src/librustc_mir/hair/pattern/mod.rs

   1 // Copyright 2016 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 //! Code to validate patterns/matches
  12
  13 mod _match;
  14 mod check_match;
  15
  16 pub use self::check_match::check_crate;
  17 pub(crate) use self::check_match::check_match;
  18
  19 use interpret::{const_val_field, const_variant_index, self};
  20
  21 use rustc::mir::{fmt_const_val, Field, BorrowKind, Mutability};
  22 use rustc::mir::interpret::{Scalar, GlobalId, ConstValue};
  23 use rustc::ty::{self, TyCtxt, AdtDef, Ty, Region};
  24 use rustc::ty::subst::{Substs, Kind};
  25 use rustc::hir::{self, PatKind, RangeEnd};
  26 use rustc::hir::def::{Def, CtorKind};
  27 use rustc::hir::pat_util::EnumerateAndAdjustIterator;
  28
  29 use rustc_data_structures::indexed_vec::Idx;
  30
  31 use std::cmp::Ordering;
  32 use std::fmt;
  33 use syntax::ast;
  34 use syntax::ptr::P;
  35 use syntax_pos::Span;
  36 use syntax_pos::symbol::Symbol;
  37
  38 #[derive(Clone, Debug)]
  39 pub enum PatternError {
  40     AssociatedConstInPattern(Span),
  41     StaticInPattern(Span),
  42     FloatBug,
  43     NonConstPath(Span),
  44 }
  45
  46 #[derive(Copy, Clone, Debug)]
  47 pub enum BindingMode<'tcx> {
  48     ByValue,
  49     ByRef(Region<'tcx>, BorrowKind),
  50 }
  51
  52 #[derive(Clone, Debug)]
  53 pub struct FieldPattern<'tcx> {
  54     pub field: Field,
  55     pub pattern: Pattern<'tcx>,
  56 }
  57
  58 #[derive(Clone, Debug)]
  59 pub struct Pattern<'tcx> {
  60     pub ty: Ty<'tcx>,
  61     pub span: Span,
  62     pub kind: Box<PatternKind<'tcx>>,
  63 }
  64
  65 #[derive(Clone, Debug)]
  66 pub enum PatternKind<'tcx> {
  67     Wild,
  68
  69     /// x, ref x, x @ P, etc
  70     Binding {
  71         mutability: Mutability,
  72         name: ast::Name,
  73         mode: BindingMode<'tcx>,
  74         var: ast::NodeId,
  75         ty: Ty<'tcx>,
  76         subpattern: Option<Pattern<'tcx>>,
  77     },
  78
  79     /// Foo(...) or Foo{...} or Foo, where `Foo` is a variant name from an adt with >1 variants
  80     Variant {
  81         adt_def: &'tcx AdtDef,
  82         substs: &'tcx Substs<'tcx>,
  83         variant_index: usize,
  84         subpatterns: Vec<FieldPattern<'tcx>>,
  85     },
  86
  87     /// (...), Foo(...), Foo{...}, or Foo, where `Foo` is a variant name from an adt with 1 variant
  88     Leaf {
  89         subpatterns: Vec<FieldPattern<'tcx>>,
  90     },
  91
  92     /// box P, &P, &mut P, etc
  93     Deref {
  94         subpattern: Pattern<'tcx>,
  95     },
  96
  97     Constant {
  98         value: &'tcx ty::Const<'tcx>,
  99     },
 100
 101     Range {
 102         lo: &'tcx ty::Const<'tcx>,
 103         hi: &'tcx ty::Const<'tcx>,
 104         end: RangeEnd,
 105     },
 106
 107     /// matches against a slice, checking the length and extracting elements.
 108     /// irrefutable when there is a slice pattern and both `prefix` and `suffix` are empty.
 109     /// e.g. `&[ref xs..]`.
 110     Slice {
 111         prefix: Vec<Pattern<'tcx>>,
 112         slice: Option<Pattern<'tcx>>,
 113         suffix: Vec<Pattern<'tcx>>,
 114     },
 115
 116     /// fixed match against an array, irrefutable
 117     Array {
 118         prefix: Vec<Pattern<'tcx>>,
 119         slice: Option<Pattern<'tcx>>,
 120         suffix: Vec<Pattern<'tcx>>,
 121     },
 122 }
 123
 124 impl<'tcx> fmt::Display for Pattern<'tcx> {
 125     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
 126         match *self.kind {
 127             PatternKind::Wild => write!(f, "_"),
 128             PatternKind::Binding { mutability, name, mode, ref subpattern, .. } => {
 129                 let is_mut = match mode {
 130                     BindingMode::ByValue => mutability == Mutability::Mut,
 131                     BindingMode::ByRef(_, bk) => {
 132                         write!(f, "ref ")?;
 133                         match bk { BorrowKind::Mut { .. } => true, _ => false }
 134                     }
 135                 };
 136                 if is_mut {
 137                     write!(f, "mut ")?;
 138                 }
 139                 write!(f, "{}", name)?;
 140                 if let Some(ref subpattern) = *subpattern {
 141                     write!(f, " @ {}", subpattern)?;
 142                 }
 143                 Ok(())
 144             }
 145             PatternKind::Variant { ref subpatterns, .. } |
 146             PatternKind::Leaf { ref subpatterns } => {
 147                 let variant = match *self.kind {
 148                     PatternKind::Variant { adt_def, variant_index, .. } => {
 149                         Some(&adt_def.variants[variant_index])
 150                     }
 151                     _ => if let ty::TyAdt(adt, _) = self.ty.sty {
 152                         if !adt.is_enum() {
 153                             Some(&adt.variants[0])
 154                         } else {
 155                             None
 156                         }
 157                     } else {
 158                         None
 159                     }
 160                 };
 161
 162                 let mut first = true;
 163                 let mut start_or_continue = || if first { first = false; "" } else { ", " };
 164
 165                 if let Some(variant) = variant {
 166                     write!(f, "{}", variant.name)?;
 167
 168                     // Only for TyAdt we can have `S {...}`,
 169                     // which we handle separately here.
