src/librustc_mir/hair/pattern/mod.rs

   1 //! Validation of patterns/matches.
   2
   3 mod _match;
   4 mod check_match;
   5 mod const_to_pat;
   6
   7 pub(crate) use self::check_match::check_match;
   8
   9 use crate::hair::constant::*;
  10 use crate::hair::util::UserAnnotatedTyHelpers;
  11
  12 use rustc::hir::def::{CtorKind, CtorOf, DefKind, Res};
  13 use rustc::hir::pat_util::EnumerateAndAdjustIterator;
  14 use rustc::hir::ptr::P;
  15 use rustc::hir::{self, RangeEnd};
  16 use rustc::mir::interpret::{get_slice_bytes, sign_extend, ConstValue, ErrorHandled};
  17 use rustc::mir::UserTypeProjection;
  18 use rustc::mir::{BorrowKind, Field, Mutability};
  19 use rustc::ty::layout::VariantIdx;
  20 use rustc::ty::subst::{GenericArg, SubstsRef};
  21 use rustc::ty::{self, AdtDef, DefIdTree, Region, Ty, TyCtxt, UserType};
  22 use rustc::ty::{CanonicalUserType, CanonicalUserTypeAnnotation, CanonicalUserTypeAnnotations};
  23
  24 use rustc_index::vec::Idx;
  25
  26 use std::cmp::Ordering;
  27 use std::fmt;
  28 use syntax::ast;
  29 use syntax_pos::{Span, DUMMY_SP};
  30
  31 use rustc_error_codes::*;
  32
  33 #[derive(Clone, Debug)]
  34 pub enum PatternError {
  35     AssocConstInPattern(Span),
  36     StaticInPattern(Span),
  37     FloatBug,
  38     NonConstPath(Span),
  39 }
  40
  41 #[derive(Copy, Clone, Debug)]
  42 pub enum BindingMode {
  43     ByValue,
  44     ByRef(BorrowKind),
  45 }
  46
  47 #[derive(Clone, Debug)]
  48 pub struct FieldPat<'tcx> {
  49     pub field: Field,
  50     pub pattern: Pat<'tcx>,
  51 }
  52
  53 #[derive(Clone, Debug)]
  54 pub struct Pat<'tcx> {
  55     pub ty: Ty<'tcx>,
  56     pub span: Span,
  57     pub kind: Box<PatKind<'tcx>>,
  58 }
  59
  60 impl<'tcx> Pat<'tcx> {
  61     pub(crate) fn wildcard_from_ty(ty: Ty<'tcx>) -> Self {
  62         Pat { ty, span: DUMMY_SP, kind: Box::new(PatKind::Wild) }
  63     }
  64 }
  65
  66 #[derive(Copy, Clone, Debug, PartialEq)]
  67 pub struct PatTyProj<'tcx> {
  68     pub user_ty: CanonicalUserType<'tcx>,
  69 }
  70
  71 impl<'tcx> PatTyProj<'tcx> {
  72     pub(crate) fn from_user_type(user_annotation: CanonicalUserType<'tcx>) -> Self {
  73         Self { user_ty: user_annotation }
  74     }
  75
  76     pub(crate) fn user_ty(
  77         self,
  78         annotations: &mut CanonicalUserTypeAnnotations<'tcx>,
  79         inferred_ty: Ty<'tcx>,
  80         span: Span,
  81     ) -> UserTypeProjection {
  82         UserTypeProjection {
  83             base: annotations.push(CanonicalUserTypeAnnotation {
  84                 span,
  85                 user_ty: self.user_ty,
  86                 inferred_ty,
  87             }),
  88             projs: Vec::new(),
  89         }
  90     }
  91 }
  92
  93 #[derive(Copy, Clone, Debug, PartialEq)]
  94 pub struct Ascription<'tcx> {
  95     pub user_ty: PatTyProj<'tcx>,
  96     /// Variance to use when relating the type `user_ty` to the **type of the value being
  97     /// matched**. Typically, this is `Variance::Covariant`, since the value being matched must
  98     /// have a type that is some subtype of the ascribed type.
  99     ///
 100     /// Note that this variance does not apply for any bindings within subpatterns. The type
 101     /// assigned to those bindings must be exactly equal to the `user_ty` given here.
 102     ///
 103     /// The only place where this field is not `Covariant` is when matching constants, where
 104     /// we currently use `Contravariant` -- this is because the constant type just needs to
 105     /// be "comparable" to the type of the input value. So, for example:
 106     ///
 107     /// ```text
 108     /// match x { "foo" => .. }
 109     /// ```
 110     ///
 111     /// requires that `&'static str <: T_x`, where `T_x` is the type of `x`. Really, we should
 112     /// probably be checking for a `PartialEq` impl instead, but this preserves the behavior
 113     /// of the old type-check for now. See #57280 for details.
 114     pub variance: ty::Variance,
 115     pub user_ty_span: Span,
 116 }
 117
 118 #[derive(Clone, Debug)]
 119 pub enum PatKind<'tcx> {
 120     Wild,
 121
 122     AscribeUserType {
 123         ascription: Ascription<'tcx>,
 124         subpattern: Pat<'tcx>,
 125     },
 126
 127     /// `x`, `ref x`, `x @ P`, etc.
 128     Binding {
 129         mutability: Mutability,
 130         name: ast::Name,
 131         mode: BindingMode,
 132         var: hir::HirId,
 133         ty: Ty<'tcx>,
 134         subpattern: Option<Pat<'tcx>>,
 135     },
 136
 137     /// `Foo(...)` or `Foo{...}` or `Foo`, where `Foo` is a variant name from an ADT with
 138     /// multiple variants.
