1 //! Trait Resolution. See the [rustc dev guide] for more information on how this works.
3 //! [rustc dev guide]: https://rustc-dev-guide.rust-lang.org/traits/resolution.html
8 pub mod specialization_graph;
12 use crate::infer::canonical::Canonical;
13 use crate::thir::abstract_const::NotConstEvaluatable;
14 use crate::ty::subst::SubstsRef;
15 use crate::ty::{self, AdtKind, Ty, TyCtxt};
17 use rustc_data_structures::sync::Lrc;
18 use rustc_errors::{Applicability, DiagnosticBuilder};
20 use rustc_hir::def_id::{DefId, LocalDefId};
21 use rustc_span::symbol::Symbol;
22 use rustc_span::{Span, DUMMY_SP};
23 use smallvec::SmallVec;
27 use std::hash::{Hash, Hasher};
30 pub use self::select::{EvaluationCache, EvaluationResult, OverflowError, SelectionCache};
32 pub type CanonicalChalkEnvironmentAndGoal<'tcx> = Canonical<'tcx, ChalkEnvironmentAndGoal<'tcx>>;
34 pub use self::ObligationCauseCode::*;
36 pub use self::chalk::{ChalkEnvironmentAndGoal, RustInterner as ChalkRustInterner};
38 /// Depending on the stage of compilation, we want projection to be
39 /// more or less conservative.
40 #[derive(Debug, Copy, Clone, PartialEq, Eq, Hash, HashStable)]
42 /// At type-checking time, we refuse to project any associated
43 /// type that is marked `default`. Non-`default` ("final") types
44 /// are always projected. This is necessary in general for
45 /// soundness of specialization. However, we *could* allow
46 /// projections in fully-monomorphic cases. We choose not to,
47 /// because we prefer for `default type` to force the type
48 /// definition to be treated abstractly by any consumers of the
49 /// impl. Concretely, that means that the following example will
57 /// impl<T> Assoc for T {
58 /// default type Output = bool;
62 /// let <() as Assoc>::Output = true;
67 /// At codegen time, all monomorphic projections will succeed.
68 /// Also, `impl Trait` is normalized to the concrete type,
69 /// which has to be already collected by type-checking.
71 /// NOTE: as `impl Trait`'s concrete type should *never*
72 /// be observable directly by the user, `Reveal::All`
73 /// should not be used by checks which may expose
74 /// type equality or type contents to the user.
75 /// There are some exceptions, e.g., around auto traits and
76 /// transmute-checking, which expose some details, but
77 /// not the whole concrete type of the `impl Trait`.
81 /// The reason why we incurred this obligation; used for error reporting.
83 /// As the happy path does not care about this struct, storing this on the heap
84 /// ends up increasing performance.
86 /// We do not want to intern this as there are a lot of obligation causes which
87 /// only live for a short period of time.
88 #[derive(Clone, PartialEq, Eq, Hash, Lift)]
89 pub struct ObligationCause<'tcx> {
90 /// `None` for `ObligationCause::dummy`, `Some` otherwise.
91 data: Option<Lrc<ObligationCauseData<'tcx>>>,
94 const DUMMY_OBLIGATION_CAUSE_DATA: ObligationCauseData<'static> =
95 ObligationCauseData { span: DUMMY_SP, body_id: hir::CRATE_HIR_ID, code: MiscObligation };
97 // Correctly format `ObligationCause::dummy`.
