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};
  12 use syntax::codemap::{self, BytePos, Span};
  13 use syntax::ptr;
  14
  15 use {Shape, 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, SeparatorTactic};
  22 use rewrite::{Rewrite, RewriteContext};
  23 use types::{rewrite_path, PathContext};
  24 use utils::{format_mutability, mk_sp, wrap_str};
  25
  26 impl Rewrite for Pat {
  27     fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
  28         match self.node {
  29             PatKind::Box(ref pat) => rewrite_unary_prefix(context, "box ", &**pat, shape),
  30             PatKind::Ident(binding_mode, ident, ref sub_pat) => {
  31                 let (prefix, mutability) = match binding_mode {
  32                     BindingMode::ByRef(mutability) => ("ref ", mutability),
  33                     BindingMode::ByValue(mutability) => ("", mutability),
  34                 };
  35                 let mut_infix = format_mutability(mutability);
  36                 let id_str = ident.node.to_string();
  37                 let sub_pat = match *sub_pat {
  38                     Some(ref p) => {
  39                         // 3 - ` @ `.
  40                         let width = try_opt!(
  41                             shape
  42                                 .width
  43                                 .checked_sub(prefix.len() + mut_infix.len() + id_str.len() + 3)
  44                         );
  45                         format!(
  46                             " @ {}",
  47                             try_opt!(p.rewrite(context, Shape::legacy(width, shape.indent)))
  48                         )
  49                     }
  50                     None => "".to_owned(),
  51                 };
  52
  53                 let result = format!("{}{}{}{}", prefix, mut_infix, id_str, sub_pat);
  54                 wrap_str(result, context.config.max_width(), shape)
  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) => match *end_kind {
  62                 RangeEnd::Included => rewrite_pair(&**lhs, &**rhs, "", "...", "", context, shape),
  63                 RangeEnd::Excluded => rewrite_pair(&**lhs, &**rhs, "", "..", "", context, shape),
  64             },
  65             PatKind::Ref(ref pat, mutability) => {
  66                 let prefix = format!("&{}", format_mutability(mutability));
  67                 rewrite_unary_prefix(context, &prefix, &**pat, shape)
  68             }
  69             PatKind::Tuple(ref items, dotdot_pos) => {
  70                 rewrite_tuple_pat(items, dotdot_pos, None, self.span, context, shape)
  71             }
  72             PatKind::Path(ref q_self, ref path) => {
  73                 rewrite_path(context, PathContext::Expr, q_self.as_ref(), path, shape)
  74             }
  75             PatKind::TupleStruct(ref path, ref pat_vec, dotdot_pos) => {
  76                 let path_str =
  77                     try_opt!(rewrite_path(context, PathContext::Expr, None, path, shape));
  78                 rewrite_tuple_pat(
  79                     pat_vec,
  80                     dotdot_pos,
  81                     Some(path_str),
  82                     self.span,
  83                     context,
  84                     shape,
  85                 )
  86             }
  87             PatKind::Lit(ref expr) => expr.rewrite(context, shape),
  88             PatKind::Slice(ref prefix, ref slice_pat, ref suffix) => {
  89                 // Rewrite all the sub-patterns.
  90                 let prefix = prefix.iter().map(|p| p.rewrite(context, shape));
  91                 let slice_pat = slice_pat.as_ref().map(|p| {
  92                     Some(format!("{}..", try_opt!(p.rewrite(context, shape))))
  93                 });
  94                 let suffix = suffix.iter().map(|p| p.rewrite(context, shape));
  95
  96                 // Munge them together.
  97                 let pats: Option<Vec<String>> =
  98                     prefix.chain(slice_pat.into_iter()).chain(suffix).collect();
  99
 100                 // Check that all the rewrites succeeded, and if not return None.
 101                 let pats = try_opt!(pats);
 102
 103                 // Unwrap all the sub-strings and join them with commas.
 104                 let result = if context.config.spaces_within_square_brackets() {
 105                     format!("[ {} ]", pats.join(", "))
 106                 } else {
 107                     format!("[{}]", pats.join(", "))
 108                 };
 109                 wrap_str(result, context.config.max_width(), shape)
 110             }
 111             PatKind::Struct(ref path, ref fields, elipses) => {
 112                 rewrite_struct_pat(path, fields, elipses, self.span, context, shape)
 113             }
 114             // FIXME(#819) format pattern macros.