 139     Variant {
 140         adt_def: &'tcx AdtDef,
 141         substs: SubstsRef<'tcx>,
 142         variant_index: VariantIdx,
 143         subpatterns: Vec<FieldPat<'tcx>>,
 144     },
 145
 146     /// `(...)`, `Foo(...)`, `Foo{...}`, or `Foo`, where `Foo` is a variant name from an ADT with
 147     /// a single variant.
 148     Leaf {
 149         subpatterns: Vec<FieldPat<'tcx>>,
 150     },
 151
 152     /// `box P`, `&P`, `&mut P`, etc.
 153     Deref {
 154         subpattern: Pat<'tcx>,
 155     },
 156
 157     Constant {
 158         value: &'tcx ty::Const<'tcx>,
 159     },
 160
 161     Range(PatRange<'tcx>),
 162
 163     /// Matches against a slice, checking the length and extracting elements.
 164     /// irrefutable when there is a slice pattern and both `prefix` and `suffix` are empty.
 165     /// e.g., `&[ref xs @ ..]`.
 166     Slice {
 167         prefix: Vec<Pat<'tcx>>,
 168         slice: Option<Pat<'tcx>>,
 169         suffix: Vec<Pat<'tcx>>,
 170     },
 171
 172     /// Fixed match against an array; irrefutable.
 173     Array {
 174         prefix: Vec<Pat<'tcx>>,
 175         slice: Option<Pat<'tcx>>,
 176         suffix: Vec<Pat<'tcx>>,
 177     },
 178
 179     /// An or-pattern, e.g. `p | q`.
 180     /// Invariant: `pats.len() >= 2`.
 181     Or {
 182         pats: Vec<Pat<'tcx>>,
 183     },
 184 }
 185
 186 #[derive(Copy, Clone, Debug, PartialEq)]
 187 pub struct PatRange<'tcx> {
 188     pub lo: &'tcx ty::Const<'tcx>,
 189     pub hi: &'tcx ty::Const<'tcx>,
 190     pub end: RangeEnd,
 191 }
 192
 193 impl<'tcx> fmt::Display for Pat<'tcx> {
 194     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 195         // Printing lists is a chore.
 196         let mut first = true;
 197         let mut start_or_continue = |s| {
 198             if first {
 199                 first = false;
 200                 ""
 201             } else {
 202                 s
 203             }
 204         };
 205         let mut start_or_comma = || start_or_continue(", ");
 206
 207         match *self.kind {
 208             PatKind::Wild => write!(f, "_"),
 209             PatKind::AscribeUserType { ref subpattern, .. } => write!(f, "{}: _", subpattern),
 210             PatKind::Binding { mutability, name, mode, ref subpattern, .. } => {
 211                 let is_mut = match mode {
 212                     BindingMode::ByValue => mutability == Mutability::Mut,
 213                     BindingMode::ByRef(bk) => {
 214                         write!(f, "ref ")?;
 215                         match bk {
 216                             BorrowKind::Mut { .. } => true,
 217                             _ => false,
 218                         }
 219                     }
 220                 };
 221                 if is_mut {
 222                     write!(f, "mut ")?;
 223                 }
 224                 write!(f, "{}", name)?;
 225                 if let Some(ref subpattern) = *subpattern {
 226                     write!(f, " @ {}", subpattern)?;
 227                 }
 228                 Ok(())
 229             }
 230             PatKind::Variant { ref subpatterns, .. } | PatKind::Leaf { ref subpatterns } => {
 231                 let variant = match *self.kind {
 232                     PatKind::Variant { adt_def, variant_index, .. } => {
 233                         Some(&adt_def.variants[variant_index])
 234                     }
 235                     _ => {
 236                         if let ty::Adt(adt, _) = self.ty.kind {
 237                             if !adt.is_enum() {
 238                                 Some(&adt.variants[VariantIdx::new(0)])
 239                             } else {
 240                                 None
 241                             }
 242                         } else {
 243                             None
 244                         }
 245                     }
 246                 };
 247
 248                 if let Some(variant) = variant {
 249                     write!(f, "{}", variant.ident)?;
 250
 251                     // Only for Adt we can have `S {...}`,
 252                     // which we handle separately here.
 253                     if variant.ctor_kind == CtorKind::Fictive {
 254                         write!(f, " {{ ")?;
 255
 256                         let mut printed = 0;
 257                         for p in subpatterns {
 258                             if let PatKind::Wild = *p.pattern.kind {
 259                                 continue;
 260                             }
 261                             let name = variant.fields[p.field.index()].ident;
 262                             write!(f, "{}{}: {}", start_or_comma(), name, p.pattern)?;
 263                             printed += 1;
 264                         }
 265
 266                         if printed < variant.fields.len() {
 267                             write!(f, "{}..", start_or_comma())?;
 268                         }
 269
 270                         return write!(f, " }}");
 271                     }
 272                 }
 273
 274                 let num_fields = variant.map_or(subpatterns.len(), |v| v.fields.len());
 275                 if num_fields != 0 || variant.is_none() {
 276                     write!(f, "(")?;
 277                     for i in 0..num_fields {
 278                         write!(f, "{}", start_or_comma())?;
 279
 280                         // Common case: the field is where we expect it.
 281                         if let Some(p) = subpatterns.get(i) {
 282                             if p.field.index() == i {
 283                                 write!(f, "{}", p.pattern)?;
 284                                 continue;
 285                             }
 286                         }
 287
 288                         // Otherwise, we have to go looking for it.