98 impl<'tcx> fmt::Debug for ObligationCause<'tcx> {
99 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
100 ObligationCauseData::fmt(self, f)
104 impl Deref for ObligationCause<'tcx> {
105 type Target = ObligationCauseData<'tcx>;
108 fn deref(&self) -> &Self::Target {
109 self.data.as_deref().unwrap_or(&DUMMY_OBLIGATION_CAUSE_DATA)
113 #[derive(Clone, Debug, PartialEq, Eq, Lift)]
114 pub struct ObligationCauseData<'tcx> {
117 /// The ID of the fn body that triggered this obligation. This is
118 /// used for region obligations to determine the precise
119 /// environment in which the region obligation should be evaluated
120 /// (in particular, closures can add new assumptions). See the
121 /// field `region_obligations` of the `FulfillmentContext` for more
123 pub body_id: hir::HirId,
125 pub code: ObligationCauseCode<'tcx>,
128 impl Hash for ObligationCauseData<'_> {
129 fn hash<H: Hasher>(&self, state: &mut H) {
130 self.body_id.hash(state);
131 self.span.hash(state);
132 std::mem::discriminant(&self.code).hash(state);
136 impl<'tcx> ObligationCause<'tcx> {
141 code: ObligationCauseCode<'tcx>,
142 ) -> ObligationCause<'tcx> {
143 ObligationCause { data: Some(Lrc::new(ObligationCauseData { span, body_id, code })) }
146 pub fn misc(span: Span, body_id: hir::HirId) -> ObligationCause<'tcx> {
147 ObligationCause::new(span, body_id, MiscObligation)
150 pub fn dummy_with_span(span: Span) -> ObligationCause<'tcx> {
151 ObligationCause::new(span, hir::CRATE_HIR_ID, MiscObligation)
155 pub fn dummy() -> ObligationCause<'tcx> {
156 ObligationCause { data: None }
159 pub fn make_mut(&mut self) -> &mut ObligationCauseData<'tcx> {
160 Lrc::make_mut(self.data.get_or_insert_with(|| Lrc::new(DUMMY_OBLIGATION_CAUSE_DATA)))
163 pub fn span(&self, tcx: TyCtxt<'tcx>) -> Span {
165 ObligationCauseCode::CompareImplMethodObligation { .. }
166 | ObligationCauseCode::MainFunctionType
167 | ObligationCauseCode::StartFunctionType => {
168 tcx.sess.source_map().guess_head_span(self.span)
170 ObligationCauseCode::MatchExpressionArm(box MatchExpressionArmCause {
179 #[derive(Clone, Debug, PartialEq, Eq, Hash, Lift)]
180 pub struct UnifyReceiverContext<'tcx> {
181 pub assoc_item: ty::AssocItem,
182 pub param_env: ty::ParamEnv<'tcx>,
183 pub substs: SubstsRef<'tcx>,
186 #[derive(Clone, Debug, PartialEq, Eq, Hash, Lift)]
187 pub enum ObligationCauseCode<'tcx> {
188 /// Not well classified or should be obvious from the span.
191 /// A slice or array is WF only if `T: Sized`.
194 /// A tuple is WF only if its middle elements are `Sized`.
197 /// This is the trait reference from the given projection.
198 ProjectionWf(ty::ProjectionTy<'tcx>),
200 /// In an impl of trait `X` for type `Y`, type `Y` must
201 /// also implement all supertraits of `X`.
202 ItemObligation(DefId),
204 /// Like `ItemObligation`, but with extra detail on the source of the obligation.
205 BindingObligation(DefId, Span),
207 /// A type like `&'a T` is WF only if `T: 'a`.
208 ReferenceOutlivesReferent(Ty<'tcx>),
210 /// A type like `Box<Foo<'a> + 'b>` is WF only if `'b: 'a`.
211 ObjectTypeBound(Ty<'tcx>, ty::Region<'tcx>),
213 /// Obligation incurred due to an object cast.
214 ObjectCastObligation(/* Object type */ Ty<'tcx>),
216 /// Obligation incurred due to a coercion.
222 /// Various cases where expressions must be `Sized` / `Copy` / etc.
223 /// `L = X` implies that `L` is `Sized`.
225 /// `(x1, .., xn)` must be `Sized`.
226 TupleInitializerSized,
227 /// `S { ... }` must be `Sized`.
228 StructInitializerSized,
229 /// Type of each variable must be `Sized`.
230 VariableType(hir::HirId),
231 /// Argument type must be `Sized`.
232 SizedArgumentType(Option<Span>),
233 /// Return type must be `Sized`.
235 /// Yield type must be `Sized`.
237 /// Box expression result type must be `Sized`.
239 /// Inline asm operand type must be `Sized`.
241 /// `[T, ..n]` implies that `T` must be `Copy`.
242 /// If the function in the array repeat expression is a `const fn`,
243 /// display a help message suggesting to move the function call to a
244 /// new `const` item while saying that `T` doesn't implement `Copy`.
247 /// Types of fields (other than the last, except for packed structs) in a struct must be sized.
254 /// Constant expressions must be sized.
257 /// `static` items must have `Sync` type.
