| //! Trait Resolution. See the [rustc guide] for more information on how this works. |
| //! |
| //! [rustc guide]: https://rust-lang.github.io/rustc-guide/traits/resolution.html |
| |
| pub mod query; |
| pub mod select; |
| pub mod specialization_graph; |
| mod structural_impls; |
| |
| use crate::mir::interpret::ErrorHandled; |
| use crate::ty::subst::SubstsRef; |
| use crate::ty::{self, AdtKind, List, Ty, TyCtxt}; |
| |
| use rustc_ast::ast; |
| use rustc_hir as hir; |
| use rustc_hir::def_id::DefId; |
| use rustc_span::{Span, DUMMY_SP}; |
| use smallvec::SmallVec; |
| |
| use std::borrow::Cow; |
| use std::fmt::Debug; |
| use std::rc::Rc; |
| |
| pub use self::select::{EvaluationCache, EvaluationResult, OverflowError, SelectionCache}; |
| |
| pub use self::ObligationCauseCode::*; |
| pub use self::SelectionError::*; |
| pub use self::Vtable::*; |
| |
| /// Depending on the stage of compilation, we want projection to be |
| /// more or less conservative. |
| #[derive(Debug, Copy, Clone, PartialEq, Eq, Hash, HashStable)] |
| pub enum Reveal { |
| /// At type-checking time, we refuse to project any associated |
| /// type that is marked `default`. Non-`default` ("final") types |
| /// are always projected. This is necessary in general for |
| /// soundness of specialization. However, we *could* allow |
| /// projections in fully-monomorphic cases. We choose not to, |
| /// because we prefer for `default type` to force the type |
| /// definition to be treated abstractly by any consumers of the |
| /// impl. Concretely, that means that the following example will |
| /// fail to compile: |
| /// |
| /// ``` |
| /// trait Assoc { |
| /// type Output; |
| /// } |
| /// |
| /// impl<T> Assoc for T { |
| /// default type Output = bool; |
| /// } |
| /// |
| /// fn main() { |
| /// let <() as Assoc>::Output = true; |
| /// } |
| /// ``` |
| UserFacing, |
| |
| /// At codegen time, all monomorphic projections will succeed. |
| /// Also, `impl Trait` is normalized to the concrete type, |
| /// which has to be already collected by type-checking. |
| /// |
| /// NOTE: as `impl Trait`'s concrete type should *never* |
| /// be observable directly by the user, `Reveal::All` |
| /// should not be used by checks which may expose |
| /// type equality or type contents to the user. |
| /// There are some exceptions, e.g., around OIBITS and |
| /// transmute-checking, which expose some details, but |
| /// not the whole concrete type of the `impl Trait`. |
| All, |
| } |
| |
| /// The reason why we incurred this obligation; used for error reporting. |
| #[derive(Clone, Debug, PartialEq, Eq, Hash)] |
| pub struct ObligationCause<'tcx> { |
| pub span: Span, |
| |
| /// The ID of the fn body that triggered this obligation. This is |
| /// used for region obligations to determine the precise |
| /// environment in which the region obligation should be evaluated |
| /// (in particular, closures can add new assumptions). See the |
| /// field `region_obligations` of the `FulfillmentContext` for more |
| /// information. |
| pub body_id: hir::HirId, |
| |
| pub code: ObligationCauseCode<'tcx>, |
| } |
| |
| impl<'tcx> ObligationCause<'tcx> { |
| #[inline] |
| pub fn new( |
| span: Span, |
| body_id: hir::HirId, |
| code: ObligationCauseCode<'tcx>, |
| ) -> ObligationCause<'tcx> { |
| ObligationCause { span, body_id, code } |
| } |
| |
| pub fn misc(span: Span, body_id: hir::HirId) -> ObligationCause<'tcx> { |
| ObligationCause { span, body_id, code: MiscObligation } |
| } |
| |
| pub fn dummy() -> ObligationCause<'tcx> { |
| ObligationCause { span: DUMMY_SP, body_id: hir::CRATE_HIR_ID, code: MiscObligation } |
| } |
| |
| pub fn span(&self, tcx: TyCtxt<'tcx>) -> Span { |
| match self.code { |