 170                     if variant.ctor_kind == CtorKind::Fictive {
 171                         write!(f, " {{ ")?;
 172
 173                         let mut printed = 0;
 174                         for p in subpatterns {
 175                             if let PatternKind::Wild = *p.pattern.kind {
 176                                 continue;
 177                             }
 178                             let name = variant.fields[p.field.index()].ident;
 179                             write!(f, "{}{}: {}", start_or_continue(), name, p.pattern)?;
 180                             printed += 1;
 181                         }
 182
 183                         if printed < variant.fields.len() {
 184                             write!(f, "{}..", start_or_continue())?;
 185                         }
 186
 187                         return write!(f, " }}");
 188                     }
 189                 }
 190
 191                 let num_fields = variant.map_or(subpatterns.len(), |v| v.fields.len());
 192                 if num_fields != 0 || variant.is_none() {
 193                     write!(f, "(")?;
 194                     for i in 0..num_fields {
 195                         write!(f, "{}", start_or_continue())?;
 196
 197                         // Common case: the field is where we expect it.
 198                         if let Some(p) = subpatterns.get(i) {
 199                             if p.field.index() == i {
 200                                 write!(f, "{}", p.pattern)?;
 201                                 continue;
 202                             }
 203                         }
 204
 205                         // Otherwise, we have to go looking for it.
 206                         if let Some(p) = subpatterns.iter().find(|p| p.field.index() == i) {
 207                             write!(f, "{}", p.pattern)?;
 208                         } else {
 209                             write!(f, "_")?;
 210                         }
 211                     }
 212                     write!(f, ")")?;
 213                 }
 214
 215                 Ok(())
 216             }
 217             PatternKind::Deref { ref subpattern } => {
 218                 match self.ty.sty {
 219                     ty::TyAdt(def, _) if def.is_box() => write!(f, "box ")?,
 220                     ty::TyRef(_, _, mutbl) => {
 221                         write!(f, "&")?;
 222                         if mutbl == hir::MutMutable {
 223                             write!(f, "mut ")?;
 224                         }
 225                     }
 226                     _ => bug!("{} is a bad Deref pattern type", self.ty)
 227                 }
 228                 write!(f, "{}", subpattern)
 229             }
 230             PatternKind::Constant { value } => {
 231                 fmt_const_val(f, value)
 232             }
 233             PatternKind::Range { lo, hi, end } => {
 234                 fmt_const_val(f, lo)?;
 235                 match end {
 236                     RangeEnd::Included => write!(f, "...")?,
 237                     RangeEnd::Excluded => write!(f, "..")?,
 238                 }
 239                 fmt_const_val(f, hi)
 240             }
 241             PatternKind::Slice { ref prefix, ref slice, ref suffix } |
 242             PatternKind::Array { ref prefix, ref slice, ref suffix } => {
 243                 let mut first = true;
 244                 let mut start_or_continue = || if first { first = false; "" } else { ", " };
 245                 write!(f, "[")?;
 246                 for p in prefix {
 247                     write!(f, "{}{}", start_or_continue(), p)?;
 248                 }
 249                 if let Some(ref slice) = *slice {
 250                     write!(f, "{}", start_or_continue())?;
 251                     match *slice.kind {
 252                         PatternKind::Wild => {}
 253                         _ => write!(f, "{}", slice)?
 254                     }
 255                     write!(f, "..")?;
 256                 }
 257                 for p in suffix {
 258                     write!(f, "{}{}", start_or_continue(), p)?;
 259                 }
 260                 write!(f, "]")
 261             }
 262         }
 263     }
 264 }
 265
 266 pub struct PatternContext<'a, 'tcx: 'a> {
 267     pub tcx: TyCtxt<'a, 'tcx, 'tcx>,
 268     pub param_env: ty::ParamEnv<'tcx>,
 269     pub tables: &'a ty::TypeckTables<'tcx>,
 270     pub substs: &'tcx Substs<'tcx>,
 271     pub errors: Vec<PatternError>,
 272 }
 273
 274 impl<'a, 'tcx> Pattern<'tcx> {
 275     pub fn from_hir(tcx: TyCtxt<'a, 'tcx, 'tcx>,
 276                     param_env_and_substs: ty::ParamEnvAnd<'tcx, &'tcx Substs<'tcx>>,
 277                     tables: &'a ty::TypeckTables<'tcx>,
 278                     pat: &'tcx hir::Pat) -> Self {
 279         let mut pcx = PatternContext::new(tcx, param_env_and_substs, tables);
 280         let result = pcx.lower_pattern(pat);
 281         if !pcx.errors.is_empty() {
 282             let msg = format!("encountered errors lowering pattern: {:?}", pcx.errors);
 283             tcx.sess.delay_span_bug(pat.span, &msg);
 284         }
 285         debug!("Pattern::from_hir({:?}) = {:?}", pat, result);
 286         result
 287     }
 288 }
 289
 290 impl<'a, 'tcx> PatternContext<'a, 'tcx> {
 291     pub fn new(tcx: TyCtxt<'a, 'tcx, 'tcx>,
 292                param_env_and_substs: ty::ParamEnvAnd<'tcx, &'tcx Substs<'tcx>>,
 293                tables: &'a ty::TypeckTables<'tcx>) -> Self {
 294         PatternContext {
 295             tcx,
 296             param_env: param_env_and_substs.param_env,
 297             tables,
 298             substs: param_env_and_substs.value,
 299             errors: vec![]
 300         }
 301     }
 302
 303     pub fn lower_pattern(&mut self, pat: &'tcx hir::Pat) -> Pattern<'tcx> {
 304         // When implicit dereferences have been inserted in this pattern, the unadjusted lowered
 305         // pattern has the type that results *after* dereferencing. For example, in this code:
 306         //
 307         // ```
 308         // match &&Some(0i32) {
 309         //     Some(n) => { ... },
 310         //     _ => { ... },
 311         // }
 312         // ```
 313         //
 314         // the type assigned to `Some(n)` in `unadjusted_pat` would be `Option<i32>` (this is
 315         // determined in rustc_typeck::check::match). The adjustments would be
 316         //
 317         // `vec![&&Option<i32>, &Option<i32>]`.
 318         //
 319         // Applying the adjustments, we want to instead output `&&Some(n)` (as a HAIR pattern). So
 320         // we wrap the unadjusted pattern in `PatternKind::Deref` repeatedly, consuming the
 321         // adjustments in *reverse order* (last-in-first-out, so that the last `Deref` inserted
 322         // gets the least-dereferenced type).