260 BuiltinDerivedObligation(DerivedObligationCause<'tcx>),
262 ImplDerivedObligation(DerivedObligationCause<'tcx>),
264 DerivedObligation(DerivedObligationCause<'tcx>),
266 FunctionArgumentObligation {
267 /// The node of the relevant argument in the function call.
268 arg_hir_id: hir::HirId,
269 /// The node of the function call.
270 call_hir_id: hir::HirId,
271 /// The obligation introduced by this argument.
272 parent_code: Lrc<ObligationCauseCode<'tcx>>,
275 /// Error derived when matching traits/impls; see ObligationCause for more details
276 CompareImplConstObligation,
278 /// Error derived when matching traits/impls; see ObligationCause for more details
279 CompareImplMethodObligation {
280 impl_item_def_id: DefId,
281 trait_item_def_id: DefId,
284 /// Error derived when matching traits/impls; see ObligationCause for more details
285 CompareImplTypeObligation {
286 impl_item_def_id: DefId,
287 trait_item_def_id: DefId,
290 /// Checking that this expression can be assigned where it needs to be
291 // FIXME(eddyb) #11161 is the original Expr required?
294 /// Computing common supertype in the arms of a match expression
295 MatchExpressionArm(Box<MatchExpressionArmCause<'tcx>>),
297 /// Type error arising from type checking a pattern against an expected type.
299 /// The span of the scrutinee or type expression which caused the `root_ty` type.
301 /// The root expected type induced by a scrutinee or type expression.
303 /// Whether the `Span` came from an expression or a type expression.
307 /// Constants in patterns must have `Structural` type.
308 ConstPatternStructural,
310 /// Computing common supertype in an if expression
311 IfExpression(Box<IfExpressionCause>),
313 /// Computing common supertype of an if expression with no else counter-part
314 IfExpressionWithNoElse,
316 /// `main` has wrong type
319 /// `start` has wrong type
322 /// Intrinsic has wrong type
325 /// A let else block does not diverge
331 UnifyReceiver(Box<UnifyReceiverContext<'tcx>>),
333 /// `return` with no expression
336 /// `return` with an expression
337 ReturnValue(hir::HirId),
339 /// Return type of this function
342 /// Block implicit return
343 BlockTailExpression(hir::HirId),
345 /// #[feature(trivial_bounds)] is not enabled
348 /// If `X` is the concrete type of an opaque type `impl Y`, then `X` must implement `Y`
351 /// Well-formed checking. If a `WellFormedLoc` is provided,
352 /// then it will be used to eprform HIR-based wf checking
353 /// after an error occurs, in order to generate a more precise error span.
354 /// This is purely for diagnostic purposes - it is always
355 /// correct to use `MiscObligation` instead, or to specify
356 /// `WellFormed(None)`
357 WellFormed(Option<WellFormedLoc>),
359 /// From `match_impl`. The cause for us having to match an impl, and the DefId we are matching against.
360 MatchImpl(ObligationCause<'tcx>, DefId),
363 /// The 'location' at which we try to perform HIR-based wf checking.
364 /// This information is used to obtain an `hir::Ty`, which
365 /// we can walk in order to obtain precise spans for any
366 /// 'nested' types (e.g. `Foo` in `Option<Foo>`).
367 #[derive(Copy, Clone, Debug, PartialEq, Eq, Hash, HashStable)]
368 pub enum WellFormedLoc {
369 /// Use the type of the provided definition.
371 /// Use the type of the parameter of the provided function.
372 /// We cannot use `hir::Param`, since the function may
373 /// not have a body (e.g. a trait method definition)
375 /// The function to lookup the parameter in
376 function: LocalDefId,
377 /// The index of the parameter to use.
378 /// Parameters are indexed from 0, with the return type
379 /// being the last 'parameter'
384 impl ObligationCauseCode<'_> {
385 // Return the base obligation, ignoring derived obligations.
386 pub fn peel_derives(&self) -> &Self {
387 let mut base_cause = self;
388 while let BuiltinDerivedObligation(DerivedObligationCause { parent_code, .. })
389 | ImplDerivedObligation(DerivedObligationCause { parent_code, .. })
390 | DerivedObligation(DerivedObligationCause { parent_code, .. })
391 | FunctionArgumentObligation { parent_code, .. } = base_cause
393 base_cause = &parent_code;
399 // `ObligationCauseCode` is used a lot. Make sure it doesn't unintentionally get bigger.
