compiler/rustc_middle/src/mir/query.rs

   1 //! Values computed by queries that use MIR.
   2
   3 use crate::mir::{Body, ConstantKind, Promoted};
   4 use crate::ty::{self, OpaqueHiddenType, Ty, TyCtxt};
   5 use rustc_data_structures::fx::FxHashSet;
   6 use rustc_data_structures::vec_map::VecMap;
   7 use rustc_errors::ErrorGuaranteed;
   8 use rustc_hir as hir;
   9 use rustc_hir::def_id::{DefId, LocalDefId};
  10 use rustc_index::bit_set::BitMatrix;
  11 use rustc_index::vec::IndexVec;
  12 use rustc_span::Span;
  13 use rustc_target::abi::VariantIdx;
  14 use smallvec::SmallVec;
  15 use std::cell::Cell;
  16 use std::fmt::{self, Debug};
  17
  18 use super::{Field, SourceInfo};
  19
  20 #[derive(Copy, Clone, PartialEq, TyEncodable, TyDecodable, HashStable, Debug)]
  21 pub enum UnsafetyViolationKind {
  22     /// Unsafe operation outside `unsafe`.
  23     General,
  24     /// Unsafe operation in an `unsafe fn` but outside an `unsafe` block.
  25     /// Has to be handled as a lint for backwards compatibility.
  26     UnsafeFn,
  27 }
  28
  29 #[derive(Copy, Clone, PartialEq, TyEncodable, TyDecodable, HashStable, Debug)]
  30 pub enum UnsafetyViolationDetails {
  31     CallToUnsafeFunction,
  32     UseOfInlineAssembly,
  33     InitializingTypeWith,
  34     CastOfPointerToInt,
  35     UseOfMutableStatic,
  36     UseOfExternStatic,
  37     DerefOfRawPointer,
  38     AccessToUnionField,
  39     MutationOfLayoutConstrainedField,
  40     BorrowOfLayoutConstrainedField,
  41     CallToFunctionWith,
  42 }
  43
  44 impl UnsafetyViolationDetails {
  45     pub fn description_and_note(&self) -> (&'static str, &'static str) {
  46         use UnsafetyViolationDetails::*;
  47         match self {
  48             CallToUnsafeFunction => (
  49                 "call to unsafe function",
  50                 "consult the function's documentation for information on how to avoid undefined \
  51                  behavior",
  52             ),
  53             UseOfInlineAssembly => (
  54                 "use of inline assembly",
  55                 "inline assembly is entirely unchecked and can cause undefined behavior",
  56             ),
  57             InitializingTypeWith => (
  58                 "initializing type with `rustc_layout_scalar_valid_range` attr",
  59                 "initializing a layout restricted type's field with a value outside the valid \
  60                  range is undefined behavior",
  61             ),
  62             CastOfPointerToInt => {
  63                 ("cast of pointer to int", "casting pointers to integers in constants")
  64             }
  65             UseOfMutableStatic => (
  66                 "use of mutable static",
  67                 "mutable statics can be mutated by multiple threads: aliasing violations or data \
  68                  races will cause undefined behavior",
  69             ),
  70             UseOfExternStatic => (
  71                 "use of extern static",
  72                 "extern statics are not controlled by the Rust type system: invalid data, \
  73                  aliasing violations or data races will cause undefined behavior",
  74             ),
  75             DerefOfRawPointer => (
  76                 "dereference of raw pointer",
  77                 "raw pointers may be null, dangling or unaligned; they can violate aliasing rules \
  78                  and cause data races: all of these are undefined behavior",
  79             ),
  80             AccessToUnionField => (
  81                 "access to union field",
  82                 "the field may not be properly initialized: using uninitialized data will cause \
  83                  undefined behavior",
  84             ),
  85             MutationOfLayoutConstrainedField => (
  86                 "mutation of layout constrained field",