| ObligationCauseCode::CompareImplMethodObligation { .. } |
| | ObligationCauseCode::MainFunctionType |
| | ObligationCauseCode::StartFunctionType => tcx.sess.source_map().def_span(self.span), |
| ObligationCauseCode::MatchExpressionArm(box MatchExpressionArmCause { |
| arm_span, |
| .. |
| }) => arm_span, |
| _ => self.span, |
| } |
| } |
| } |
| |
| #[derive(Clone, Debug, PartialEq, Eq, Hash)] |
| pub enum ObligationCauseCode<'tcx> { |
| /// Not well classified or should be obvious from the span. |
| MiscObligation, |
| |
| /// A slice or array is WF only if `T: Sized`. |
| SliceOrArrayElem, |
| |
| /// A tuple is WF only if its middle elements are `Sized`. |
| TupleElem, |
| |
| /// This is the trait reference from the given projection. |
| ProjectionWf(ty::ProjectionTy<'tcx>), |
| |
| /// In an impl of trait `X` for type `Y`, type `Y` must |
| /// also implement all supertraits of `X`. |
| ItemObligation(DefId), |
| |
| /// Like `ItemObligation`, but with extra detail on the source of the obligation. |
| BindingObligation(DefId, Span), |
| |
| /// A type like `&'a T` is WF only if `T: 'a`. |
| ReferenceOutlivesReferent(Ty<'tcx>), |
| |
| /// A type like `Box<Foo<'a> + 'b>` is WF only if `'b: 'a`. |
| ObjectTypeBound(Ty<'tcx>, ty::Region<'tcx>), |
| |
| /// Obligation incurred due to an object cast. |
| ObjectCastObligation(/* Object type */ Ty<'tcx>), |
| |
| /// Obligation incurred due to a coercion. |
| Coercion { |
| source: Ty<'tcx>, |
| target: Ty<'tcx>, |
| }, |
| |
| /// Various cases where expressions must be `Sized` / `Copy` / etc. |
| /// `L = X` implies that `L` is `Sized`. |
| AssignmentLhsSized, |
| /// `(x1, .., xn)` must be `Sized`. |
| TupleInitializerSized, |
| /// `S { ... }` must be `Sized`. |
| StructInitializerSized, |
| /// Type of each variable must be `Sized`. |
| VariableType(hir::HirId), |
| /// Argument type must be `Sized`. |
| SizedArgumentType, |
| /// Return type must be `Sized`. |
| SizedReturnType, |
| /// Yield type must be `Sized`. |
| SizedYieldType, |
| /// `[T, ..n]` implies that `T` must be `Copy`. |
| /// If `true`, suggest `const_in_array_repeat_expressions` feature flag. |
| RepeatVec(bool), |
| |
| /// Types of fields (other than the last, except for packed structs) in a struct must be sized. |
| FieldSized { |
| adt_kind: AdtKind, |
| last: bool, |
| }, |
| |
| /// Constant expressions must be sized. |
| ConstSized, |
| |
| /// `static` items must have `Sync` type. |
| SharedStatic, |
| |
| BuiltinDerivedObligation(DerivedObligationCause<'tcx>), |
| |
| ImplDerivedObligation(DerivedObligationCause<'tcx>), |
| |
| /// Error derived when matching traits/impls; see ObligationCause for more details |
| CompareImplMethodObligation { |
| item_name: ast::Name, |
| impl_item_def_id: DefId, |
| trait_item_def_id: DefId, |
| }, |
| |
| /// Error derived when matching traits/impls; see ObligationCause for more details |
| CompareImplTypeObligation { |
| item_name: ast::Name, |
| impl_item_def_id: DefId, |
| trait_item_def_id: DefId, |
| }, |
| |
| /// Checking that this expression can be assigned where it needs to be |
| // FIXME(eddyb) #11161 is the original Expr required? |
| ExprAssignable, |
| |
| /// Computing common supertype in the arms of a match expression |
| MatchExpressionArm(Box<MatchExpressionArmCause<'tcx>>), |
| |
| /// Type error arising from type checking a pattern against an expected type. |
| Pattern { |
| /// The span of the scrutinee or type expression which caused the `root_ty` type. |
| span: Option<Span>, |
| /// The root expected type induced by a scrutinee or type expression. |
| root_ty: Ty<'tcx>, |
| /// Whether the `Span` came from an expression or a type expression. |
| origin_expr: bool, |
| }, |
| |
| /// Constants in patterns must have `Structural` type. |