 323         let unadjusted_pat = self.lower_pattern_unadjusted(pat);
 324         self.tables
 325             .pat_adjustments()
 326             .get(pat.hir_id)
 327             .unwrap_or(&vec![])
 328             .iter()
 329             .rev()
 330             .fold(unadjusted_pat, |pat, ref_ty| {
 331                     debug!("{:?}: wrapping pattern with type {:?}", pat, ref_ty);
 332                     Pattern {
 333                         span: pat.span,
 334                         ty: ref_ty,
 335                         kind: Box::new(PatternKind::Deref { subpattern: pat }),
 336                     }
 337                 },
 338             )
 339     }
 340
 341     fn lower_pattern_unadjusted(&mut self, pat: &'tcx hir::Pat) -> Pattern<'tcx> {
 342         let mut ty = self.tables.node_id_to_type(pat.hir_id);
 343
 344         let kind = match pat.node {
 345             PatKind::Wild => PatternKind::Wild,
 346
 347             PatKind::Lit(ref value) => self.lower_lit(value),
 348
 349             PatKind::Range(ref lo_expr, ref hi_expr, end) => {
 350                 match (self.lower_lit(lo_expr), self.lower_lit(hi_expr)) {
 351                     (PatternKind::Constant { value: lo },
 352                      PatternKind::Constant { value: hi }) => {
 353                         use std::cmp::Ordering;
 354                         let cmp = compare_const_vals(
 355                             self.tcx,
 356                             lo,
 357                             hi,
 358                             self.param_env.and(ty),
 359                         );
 360                         match (end, cmp) {
 361                             (RangeEnd::Excluded, Some(Ordering::Less)) =>
 362                                 PatternKind::Range { lo, hi, end },
 363                             (RangeEnd::Excluded, _) => {
 364                                 span_err!(
 365                                     self.tcx.sess,
 366                                     lo_expr.span,
 367                                     E0579,
 368                                     "lower range bound must be less than upper",
 369                                 );
 370                                 PatternKind::Wild
 371                             },
 372                             (RangeEnd::Included, None) |
 373                             (RangeEnd::Included, Some(Ordering::Greater)) => {
 374                                 let mut err = struct_span_err!(
 375                                     self.tcx.sess,
 376                                     lo_expr.span,
 377                                     E0030,
 378                                     "lower range bound must be less than or equal to upper"
 379                                 );
 380                                 err.span_label(
 381                                     lo_expr.span,
 382                                     "lower bound larger than upper bound",
 383                                 );
 384                                 if self.tcx.sess.teach(&err.get_code().unwrap()) {
 385                                     err.note("When matching against a range, the compiler \
 386                                               verifies that the range is non-empty. Range \
 387                                               patterns include both end-points, so this is \
 388                                               equivalent to requiring the start of the range \
 389                                               to be less than or equal to the end of the range.");
 390                                 }
 391                                 err.emit();
 392                                 PatternKind::Wild
 393                             },
 394                             (RangeEnd::Included, Some(_)) => PatternKind::Range { lo, hi, end },
 395                         }
 396                     }
 397                     _ => PatternKind::Wild
 398                 }
 399             }
 400
 401             PatKind::Path(ref qpath) => {
 402                 return self.lower_path(qpath, pat.hir_id, pat.span);
 403             }
 404
 405             PatKind::Ref(ref subpattern, _) |
 406             PatKind::Box(ref subpattern) => {
 407                 PatternKind::Deref { subpattern: self.lower_pattern(subpattern) }
 408             }
 409
 410             PatKind::Slice(ref prefix, ref slice, ref suffix) => {
 411                 match ty.sty {
 412                     ty::TyRef(_, ty, _) =>
 413                         PatternKind::Deref {
 414                             subpattern: Pattern {
 415                                 ty,
 416                                 span: pat.span,
 417                                 kind: Box::new(self.slice_or_array_pattern(
 418                                     pat.span, ty, prefix, slice, suffix))
 419                             },
 420                         },
 421                     ty::TySlice(..) |
 422                     ty::TyArray(..) =>
 423                         self.slice_or_array_pattern(pat.span, ty, prefix, slice, suffix),
 424                     ty::TyError => { // Avoid ICE
 425                         return Pattern { span: pat.span, ty, kind: Box::new(PatternKind::Wild) };
 426                     }
 427                     ref sty =>
 428                         span_bug!(
 429                             pat.span,
 430                             "unexpanded type for vector pattern: {:?}",
 431                             sty),
 432                 }
 433             }
 434
 435             PatKind::Tuple(ref subpatterns, ddpos) => {
 436                 match ty.sty {
 437                     ty::TyTuple(ref tys) => {
 438                         let subpatterns =
 439                             subpatterns.iter()
 440                                        .enumerate_and_adjust(tys.len(), ddpos)
 441                                        .map(|(i, subpattern)| FieldPattern {
 442                                             field: Field::new(i),
 443                                             pattern: self.lower_pattern(subpattern)
 444                                        })
 445                                        .collect();
 446
 447                         PatternKind::Leaf { subpatterns: subpatterns }
 448                     }
 449                     ty::TyError => { // Avoid ICE (#50577)
 450                         return Pattern { span: pat.span, ty, kind: Box::new(PatternKind::Wild) };
 451                     }
 452                     ref sty => span_bug!(pat.span, "unexpected type for tuple pattern: {:?}", sty),
 453                 }
 454             }
 455
 456             PatKind::Binding(_, id, ident, ref sub) => {
 457                 let var_ty = self.tables.node_id_to_type(pat.hir_id);
 458                 let region = match var_ty.sty {
 459                     ty::TyRef(r, _, _) => Some(r),
 460                     ty::TyError => { // Avoid ICE
 461                         return Pattern { span: pat.span, ty, kind: Box::new(PatternKind::Wild) };
 462                     }
 463                     _ => None,
 464                 };
 465                 let bm = *self.tables.pat_binding_modes().get(pat.hir_id)
 466                                                          .expect("missing binding mode");
 467                 let (mutability, mode) = match bm {
 468                     ty::BindByValue(hir::MutMutable) =>
 469                         (Mutability::Mut, BindingMode::ByValue),
 470                     ty::BindByValue(hir::MutImmutable) =>
 471                         (Mutability::Not, BindingMode::ByValue),
 472                     ty::BindByReference(hir::MutMutable) =>
 473                         (Mutability::Not, BindingMode::ByRef(
 474                             region.unwrap(), BorrowKind::Mut { allow_two_phase_borrow: false })),
 475                     ty::BindByReference(hir::MutImmutable) =>
 476                         (Mutability::Not, BindingMode::ByRef(
 477                             region.unwrap(), BorrowKind::Shared)),
 478                 };
 479
 480                 // A ref x pattern is the same node used for x, and as such it has
 481                 // x's type, which is &T, where we want T (the type being matched).