 289                         if let Some(p) = subpatterns.iter().find(|p| p.field.index() == i) {
 290                             write!(f, "{}", p.pattern)?;
 291                         } else {
 292                             write!(f, "_")?;
 293                         }
 294                     }
 295                     write!(f, ")")?;
 296                 }
 297
 298                 Ok(())
 299             }
 300             PatKind::Deref { ref subpattern } => {
 301                 match self.ty.kind {
 302                     ty::Adt(def, _) if def.is_box() => write!(f, "box ")?,
 303                     ty::Ref(_, _, mutbl) => {
 304                         write!(f, "&{}", mutbl.prefix_str())?;
 305                     }
 306                     _ => bug!("{} is a bad Deref pattern type", self.ty),
 307                 }
 308                 write!(f, "{}", subpattern)
 309             }
 310             PatKind::Constant { value } => write!(f, "{}", value),
 311             PatKind::Range(PatRange { lo, hi, end }) => {
 312                 write!(f, "{}", lo)?;
 313                 write!(f, "{}", end)?;
 314                 write!(f, "{}", hi)
 315             }
 316             PatKind::Slice { ref prefix, ref slice, ref suffix }
 317             | PatKind::Array { ref prefix, ref slice, ref suffix } => {
 318                 write!(f, "[")?;
 319                 for p in prefix {
 320                     write!(f, "{}{}", start_or_comma(), p)?;
 321                 }
 322                 if let Some(ref slice) = *slice {
 323                     write!(f, "{}", start_or_comma())?;
 324                     match *slice.kind {
 325                         PatKind::Wild => {}
 326                         _ => write!(f, "{}", slice)?,
 327                     }
 328                     write!(f, "..")?;
 329                 }
 330                 for p in suffix {
 331                     write!(f, "{}{}", start_or_comma(), p)?;
 332                 }
 333                 write!(f, "]")
 334             }
 335             PatKind::Or { ref pats } => {
 336                 for pat in pats {
 337                     write!(f, "{}{}", start_or_continue(" | "), pat)?;
 338                 }
 339                 Ok(())
 340             }
 341         }
 342     }
 343 }
 344
 345 pub struct PatCtxt<'a, 'tcx> {
 346     pub tcx: TyCtxt<'tcx>,
 347     pub param_env: ty::ParamEnv<'tcx>,
 348     pub tables: &'a ty::TypeckTables<'tcx>,
 349     pub substs: SubstsRef<'tcx>,
 350     pub errors: Vec<PatternError>,
 351     include_lint_checks: bool,
 352 }
 353
 354 impl<'a, 'tcx> Pat<'tcx> {
 355     pub fn from_hir(
 356         tcx: TyCtxt<'tcx>,
 357         param_env_and_substs: ty::ParamEnvAnd<'tcx, SubstsRef<'tcx>>,
 358         tables: &'a ty::TypeckTables<'tcx>,
 359         pat: &'tcx hir::Pat,
 360     ) -> Self {
 361         let mut pcx = PatCtxt::new(tcx, param_env_and_substs, tables);
 362         let result = pcx.lower_pattern(pat);
 363         if !pcx.errors.is_empty() {
 364             let msg = format!("encountered errors lowering pattern: {:?}", pcx.errors);
 365             tcx.sess.delay_span_bug(pat.span, &msg);
 366         }
 367         debug!("Pat::from_hir({:?}) = {:?}", pat, result);
 368         result
 369     }
 370 }
 371
 372 impl<'a, 'tcx> PatCtxt<'a, 'tcx> {
 373     pub fn new(
 374         tcx: TyCtxt<'tcx>,
 375         param_env_and_substs: ty::ParamEnvAnd<'tcx, SubstsRef<'tcx>>,
 376         tables: &'a ty::TypeckTables<'tcx>,
 377     ) -> Self {
 378         PatCtxt {
 379             tcx,
 380             param_env: param_env_and_substs.param_env,
 381             tables,
 382             substs: param_env_and_substs.value,
 383             errors: vec![],
 384             include_lint_checks: false,
 385         }
 386     }
 387
 388     pub fn include_lint_checks(&mut self) -> &mut Self {
 389         self.include_lint_checks = true;
 390         self
 391     }
 392
 393     pub fn lower_pattern(&mut self, pat: &'tcx hir::Pat) -> Pat<'tcx> {
 394         // When implicit dereferences have been inserted in this pattern, the unadjusted lowered
 395         // pattern has the type that results *after* dereferencing. For example, in this code:
 396         //
 397         // ```
 398         // match &&Some(0i32) {
 399         //     Some(n) => { ... },
 400         //     _ => { ... },
 401         // }
 402         // ```
 403         //
 404         // the type assigned to `Some(n)` in `unadjusted_pat` would be `Option<i32>` (this is
 405         // determined in rustc_typeck::check::match). The adjustments would be
 406         //
 407         // `vec![&&Option<i32>, &Option<i32>]`.
 408         //
 409         // Applying the adjustments, we want to instead output `&&Some(n)` (as a HAIR pattern). So
 410         // we wrap the unadjusted pattern in `PatKind::Deref` repeatedly, consuming the
 411         // adjustments in *reverse order* (last-in-first-out, so that the last `Deref` inserted
 412         // gets the least-dereferenced type).