400 #[cfg(all(target_arch = "x86_64", target_pointer_width = "64"))]
401 static_assert_size!(ObligationCauseCode<'_>, 40);
403 #[derive(Copy, Clone, Debug, PartialEq, Eq, Hash)]
404 pub enum StatementAsExpression {
409 impl<'tcx> ty::Lift<'tcx> for StatementAsExpression {
410 type Lifted = StatementAsExpression;
411 fn lift_to_tcx(self, _tcx: TyCtxt<'tcx>) -> Option<StatementAsExpression> {
416 #[derive(Clone, Debug, PartialEq, Eq, Hash, Lift)]
417 pub struct MatchExpressionArmCause<'tcx> {
419 pub scrut_span: Span,
420 pub semi_span: Option<(Span, StatementAsExpression)>,
421 pub source: hir::MatchSource,
422 pub prior_arms: Vec<Span>,
423 pub last_ty: Ty<'tcx>,
424 pub scrut_hir_id: hir::HirId,
425 pub opt_suggest_box_span: Option<Span>,
428 #[derive(Clone, Debug, PartialEq, Eq, Hash)]
429 pub struct IfExpressionCause {
432 pub outer: Option<Span>,
433 pub semicolon: Option<(Span, StatementAsExpression)>,
434 pub opt_suggest_box_span: Option<Span>,
437 #[derive(Clone, Debug, PartialEq, Eq, Hash, Lift)]
438 pub struct DerivedObligationCause<'tcx> {
439 /// The trait reference of the parent obligation that led to the
440 /// current obligation. Note that only trait obligations lead to
441 /// derived obligations, so we just store the trait reference here
443 pub parent_trait_ref: ty::PolyTraitRef<'tcx>,
445 /// The parent trait had this cause.
446 pub parent_code: Lrc<ObligationCauseCode<'tcx>>,
449 #[derive(Clone, Debug, TypeFoldable, Lift)]
450 pub enum SelectionError<'tcx> {
451 /// The trait is not implemented.
453 /// After a closure impl has selected, its "outputs" were evaluated
454 /// (which for closures includes the "input" type params) and they
455 /// didn't resolve. See `confirm_poly_trait_refs` for more.
456 OutputTypeParameterMismatch(
457 ty::PolyTraitRef<'tcx>,
458 ty::PolyTraitRef<'tcx>,
459 ty::error::TypeError<'tcx>,
461 /// The trait pointed by `DefId` is not object safe.
462 TraitNotObjectSafe(DefId),
463 /// A given constant couldn't be evaluated.
464 NotConstEvaluatable(NotConstEvaluatable),
465 /// Exceeded the recursion depth during type projection.
467 /// Signaling that an error has already been emitted, to avoid
468 /// multiple errors being shown.
470 /// Multiple applicable `impl`s where found. The `DefId`s correspond to
471 /// all the `impl`s' Items.
472 Ambiguous(Vec<DefId>),
475 /// When performing resolution, it is typically the case that there
476 /// can be one of three outcomes:
478 /// - `Ok(Some(r))`: success occurred with result `r`
479 /// - `Ok(None)`: could not definitely determine anything, usually due
480 /// to inconclusive type inference.
481 /// - `Err(e)`: error `e` occurred
482 pub type SelectionResult<'tcx, T> = Result<Option<T>, SelectionError<'tcx>>;
484 /// Given the successful resolution of an obligation, the `ImplSource`
485 /// indicates where the impl comes from.
487 /// For example, the obligation may be satisfied by a specific impl (case A),
488 /// or it may be relative to some bound that is in scope (case B).
491 /// impl<T:Clone> Clone<T> for Option<T> { ... } // Impl_1
492 /// impl<T:Clone> Clone<T> for Box<T> { ... } // Impl_2
493 /// impl Clone for i32 { ... } // Impl_3
495 /// fn foo<T: Clone>(concrete: Option<Box<i32>>, param: T, mixed: Option<T>) {
496 /// // Case A: ImplSource points at a specific impl. Only possible when
497 /// // type is concretely known. If the impl itself has bounded
498 /// // type parameters, ImplSource will carry resolutions for those as well:
499 /// concrete.clone(); // ImpleSource(Impl_1, [ImplSource(Impl_2, [ImplSource(Impl_3)])])
501 /// // Case A: ImplSource points at a specific impl. Only possible when
502 /// // type is concretely known. If the impl itself has bounded
503 /// // type parameters, ImplSource will carry resolutions for those as well:
504 /// concrete.clone(); // ImplSource(Impl_1, [ImplSource(Impl_2, [ImplSource(Impl_3)])])
506 /// // Case B: ImplSource must be provided by caller. This applies when
507 /// // type is a type parameter.