| ConstPatternStructural, |
| |
| /// Computing common supertype in an if expression |
| IfExpression(Box<IfExpressionCause>), |
| |
| /// Computing common supertype of an if expression with no else counter-part |
| IfExpressionWithNoElse, |
| |
| /// `main` has wrong type |
| MainFunctionType, |
| |
| /// `start` has wrong type |
| StartFunctionType, |
| |
| /// Intrinsic has wrong type |
| IntrinsicType, |
| |
| /// Method receiver |
| MethodReceiver, |
| |
| /// `return` with no expression |
| ReturnNoExpression, |
| |
| /// `return` with an expression |
| ReturnValue(hir::HirId), |
| |
| /// Return type of this function |
| ReturnType, |
| |
| /// Block implicit return |
| BlockTailExpression(hir::HirId), |
| |
| /// #[feature(trivial_bounds)] is not enabled |
| TrivialBound, |
| |
| AssocTypeBound(Box<AssocTypeBoundData>), |
| } |
| |
| impl ObligationCauseCode<'_> { |
| // Return the base obligation, ignoring derived obligations. |
| pub fn peel_derives(&self) -> &Self { |
| let mut base_cause = self; |
| while let BuiltinDerivedObligation(cause) | ImplDerivedObligation(cause) = base_cause { |
| base_cause = &cause.parent_code; |
| } |
| base_cause |
| } |
| } |
| |
| #[derive(Clone, Debug, PartialEq, Eq, Hash)] |
| pub struct AssocTypeBoundData { |
| pub impl_span: Option<Span>, |
| pub original: Span, |
| pub bounds: Vec<Span>, |
| } |
| |
| // `ObligationCauseCode` is used a lot. Make sure it doesn't unintentionally get bigger. |
| #[cfg(target_arch = "x86_64")] |
| static_assert_size!(ObligationCauseCode<'_>, 32); |
| |
| #[derive(Clone, Debug, PartialEq, Eq, Hash)] |
| pub struct MatchExpressionArmCause<'tcx> { |
| pub arm_span: Span, |
| pub source: hir::MatchSource, |
| pub prior_arms: Vec<Span>, |
| pub last_ty: Ty<'tcx>, |
| pub scrut_hir_id: hir::HirId, |
| } |
| |
| #[derive(Clone, Debug, PartialEq, Eq, Hash)] |
| pub struct IfExpressionCause { |
| pub then: Span, |
| pub outer: Option<Span>, |
| pub semicolon: Option<Span>, |
| } |
| |
| #[derive(Clone, Debug, PartialEq, Eq, Hash)] |
| pub struct DerivedObligationCause<'tcx> { |
| /// The trait reference of the parent obligation that led to the |
| /// current obligation. Note that only trait obligations lead to |
| /// derived obligations, so we just store the trait reference here |
| /// directly. |
| pub parent_trait_ref: ty::PolyTraitRef<'tcx>, |
| |
| /// The parent trait had this cause. |
| pub parent_code: Rc<ObligationCauseCode<'tcx>>, |
| } |
| |
| /// The following types: |
| /// * `WhereClause`, |
| /// * `WellFormed`, |
| /// * `FromEnv`, |
| /// * `DomainGoal`, |
| /// * `Goal`, |
| /// * `Clause`, |
| /// * `Environment`, |
| /// * `InEnvironment`, |
| /// are used for representing the trait system in the form of |
| /// logic programming clauses. They are part of the interface |
| /// for the chalk SLG solver. |
| #[derive(Clone, Copy, PartialEq, Eq, Hash, Debug, HashStable, TypeFoldable, Lift)] |
| pub enum WhereClause<'tcx> { |
| Implemented(ty::TraitPredicate<'tcx>), |
| ProjectionEq(ty::ProjectionPredicate<'tcx>), |
| RegionOutlives(ty::RegionOutlivesPredicate<'tcx>), |
| TypeOutlives(ty::TypeOutlivesPredicate<'tcx>), |
| } |
| |
| #[derive(Clone, Copy, PartialEq, Eq, Hash, Debug, HashStable, TypeFoldable, Lift)] |
| pub enum WellFormed<'tcx> { |
| Trait(ty::TraitPredicate<'tcx>), |
| Ty(Ty<'tcx>), |
| } |
| |
| #[derive(Clone, Copy, PartialEq, Eq, Hash, Debug, HashStable, TypeFoldable, Lift)] |
| pub enum FromEnv<'tcx> { |
| Trait(ty::TraitPredicate<'tcx>), |
| Ty(Ty<'tcx>), |
| } |
| |
| #[derive(Clone, Copy, PartialEq, Eq, Hash, Debug, HashStable, TypeFoldable, Lift)] |
| pub enum DomainGoal<'tcx> { |
| Holds(WhereClause<'tcx>), |
| WellFormed(WellFormed<'tcx>), |
| FromEnv(FromEnv<'tcx>), |