  87                 "mutating layout constrained fields cannot statically be checked for valid values",
  88             ),
  89             BorrowOfLayoutConstrainedField => (
  90                 "borrow of layout constrained field with interior mutability",
  91                 "references to fields of layout constrained fields lose the constraints. Coupled \
  92                  with interior mutability, the field can be changed to invalid values",
  93             ),
  94             CallToFunctionWith => (
  95                 "call to function with `#[target_feature]`",
  96                 "can only be called if the required target features are available",
  97             ),
  98         }
  99     }
 100 }
 101
 102 #[derive(Copy, Clone, PartialEq, TyEncodable, TyDecodable, HashStable, Debug)]
 103 pub struct UnsafetyViolation {
 104     pub source_info: SourceInfo,
 105     pub lint_root: hir::HirId,
 106     pub kind: UnsafetyViolationKind,
 107     pub details: UnsafetyViolationDetails,
 108 }
 109
 110 #[derive(Copy, Clone, PartialEq, TyEncodable, TyDecodable, HashStable, Debug)]
 111 pub enum UnusedUnsafe {
 112     /// `unsafe` block contains no unsafe operations
 113     /// > ``unnecessary `unsafe` block``
 114     Unused,
 115     /// `unsafe` block nested under another (used) `unsafe` block
 116     /// > ``… because it's nested under this `unsafe` block``
 117     InUnsafeBlock(hir::HirId),
 118 }
 119
 120 #[derive(TyEncodable, TyDecodable, HashStable, Debug)]
 121 pub struct UnsafetyCheckResult {
 122     /// Violations that are propagated *upwards* from this function.
 123     pub violations: Vec<UnsafetyViolation>,
 124
 125     /// Used `unsafe` blocks in this function. This is used for the "unused_unsafe" lint.
 126     pub used_unsafe_blocks: FxHashSet<hir::HirId>,
 127
 128     /// This is `Some` iff the item is not a closure.
 129     pub unused_unsafes: Option<Vec<(hir::HirId, UnusedUnsafe)>>,
 130 }
 131
 132 rustc_index::newtype_index! {
 133     #[derive(HashStable)]
 134     #[debug_format = "_{}"]
 135     pub struct GeneratorSavedLocal {}
 136 }
 137
 138 /// The layout of generator state.
 139 #[derive(Clone, TyEncodable, TyDecodable, HashStable, TypeFoldable, TypeVisitable)]
 140 pub struct GeneratorLayout<'tcx> {
 141     /// The type of every local stored inside the generator.
 142     pub field_tys: IndexVec<GeneratorSavedLocal, Ty<'tcx>>,
 143
 144     /// Which of the above fields are in each variant. Note that one field may
 145     /// be stored in multiple variants.
 146     pub variant_fields: IndexVec<VariantIdx, IndexVec<Field, GeneratorSavedLocal>>,
 147
 148     /// The source that led to each variant being created (usually, a yield or
 149     /// await).
 150     pub variant_source_info: IndexVec<VariantIdx, SourceInfo>,
 151
 152     /// Which saved locals are storage-live at the same time. Locals that do not
 153     /// have conflicts with each other are allowed to overlap in the computed
 154     /// layout.
 155     pub storage_conflicts: BitMatrix<GeneratorSavedLocal, GeneratorSavedLocal>,
 156 }
 157
 158 impl Debug for GeneratorLayout<'_> {
 159     fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
 160         /// Prints an iterator of (key, value) tuples as a map.
 161         struct MapPrinter<'a, K, V>(Cell<Option<Box<dyn Iterator<Item = (K, V)> + 'a>>>);
 162         impl<'a, K, V> MapPrinter<'a, K, V> {
 163             fn new(iter: impl Iterator<Item = (K, V)> + 'a) -> Self {
 164                 Self(Cell::new(Some(Box::new(iter))))
 165             }
 166         }
 167         impl<'a, K: Debug, V: Debug> Debug for MapPrinter<'a, K, V> {
 168             fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
 169                 fmt.debug_map().entries(self.0.take().unwrap()).finish()
 170             }
 171         }
 172
 173         /// Prints the generator variant name.