508 /// param.clone(); // ImplSource::Param
510 /// // Case C: A mix of cases A and B.
511 /// mixed.clone(); // ImplSource(Impl_1, [ImplSource::Param])
515 /// ### The type parameter `N`
517 /// See explanation on `ImplSourceUserDefinedData`.
518 #[derive(Clone, PartialEq, Eq, TyEncodable, TyDecodable, HashStable, TypeFoldable, Lift)]
519 pub enum ImplSource<'tcx, N> {
520 /// ImplSource identifying a particular impl.
521 UserDefined(ImplSourceUserDefinedData<'tcx, N>),
523 /// ImplSource for auto trait implementations.
524 /// This carries the information and nested obligations with regards
525 /// to an auto implementation for a trait `Trait`. The nested obligations
526 /// ensure the trait implementation holds for all the constituent types.
527 AutoImpl(ImplSourceAutoImplData<N>),
529 /// Successful resolution to an obligation provided by the caller
530 /// for some type parameter. The `Vec<N>` represents the
531 /// obligations incurred from normalizing the where-clause (if
533 Param(Vec<N>, ty::BoundConstness),
535 /// Virtual calls through an object.
536 Object(ImplSourceObjectData<'tcx, N>),
538 /// Successful resolution for a builtin trait.
539 Builtin(ImplSourceBuiltinData<N>),
541 /// ImplSource for trait upcasting coercion
542 TraitUpcasting(ImplSourceTraitUpcastingData<'tcx, N>),
544 /// ImplSource automatically generated for a closure. The `DefId` is the ID
545 /// of the closure expression. This is an `ImplSource::UserDefined` in spirit, but the
546 /// impl is generated by the compiler and does not appear in the source.
547 Closure(ImplSourceClosureData<'tcx, N>),
549 /// Same as above, but for a function pointer type with the given signature.
550 FnPointer(ImplSourceFnPointerData<'tcx, N>),
552 /// ImplSource for a builtin `DeterminantKind` trait implementation.
553 DiscriminantKind(ImplSourceDiscriminantKindData),
555 /// ImplSource for a builtin `Pointee` trait implementation.
556 Pointee(ImplSourcePointeeData),
558 /// ImplSource automatically generated for a generator.
559 Generator(ImplSourceGeneratorData<'tcx, N>),
561 /// ImplSource for a trait alias.
562 TraitAlias(ImplSourceTraitAliasData<'tcx, N>),
564 /// ImplSource for a `const Drop` implementation.
565 ConstDrop(ImplSourceConstDropData),
568 impl<'tcx, N> ImplSource<'tcx, N> {
569 pub fn nested_obligations(self) -> Vec<N> {
571 ImplSource::UserDefined(i) => i.nested,
572 ImplSource::Param(n, _) => n,
573 ImplSource::Builtin(i) => i.nested,
574 ImplSource::AutoImpl(d) => d.nested,
575 ImplSource::Closure(c) => c.nested,
576 ImplSource::Generator(c) => c.nested,
577 ImplSource::Object(d) => d.nested,
578 ImplSource::FnPointer(d) => d.nested,
579 ImplSource::DiscriminantKind(ImplSourceDiscriminantKindData)
580 | ImplSource::Pointee(ImplSourcePointeeData)
581 | ImplSource::ConstDrop(ImplSourceConstDropData) => Vec::new(),
582 ImplSource::TraitAlias(d) => d.nested,
583 ImplSource::TraitUpcasting(d) => d.nested,
587 pub fn borrow_nested_obligations(&self) -> &[N] {
589 ImplSource::UserDefined(i) => &i.nested[..],
590 ImplSource::Param(n, _) => &n[..],
591 ImplSource::Builtin(i) => &i.nested[..],
592 ImplSource::AutoImpl(d) => &d.nested[..],
593 ImplSource::Closure(c) => &c.nested[..],
594 ImplSource::Generator(c) => &c.nested[..],
595 ImplSource::Object(d) => &d.nested[..],
596 ImplSource::FnPointer(d) => &d.nested[..],