 482                 if let ty::BindByReference(_) = bm {
 483                     if let ty::TyRef(_, rty, _) = ty.sty {
 484                         ty = rty;
 485                     } else {
 486                         bug!("`ref {}` has wrong type {}", ident, ty);
 487                     }
 488                 }
 489
 490                 PatternKind::Binding {
 491                     mutability,
 492                     mode,
 493                     name: ident.name,
 494                     var: id,
 495                     ty: var_ty,
 496                     subpattern: self.lower_opt_pattern(sub),
 497                 }
 498             }
 499
 500             PatKind::TupleStruct(ref qpath, ref subpatterns, ddpos) => {
 501                 let def = self.tables.qpath_def(qpath, pat.hir_id);
 502                 let adt_def = match ty.sty {
 503                     ty::TyAdt(adt_def, _) => adt_def,
 504                     ty::TyError => { // Avoid ICE (#50585)
 505                         return Pattern { span: pat.span, ty, kind: Box::new(PatternKind::Wild) };
 506                     }
 507                     _ => span_bug!(pat.span,
 508                                    "tuple struct pattern not applied to an ADT {:?}",
 509                                    ty.sty),
 510                 };
 511                 let variant_def = adt_def.variant_of_def(def);
 512
 513                 let subpatterns =
 514                         subpatterns.iter()
 515                                    .enumerate_and_adjust(variant_def.fields.len(), ddpos)
 516                                    .map(|(i, field)| FieldPattern {
 517                                        field: Field::new(i),
 518                                        pattern: self.lower_pattern(field),
 519                                    })
 520                                    .collect();
 521                 self.lower_variant_or_leaf(def, pat.span, ty, subpatterns)
 522             }
 523
 524             PatKind::Struct(ref qpath, ref fields, _) => {
 525                 let def = self.tables.qpath_def(qpath, pat.hir_id);
 526                 let subpatterns =
 527                     fields.iter()
 528                           .map(|field| {
 529                               FieldPattern {
 530                                   field: Field::new(self.tcx.field_index(field.node.id,
 531                                                                          self.tables)),
 532                                   pattern: self.lower_pattern(&field.node.pat),
 533                               }
 534                           })
 535                           .collect();
 536
 537                 self.lower_variant_or_leaf(def, pat.span, ty, subpatterns)
 538             }
 539         };
 540
 541         Pattern {
 542             span: pat.span,
 543             ty,
 544             kind: Box::new(kind),
 545         }
 546     }
 547
 548     fn lower_patterns(&mut self, pats: &'tcx [P<hir::Pat>]) -> Vec<Pattern<'tcx>> {
 549         pats.iter().map(|p| self.lower_pattern(p)).collect()
 550     }
 551
 552     fn lower_opt_pattern(&mut self, pat: &'tcx Option<P<hir::Pat>>) -> Option<Pattern<'tcx>>
 553     {
 554         pat.as_ref().map(|p| self.lower_pattern(p))
 555     }
 556
 557     fn flatten_nested_slice_patterns(
 558         &mut self,
 559         prefix: Vec<Pattern<'tcx>>,
 560         slice: Option<Pattern<'tcx>>,
 561         suffix: Vec<Pattern<'tcx>>)
 562         -> (Vec<Pattern<'tcx>>, Option<Pattern<'tcx>>, Vec<Pattern<'tcx>>)
 563     {
 564         let orig_slice = match slice {
 565             Some(orig_slice) => orig_slice,
 566             None => return (prefix, slice, suffix)
 567         };
 568         let orig_prefix = prefix;
 569         let orig_suffix = suffix;
 570
 571         // dance because of intentional borrow-checker stupidity.
 572         let kind = *orig_slice.kind;
 573         match kind {
 574             PatternKind::Slice { prefix, slice, mut suffix } |
 575             PatternKind::Array { prefix, slice, mut suffix } => {
 576                 let mut orig_prefix = orig_prefix;
 577
 578                 orig_prefix.extend(prefix);
 579                 suffix.extend(orig_suffix);
 580
 581                 (orig_prefix, slice, suffix)
 582             }
 583             _ => {
 584                 (orig_prefix, Some(Pattern {
 585                     kind: box kind, ..orig_slice
 586                 }), orig_suffix)
 587             }
 588         }
 589     }
 590
 591     fn slice_or_array_pattern(
 592         &mut self,
 593         span: Span,
 594         ty: Ty<'tcx>,
 595         prefix: &'tcx [P<hir::Pat>],
 596         slice: &'tcx Option<P<hir::Pat>>,
 597         suffix: &'tcx [P<hir::Pat>])
 598         -> PatternKind<'tcx>
 599     {
 600         let prefix = self.lower_patterns(prefix);
 601         let slice = self.lower_opt_pattern(slice);
 602         let suffix = self.lower_patterns(suffix);
 603         let (prefix, slice, suffix) =
 604             self.flatten_nested_slice_patterns(prefix, slice, suffix);
 605
 606         match ty.sty {
 607             ty::TySlice(..) => {
 608                 // matching a slice or fixed-length array
 609                 PatternKind::Slice { prefix: prefix, slice: slice, suffix: suffix }
 610             }
 611
 612             ty::TyArray(_, len) => {
 613                 // fixed-length array
 614                 let len = len.unwrap_usize(self.tcx);
 615                 assert!(len >= prefix.len() as u64 + suffix.len() as u64);
 616                 PatternKind::Array { prefix: prefix, slice: slice, suffix: suffix }
 617             }
 618
 619             _ => {
 620                 span_bug!(span, "bad slice pattern type {:?}", ty);
 621             }
 622         }
 623     }
 624
 625     fn lower_variant_or_leaf(
 626         &mut self,
 627         def: Def,
 628         span: Span,
 629         ty: Ty<'tcx>,
 630         subpatterns: Vec<FieldPattern<'tcx>>)
 631         -> PatternKind<'tcx>
 632     {
 633         match def {
 634             Def::Variant(variant_id) | Def::VariantCtor(variant_id, ..) => {
 635                 let enum_id = self.tcx.parent_def_id(variant_id).unwrap();
 636                 let adt_def = self.tcx.adt_def(enum_id);
 637                 if adt_def.is_enum() {
 638                     let substs = match ty.sty {
 639                         ty::TyAdt(_, substs) |
 640                         ty::TyFnDef(_, substs) => substs,
 641                         ty::TyError => {  // Avoid ICE (#50585)