 413         let unadjusted_pat = self.lower_pattern_unadjusted(pat);
 414         self.tables.pat_adjustments().get(pat.hir_id).unwrap_or(&vec![]).iter().rev().fold(
 415             unadjusted_pat,
 416             |pat, ref_ty| {
 417                 debug!("{:?}: wrapping pattern with type {:?}", pat, ref_ty);
 418                 Pat {
 419                     span: pat.span,
 420                     ty: ref_ty,
 421                     kind: Box::new(PatKind::Deref { subpattern: pat }),
 422                 }
 423             },
 424         )
 425     }
 426
 427     fn lower_range_expr(
 428         &mut self,
 429         expr: &'tcx hir::Expr,
 430     ) -> (PatKind<'tcx>, Option<Ascription<'tcx>>) {
 431         match self.lower_lit(expr) {
 432             PatKind::AscribeUserType {
 433                 ascription: lo_ascription,
 434                 subpattern: Pat { kind: box kind, .. },
 435             } => (kind, Some(lo_ascription)),
 436             kind => (kind, None),
 437         }
 438     }
 439
 440     fn lower_pattern_unadjusted(&mut self, pat: &'tcx hir::Pat) -> Pat<'tcx> {
 441         let mut ty = self.tables.node_type(pat.hir_id);
 442
 443         if let ty::Error = ty.kind {
 444             // Avoid ICEs (e.g., #50577 and #50585).
 445             return Pat { span: pat.span, ty, kind: Box::new(PatKind::Wild) };
 446         }
 447
 448         let kind = match pat.kind {
 449             hir::PatKind::Wild => PatKind::Wild,
 450
 451             hir::PatKind::Lit(ref value) => self.lower_lit(value),
 452
 453             hir::PatKind::Range(ref lo_expr, ref hi_expr, end) => {
 454                 let (lo, lo_ascription) = self.lower_range_expr(lo_expr);
 455                 let (hi, hi_ascription) = self.lower_range_expr(hi_expr);
 456
 457                 let mut kind = match (lo, hi) {
 458                     (PatKind::Constant { value: lo }, PatKind::Constant { value: hi }) => {
 459                         assert_eq!(lo.ty, ty);
 460                         assert_eq!(hi.ty, ty);
 461                         let cmp = compare_const_vals(self.tcx, lo, hi, self.param_env, ty);
 462                         match (end, cmp) {
 463                             (RangeEnd::Excluded, Some(Ordering::Less)) => {
 464                                 PatKind::Range(PatRange { lo, hi, end })
 465                             }
 466                             (RangeEnd::Excluded, _) => {
 467                                 span_err!(
 468                                     self.tcx.sess,
 469                                     lo_expr.span,
 470                                     E0579,
 471                                     "lower range bound must be less than upper",
 472                                 );
 473                                 PatKind::Wild
 474                             }
 475                             (RangeEnd::Included, Some(Ordering::Equal)) => {
 476                                 PatKind::Constant { value: lo }
 477                             }
 478                             (RangeEnd::Included, Some(Ordering::Less)) => {
 479                                 PatKind::Range(PatRange { lo, hi, end })
 480                             }
 481                             (RangeEnd::Included, _) => {
 482                                 let mut err = struct_span_err!(
 483                                     self.tcx.sess,
 484                                     lo_expr.span,
 485                                     E0030,
 486                                     "lower range bound must be less than or equal to upper"
 487                                 );
 488                                 err.span_label(lo_expr.span, "lower bound larger than upper bound");
 489                                 if self.tcx.sess.teach(&err.get_code().unwrap()) {
 490                                     err.note(
 491                                         "When matching against a range, the compiler \
 492                                               verifies that the range is non-empty. Range \
 493                                               patterns include both end-points, so this is \
 494                                               equivalent to requiring the start of the range \
 495                                               to be less than or equal to the end of the range.",
 496                                     );
 497                                 }
 498                                 err.emit();
 499                                 PatKind::Wild
 500                             }
 501                         }
 502                     }
 503                     ref pats => {
 504                         self.tcx.sess.delay_span_bug(
 505                             pat.span,
 506                             &format!(
 507                                 "found bad range pattern `{:?}` outside of error recovery",
 508                                 pats,
 509                             ),
 510                         );
 511
 512                         PatKind::Wild
 513                     }
 514                 };
 515
 516                 // If we are handling a range with associated constants (e.g.
 517                 // `Foo::<'a>::A..=Foo::B`), we need to put the ascriptions for the associated
 518                 // constants somewhere. Have them on the range pattern.
 519                 for ascription in &[lo_ascription, hi_ascription] {
 520                     if let Some(ascription) = ascription {
 521                         kind = PatKind::AscribeUserType {
 522                             ascription: *ascription,
 523                             subpattern: Pat { span: pat.span, ty, kind: Box::new(kind) },
 524                         };
 525                     }
 526                 }
 527
 528                 kind
 529             }
 530
 531             hir::PatKind::Path(ref qpath) => {
 532                 return self.lower_path(qpath, pat.hir_id, pat.span);
 533             }
 534
 535             hir::PatKind::Ref(ref subpattern, _) | hir::PatKind::Box(ref subpattern) => {
 536                 PatKind::Deref { subpattern: self.lower_pattern(subpattern) }
 537             }
 538
 539             hir::PatKind::Slice(ref prefix, ref slice, ref suffix) => {
 540                 self.slice_or_array_pattern(pat.span, ty, prefix, slice, suffix)
 541             }
 542
 543             hir::PatKind::Tuple(ref pats, ddpos) => {
 544                 let tys = match ty.kind {
 545                     ty::Tuple(ref tys) => tys,
 546                     _ => span_bug!(pat.span, "unexpected type for tuple pattern: {:?}", ty),
 547                 };
 548                 let subpatterns = self.lower_tuple_subpats(pats, tys.len(), ddpos);
 549                 PatKind::Leaf { subpatterns }
 550             }
 551
 552             hir::PatKind::Binding(_, id, ident, ref sub) => {
 553                 let bm =
 554                     *self.tables.pat_binding_modes().get(pat.hir_id).expect("missing binding mode");
 555                 let (mutability, mode) = match bm {
 556                     ty::BindByValue(mutbl) => (mutbl, BindingMode::ByValue),
 557                     ty::BindByReference(hir::Mutability::Mut) => (
 558                         Mutability::Not,
 559                         BindingMode::ByRef(BorrowKind::Mut { allow_two_phase_borrow: false }),
 560                     ),
 561                     ty::BindByReference(hir::Mutability::Not) => {
 562                         (Mutability::Not, BindingMode::ByRef(BorrowKind::Shared))
 563                     }
 564                 };
 565
 566                 // A ref x pattern is the same node used for x, and as such it has
 567                 // x's type, which is &T, where we want T (the type being matched).
