shape))))
 106                 });
 107                 let suffix = suffix.iter().map(|p| p.rewrite(context, shape));
 108
 109                 // Munge them together.
 110                 let pats: Option<Vec<String>> =
 111                     prefix.chain(slice_pat.into_iter()).chain(suffix).collect();
 112
 113                 // Check that all the rewrites succeeded, and if not return None.
 114                 let pats = try_opt!(pats);
 115
 116                 // Unwrap all the sub-strings and join them with commas.
 117                 let result = if context.config.spaces_within_square_brackets() {
 118                     format!("[ {} ]", pats.join(", "))
 119                 } else {
 120                     format!("[{}]", pats.join(", "))
 121                 };
 122                 Some(result)
 123             }
 124             PatKind::Struct(ref path, ref fields, elipses) => {
 125                 rewrite_struct_pat(path, fields, elipses, self.span, context, shape)
 126             }
 127             // FIXME(#819) format pattern macros.
 128             PatKind::Mac(..) => Some(context.snippet(self.span)),
 129         }
 130     }
 131 }
 132
 133 fn rewrite_struct_pat(
 134     path: &ast::Path,
 135     fields: &[codemap::Spanned<ast::FieldPat>],
 136     elipses: bool,
 137     span: Span,
 138     context: &RewriteContext,
 139     shape: Shape,
 140 ) -> Option<String> {
 141     // 2 =  ` {`
 142     let path_shape = try_opt!(shape.sub_width(2));
 143     let path_str = try_opt!(rewrite_path(
 144         context,
 145         PathContext::Expr,
 146         None,
 147         path,
 148         path_shape,
 149     ));
 150
 151     if fields.is_empty() && !elipses {
 152         return Some(format!("{} {{}}", path_str));
 153     }
 154
 155     let (elipses_str, terminator) = if elipses { (", ..", "..") } else { ("", "}") };
 156
 157     // 3 = ` { `, 2 = ` }`.
 158     let (h_shape, v_shape) = try_opt!(struct_lit_shape(
 159         shape,
 160         context,
 161         path_str.len() + 3,
 162         elipses_str.len() + 2,
 163     ));
 164
 165     let items = itemize_list(
 166         context.codemap,
 167         fields.iter(),
 168         terminator,
 169         |f| f.span.lo(),
 170         |f| f.span.hi(),
 171         |f| f.node.rewrite(context, v_shape),
 172         context.codemap.span_after(span, "{"),
 173         span.hi(),
 174         false,
 175     );
 176     let item_vec = items.collect::<Vec<_>>();
 177
 178     let tactic = struct_lit_tactic(h_shape, context, &item_vec);
 179     let nested_shape = shape_for_tactic(tactic, h_shape, v_shape);
 180     let fmt = struct_lit_formatting(nested_shape, tactic, context, false);
 181
 182     let mut fields_str = try_opt!(write_list(&item_vec, &fmt));
 183     let one_line_width = h_shape.map_or(0, |shape| shape.width);
 184
 185     if elipses {
 186         if fields_str.contains('\n') || fields_str.len() > one_line_width {
 187             // Add a missing trailing comma.
 188             if fmt.trailing_separator == SeparatorTactic::Never {
 189                 fields_str.push_str(",");
 190             }
 191             fields_str.push_str("\n");
 192             fields_str.push_str(&nested_shape.indent.to_string(context.config));
 193             fields_str.push_str("..");
 194         } else {
 195             if !fields_str.is_empty() {
 196                 // there are preceeding struct fields being matched on
 197                 if fmt.tactic == DefinitiveListTactic::Vertical {
 198                     // if the tactic is Vertical, write_list already added a trailing ,
 199                     fields_str.push_str(" ");
 200                 } else {
 201                     fields_str.push_str(", ");
 202                 }
 203             }
 204             fields_str.push_str("..");
 205         }
 206     }
 207
 208     let fields_str = wrap_struct_field(context, &fields_str, shape, v_shape, one_line_width);
 209     Some(format!("{} {{{}}}", path_str, fields_str))
 210 }
 211
 212 impl Rewrite for FieldPat {
 213     fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
 214         let pat = self.pat.rewrite(context, shape);
 215         if self.is_shorthand {
 216             pat
 217         } else {
 218             let pat_str = try_opt!(pat);
 219             let id_str = self.ident.to_string();
 220             let one_line_width = id_str.len() + 2 + pat_str.len();
 221             if one_line_width <= shape.width {
 222                 Some(format!("{}: {}", id_str, pat_str))
 223             } else {
 224                 let nested_shape = shape.block_indent(context.config.tab_spaces());
 225                 let pat_str = try_opt!(self.pat.rewrite(context, nested_shape));
 226                 Some(format!(
 227                     "{}:\n{}{}",
 228                     id_str,
 229                     nested_shape.indent.to_string(context.config),
 230                     pat_str,
 231                 ))
 232             }
 233         }
 234     }
 235 }
 236
 237 pub enum TuplePatField<'a> {