 642                             return PatternKind::Wild;
 643                         }
 644                         _ => bug!("inappropriate type for def: {:?}", ty.sty),
 645                     };
 646                     PatternKind::Variant {
 647                         adt_def,
 648                         substs,
 649                         variant_index: adt_def.variant_index_with_id(variant_id),
 650                         subpatterns,
 651                     }
 652                 } else {
 653                     PatternKind::Leaf { subpatterns: subpatterns }
 654                 }
 655             }
 656
 657             Def::Struct(..) | Def::StructCtor(..) | Def::Union(..) |
 658             Def::TyAlias(..) | Def::AssociatedTy(..) | Def::SelfTy(..) => {
 659                 PatternKind::Leaf { subpatterns: subpatterns }
 660             }
 661
 662             _ => {
 663                 self.errors.push(PatternError::NonConstPath(span));
 664                 PatternKind::Wild
 665             }
 666         }
 667     }
 668
 669     /// Takes a HIR Path. If the path is a constant, evaluates it and feeds
 670     /// it to `const_to_pat`. Any other path (like enum variants without fields)
 671     /// is converted to the corresponding pattern via `lower_variant_or_leaf`
 672     fn lower_path(&mut self,
 673                   qpath: &hir::QPath,
 674                   id: hir::HirId,
 675                   span: Span)
 676                   -> Pattern<'tcx> {
 677         let ty = self.tables.node_id_to_type(id);
 678         let def = self.tables.qpath_def(qpath, id);
 679         let is_associated_const = match def {
 680             Def::AssociatedConst(_) => true,
 681             _ => false,
 682         };
 683         let kind = match def {
 684             Def::Const(def_id) | Def::AssociatedConst(def_id) => {
 685                 let substs = self.tables.node_substs(id);
 686                 match ty::Instance::resolve(
 687                     self.tcx,
 688                     self.param_env,
 689                     def_id,
 690                     substs,
 691                 ) {
 692                     Some(instance) => {
 693                         let cid = GlobalId {
 694                             instance,
 695                             promoted: None,
 696                         };
 697                         match self.tcx.at(span).const_eval(self.param_env.and(cid)) {
 698                             Ok(value) => {
 699                                 return self.const_to_pat(instance, value, id, span)
 700                             },
 701                             Err(err) => {
 702                                 err.report_as_error(
 703                                     self.tcx.at(span),
 704                                     "could not evaluate constant pattern",
 705                                 );
 706                                 PatternKind::Wild
 707                             },
 708                         }
 709                     },
 710                     None => {
 711                         self.errors.push(if is_associated_const {
 712                             PatternError::AssociatedConstInPattern(span)
 713                         } else {
 714                             PatternError::StaticInPattern(span)
 715                         });
 716                         PatternKind::Wild
 717                     },
 718                 }
 719             }
 720             _ => self.lower_variant_or_leaf(def, span, ty, vec![]),
 721         };
 722
 723         Pattern {
 724             span,
 725             ty,
 726             kind: Box::new(kind),
 727         }
 728     }
 729
 730     /// Converts literals, paths and negation of literals to patterns.
 731     /// The special case for negation exists to allow things like -128i8
 732     /// which would overflow if we tried to evaluate 128i8 and then negate
 733     /// afterwards.
 734     fn lower_lit(&mut self, expr: &'tcx hir::Expr) -> PatternKind<'tcx> {
 735         match expr.node {
 736             hir::ExprKind::Lit(ref lit) => {
 737                 let ty = self.tables.expr_ty(expr);
 738                 match lit_to_const(&lit.node, self.tcx, ty, false) {
 739                     Ok(val) => {
 740                         let instance = ty::Instance::new(
 741                             self.tables.local_id_root.expect("literal outside any scope"),
 742                             self.substs,
 743                         );
 744                         *self.const_to_pat(instance, val, expr.hir_id, lit.span).kind
 745                     },
 746                     Err(e) => {
 747                         if e == LitToConstError::UnparseableFloat {
 748                             self.errors.push(PatternError::FloatBug);
 749                         }
 750                         PatternKind::Wild
 751                     },
 752                 }
 753             },
 754             hir::ExprKind::Path(ref qpath) => *self.lower_path(qpath, expr.hir_id, expr.span).kind,
 755             hir::ExprKind::Unary(hir::UnNeg, ref expr) => {
 756                 let ty = self.tables.expr_ty(expr);
 757                 let lit = match expr.node {
 758                     hir::ExprKind::Lit(ref lit) => lit,
 759                     _ => span_bug!(expr.span, "not a literal: {:?}", expr),
 760                 };
 761                 match lit_to_const(&lit.node, self.tcx, ty, true) {
 762                     Ok(val) => {
 763                         let instance = ty::Instance::new(
 764                             self.tables.local_id_root.expect("literal outside any scope"),
 765                             self.substs,
 766                         );
 767                         *self.const_to_pat(instance, val, expr.hir_id, lit.span).kind
 768                     },
 769                     Err(e) => {
 770                         if e == LitToConstError::UnparseableFloat {
 771                             self.errors.push(PatternError::FloatBug);
 772                         }
 773                         PatternKind::Wild
 774                     },
 775                 }
 776             }
 777             _ => span_bug!(expr.span, "not a literal: {:?}", expr),
 778         }
 779     }
 780
 781     /// Converts an evaluated constant to a pattern (if possible).
 782     /// This means aggregate values (like structs and enums) are converted
 783     /// to a pattern that matches the value (as if you'd compare via eq).