 115             PatKind::Mac(..) => wrap_str(
 116                 context.snippet(self.span),
 117                 context.config.max_width(),
 118                 shape,
 119             ),
 120         }
 121     }
 122 }
 123
 124 fn rewrite_struct_pat(
 125     path: &ast::Path,
 126     fields: &[codemap::Spanned<ast::FieldPat>],
 127     elipses: bool,
 128     span: Span,
 129     context: &RewriteContext,
 130     shape: Shape,
 131 ) -> Option<String> {
 132     // 2 =  ` {`
 133     let path_shape = try_opt!(shape.sub_width(2));
 134     let path_str = try_opt!(rewrite_path(
 135         context,
 136         PathContext::Expr,
 137         None,
 138         path,
 139         path_shape,
 140     ));
 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) = try_opt!(struct_lit_shape(
 150         shape,
 151         context,
 152         path_str.len() + 3,
 153         elipses_str.len() + 2,
 154     ));
 155
 156     let items = itemize_list(
 157         context.codemap,
 158         fields.iter(),
 159         terminator,
 160         |f| f.span.lo(),
 161         |f| f.span.hi(),
 162         |f| f.node.rewrite(context, v_shape),
 163         context.codemap.span_after(span, "{"),
 164         span.hi(),
 165         false,
 166     );
 167     let item_vec = items.collect::<Vec<_>>();
 168
 169     let tactic = struct_lit_tactic(h_shape, context, &item_vec);
 170     let nested_shape = shape_for_tactic(tactic, h_shape, v_shape);
 171     let fmt = struct_lit_formatting(nested_shape, tactic, context, false);
 172
 173     let mut fields_str = try_opt!(write_list(&item_vec, &fmt));
 174     let one_line_width = h_shape.map_or(0, |shape| shape.width);
 175
 176     if elipses {
 177         if fields_str.contains('\n') || fields_str.len() > one_line_width {
 178             // Add a missing trailing comma.
 179             if fmt.trailing_separator == SeparatorTactic::Never {
 180                 fields_str.push_str(",");
 181             }
 182             fields_str.push_str("\n");
 183             fields_str.push_str(&nested_shape.indent.to_string(context.config));
 184             fields_str.push_str("..");
 185         } else {
 186             if !fields_str.is_empty() {
 187                 // there are preceeding struct fields being matched on
 188                 if fmt.tactic == DefinitiveListTactic::Vertical {
 189                     // if the tactic is Vertical, write_list already added a trailing ,
 190                     fields_str.push_str(" ");
 191                 } else {
 192                     fields_str.push_str(", ");
 193                 }
 194             }
 195             fields_str.push_str("..");
 196         }
 197     }
 198
 199     let fields_str = wrap_struct_field(context, &fields_str, shape, v_shape, one_line_width);
 200     Some(format!("{} {{{}}}", path_str, fields_str))
 201 }
 202
 203 impl Rewrite for FieldPat {
 204     fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
 205         let pat = self.pat.rewrite(context, shape);
 206         if self.is_shorthand {
 207             pat
 208         } else {
 209             wrap_str(
 210                 format!("{}: {}", self.ident.to_string(), try_opt!(pat)),
 211                 context.config.max_width(),
 212                 shape,
 213             )
 214         }
 215     }
 216 }
 217
 218 pub enum TuplePatField<'a> {
 219     Pat(&'a ptr::P<ast::Pat>),
 220     Dotdot(Span),
 221 }
 222
 223 impl<'a> Rewrite for TuplePatField<'a> {
 224     fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
 225         match *self {
 226             TuplePatField::Pat(p) => p.rewrite(context, shape),
 227             TuplePatField::Dotdot(_) => Some("..".to_string()),
 228         }
 229     }
 230 }
 231
 232 impl<'a> Spanned for TuplePatField<'a> {
 233     fn span(&self) -> Span {
 234         match *self {
 235             TuplePatField::Pat(p) => p.span(),
 236             TuplePatField::Dotdot(span) => span,
 237         }
 238     }
 239 }
 240
 241 pub fn can_be_overflowed_pat(context: &RewriteContext, pat: &TuplePatField, len: usize) -> bool {
 242     match *pat {
 243         TuplePatField::Pat(pat) => match pat.node {