 238     Pat(&'a ptr::P<ast::Pat>),
 239     Dotdot(Span),
 240 }
 241
 242 impl<'a> Rewrite for TuplePatField<'a> {
 243     fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
 244         match *self {
 245             TuplePatField::Pat(p) => p.rewrite(context, shape),
 246             TuplePatField::Dotdot(_) => Some("..".to_string()),
 247         }
 248     }
 249 }
 250
 251 impl<'a> Spanned for TuplePatField<'a> {
 252     fn span(&self) -> Span {
 253         match *self {
 254             TuplePatField::Pat(p) => p.span(),
 255             TuplePatField::Dotdot(span) => span,
 256         }
 257     }
 258 }
 259
 260 pub fn can_be_overflowed_pat(context: &RewriteContext, pat: &TuplePatField, len: usize) -> bool {
 261     match *pat {
 262         TuplePatField::Pat(pat) => match pat.node {
 263             ast::PatKind::Path(..) | ast::PatKind::Tuple(..) | ast::PatKind::Struct(..) => {
 264                 context.use_block_indent() && len == 1
 265             }
 266             ast::PatKind::Ref(ref p, _) | ast::PatKind::Box(ref p) => {
 267                 can_be_overflowed_pat(context, &TuplePatField::Pat(p), len)
 268             }
 269             ast::PatKind::Lit(ref expr) => can_be_overflowed_expr(context, expr, len),
 270             _ => false,
 271         },
 272         TuplePatField::Dotdot(..) => false,
 273     }
 274 }
 275
 276 fn rewrite_tuple_pat(
 277     pats: &[ptr::P<ast::Pat>],
 278     dotdot_pos: Option<usize>,
 279     path_str: Option<String>,
 280     span: Span,
 281     context: &RewriteContext,
 282     shape: Shape,
 283 ) -> Option<String> {
 284     let mut pat_vec: Vec<_> = pats.into_iter().map(|x| TuplePatField::Pat(x)).collect();
 285
 286     if let Some(pos) = dotdot_pos {
 287         let prev = if pos == 0 {
 288             span.lo()
 289         } else {
 290             pats[pos - 1].span().hi()
 291         };
 292         let next = if pos + 1 >= pats.len() {
 293             span.hi()
 294         } else {
 295             pats[pos + 1].span().lo()
 296         };
 297         let dot_span = mk_sp(prev, next);
 298         let snippet = context.snippet(dot_span);
 299         let lo = dot_span.lo() + BytePos(snippet.find_uncommented("..").unwrap() as u32);
 300         let dotdot = TuplePatField::Dotdot(Span::new(
 301             lo,
 302             // 2 == "..".len()
 303             lo + BytePos(2),
 304             codemap::NO_EXPANSION,
 305         ));
 306         pat_vec.insert(pos, dotdot);
 307     }
 308
 309     if pat_vec.is_empty() {
 310         return Some(format!("{}()", path_str.unwrap_or_default()));
 311     }
 312
 313     let wildcard_suffix_len = count_wildcard_suffix_len(context, &pat_vec, span, shape);
 314     let (pat_vec, span) = if context.config.condense_wildcard_suffixes() && wildcard_suffix_len >= 2
 315     {
 316         let new_item_count = 1 + pat_vec.len() - wildcard_suffix_len;
 317         let sp = pat_vec[new_item_count - 1].span();
 318         let snippet = context.snippet(sp);
 319         let lo = sp.lo() + BytePos(snippet.find_uncommented("_").unwrap() as u32);
 320         pat_vec[new_item_count - 1] = TuplePatField::Dotdot(mk_sp(lo, lo + BytePos(1)));
 321         (
 322             &pat_vec[..new_item_count],
 323             mk_sp(span.lo(), lo + BytePos(1)),
 324         )
 325     } else {
 326         (&pat_vec[..], span)
 327     };
 328
 329     // add comma if `(x,)`
 330     let add_comma = path_str.is_none() && pat_vec.len() == 1 && dotdot_pos.is_none();
 331     let mut context = context.clone();
 332     if let Some(&TuplePatField::Dotdot(..)) = pat_vec.last() {
 333         context.inside_macro = true;
 334     }
 335     let path_str = path_str.unwrap_or_default();
 336     let mut pat_ref_vec = Vec::with_capacity(pat_vec.len());
 337     for pat in pat_vec {
 338         pat_ref_vec.push(pat);
 339     }
 340
 341     rewrite_call_inner(
 342         &context,
 343         &path_str,
 344         &pat_ref_vec[..],
 345         span,
 346         shape,
 347         shape.width,
 348         add_comma,
 349     ).ok()
 350 }
 351
 352 fn count_wildcard_suffix_len(
 353     context: &RewriteContext,
 354     patterns: &[TuplePatField],
 355     span: Span,
 356     shape: Shape,
 357 ) -> usize {
 358     let mut suffix_len = 0;
 359
 360     let items: Vec<_> = itemize_list(
 361         context.codemap,
 362         patterns.iter(),
 363         ")",
 364         |item| item.span().lo(),
 365         |item| item.span().hi(),
 366         |item| item.rewrite(context, shape),
 367         context.codemap.span_after(span, "("),
 368         span.hi() - BytePos(1),
 369         false,
 370     ).collect();
 371
 372     for item in items.iter().rev().take_while(|i| match i.item {
 373         Some(ref internal_string) if internal_string == "_" => true,
 374         _ => false,
 375     }) {
 376         suffix_len += 1;
 377
 378         if item.pre_comment.is_some() || item.post_comment.is_some() {
 379             break;
 380         }
 381     }
 382
 383     suffix_len
 384 }