 784     fn const_to_pat(
 785         &self,
 786         instance: ty::Instance<'tcx>,
 787         cv: &'tcx ty::Const<'tcx>,
 788         id: hir::HirId,
 789         span: Span,
 790     ) -> Pattern<'tcx> {
 791         debug!("const_to_pat: cv={:#?}", cv);
 792         let adt_subpattern = |i, variant_opt| {
 793             let field = Field::new(i);
 794             let val = const_val_field(
 795                 self.tcx, self.param_env, instance,
 796                 variant_opt, field, cv,
 797             ).expect("field access failed");
 798             self.const_to_pat(instance, val, id, span)
 799         };
 800         let adt_subpatterns = |n, variant_opt| {
 801             (0..n).map(|i| {
 802                 let field = Field::new(i);
 803                 FieldPattern {
 804                     field,
 805                     pattern: adt_subpattern(i, variant_opt),
 806                 }
 807             }).collect::<Vec<_>>()
 808         };
 809         let kind = match cv.ty.sty {
 810             ty::TyFloat(_) => {
 811                 let id = self.tcx.hir.hir_to_node_id(id);
 812                 self.tcx.lint_node(
 813                     ::rustc::lint::builtin::ILLEGAL_FLOATING_POINT_LITERAL_PATTERN,
 814                     id,
 815                     span,
 816                     "floating-point types cannot be used in patterns",
 817                 );
 818                 PatternKind::Constant {
 819                     value: cv,
 820                 }
 821             },
 822             ty::TyAdt(adt_def, _) if adt_def.is_union() => {
 823                 // Matching on union fields is unsafe, we can't hide it in constants
 824                 self.tcx.sess.span_err(span, "cannot use unions in constant patterns");
 825                 PatternKind::Wild
 826             }
 827             ty::TyAdt(adt_def, _) if !self.tcx.has_attr(adt_def.did, "structural_match") => {
 828                 let msg = format!("to use a constant of type `{}` in a pattern, \
 829                                     `{}` must be annotated with `#[derive(PartialEq, Eq)]`",
 830                                     self.tcx.item_path_str(adt_def.did),
 831                                     self.tcx.item_path_str(adt_def.did));
 832                 self.tcx.sess.span_err(span, &msg);
 833                 PatternKind::Wild
 834             },
 835             ty::TyAdt(adt_def, substs) if adt_def.is_enum() => {
 836                 let variant_index = const_variant_index(
 837                     self.tcx, self.param_env, instance, cv
 838                 ).expect("const_variant_index failed");
 839                 let subpatterns = adt_subpatterns(
 840                     adt_def.variants[variant_index].fields.len(),
 841                     Some(variant_index),
 842                 );
 843                 PatternKind::Variant {
 844                     adt_def,
 845                     substs,
 846                     variant_index,
 847                     subpatterns,
 848                 }
 849             },
 850             ty::TyAdt(adt_def, _) => {
 851                 let struct_var = adt_def.non_enum_variant();
 852                 PatternKind::Leaf {
 853                     subpatterns: adt_subpatterns(struct_var.fields.len(), None),
 854                 }
 855             }
 856             ty::TyTuple(fields) => {
 857                 PatternKind::Leaf {
 858                     subpatterns: adt_subpatterns(fields.len(), None),
 859                 }
 860             }
 861             ty::TyArray(_, n) => {
 862                 PatternKind::Array {
 863                     prefix: (0..n.unwrap_usize(self.tcx))
 864                         .map(|i| adt_subpattern(i as usize, None))
 865                         .collect(),
 866                     slice: None,
 867                     suffix: Vec::new(),
 868                 }
 869             }
 870             _ => {
 871                 PatternKind::Constant {
 872                     value: cv,
 873                 }
 874             },
 875         };
 876
 877         Pattern {
 878             span,
 879             ty: cv.ty,
 880             kind: Box::new(kind),
 881         }
 882     }
 883 }
 884
 885 pub trait PatternFoldable<'tcx> : Sized {
 886     fn fold_with<F: PatternFolder<'tcx>>(&self, folder: &mut F) -> Self {
 887         self.super_fold_with(folder)
 888     }
 889
 890     fn super_fold_with<F: PatternFolder<'tcx>>(&self, folder: &mut F) -> Self;
 891 }
 892
 893 pub trait PatternFolder<'tcx> : Sized {
 894     fn fold_pattern(&mut self, pattern: &Pattern<'tcx>) -> Pattern<'tcx> {
 895         pattern.super_fold_with(self)
 896     }
 897
 898     fn fold_pattern_kind(&mut self, kind: &PatternKind<'tcx>) -> PatternKind<'tcx> {
 899         kind.super_fold_with(self)
 900     }
 901 }
 902
 903
 904 impl<'tcx, T: PatternFoldable<'tcx>> PatternFoldable<'tcx> for Box<T> {
 905     fn super_fold_with<F: PatternFolder<'tcx>>(&self, folder: &mut F) -> Self {
 906         let content: T = (**self).fold_with(folder);
 907         box content
 908     }
 909 }
 910
 911 impl<'tcx, T: PatternFoldable<'tcx>> PatternFoldable<'tcx> for Vec<T> {
 912     fn super_fold_with<F: PatternFolder<'tcx>>(&self, folder: &mut F) -> Self {
 913         self.iter().map(|t| t.fold_with(folder)).collect()
 914     }
 915 }
 916
 917 impl<'tcx, T: PatternFoldable<'tcx>> PatternFoldable<'tcx> for Option<T> {
 918     fn super_fold_with<F: PatternFolder<'tcx>>(&self, folder: &mut F) -> Self{
 919         self.as_ref().map(|t| t.fold_with(folder))
 920     }
 921 }
 922
 923 macro_rules! CloneImpls {
 924     (<$lt_tcx:tt> $($ty:ty),+) => {
 925         $(
 926             impl<$lt_tcx> PatternFoldable<$lt_tcx> for $ty {
 927                 fn super_fold_with<F: PatternFolder<$lt_tcx>>(&self, _: &mut F) -> Self {
 928                     Clone::clone(self)
 929                 }
 930             }
 931         )+
 932     }
 933 }
 934
 935 CloneImpls!{ <'tcx>
 936     Span, Field, Mutability, ast::Name, ast::NodeId, usize, &'tcx ty::Const<'tcx>,
 937     Region<'tcx>, Ty<'tcx>, BindingMode<'tcx>, &'tcx AdtDef,
 938     &'tcx Substs<'tcx>, &'tcx Kind<'tcx>
 939 }
 940
 941 impl<'tcx> PatternFoldable<'tcx> for FieldPattern<'tcx> {
 942     fn super_fold_with<F: PatternFolder<'tcx>>(&self, folder: &mut F) -> Self {
 943         FieldPattern {