 568                 let var_ty = ty;
 569                 if let ty::BindByReference(_) = bm {
 570                     if let ty::Ref(_, rty, _) = ty.kind {
 571                         ty = rty;
 572                     } else {
 573                         bug!("`ref {}` has wrong type {}", ident, ty);
 574                     }
 575                 };
 576
 577                 PatKind::Binding {
 578                     mutability,
 579                     mode,
 580                     name: ident.name,
 581                     var: id,
 582                     ty: var_ty,
 583                     subpattern: self.lower_opt_pattern(sub),
 584                 }
 585             }
 586
 587             hir::PatKind::TupleStruct(ref qpath, ref pats, ddpos) => {
 588                 let res = self.tables.qpath_res(qpath, pat.hir_id);
 589                 let adt_def = match ty.kind {
 590                     ty::Adt(adt_def, _) => adt_def,
 591                     _ => span_bug!(pat.span, "tuple struct pattern not applied to an ADT {:?}", ty),
 592                 };
 593                 let variant_def = adt_def.variant_of_res(res);
 594                 let subpatterns = self.lower_tuple_subpats(pats, variant_def.fields.len(), ddpos);
 595                 self.lower_variant_or_leaf(res, pat.hir_id, pat.span, ty, subpatterns)
 596             }
 597
 598             hir::PatKind::Struct(ref qpath, ref fields, _) => {
 599                 let res = self.tables.qpath_res(qpath, pat.hir_id);
 600                 let subpatterns = fields
 601                     .iter()
 602                     .map(|field| FieldPat {
 603                         field: Field::new(self.tcx.field_index(field.hir_id, self.tables)),
 604                         pattern: self.lower_pattern(&field.pat),
 605                     })
 606                     .collect();
 607
 608                 self.lower_variant_or_leaf(res, pat.hir_id, pat.span, ty, subpatterns)
 609             }
 610
 611             hir::PatKind::Or(ref pats) => PatKind::Or { pats: self.lower_patterns(pats) },
 612         };
 613
 614         Pat { span: pat.span, ty, kind: Box::new(kind) }
 615     }
 616
 617     fn lower_tuple_subpats(
 618         &mut self,
 619         pats: &'tcx [P<hir::Pat>],
 620         expected_len: usize,
 621         gap_pos: Option<usize>,
 622     ) -> Vec<FieldPat<'tcx>> {
 623         pats.iter()
 624             .enumerate_and_adjust(expected_len, gap_pos)
 625             .map(|(i, subpattern)| FieldPat {
 626                 field: Field::new(i),
 627                 pattern: self.lower_pattern(subpattern),
 628             })
 629             .collect()
 630     }
 631
 632     fn lower_patterns(&mut self, pats: &'tcx [P<hir::Pat>]) -> Vec<Pat<'tcx>> {
 633         pats.iter().map(|p| self.lower_pattern(p)).collect()
 634     }
 635
 636     fn lower_opt_pattern(&mut self, pat: &'tcx Option<P<hir::Pat>>) -> Option<Pat<'tcx>> {
 637         pat.as_ref().map(|p| self.lower_pattern(p))
 638     }
 639
 640     fn slice_or_array_pattern(
 641         &mut self,
 642         span: Span,
 643         ty: Ty<'tcx>,
 644         prefix: &'tcx [P<hir::Pat>],
 645         slice: &'tcx Option<P<hir::Pat>>,
 646         suffix: &'tcx [P<hir::Pat>],
 647     ) -> PatKind<'tcx> {
 648         let prefix = self.lower_patterns(prefix);
 649         let slice = self.lower_opt_pattern(slice);
 650         let suffix = self.lower_patterns(suffix);
 651         match ty.kind {
 652             // Matching a slice, `[T]`.
 653             ty::Slice(..) => PatKind::Slice { prefix, slice, suffix },
 654             // Fixed-length array, `[T; len]`.
