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 config::lists::*;
  12 use syntax::ast::{self, BindingMode, FieldPat, Pat, PatKind, RangeEnd, RangeSyntax};
  13 use syntax::codemap::{self, BytePos, Span};
  14 use syntax::ptr;
  15
  16 use codemap::SpanUtils;
  17 use comment::FindUncommented;
  18 use expr::{can_be_overflowed_expr, rewrite_pair, rewrite_unary_prefix, wrap_struct_field,
  19            PairParts};
  20 use lists::{itemize_list, shape_for_tactic, struct_lit_formatting, struct_lit_shape,
  21             struct_lit_tactic, write_list};
  22 use macros::{rewrite_macro, MacroPosition};
  23 use overflow;
  24 use rewrite::{Rewrite, RewriteContext};
  25 use shape::Shape;
  26 use spanned::Spanned;
  27 use types::{rewrite_path, PathContext};
  28 use utils::{format_mutability, mk_sp};
  29
  30 impl Rewrite for Pat {
  31     fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
  32         match self.node {
  33             PatKind::Box(ref pat) => rewrite_unary_prefix(context, "box ", &**pat, shape),
  34             PatKind::Ident(binding_mode, ident, ref sub_pat) => {
  35                 let (prefix, mutability) = match binding_mode {
  36                     BindingMode::ByRef(mutability) => ("ref ", mutability),
  37                     BindingMode::ByValue(mutability) => ("", mutability),
  38                 };
  39                 let mut_infix = format_mutability(mutability);
  40                 let id_str = ident.node.to_string();
  41                 let sub_pat = match *sub_pat {
  42                     Some(ref p) => {
  43                         // 3 - ` @ `.
  44                         let width = shape
  45                             .width
  46                             .checked_sub(prefix.len() + mut_infix.len() + id_str.len() + 3)?;
  47                         format!(
  48                             " @ {}",
  49                             p.rewrite(context, Shape::legacy(width, shape.indent))?
  50                         )
  51                     }
  52                     None => "".to_owned(),
  53                 };
  54
  55                 Some(format!("{}{}{}{}", prefix, mut_infix, id_str, sub_pat))
  56             }
  57             PatKind::Wild => {
  58                 if 1 <= shape.width {
  59                     Some("_".to_owned())
  60                 } else {
  61                     None
  62                 }
  63             }
  64             PatKind::Range(ref lhs, ref rhs, ref end_kind) => {
  65                 let infix = match *end_kind {
  66                     RangeEnd::Included(RangeSyntax::DotDotDot) => "...",
  67                     RangeEnd::Included(RangeSyntax::DotDotEq) => "..=",
  68                     RangeEnd::Excluded => "..",
  69                 };
  70                 let infix = if context.config.spaces_around_ranges() {
  71                     format!(" {} ", infix)
  72                 } else {
  73                     infix.to_owned()
  74                 };
  75                 rewrite_pair(
  76                     &**lhs,
  77                     &**rhs,
  78                     PairParts::new("", &infix, ""),
  79                     context,
  80                     shape,
  81                     SeparatorPlace::Front,
  82                 )
  83             }
  84             PatKind::Ref(ref pat, mutability) => {
  85                 let prefix = format!("&{}", format_mutability(mutability));
  86                 rewrite_unary_prefix(context, &prefix, &**pat, shape)
  87             }
  88             PatKind::Tuple(ref items, dotdot_pos) => {
  89                 rewrite_tuple_pat(items, dotdot_pos, None, self.span, context, shape)
  90             }
  91             PatKind::Path(ref q_self, ref path) => {
  92                 rewrite_path(context, PathContext::Expr, q_self.as_ref(), path, shape)
  93             }
  94             PatKind::TupleStruct(ref path, ref pat_vec, dotdot_pos) => {
  95                 let path_str = 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
 110                     .as_ref()
 111                     .map(|p| Some(format!("{}..", p.rewrite(context, shape)?)));
 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 = pats?;
 120
 121                 // Unwrap all the sub-strings and join them with commas.
 122                 let result = if context.config.spaces_within_parens_and_brackets() {
 123                     format!("[ {} ]", pats.join(", "))
 124                 } else {
 125                     format!("[{}]", pats.join(", "))
 126                 };
 127                 Some(result)
 128             }
 129             PatKind::Struct(ref path, ref fields, ellipsis) => {
 130                 rewrite_struct_pat(path, fields, ellipsis, self.span, context, shape)