 174         struct GenVariantPrinter(VariantIdx);
 175         impl From<VariantIdx> for GenVariantPrinter {
 176             fn from(idx: VariantIdx) -> Self {
 177                 GenVariantPrinter(idx)
 178             }
 179         }
 180         impl Debug for GenVariantPrinter {
 181             fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
 182                 let variant_name = ty::GeneratorSubsts::variant_name(self.0);
 183                 if fmt.alternate() {
 184                     write!(fmt, "{:9}({:?})", variant_name, self.0)
 185                 } else {
 186                     write!(fmt, "{}", variant_name)
 187                 }
 188             }
 189         }
 190
 191         /// Forces its contents to print in regular mode instead of alternate mode.
 192         struct OneLinePrinter<T>(T);
 193         impl<T: Debug> Debug for OneLinePrinter<T> {
 194             fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
 195                 write!(fmt, "{:?}", self.0)
 196             }
 197         }
 198
 199         fmt.debug_struct("GeneratorLayout")
 200             .field("field_tys", &MapPrinter::new(self.field_tys.iter_enumerated()))
 201             .field(
 202                 "variant_fields",
 203                 &MapPrinter::new(
 204                     self.variant_fields
 205                         .iter_enumerated()
 206                         .map(|(k, v)| (GenVariantPrinter(k), OneLinePrinter(v))),
 207                 ),
 208             )
 209             .field("storage_conflicts", &self.storage_conflicts)
 210             .finish()
 211     }
 212 }
 213
 214 #[derive(Debug, TyEncodable, TyDecodable, HashStable)]
 215 pub struct BorrowCheckResult<'tcx> {
 216     /// All the opaque types that are restricted to concrete types
 217     /// by this function. Unlike the value in `TypeckResults`, this has
 218     /// unerased regions.
 219     pub concrete_opaque_types: VecMap<LocalDefId, OpaqueHiddenType<'tcx>>,
 220     pub closure_requirements: Option<ClosureRegionRequirements<'tcx>>,
 221     pub used_mut_upvars: SmallVec<[Field; 8]>,
 222     pub tainted_by_errors: Option<ErrorGuaranteed>,
 223 }
 224
 225 /// The result of the `mir_const_qualif` query.
 226 ///
 227 /// Each field (except `error_occurred`) corresponds to an implementer of the `Qualif` trait in
 228 /// `rustc_const_eval/src/transform/check_consts/qualifs.rs`. See that file for more information on each
 229 /// `Qualif`.
 230 #[derive(Clone, Copy, Debug, Default, TyEncodable, TyDecodable, HashStable)]
 231 pub struct ConstQualifs {
 232     pub has_mut_interior: bool,
 233     pub needs_drop: bool,
 234     pub needs_non_const_drop: bool,
 235     pub custom_eq: bool,
 236     pub tainted_by_errors: Option<ErrorGuaranteed>,
 237 }
 238
 239 /// After we borrow check a closure, we are left with various
 240 /// requirements that we have inferred between the free regions that
 241 /// appear in the closure's signature or on its field types. These
 242 /// requirements are then verified and proved by the closure's
 243 /// creating function. This struct encodes those requirements.
 244 ///
 245 /// The requirements are listed as being between various `RegionVid`. The 0th
 246 /// region refers to `'static`; subsequent region vids refer to the free
 247 /// regions that appear in the closure (or generator's) type, in order of
 248 /// appearance. (This numbering is actually defined by the `UniversalRegions`
 249 /// struct in the NLL region checker. See for example
 250 /// `UniversalRegions::closure_mapping`.) Note the free regions in the
 251 /// closure's signature and captures are erased.
 252 ///
 253 /// Example: If type check produces a closure with the closure substs:
 254 ///
 255 /// ```text
 256 /// ClosureSubsts = [
 257 ///     'a,                                         // From the parent.
 258 ///     'b,
 259 ///     i8,                                         // the "closure kind"
 260 ///     for<'x> fn(&'<erased> &'x u32) -> &'x u32,  // the "closure signature"
 261 ///     &'<erased> String,                          // some upvar
 262 /// ]
 263 /// ```
 264 ///
 265 /// We would "renumber" each free region to a unique vid, as follows:
 266 ///
 267 /// ```text
 268 /// ClosureSubsts = [
 269 ///     '1,                                         // From the parent.