597 ImplSource::DiscriminantKind(ImplSourceDiscriminantKindData)
598 | ImplSource::Pointee(ImplSourcePointeeData)
599 | ImplSource::ConstDrop(ImplSourceConstDropData) => &[],
600 ImplSource::TraitAlias(d) => &d.nested[..],
601 ImplSource::TraitUpcasting(d) => &d.nested[..],
605 pub fn map<M, F>(self, f: F) -> ImplSource<'tcx, M>
610 ImplSource::UserDefined(i) => ImplSource::UserDefined(ImplSourceUserDefinedData {
611 impl_def_id: i.impl_def_id,
613 nested: i.nested.into_iter().map(f).collect(),
615 ImplSource::Param(n, ct) => ImplSource::Param(n.into_iter().map(f).collect(), ct),
616 ImplSource::Builtin(i) => ImplSource::Builtin(ImplSourceBuiltinData {
617 nested: i.nested.into_iter().map(f).collect(),
619 ImplSource::Object(o) => ImplSource::Object(ImplSourceObjectData {
620 upcast_trait_ref: o.upcast_trait_ref,
621 vtable_base: o.vtable_base,
622 nested: o.nested.into_iter().map(f).collect(),
624 ImplSource::AutoImpl(d) => ImplSource::AutoImpl(ImplSourceAutoImplData {
625 trait_def_id: d.trait_def_id,
626 nested: d.nested.into_iter().map(f).collect(),
628 ImplSource::Closure(c) => ImplSource::Closure(ImplSourceClosureData {
629 closure_def_id: c.closure_def_id,
631 nested: c.nested.into_iter().map(f).collect(),
633 ImplSource::Generator(c) => ImplSource::Generator(ImplSourceGeneratorData {
634 generator_def_id: c.generator_def_id,
636 nested: c.nested.into_iter().map(f).collect(),
638 ImplSource::FnPointer(p) => ImplSource::FnPointer(ImplSourceFnPointerData {
640 nested: p.nested.into_iter().map(f).collect(),
642 ImplSource::DiscriminantKind(ImplSourceDiscriminantKindData) => {
643 ImplSource::DiscriminantKind(ImplSourceDiscriminantKindData)
645 ImplSource::Pointee(ImplSourcePointeeData) => {
646 ImplSource::Pointee(ImplSourcePointeeData)
648 ImplSource::TraitAlias(d) => ImplSource::TraitAlias(ImplSourceTraitAliasData {
649 alias_def_id: d.alias_def_id,
651 nested: d.nested.into_iter().map(f).collect(),
653 ImplSource::TraitUpcasting(d) => {
654 ImplSource::TraitUpcasting(ImplSourceTraitUpcastingData {
655 upcast_trait_ref: d.upcast_trait_ref,
656 vtable_vptr_slot: d.vtable_vptr_slot,
657 nested: d.nested.into_iter().map(f).collect(),
660 ImplSource::ConstDrop(ImplSourceConstDropData) => {
661 ImplSource::ConstDrop(ImplSourceConstDropData)
667 /// Identifies a particular impl in the source, along with a set of
668 /// substitutions from the impl's type/lifetime parameters. The
669 /// `nested` vector corresponds to the nested obligations attached to
670 /// the impl's type parameters.
672 /// The type parameter `N` indicates the type used for "nested
673 /// obligations" that are required by the impl. During type-check, this
674 /// is `Obligation`, as one might expect. During codegen, however, this
675 /// is `()`, because codegen only requires a shallow resolution of an
676 /// impl, and nested obligations are satisfied later.
677 #[derive(Clone, PartialEq, Eq, TyEncodable, TyDecodable, HashStable, TypeFoldable, Lift)]
678 pub struct ImplSourceUserDefinedData<'tcx, N> {
679 pub impl_def_id: DefId,
680 pub substs: SubstsRef<'tcx>,
684 #[derive(Clone, PartialEq, Eq, TyEncodable, TyDecodable, HashStable, TypeFoldable, Lift)]
685 pub struct ImplSourceGeneratorData<'tcx, N> {
686 pub generator_def_id: DefId,
687 pub substs: SubstsRef<'tcx>,
688 /// Nested obligations. This can be non-empty if the generator
689 /// signature contains associated types.