 655             ty::Array(_, len) => {
 656                 let len = len.eval_usize(self.tcx, self.param_env);
 657                 assert!(len >= prefix.len() as u64 + suffix.len() as u64);
 658                 PatKind::Array { prefix, slice, suffix }
 659             }
 660             _ => span_bug!(span, "bad slice pattern type {:?}", ty),
 661         }
 662     }
 663
 664     fn lower_variant_or_leaf(
 665         &mut self,
 666         res: Res,
 667         hir_id: hir::HirId,
 668         span: Span,
 669         ty: Ty<'tcx>,
 670         subpatterns: Vec<FieldPat<'tcx>>,
 671     ) -> PatKind<'tcx> {
 672         let res = match res {
 673             Res::Def(DefKind::Ctor(CtorOf::Variant, ..), variant_ctor_id) => {
 674                 let variant_id = self.tcx.parent(variant_ctor_id).unwrap();
 675                 Res::Def(DefKind::Variant, variant_id)
 676             }
 677             res => res,
 678         };
 679
 680         let mut kind = match res {
 681             Res::Def(DefKind::Variant, variant_id) => {
 682                 let enum_id = self.tcx.parent(variant_id).unwrap();
 683                 let adt_def = self.tcx.adt_def(enum_id);
 684                 if adt_def.is_enum() {
 685                     let substs = match ty.kind {
 686                         ty::Adt(_, substs) | ty::FnDef(_, substs) => substs,
 687                         ty::Error => {
 688                             // Avoid ICE (#50585)
 689                             return PatKind::Wild;
 690                         }
 691                         _ => bug!("inappropriate type for def: {:?}", ty),
 692                     };
 693                     PatKind::Variant {
 694                         adt_def,
 695                         substs,
 696                         variant_index: adt_def.variant_index_with_id(variant_id),
 697                         subpatterns,
 698                     }
 699                 } else {
 700                     PatKind::Leaf { subpatterns }
 701                 }
 702             }
 703
 704             Res::Def(DefKind::Struct, _)
 705             | Res::Def(DefKind::Ctor(CtorOf::Struct, ..), _)
 706             | Res::Def(DefKind::Union, _)
 707             | Res::Def(DefKind::TyAlias, _)
 708             | Res::Def(DefKind::AssocTy, _)
 709             | Res::SelfTy(..)
 710             | Res::SelfCtor(..) => PatKind::Leaf { subpatterns },
 711
 712             _ => {
 713                 self.errors.push(PatternError::NonConstPath(span));
 714                 PatKind::Wild
 715             }
 716         };
 717
 718         if let Some(user_ty) = self.user_substs_applied_to_ty_of_hir_id(hir_id) {
 719             debug!("lower_variant_or_leaf: kind={:?} user_ty={:?} span={:?}", kind, user_ty, span);
 720             kind = PatKind::AscribeUserType {
 721                 subpattern: Pat { span, ty, kind: Box::new(kind) },
 722                 ascription: Ascription {
 723                     user_ty: PatTyProj::from_user_type(user_ty),
 724                     user_ty_span: span,
 725                     variance: ty::Variance::Covariant,
 726                 },
 727             };
 728         }
 729
 730         kind
 731     }
 732
 733     /// Takes a HIR Path. If the path is a constant, evaluates it and feeds
 734     /// it to `const_to_pat`. Any other path (like enum variants without fields)
 735     /// is converted to the corresponding pattern via `lower_variant_or_leaf`.
 736     fn lower_path(&mut self, qpath: &hir::QPath, id: hir::HirId, span: Span) -> Pat<'tcx> {
 737         let ty = self.tables.node_type(id);
 738         let res = self.tables.qpath_res(qpath, id);
 739         let is_associated_const = match res {
 740             Res::Def(DefKind::AssocConst, _) => true,
 741             _ => false,
 742         };
 743         let kind = match res {
 744             Res::Def(DefKind::Const, def_id) | Res::Def(DefKind::AssocConst, def_id) => {
 745                 let substs = self.tables.node_substs(id);
 746                 match self.tcx.const_eval_resolve(self.param_env, def_id, substs, Some(span)) {
 747                     Ok(value) => {
 748                         let pattern = self.const_to_pat(value, id, span);
 749                         if !is_associated_const {
 750                             return pattern;
 751                         }
 752
 753                         let user_provided_types = self.tables().user_provided_types();
 754                         return if let Some(u_ty) = user_provided_types.get(id) {
 755                             let user_ty = PatTyProj::from_user_type(*u_ty);
 756                             Pat {
 757                                 span,
 758                                 kind: Box::new(PatKind::AscribeUserType {
 759                                     subpattern: pattern,
 760                                     ascription: Ascription {
 761                                         /// Note that use `Contravariant` here. See the
 762                                         /// `variance` field documentation for details.
 763                                         variance: ty::Variance::Contravariant,
 764                                         user_ty,
 765                                         user_ty_span: span,
 766                                     },
 767                                 }),
 768                                 ty: value.ty,
 769                             }
 770                         } else {
 771                             pattern
 772                         };
 773                     }
 774                     Err(ErrorHandled::TooGeneric) => {
 775                         self.errors.push(if is_associated_const {
 776                             PatternError::AssocConstInPattern(span)
 777                         } else {
 778                             PatternError::StaticInPattern(span)
 779                         });
 780                         PatKind::Wild
 781                     }
 782                     Err(_) => {
 783                         self.tcx.sess.span_err(span, "could not evaluate constant pattern");
 784                         PatKind::Wild
 785                     }
 786                 }
 787             }
 788             _ => self.lower_variant_or_leaf(res, id, span, ty, vec![]),
 789         };
 790
 791         Pat { span, ty, kind: Box::new(kind) }
 792     }
 793
 794     /// Converts literals, paths and negation of literals to patterns.
 795     /// The special case for negation exists to allow things like `-128_i8`
 796     /// which would overflow if we tried to evaluate `128_i8` and then negate
 797     /// afterwards.