 244             ast::PatKind::Path(..) | ast::PatKind::Tuple(..) | ast::PatKind::Struct(..) => {
 245                 context.use_block_indent() && len == 1
 246             }
 247             ast::PatKind::Ref(ref p, _) | ast::PatKind::Box(ref p) => {
 248                 can_be_overflowed_pat(context, &TuplePatField::Pat(p), len)
 249             }
 250             ast::PatKind::Lit(ref expr) => can_be_overflowed_expr(context, expr, len),
 251             _ => false,
 252         },
 253         TuplePatField::Dotdot(..) => false,
 254     }
 255 }
 256
 257 fn rewrite_tuple_pat(
 258     pats: &[ptr::P<ast::Pat>],
 259     dotdot_pos: Option<usize>,
 260     path_str: Option<String>,
 261     span: Span,
 262     context: &RewriteContext,
 263     shape: Shape,
 264 ) -> Option<String> {
 265     let mut pat_vec: Vec<_> = pats.into_iter().map(|x| TuplePatField::Pat(x)).collect();
 266
 267     if let Some(pos) = dotdot_pos {
 268         let prev = if pos == 0 {
 269             span.lo()
 270         } else {
 271             pats[pos - 1].span().hi()
 272         };
 273         let next = if pos + 1 >= pats.len() {
 274             span.hi()
 275         } else {
 276             pats[pos + 1].span().lo()
 277         };
 278         let dot_span = mk_sp(prev, next);
 279         let snippet = context.snippet(dot_span);
 280         let lo = dot_span.lo() + BytePos(snippet.find_uncommented("..").unwrap() as u32);
 281         let dotdot = TuplePatField::Dotdot(Span::new(
 282             lo,
 283             // 2 == "..".len()
 284             lo + BytePos(2),
 285             codemap::NO_EXPANSION,
 286         ));
 287         pat_vec.insert(pos, dotdot);
 288     }
 289
 290     if pat_vec.is_empty() {
 291         return Some(format!("{}()", path_str.unwrap_or_default()));
 292     }
 293
 294     let wildcard_suffix_len = count_wildcard_suffix_len(context, &pat_vec, span, shape);
 295     let (pat_vec, span) = if context.config.condense_wildcard_suffixes() && wildcard_suffix_len >= 2
 296     {
 297         let new_item_count = 1 + pat_vec.len() - wildcard_suffix_len;
 298         let sp = pat_vec[new_item_count - 1].span();
 299         let snippet = context.snippet(sp);
 300         let lo = sp.lo() + BytePos(snippet.find_uncommented("_").unwrap() as u32);
 301         pat_vec[new_item_count - 1] = TuplePatField::Dotdot(mk_sp(lo, lo + BytePos(1)));
 302         (
 303             &pat_vec[..new_item_count],
 304             mk_sp(span.lo(), lo + BytePos(1)),
 305         )
 306     } else {
 307         (&pat_vec[..], span)
 308     };
 309
 310     // add comma if `(x,)`
 311     let add_comma = path_str.is_none() && pat_vec.len() == 1 && dotdot_pos.is_none();
 312     let mut context = context.clone();
 313     if let Some(&TuplePatField::Dotdot(..)) = pat_vec.last() {
 314         context.inside_macro = true;
 315     }
 316     let path_str = path_str.unwrap_or_default();
 317     let mut pat_ref_vec = Vec::with_capacity(pat_vec.len());
 318     for pat in pat_vec {
 319         pat_ref_vec.push(pat);
 320     }
 321
 322     rewrite_call_inner(
 323         &context,
 324         &path_str,
 325         &pat_ref_vec[..],
 326         span,
 327         shape,
 328         shape.width,
 329         add_comma,
 330     ).ok()
 331 }
 332
 333 fn count_wildcard_suffix_len(
 334     context: &RewriteContext,
 335     patterns: &[TuplePatField],
 336     span: Span,
 337     shape: Shape,
 338 ) -> usize {
 339     let mut suffix_len = 0;
 340
 341     let items: Vec<_> = itemize_list(
 342         context.codemap,
 343         patterns.iter(),
 344         ")",
 345         |item| item.span().lo(),
 346         |item| item.span().hi(),
 347         |item| item.rewrite(context, shape),
 348         context.codemap.span_after(span, "("),
 349         span.hi() - BytePos(1),
 350         false,
 351     ).collect();
 352
 353     for item in items.iter().rev().take_while(|i| match i.item {
 354         Some(ref internal_string) if internal_string == "_" => true,
 355         _ => false,
 356     }) {
 357         suffix_len += 1;
 358
 359         if item.pre_comment.is_some() || item.post_comment.is_some() {
 360             break;
 361         }
 362     }
 363
 364     suffix_len
 365 }