693 #[derive(Clone, PartialEq, Eq, TyEncodable, TyDecodable, HashStable, TypeFoldable, Lift)]
694 pub struct ImplSourceClosureData<'tcx, N> {
695 pub closure_def_id: DefId,
696 pub substs: SubstsRef<'tcx>,
697 /// Nested obligations. This can be non-empty if the closure
698 /// signature contains associated types.
702 #[derive(Clone, PartialEq, Eq, TyEncodable, TyDecodable, HashStable, TypeFoldable, Lift)]
703 pub struct ImplSourceAutoImplData<N> {
704 pub trait_def_id: DefId,
708 #[derive(Clone, PartialEq, Eq, TyEncodable, TyDecodable, HashStable, TypeFoldable, Lift)]
709 pub struct ImplSourceTraitUpcastingData<'tcx, N> {
710 /// `Foo` upcast to the obligation trait. This will be some supertrait of `Foo`.
711 pub upcast_trait_ref: ty::PolyTraitRef<'tcx>,
713 /// The vtable is formed by concatenating together the method lists of
714 /// the base object trait and all supertraits, pointers to supertrait vtable will
715 /// be provided when necessary; this is the position of `upcast_trait_ref`'s vtable
716 /// within that vtable.
717 pub vtable_vptr_slot: Option<usize>,
722 #[derive(Clone, PartialEq, Eq, TyEncodable, TyDecodable, HashStable, TypeFoldable, Lift)]
723 pub struct ImplSourceBuiltinData<N> {
727 #[derive(PartialEq, Eq, Clone, TyEncodable, TyDecodable, HashStable, TypeFoldable, Lift)]
728 pub struct ImplSourceObjectData<'tcx, N> {
729 /// `Foo` upcast to the obligation trait. This will be some supertrait of `Foo`.
730 pub upcast_trait_ref: ty::PolyTraitRef<'tcx>,
732 /// The vtable is formed by concatenating together the method lists of
733 /// the base object trait and all supertraits, pointers to supertrait vtable will
734 /// be provided when necessary; this is the start of `upcast_trait_ref`'s methods
736 pub vtable_base: usize,
741 #[derive(Clone, PartialEq, Eq, TyEncodable, TyDecodable, HashStable, TypeFoldable, Lift)]
742 pub struct ImplSourceFnPointerData<'tcx, N> {
747 // FIXME(@lcnr): This should be refactored and merged with other builtin vtables.
748 #[derive(Clone, Debug, PartialEq, Eq, TyEncodable, TyDecodable, HashStable)]
749 pub struct ImplSourceDiscriminantKindData;
751 #[derive(Clone, Debug, PartialEq, Eq, TyEncodable, TyDecodable, HashStable)]
752 pub struct ImplSourcePointeeData;
754 #[derive(Clone, Debug, PartialEq, Eq, TyEncodable, TyDecodable, HashStable)]
755 pub struct ImplSourceConstDropData;
757 #[derive(Clone, PartialEq, Eq, TyEncodable, TyDecodable, HashStable, TypeFoldable, Lift)]
758 pub struct ImplSourceTraitAliasData<'tcx, N> {
759 pub alias_def_id: DefId,
760 pub substs: SubstsRef<'tcx>,
764 #[derive(Clone, Debug, PartialEq, Eq, Hash, HashStable, PartialOrd, Ord)]
765 pub enum ObjectSafetyViolation {
766 /// `Self: Sized` declared on the trait.
767 SizedSelf(SmallVec<[Span; 1]>),
769 /// Supertrait reference references `Self` an in illegal location
770 /// (e.g., `trait Foo : Bar<Self>`).
771 SupertraitSelf(SmallVec<[Span; 1]>),
773 /// Method has something illegal.
774 Method(Symbol, MethodViolationCode, Span),
776 /// Associated const.