 798     fn lower_lit(&mut self, expr: &'tcx hir::Expr) -> PatKind<'tcx> {
 799         match expr.kind {
 800             hir::ExprKind::Lit(ref lit) => {
 801                 let ty = self.tables.expr_ty(expr);
 802                 match lit_to_const(&lit.node, self.tcx, ty, false) {
 803                     Ok(val) => *self.const_to_pat(val, expr.hir_id, lit.span).kind,
 804                     Err(LitToConstError::UnparseableFloat) => {
 805                         self.errors.push(PatternError::FloatBug);
 806                         PatKind::Wild
 807                     }
 808                     Err(LitToConstError::Reported) => PatKind::Wild,
 809                 }
 810             }
 811             hir::ExprKind::Path(ref qpath) => *self.lower_path(qpath, expr.hir_id, expr.span).kind,
 812             hir::ExprKind::Unary(hir::UnNeg, ref expr) => {
 813                 let ty = self.tables.expr_ty(expr);
 814                 let lit = match expr.kind {
 815                     hir::ExprKind::Lit(ref lit) => lit,
 816                     _ => span_bug!(expr.span, "not a literal: {:?}", expr),
 817                 };
 818                 match lit_to_const(&lit.node, self.tcx, ty, true) {
 819                     Ok(val) => *self.const_to_pat(val, expr.hir_id, lit.span).kind,
 820                     Err(LitToConstError::UnparseableFloat) => {
 821                         self.errors.push(PatternError::FloatBug);
 822                         PatKind::Wild
 823                     }
 824                     Err(LitToConstError::Reported) => PatKind::Wild,
 825                 }
 826             }
 827             _ => span_bug!(expr.span, "not a literal: {:?}", expr),
 828         }
 829     }
 830 }
 831
 832 impl UserAnnotatedTyHelpers<'tcx> for PatCtxt<'_, 'tcx> {
 833     fn tcx(&self) -> TyCtxt<'tcx> {
 834         self.tcx
 835     }
 836
 837     fn tables(&self) -> &ty::TypeckTables<'tcx> {
 838         self.tables
 839     }
 840 }
 841
 842 pub trait PatternFoldable<'tcx>: Sized {
 843     fn fold_with<F: PatternFolder<'tcx>>(&self, folder: &mut F) -> Self {
 844         self.super_fold_with(folder)
 845     }
 846
 847     fn super_fold_with<F: PatternFolder<'tcx>>(&self, folder: &mut F) -> Self;
 848 }
 849
 850 pub trait PatternFolder<'tcx>: Sized {
 851     fn fold_pattern(&mut self, pattern: &Pat<'tcx>) -> Pat<'tcx> {
 852         pattern.super_fold_with(self)
 853     }
 854
 855     fn fold_pattern_kind(&mut self, kind: &PatKind<'tcx>) -> PatKind<'tcx> {
 856         kind.super_fold_with(self)
 857     }
 858 }
 859
 860 impl<'tcx, T: PatternFoldable<'tcx>> PatternFoldable<'tcx> for Box<T> {
 861     fn super_fold_with<F: PatternFolder<'tcx>>(&self, folder: &mut F) -> Self {
 862         let content: T = (**self).fold_with(folder);
 863         box content
 864     }
 865 }
 866
 867 impl<'tcx, T: PatternFoldable<'tcx>> PatternFoldable<'tcx> for Vec<T> {
 868     fn super_fold_with<F: PatternFolder<'tcx>>(&self, folder: &mut F) -> Self {
 869         self.iter().map(|t| t.fold_with(folder)).collect()
 870     }
 871 }
 872
 873 impl<'tcx, T: PatternFoldable<'tcx>> PatternFoldable<'tcx> for Option<T> {
 874     fn super_fold_with<F: PatternFolder<'tcx>>(&self, folder: &mut F) -> Self {
 875         self.as_ref().map(|t| t.fold_with(folder))
 876     }
 877 }
 878
 879 macro_rules! CloneImpls {
 880     (<$lt_tcx:tt> $($ty:ty),+) => {
 881         $(
 882             impl<$lt_tcx> PatternFoldable<$lt_tcx> for $ty {
 883                 fn super_fold_with<F: PatternFolder<$lt_tcx>>(&self, _: &mut F) -> Self {
 884                     Clone::clone(self)
 885                 }
 886             }
 887         )+
 888     }
 889 }
 890
 891 CloneImpls! { <'tcx>
 892     Span, Field, Mutability, ast::Name, hir::HirId, usize, ty::Const<'tcx>,
 893     Region<'tcx>, Ty<'tcx>, BindingMode, &'tcx AdtDef,
 894     SubstsRef<'tcx>, &'tcx GenericArg<'tcx>, UserType<'tcx>,
 895     UserTypeProjection, PatTyProj<'tcx>
 896 }
 897
 898 impl<'tcx> PatternFoldable<'tcx> for FieldPat<'tcx> {
 899     fn super_fold_with<F: PatternFolder<'tcx>>(&self, folder: &mut F) -> Self {
 900         FieldPat { field: self.field.fold_with(folder), pattern: self.pattern.fold_with(folder) }
 901     }
 902 }
 903
 904 impl<'tcx> PatternFoldable<'tcx> for Pat<'tcx> {
 905     fn fold_with<F: PatternFolder<'tcx>>(&self, folder: &mut F) -> Self {
 906         folder.fold_pattern(self)
 907     }
 908
 909     fn super_fold_with<F: PatternFolder<'tcx>>(&self, folder: &mut F) -> Self {
 910         Pat {
 911             ty: self.ty.fold_with(folder),
 912             span: self.span.fold_with(folder),
 913             kind: self.kind.fold_with(folder),
 914         }
 915     }
 916 }
 917
 918 impl<'tcx> PatternFoldable<'tcx> for PatKind<'tcx> {
 919     fn fold_with<F: PatternFolder<'tcx>>(&self, folder: &mut F) -> Self {
 920         folder.fold_pattern_kind(self)
 921     }
 922
 923     fn super_fold_with<F: PatternFolder<'tcx>>(&self, folder: &mut F) -> Self {