 944             field: self.field.fold_with(folder),
 945             pattern: self.pattern.fold_with(folder)
 946         }
 947     }
 948 }
 949
 950 impl<'tcx> PatternFoldable<'tcx> for Pattern<'tcx> {
 951     fn fold_with<F: PatternFolder<'tcx>>(&self, folder: &mut F) -> Self {
 952         folder.fold_pattern(self)
 953     }
 954
 955     fn super_fold_with<F: PatternFolder<'tcx>>(&self, folder: &mut F) -> Self {
 956         Pattern {
 957             ty: self.ty.fold_with(folder),
 958             span: self.span.fold_with(folder),
 959             kind: self.kind.fold_with(folder)
 960         }
 961     }
 962 }
 963
 964 impl<'tcx> PatternFoldable<'tcx> for PatternKind<'tcx> {
 965     fn fold_with<F: PatternFolder<'tcx>>(&self, folder: &mut F) -> Self {
 966         folder.fold_pattern_kind(self)
 967     }
 968
 969     fn super_fold_with<F: PatternFolder<'tcx>>(&self, folder: &mut F) -> Self {
 970         match *self {
 971             PatternKind::Wild => PatternKind::Wild,
 972             PatternKind::Binding {
 973                 mutability,
 974                 name,
 975                 mode,
 976                 var,
 977                 ty,
 978                 ref subpattern,
 979             } => PatternKind::Binding {
 980                 mutability: mutability.fold_with(folder),
 981                 name: name.fold_with(folder),
 982                 mode: mode.fold_with(folder),
 983                 var: var.fold_with(folder),
 984                 ty: ty.fold_with(folder),
 985                 subpattern: subpattern.fold_with(folder),
 986             },
 987             PatternKind::Variant {
 988                 adt_def,
 989                 substs,
 990                 variant_index,
 991                 ref subpatterns,
 992             } => PatternKind::Variant {
 993                 adt_def: adt_def.fold_with(folder),
 994                 substs: substs.fold_with(folder),
 995                 variant_index: variant_index.fold_with(folder),
 996                 subpatterns: subpatterns.fold_with(folder)
 997             },
 998             PatternKind::Leaf {
 999                 ref subpatterns,
1000             } => PatternKind::Leaf {
1001                 subpatterns: subpatterns.fold_with(folder),
1002             },
1003             PatternKind::Deref {
1004                 ref subpattern,
1005             } => PatternKind::Deref {
1006                 subpattern: subpattern.fold_with(folder),
1007             },
1008             PatternKind::Constant {
1009                 value
1010             } => PatternKind::Constant {
1011                 value: value.fold_with(folder)
1012             },
1013             PatternKind::Range {
1014                 lo,
1015                 hi,
1016                 end,
1017             } => PatternKind::Range {
1018                 lo: lo.fold_with(folder),
1019                 hi: hi.fold_with(folder),
1020                 end,
1021             },
1022             PatternKind::Slice {
1023                 ref prefix,
1024                 ref slice,
1025                 ref suffix,
1026             } => PatternKind::Slice {
1027                 prefix: prefix.fold_with(folder),
1028                 slice: slice.fold_with(folder),
1029                 suffix: suffix.fold_with(folder)
1030             },
1031             PatternKind::Array {
1032                 ref prefix,
1033                 ref slice,
1034                 ref suffix
1035             } => PatternKind::Array {
1036                 prefix: prefix.fold_with(folder),
1037                 slice: slice.fold_with(folder),
1038                 suffix: suffix.fold_with(folder)
1039             },
1040         }
1041     }
1042 }
1043
1044 pub fn compare_const_vals<'a, 'tcx>(
1045     tcx: TyCtxt<'a, 'tcx, 'tcx>,
1046     a: &'tcx ty::Const<'tcx>,
1047     b: &'tcx ty::Const<'tcx>,
1048     ty: ty::ParamEnvAnd<'tcx, Ty<'tcx>>,
1049 ) -> Option<Ordering> {
1050     trace!("compare_const_vals: {:?}, {:?}", a, b);
1051
1052     let from_bool = |v: bool| {
1053         if v {
1054             Some(Ordering::Equal)
1055         } else {
1056             None
1057         }
1058     };
1059
1060     let fallback = || from_bool(a == b);
1061
1062     // Use the fallback if any type differs
1063     if a.ty != b.ty || a.ty != ty.value {
1064         return fallback();
1065     }
1066
1067     // FIXME: This should use assert_bits(ty) instead of use_bits
1068     // but triggers possibly bugs due to mismatching of arrays and slices
1069     if let (Some(a), Some(b)) = (a.to_bits(tcx, ty), b.to_bits(tcx, ty)) {
1070         use ::rustc_apfloat::Float;
1071         return match ty.value.sty {
1072             ty::TyFloat(ast::FloatTy::F32) => {
1073                 let l = ::rustc_apfloat::ieee::Single::from_bits(a);
1074                 let r = ::rustc_apfloat::ieee::Single::from_bits(b);
1075                 l.partial_cmp(&r)
1076             },
1077             ty::TyFloat(ast::FloatTy::F64) => {
1078                 let l = ::rustc_apfloat::ieee::Double::from_bits(a);
1079                 let r = ::rustc_apfloat::ieee::Double::from_bits(b);
1080                 l.partial_cmp(&r)
1081             },
1082             ty::TyInt(_) => {
1083                 let layout = tcx.layout_of(ty).ok()?;
1084                 let a = interpret::sign_extend(a, layout);
1085                 let b = interpret::sign_extend(b, layout);
1086                 Some((a as i128).cmp(&(b as i128)))
1087             },
1088             _ => Some(a.cmp(&b)),
1089         }
1090     }
1091
1092     if let ty::TyRef(_, rty, _) = ty.value.sty {
1093         if let ty::TyStr = rty.sty {
1094             match (a.val, b.val) {
1095                 (
1096                     ConstValue::ScalarPair(
1097                         Scalar::Ptr(ptr_a),
1098                         len_a,
1099                     ),
1100                     ConstValue::ScalarPair(
1101                         Scalar::Ptr(ptr_b),
1102                         len_b,
1103                     ),
1104                 ) if ptr_a.offset.bytes() == 0 && ptr_b.offset.bytes() == 0 => {
1105                     let len_a = len_a.unwrap_or_err().ok();
1106                     let len_b = len_b.unwrap_or_err().ok();
1107                     if len_a.is_none() || len_b.is_none() {
1108                         tcx.sess.struct_err("str slice len is undef").delay_as_bug();