777 AssocConst(Symbol, Span),
783 impl ObjectSafetyViolation {
784 pub fn error_msg(&self) -> Cow<'static, str> {
786 ObjectSafetyViolation::SizedSelf(_) => "it requires `Self: Sized`".into(),
787 ObjectSafetyViolation::SupertraitSelf(ref spans) => {
788 if spans.iter().any(|sp| *sp != DUMMY_SP) {
789 "it uses `Self` as a type parameter".into()
791 "it cannot use `Self` as a type parameter in a supertrait or `where`-clause"
795 ObjectSafetyViolation::Method(name, MethodViolationCode::StaticMethod(_, _, _), _) => {
796 format!("associated function `{}` has no `self` parameter", name).into()
798 ObjectSafetyViolation::Method(
800 MethodViolationCode::ReferencesSelfInput(_),
802 ) => format!("method `{}` references the `Self` type in its parameters", name).into(),
803 ObjectSafetyViolation::Method(name, MethodViolationCode::ReferencesSelfInput(_), _) => {
804 format!("method `{}` references the `Self` type in this parameter", name).into()
806 ObjectSafetyViolation::Method(name, MethodViolationCode::ReferencesSelfOutput, _) => {
807 format!("method `{}` references the `Self` type in its return type", name).into()
809 ObjectSafetyViolation::Method(
811 MethodViolationCode::WhereClauseReferencesSelf,
814 format!("method `{}` references the `Self` type in its `where` clause", name).into()
816 ObjectSafetyViolation::Method(name, MethodViolationCode::Generic, _) => {
817 format!("method `{}` has generic type parameters", name).into()
819 ObjectSafetyViolation::Method(name, MethodViolationCode::UndispatchableReceiver, _) => {
820 format!("method `{}`'s `self` parameter cannot be dispatched on", name).into()
822 ObjectSafetyViolation::AssocConst(name, DUMMY_SP) => {
823 format!("it contains associated `const` `{}`", name).into()
825 ObjectSafetyViolation::AssocConst(..) => "it contains this associated `const`".into(),
826 ObjectSafetyViolation::GAT(name, _) => {
827 format!("it contains the generic associated type `{}`", name).into()
832 pub fn solution(&self, err: &mut DiagnosticBuilder<'_>) {
834 ObjectSafetyViolation::SizedSelf(_) | ObjectSafetyViolation::SupertraitSelf(_) => {}
835 ObjectSafetyViolation::Method(
837 MethodViolationCode::StaticMethod(sugg, self_span, has_args),
843 "consider turning `{}` into a method by giving it a `&self` argument",
846 format!("&self{}", if has_args { ", " } else { "" }),
847 Applicability::MaybeIncorrect,
850 Some((sugg, span)) => {
854 "alternatively, consider constraining `{}` so it does not apply to \
859 Applicability::MaybeIncorrect,
864 "consider turning `{}` into a method by giving it a `&self` \
865 argument or constraining it so it does not apply to trait objects",
871 ObjectSafetyViolation::Method(
873 MethodViolationCode::UndispatchableReceiver,
879 "consider changing method `{}`'s `self` parameter to be `&self`",
883 Applicability::MachineApplicable,
886 ObjectSafetyViolation::AssocConst(name, _)
887 | ObjectSafetyViolation::GAT(name, _)
888 | ObjectSafetyViolation::Method(name, ..) => {
889 err.help(&format!("consider moving `{}` to another trait", name));
894 pub fn spans(&self) -> SmallVec<[Span; 1]> {
895 // When `span` comes from a separate crate, it'll be `DUMMY_SP`. Treat it as `None` so
896 // diagnostics use a `note` instead of a `span_label`.
898 ObjectSafetyViolation::SupertraitSelf(spans)
899 | ObjectSafetyViolation::SizedSelf(spans) => spans.clone(),
900 ObjectSafetyViolation::AssocConst(_, span)
901 | ObjectSafetyViolation::GAT(_, span)
902 | ObjectSafetyViolation::Method(_, _, span)
903 if *span != DUMMY_SP =>
912 /// Reasons a method might not be object-safe.
913 #[derive(Copy, Clone, Debug, PartialEq, Eq, Hash, HashStable, PartialOrd, Ord)]
914 pub enum MethodViolationCode {
916 StaticMethod(Option<(&'static str, Span)>, Span, bool /* has args */),
918 /// e.g., `fn foo(&self, x: Self)`
919 ReferencesSelfInput(usize),
921 /// e.g., `fn foo(&self) -> Self`
922 ReferencesSelfOutput,
924 /// e.g., `fn foo(&self) where Self: Clone`
925 WhereClauseReferencesSelf,
927 /// e.g., `fn foo<A>()`
930 /// the method's receiver (`self` argument) can't be dispatched on
931 UndispatchableReceiver,