 270 ///     '2,
 271 ///     i8,                                         // the "closure kind"
 272 ///     for<'x> fn(&'3 &'x u32) -> &'x u32,         // the "closure signature"
 273 ///     &'4 String,                                 // some upvar
 274 /// ]
 275 /// ```
 276 ///
 277 /// Now the code might impose a requirement like `'1: '2`. When an
 278 /// instance of the closure is created, the corresponding free regions
 279 /// can be extracted from its type and constrained to have the given
 280 /// outlives relationship.
 281 ///
 282 /// In some cases, we have to record outlives requirements between types and
 283 /// regions as well. In that case, if those types include any regions, those
 284 /// regions are recorded using their external names (`ReStatic`,
 285 /// `ReEarlyBound`, `ReFree`). We use these because in a query response we
 286 /// cannot use `ReVar` (which is what we use internally within the rest of the
 287 /// NLL code).
 288 #[derive(Clone, Debug, TyEncodable, TyDecodable, HashStable)]
 289 pub struct ClosureRegionRequirements<'tcx> {
 290     /// The number of external regions defined on the closure. In our
 291     /// example above, it would be 3 -- one for `'static`, then `'1`
 292     /// and `'2`. This is just used for a sanity check later on, to
 293     /// make sure that the number of regions we see at the callsite
 294     /// matches.
 295     pub num_external_vids: usize,
 296
 297     /// Requirements between the various free regions defined in
 298     /// indices.
 299     pub outlives_requirements: Vec<ClosureOutlivesRequirement<'tcx>>,
 300 }
 301
 302 /// Indicates an outlives-constraint between a type or between two
 303 /// free regions declared on the closure.
 304 #[derive(Copy, Clone, Debug, TyEncodable, TyDecodable, HashStable)]
 305 pub struct ClosureOutlivesRequirement<'tcx> {
 306     // This region or type ...
 307     pub subject: ClosureOutlivesSubject<'tcx>,
 308
 309     // ... must outlive this one.
 310     pub outlived_free_region: ty::RegionVid,
 311
 312     // If not, report an error here ...
 313     pub blame_span: Span,
 314
 315     // ... due to this reason.
 316     pub category: ConstraintCategory<'tcx>,
 317 }
 318
 319 // Make sure this enum doesn't unintentionally grow
 320 #[cfg(all(target_arch = "x86_64", target_pointer_width = "64"))]
 321 rustc_data_structures::static_assert_size!(ConstraintCategory<'_>, 16);
 322
 323 /// Outlives-constraints can be categorized to determine whether and why they
 324 /// are interesting (for error reporting). Order of variants indicates sort
 325 /// order of the category, thereby influencing diagnostic output.
 326 ///
 327 /// See also `rustc_const_eval::borrow_check::constraints`.
 328 #[derive(Copy, Clone, Debug, Eq, PartialEq, PartialOrd, Ord, Hash)]
 329 #[derive(TyEncodable, TyDecodable, HashStable, Lift, TypeVisitable, TypeFoldable)]
 330 pub enum ConstraintCategory<'tcx> {
 331     Return(ReturnConstraint),
 332     Yield,
 333     UseAsConst,
 334     UseAsStatic,
 335     TypeAnnotation,
 336     Cast,
 337
 338     /// A constraint that came from checking the body of a closure.
 339     ///
 340     /// We try to get the category that the closure used when reporting this.
 341     ClosureBounds,
 342
 343     /// Contains the function type if available.
 344     CallArgument(Option<Ty<'tcx>>),
 345     CopyBound,
 346     SizedBound,
 347     Assignment,
 348     /// A constraint that came from a usage of a variable (e.g. in an ADT expression
 349     /// like `Foo { field: my_val }`)
 350     Usage,
 351     OpaqueType,
 352     ClosureUpvar(Field),
 353
 354     /// A constraint from a user-written predicate
 355     /// with the provided span, written on the item
 356     /// with the given `DefId`
 357     Predicate(Span),
 358
 359     /// A "boring" constraint (caused by the given location) is one that
 360     /// the user probably doesn't want to see described in diagnostics,
 361     /// because it is kind of an artifact of the type system setup.