1109                     }
1110                     let len_a = len_a?;
1111                     let len_b = len_b?;
1112                     if let Ok(len_a) = len_a.to_bits(tcx.data_layout.pointer_size) {
1113                         if let Ok(len_b) = len_b.to_bits(tcx.data_layout.pointer_size) {
1114                             if len_a == len_b {
1115                                 let map = tcx.alloc_map.lock();
1116                                 let alloc_a = map.unwrap_memory(ptr_a.alloc_id);
1117                                 let alloc_b = map.unwrap_memory(ptr_b.alloc_id);
1118                                 if alloc_a.bytes.len() as u128 == len_a {
1119                                     return from_bool(alloc_a == alloc_b);
1120                                 }
1121                             }
1122                         }
1123                     }
1124                 }
1125                 _ => (),
1126             }
1127         }
1128     }
1129
1130     fallback()
1131 }
1132
1133 #[derive(PartialEq)]
1134 enum LitToConstError {
1135     UnparseableFloat,
1136     Propagated,
1137 }
1138
1139 // FIXME: Combine with rustc_mir::hair::cx::const_eval_literal
1140 fn lit_to_const<'a, 'tcx>(lit: &'tcx ast::LitKind,
1141                           tcx: TyCtxt<'a, 'tcx, 'tcx>,
1142                           ty: Ty<'tcx>,
1143                           neg: bool)
1144                           -> Result<&'tcx ty::Const<'tcx>, LitToConstError> {
1145     use syntax::ast::*;
1146
1147     use rustc::mir::interpret::*;
1148     let lit = match *lit {
1149         LitKind::Str(ref s, _) => {
1150             let s = s.as_str();
1151             let id = tcx.allocate_bytes(s.as_bytes());
1152             let value = Scalar::Ptr(id.into()).to_value_with_len(s.len() as u64, tcx);
1153             ConstValue::from_byval_value(value).unwrap()
1154         },
1155         LitKind::ByteStr(ref data) => {
1156             let id = tcx.allocate_bytes(data);
1157             ConstValue::Scalar(Scalar::Ptr(id.into()))
1158         },
1159         LitKind::Byte(n) => ConstValue::Scalar(Scalar::Bits {
1160             bits: n as u128,
1161             size: 1,
1162         }),
1163         LitKind::Int(n, _) => {
1164             enum Int {
1165                 Signed(IntTy),
1166                 Unsigned(UintTy),
1167             }
1168             let ity = match ty.sty {
1169                 ty::TyInt(IntTy::Isize) => Int::Signed(tcx.sess.target.isize_ty),
1170                 ty::TyInt(other) => Int::Signed(other),
1171                 ty::TyUint(UintTy::Usize) => Int::Unsigned(tcx.sess.target.usize_ty),
1172                 ty::TyUint(other) => Int::Unsigned(other),
1173                 ty::TyError => { // Avoid ICE (#51963)
1174                     return Err(LitToConstError::Propagated);
1175                 }
1176                 _ => bug!("literal integer type with bad type ({:?})", ty.sty),
1177             };
1178             // This converts from LitKind::Int (which is sign extended) to
1179             // Scalar::Bytes (which is zero extended)
1180             let n = match ity {
1181                 // FIXME(oli-obk): are these casts correct?
1182                 Int::Signed(IntTy::I8) if neg =>
1183                     (n as i8).overflowing_neg().0 as u8 as u128,
1184                 Int::Signed(IntTy::I16) if neg =>
1185                     (n as i16).overflowing_neg().0 as u16 as u128,
1186                 Int::Signed(IntTy::I32) if neg =>
1187                     (n as i32).overflowing_neg().0 as u32 as u128,
1188                 Int::Signed(IntTy::I64) if neg =>
1189                     (n as i64).overflowing_neg().0 as u64 as u128,
1190                 Int::Signed(IntTy::I128) if neg =>
1191                     (n as i128).overflowing_neg().0 as u128,
1192                 Int::Signed(IntTy::I8) | Int::Unsigned(UintTy::U8) => n as u8 as u128,
1193                 Int::Signed(IntTy::I16) | Int::Unsigned(UintTy::U16) => n as u16 as u128,
1194                 Int::Signed(IntTy::I32) | Int::Unsigned(UintTy::U32) => n as u32 as u128,
1195                 Int::Signed(IntTy::I64) | Int::Unsigned(UintTy::U64) => n as u64 as u128,
1196                 Int::Signed(IntTy::I128)| Int::Unsigned(UintTy::U128) => n,
1197                 _ => bug!(),
1198             };
1199             let size = tcx.layout_of(ty::ParamEnv::empty().and(ty)).unwrap().size.bytes() as u8;
1200             ConstValue::Scalar(Scalar::Bits {
1201                 bits: n,
1202                 size,
1203             })
1204         },
1205         LitKind::Float(n, fty) => {
1206             parse_float(n, fty, neg).map_err(|_| LitToConstError::UnparseableFloat)?
1207         }
1208         LitKind::FloatUnsuffixed(n) => {
1209             let fty = match ty.sty {
1210                 ty::TyFloat(fty) => fty,
1211                 _ => bug!()
1212             };
1213             parse_float(n, fty, neg).map_err(|_| LitToConstError::UnparseableFloat)?
1214         }
1215         LitKind::Bool(b) => ConstValue::Scalar(Scalar::from_bool(b)),
1216         LitKind::Char(c) => ConstValue::Scalar(Scalar::from_char(c)),
1217     };
1218     Ok(ty::Const::from_const_value(tcx, lit, ty))
1219 }
1220
1221 pub fn parse_float<'tcx>(
1222     num: Symbol,
1223     fty: ast::FloatTy,
1224     neg: bool,
1225 ) -> Result<ConstValue<'tcx>, ()> {
1226     let num = num.as_str();
1227     use rustc_apfloat::ieee::{Single, Double};
1228     use rustc_apfloat::Float;
1229     let (bits, size) = match fty {
1230         ast::FloatTy::F32 => {
1231             num.parse::<f32>().map_err(|_| ())?;
1232             let mut f = num.parse::<Single>().unwrap_or_else(|e| {
1233                 panic!("apfloat::ieee::Single failed to parse `{}`: {:?}", num, e)
1234             });
1235             if neg {
1236                 f = -f;
1237             }
1238             (f.to_bits(), 4)
1239         }
1240         ast::FloatTy::F64 => {
1241             num.parse::<f64>().map_err(|_| ())?;
1242             let mut f = num.parse::<Double>().unwrap_or_else(|e| {
1243                 panic!("apfloat::ieee::Single failed to parse `{}`: {:?}", num, e)
1244             });
1245             if neg {
1246                 f = -f;
1247             }
1248             (f.to_bits(), 8)
1249         }
1250     };
1251
1252     Ok(ConstValue::Scalar(Scalar::Bits { bits, size }))
1253 }