 131             }
 132             PatKind::Mac(ref mac) => rewrite_macro(mac, None, context, shape, MacroPosition::Pat),
 133             PatKind::Paren(ref pat) => pat.rewrite(context, shape.offset_left(1)?.sub_width(1)?)
 134                 .map(|inner_pat| format!("({})", inner_pat)),
 135         }
 136     }
 137 }
 138
 139 fn rewrite_struct_pat(
 140     path: &ast::Path,
 141     fields: &[codemap::Spanned<ast::FieldPat>],
 142     ellipsis: bool,
 143     span: Span,
 144     context: &RewriteContext,
 145     shape: Shape,
 146 ) -> Option<String> {
 147     // 2 =  ` {`
 148     let path_shape = shape.sub_width(2)?;
 149     let path_str = rewrite_path(context, PathContext::Expr, None, path, path_shape)?;
 150
 151     if fields.is_empty() && !ellipsis {
 152         return Some(format!("{} {{}}", path_str));
 153     }
 154
 155     let (ellipsis_str, terminator) = if ellipsis { (", ..", "..") } else { ("", "}") };
 156
 157     // 3 = ` { `, 2 = ` }`.
 158     let (h_shape, v_shape) =
 159         struct_lit_shape(shape, context, path_str.len() + 3, ellipsis_str.len() + 2)?;
 160
 161     let items = itemize_list(
 162         context.snippet_provider,
 163         fields.iter(),
 164         terminator,
 165         ",",
 166         |f| f.span.lo(),
 167         |f| f.span.hi(),
 168         |f| f.node.rewrite(context, v_shape),
 169         context.snippet_provider.span_after(span, "{"),
 170         span.hi(),
 171         false,
 172     );
 173     let item_vec = items.collect::<Vec<_>>();
 174
 175     let tactic = struct_lit_tactic(h_shape, context, &item_vec);
 176     let nested_shape = shape_for_tactic(tactic, h_shape, v_shape);
 177     let fmt = struct_lit_formatting(nested_shape, tactic, context, false);
 178
 179     let mut fields_str = write_list(&item_vec, &fmt)?;
 180     let one_line_width = h_shape.map_or(0, |shape| shape.width);
 181
 182     if ellipsis {
 183         if fields_str.contains('\n') || fields_str.len() > one_line_width {
 184             // Add a missing trailing comma.
 185             if fmt.trailing_separator == SeparatorTactic::Never {
 186                 fields_str.push_str(",");
 187             }
 188             fields_str.push_str("\n");
 189             fields_str.push_str(&nested_shape.indent.to_string(context.config));
 190             fields_str.push_str("..");
 191         } else {
 192             if !fields_str.is_empty() {
 193                 // there are preceding struct fields being matched on
 194                 if fmt.tactic == DefinitiveListTactic::Vertical {
 195                     // if the tactic is Vertical, write_list already added a trailing ,
 196                     fields_str.push_str(" ");
 197                 } else {
 198                     fields_str.push_str(", ");
 199                 }
 200             }
 201             fields_str.push_str("..");
 202         }
 203     }
 204
 205     let fields_str = wrap_struct_field(context, &fields_str, shape, v_shape, one_line_width);
 206     Some(format!("{} {{{}}}", path_str, fields_str))
 207 }
 208
 209 impl Rewrite for FieldPat {
 210     fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
 211         let pat = self.pat.rewrite(context, shape);
 212         if self.is_shorthand {
 213             pat
 214         } else {
 215             let pat_str = pat?;
 216             let id_str = self.ident.to_string();
 217             let one_line_width = id_str.len() + 2 + pat_str.len();
 218             if one_line_width <= shape.width {
 219                 Some(format!("{}: {}", id_str, pat_str))
 220             } else {
 221                 let nested_shape = shape.block_indent(context.config.tab_spaces());
 222                 let pat_str = self.pat.rewrite(context, nested_shape)?;
 223                 Some(format!(
 224                     "{}:\n{}{}",
 225                     id_str,
 226                     nested_shape.indent.to_string(context.config),
 227                     pat_str,
 228                 ))
 229             }
 230         }
 231     }
 232 }
 233
 234 pub enum TuplePatField<'a> {
 235     Pat(&'a ptr::P<ast::Pat>),
 236     Dotdot(Span),
 237 }
 238
 239 impl<'a> Rewrite for TuplePatField<'a> {
 240     fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
 241         match *self {
 242             TuplePatField::Pat(p) => p.rewrite(context, shape),
 243             TuplePatField::Dotdot(_) => Some("..".to_string()),
 244         }
 245     }
 246 }
 247
 248 impl<'a> Spanned for TuplePatField<'a> {
 249     fn span(&self) -> Span {
 250         match *self {
 251             TuplePatField::Pat(p) => p.span(),
 252             TuplePatField::Dotdot(span) => span,
 253         }
 254     }
 255 }
 256
 257 pub fn can_be_overflowed_pat(context: &RewriteContext, pat: &TuplePatField, len: usize) -> bool {
 258     match *pat {
 259         TuplePatField::Pat(pat) => match pat.node {
 260             ast::PatKind::Path(..)
 261             | ast::PatKind::Tuple(..)