 362     Boring,
 363     // Boring and applicable everywhere.
 364     BoringNoLocation,
 365
 366     /// A constraint that doesn't correspond to anything the user sees.
 367     Internal,
 368 }
 369
 370 #[derive(Copy, Clone, Debug, Eq, PartialEq, PartialOrd, Ord, Hash)]
 371 #[derive(TyEncodable, TyDecodable, HashStable, TypeVisitable, TypeFoldable)]
 372 pub enum ReturnConstraint {
 373     Normal,
 374     ClosureUpvar(Field),
 375 }
 376
 377 /// The subject of a `ClosureOutlivesRequirement` -- that is, the thing
 378 /// that must outlive some region.
 379 #[derive(Copy, Clone, Debug, TyEncodable, TyDecodable, HashStable)]
 380 pub enum ClosureOutlivesSubject<'tcx> {
 381     /// Subject is a type, typically a type parameter, but could also
 382     /// be a projection. Indicates a requirement like `T: 'a` being
 383     /// passed to the caller, where the type here is `T`.
 384     ///
 385     /// The type here is guaranteed not to contain any free regions at
 386     /// present.
 387     Ty(Ty<'tcx>),
 388
 389     /// Subject is a free region from the closure. Indicates a requirement
 390     /// like `'a: 'b` being passed to the caller; the region here is `'a`.
 391     Region(ty::RegionVid),
 392 }
 393
 394 /// The constituent parts of a mir constant of kind ADT or array.
 395 #[derive(Copy, Clone, Debug, HashStable)]
 396 pub struct DestructuredConstant<'tcx> {
 397     pub variant: Option<VariantIdx>,
 398     pub fields: &'tcx [ConstantKind<'tcx>],
 399 }
 400
 401 /// Coverage information summarized from a MIR if instrumented for source code coverage (see
 402 /// compiler option `-Cinstrument-coverage`). This information is generated by the
 403 /// `InstrumentCoverage` MIR pass and can be retrieved via the `coverageinfo` query.
 404 #[derive(Clone, TyEncodable, TyDecodable, Debug, HashStable)]
 405 pub struct CoverageInfo {
 406     /// The total number of coverage region counters added to the MIR `Body`.
 407     pub num_counters: u32,
 408
 409     /// The total number of coverage region counter expressions added to the MIR `Body`.
 410     pub num_expressions: u32,
 411 }
 412
 413 /// Shims which make dealing with `WithOptConstParam` easier.
 414 ///
 415 /// For more information on why this is needed, consider looking
 416 /// at the docs for `WithOptConstParam` itself.
 417 impl<'tcx> TyCtxt<'tcx> {
 418     #[inline]
 419     pub fn mir_const_qualif_opt_const_arg(
 420         self,
 421         def: ty::WithOptConstParam<LocalDefId>,
 422     ) -> ConstQualifs {
 423         if let Some(param_did) = def.const_param_did {
 424             self.mir_const_qualif_const_arg((def.did, param_did))
 425         } else {
 426             self.mir_const_qualif(def.did)
 427         }
 428     }
 429
 430     #[inline]
 431     pub fn promoted_mir_opt_const_arg(
 432         self,
 433         def: ty::WithOptConstParam<DefId>,
 434     ) -> &'tcx IndexVec<Promoted, Body<'tcx>> {
 435         if let Some((did, param_did)) = def.as_const_arg() {
 436             self.promoted_mir_of_const_arg((did, param_did))
 437         } else {
 438             self.promoted_mir(def.did)
 439         }
 440     }
 441
 442     #[inline]
 443     pub fn mir_for_ctfe_opt_const_arg(self, def: ty::WithOptConstParam<DefId>) -> &'tcx Body<'tcx> {
 444         if let Some((did, param_did)) = def.as_const_arg() {
 445             self.mir_for_ctfe_of_const_arg((did, param_did))
 446         } else {
 447             self.mir_for_ctfe(def.did)
 448         }
 449     }
 450 }