 924         match *self {
 925             PatKind::Wild => PatKind::Wild,
 926             PatKind::AscribeUserType {
 927                 ref subpattern,
 928                 ascription: Ascription { variance, ref user_ty, user_ty_span },
 929             } => PatKind::AscribeUserType {
 930                 subpattern: subpattern.fold_with(folder),
 931                 ascription: Ascription {
 932                     user_ty: user_ty.fold_with(folder),
 933                     variance,
 934                     user_ty_span,
 935                 },
 936             },
 937             PatKind::Binding { mutability, name, mode, var, ty, ref subpattern } => {
 938                 PatKind::Binding {
 939                     mutability: mutability.fold_with(folder),
 940                     name: name.fold_with(folder),
 941                     mode: mode.fold_with(folder),
 942                     var: var.fold_with(folder),
 943                     ty: ty.fold_with(folder),
 944                     subpattern: subpattern.fold_with(folder),
 945                 }
 946             }
 947             PatKind::Variant { adt_def, substs, variant_index, ref subpatterns } => {
 948                 PatKind::Variant {
 949                     adt_def: adt_def.fold_with(folder),
 950                     substs: substs.fold_with(folder),
 951                     variant_index,
 952                     subpatterns: subpatterns.fold_with(folder),
 953                 }
 954             }
 955             PatKind::Leaf { ref subpatterns } => {
 956                 PatKind::Leaf { subpatterns: subpatterns.fold_with(folder) }
 957             }
 958             PatKind::Deref { ref subpattern } => {
 959                 PatKind::Deref { subpattern: subpattern.fold_with(folder) }
 960             }
 961             PatKind::Constant { value } => PatKind::Constant { value },
 962             PatKind::Range(range) => PatKind::Range(range),
 963             PatKind::Slice { ref prefix, ref slice, ref suffix } => PatKind::Slice {
 964                 prefix: prefix.fold_with(folder),
 965                 slice: slice.fold_with(folder),
 966                 suffix: suffix.fold_with(folder),
 967             },
 968             PatKind::Array { ref prefix, ref slice, ref suffix } => PatKind::Array {
 969                 prefix: prefix.fold_with(folder),
 970                 slice: slice.fold_with(folder),
 971                 suffix: suffix.fold_with(folder),
 972             },
 973             PatKind::Or { ref pats } => PatKind::Or { pats: pats.fold_with(folder) },
 974         }
 975     }
 976 }
 977
 978 pub fn compare_const_vals<'tcx>(
 979     tcx: TyCtxt<'tcx>,
 980     a: &'tcx ty::Const<'tcx>,
 981     b: &'tcx ty::Const<'tcx>,
 982     param_env: ty::ParamEnv<'tcx>,
 983     ty: Ty<'tcx>,
 984 ) -> Option<Ordering> {
 985     trace!("compare_const_vals: {:?}, {:?}", a, b);
 986
 987     let from_bool = |v: bool| v.then_some(Ordering::Equal);
 988
 989     let fallback = || from_bool(a == b);
 990
 991     // Use the fallback if any type differs
 992     if a.ty != b.ty || a.ty != ty {
 993         return fallback();
 994     }
 995
 996     let a_bits = a.try_eval_bits(tcx, param_env, ty);
 997     let b_bits = b.try_eval_bits(tcx, param_env, ty);
 998
 999     if let (Some(a), Some(b)) = (a_bits, b_bits) {
1000         use ::rustc_apfloat::Float;
1001         return match ty.kind {
1002             ty::Float(ast::FloatTy::F32) => {
1003                 let l = ::rustc_apfloat::ieee::Single::from_bits(a);
1004                 let r = ::rustc_apfloat::ieee::Single::from_bits(b);
1005                 l.partial_cmp(&r)
1006             }
1007             ty::Float(ast::FloatTy::F64) => {
1008                 let l = ::rustc_apfloat::ieee::Double::from_bits(a);
1009                 let r = ::rustc_apfloat::ieee::Double::from_bits(b);
1010                 l.partial_cmp(&r)
1011             }
1012             ty::Int(ity) => {
1013                 use rustc::ty::layout::{Integer, IntegerExt};
1014                 use syntax::attr::SignedInt;
1015                 let size = Integer::from_attr(&tcx, SignedInt(ity)).size();
1016                 let a = sign_extend(a, size);
1017                 let b = sign_extend(b, size);
1018                 Some((a as i128).cmp(&(b as i128)))
1019             }
1020             _ => Some(a.cmp(&b)),
1021         };
1022     }
1023
1024     if let ty::Str = ty.kind {
1025         match (a.val, b.val) {
1026             (
1027                 ty::ConstKind::Value(a_val @ ConstValue::Slice { .. }),
1028                 ty::ConstKind::Value(b_val @ ConstValue::Slice { .. }),
1029             ) => {
1030                 let a_bytes = get_slice_bytes(&tcx, a_val);
1031                 let b_bytes = get_slice_bytes(&tcx, b_val);
1032                 return from_bool(a_bytes == b_bytes);
1033             }
1034             _ => (),
1035         }
1036     }
1037
1038     fallback()
1039 }