 262             | ast::PatKind::Struct(..)
 263             | ast::PatKind::TupleStruct(..) => context.use_block_indent() && len == 1,
 264             ast::PatKind::Ref(ref p, _) | ast::PatKind::Box(ref p) => {
 265                 can_be_overflowed_pat(context, &TuplePatField::Pat(p), len)
 266             }
 267             ast::PatKind::Lit(ref expr) => can_be_overflowed_expr(context, expr, len),
 268             _ => false,
 269         },
 270         TuplePatField::Dotdot(..) => false,
 271     }
 272 }
 273
 274 fn rewrite_tuple_pat(
 275     pats: &[ptr::P<ast::Pat>],
 276     dotdot_pos: Option<usize>,
 277     path_str: Option<String>,
 278     span: Span,
 279     context: &RewriteContext,
 280     shape: Shape,
 281 ) -> Option<String> {
 282     let mut pat_vec: Vec<_> = pats.into_iter().map(|x| TuplePatField::Pat(x)).collect();
 283
 284     if let Some(pos) = dotdot_pos {
 285         let prev = if pos == 0 {
 286             span.lo()
 287         } else {
 288             pats[pos - 1].span().hi()
 289         };
 290         let next = if pos + 1 >= pats.len() {
 291             span.hi()
 292         } else {
 293             pats[pos + 1].span().lo()
 294         };
 295         let dot_span = mk_sp(prev, next);
 296         let snippet = context.snippet(dot_span);
 297         let lo = dot_span.lo() + BytePos(snippet.find_uncommented("..").unwrap() as u32);
 298         let dotdot = TuplePatField::Dotdot(Span::new(
 299             lo,
 300             // 2 == "..".len()
 301             lo + BytePos(2),
 302             codemap::NO_EXPANSION,
 303         ));
 304         pat_vec.insert(pos, dotdot);
 305     }
 306
 307     if pat_vec.is_empty() {
 308         return Some(format!("{}()", path_str.unwrap_or_default()));
 309     }
 310
 311     let wildcard_suffix_len = count_wildcard_suffix_len(context, &pat_vec, span, shape);
 312     let (pat_vec, span) = if context.config.condense_wildcard_suffixes() && wildcard_suffix_len >= 2
 313     {
 314         let new_item_count = 1 + pat_vec.len() - wildcard_suffix_len;
 315         let sp = pat_vec[new_item_count - 1].span();
 316         let snippet = context.snippet(sp);
 317         let lo = sp.lo() + BytePos(snippet.find_uncommented("_").unwrap() as u32);
 318         pat_vec[new_item_count - 1] = TuplePatField::Dotdot(mk_sp(lo, lo + BytePos(1)));
 319         (
 320             &pat_vec[..new_item_count],
 321             mk_sp(span.lo(), lo + BytePos(1)),
 322         )
 323     } else {
 324         (&pat_vec[..], span)
 325     };
 326
 327     // add comma if `(x,)`
 328     let add_comma = path_str.is_none() && pat_vec.len() == 1 && dotdot_pos.is_none();
 329     let mut context = context.clone();
 330     if let Some(&TuplePatField::Dotdot(..)) = pat_vec.last() {
 331         context.inside_macro = true;
 332     }
 333     let path_str = path_str.unwrap_or_default();
 334     let mut pat_ref_vec = Vec::with_capacity(pat_vec.len());
 335     for pat in pat_vec {
 336         pat_ref_vec.push(pat);
 337     }
 338
 339     overflow::rewrite_with_parens(
 340         &context,
 341         &path_str,
 342         &pat_ref_vec[..],
 343         shape,
 344         span,
 345         context.config.max_width(),
 346         if add_comma {
 347             Some(SeparatorTactic::Always)
 348         } else {
 349             None
 350         },
 351     )
 352 }
 353
 354 fn count_wildcard_suffix_len(
 355     context: &RewriteContext,
 356     patterns: &[TuplePatField],
 357     span: Span,
 358     shape: Shape,
 359 ) -> usize {
 360     let mut suffix_len = 0;
 361
 362     let items: Vec<_> = itemize_list(
 363         context.snippet_provider,
 364         patterns.iter(),
 365         ")",
 366         ",",
 367         |item| item.span().lo(),
 368         |item| item.span().hi(),
 369         |item| item.rewrite(context, shape),
 370         context.snippet_provider.span_after(span, "("),
 371         span.hi() - BytePos(1),
 372         false,
 373     ).collect();
 374
 375     for item in items.iter().rev().take_while(|i| match i.item {
 376         Some(ref internal_string) if internal_string == "_" => true,
 377         _ => false,
 378     }) {
 379         suffix_len += 1;
 380
 381         if item.pre_comment.is_some() || item.post_comment.is_some() {
 382             break;
 383         }
 384     }
 385
 386     suffix_len
 387 }