| Normalize(ty::ProjectionPredicate<'tcx>), |
| } |
| |
| pub type PolyDomainGoal<'tcx> = ty::Binder<DomainGoal<'tcx>>; |
| |
| #[derive(Copy, Clone, PartialEq, Eq, Hash, Debug, HashStable)] |
| pub enum QuantifierKind { |
| Universal, |
| Existential, |
| } |
| |
| #[derive(Copy, Clone, PartialEq, Eq, Hash, Debug, HashStable, TypeFoldable, Lift)] |
| pub enum GoalKind<'tcx> { |
| Implies(Clauses<'tcx>, Goal<'tcx>), |
| And(Goal<'tcx>, Goal<'tcx>), |
| Not(Goal<'tcx>), |
| DomainGoal(DomainGoal<'tcx>), |
| Quantified(QuantifierKind, ty::Binder<Goal<'tcx>>), |
| Subtype(Ty<'tcx>, Ty<'tcx>), |
| CannotProve, |
| } |
| |
| pub type Goal<'tcx> = &'tcx GoalKind<'tcx>; |
| |
| pub type Goals<'tcx> = &'tcx List<Goal<'tcx>>; |
| |
| impl<'tcx> DomainGoal<'tcx> { |
| pub fn into_goal(self) -> GoalKind<'tcx> { |
| GoalKind::DomainGoal(self) |
| } |
| |
| pub fn into_program_clause(self) -> ProgramClause<'tcx> { |
| ProgramClause { |
| goal: self, |
| hypotheses: ty::List::empty(), |
| category: ProgramClauseCategory::Other, |
| } |
| } |
| } |
| |
| impl<'tcx> GoalKind<'tcx> { |
| pub fn from_poly_domain_goal( |
| domain_goal: PolyDomainGoal<'tcx>, |
| tcx: TyCtxt<'tcx>, |
| ) -> GoalKind<'tcx> { |
| match domain_goal.no_bound_vars() { |
| Some(p) => p.into_goal(), |
| None => GoalKind::Quantified( |
| QuantifierKind::Universal, |
| domain_goal.map_bound(|p| tcx.mk_goal(p.into_goal())), |
| ), |
| } |
| } |
| } |
| |
| /// This matches the definition from Page 7 of "A Proof Procedure for the Logic of Hereditary |
| /// Harrop Formulas". |
| #[derive(Copy, Clone, PartialEq, Eq, Hash, Debug, HashStable, TypeFoldable)] |
| pub enum Clause<'tcx> { |
| Implies(ProgramClause<'tcx>), |
| ForAll(ty::Binder<ProgramClause<'tcx>>), |
| } |
| |
| impl Clause<'tcx> { |
| pub fn category(self) -> ProgramClauseCategory { |
| match self { |
| Clause::Implies(clause) => clause.category, |
| Clause::ForAll(clause) => clause.skip_binder().category, |
| } |
| } |
| } |
| |
| /// Multiple clauses. |
| pub type Clauses<'tcx> = &'tcx List<Clause<'tcx>>; |
| |
| /// A "program clause" has the form `D :- G1, ..., Gn`. It is saying |
| /// that the domain goal `D` is true if `G1...Gn` are provable. This |
| /// is equivalent to the implication `G1..Gn => D`; we usually write |
| /// it with the reverse implication operator `:-` to emphasize the way |
| /// that programs are actually solved (via backchaining, which starts |
| /// with the goal to solve and proceeds from there). |
| #[derive(Copy, Clone, PartialEq, Eq, Hash, Debug, HashStable, TypeFoldable)] |
| pub struct ProgramClause<'tcx> { |
| /// This goal will be considered true ... |
| pub goal: DomainGoal<'tcx>, |
| |
| /// ... if we can prove these hypotheses (there may be no hypotheses at all): |
| pub hypotheses: Goals<'tcx>, |
| |
| /// Useful for filtering clauses. |
| pub category: ProgramClauseCategory, |
| } |
| |
| #[derive(Copy, Clone, PartialEq, Eq, Hash, Debug, HashStable)] |
| pub enum ProgramClauseCategory { |
| ImpliedBound, |
| WellFormed, |
| Other, |
| } |
| |
| /// A set of clauses that we assume to be true. |
| #[derive(Copy, Clone, PartialEq, Eq, Hash, Debug, HashStable, TypeFoldable)] |
| pub struct Environment<'tcx> { |
| pub clauses: Clauses<'tcx>, |
| } |
| |
| impl Environment<'tcx> { |
| pub fn with<G>(self, goal: G) -> InEnvironment<'tcx, G> { |
| InEnvironment { environment: self, goal } |
| } |
| } |
| |
| /// Something (usually a goal), along with an environment. |
| #[derive(Copy, Clone, PartialEq, Eq, Hash, Debug, HashStable, TypeFoldable)] |
| pub struct InEnvironment<'tcx, G> { |
| pub environment: Environment<'tcx>, |
| pub goal: G, |
| } |
| |
| #[derive(Clone, Debug, TypeFoldable)] |
| pub enum SelectionError<'tcx> { |
| Unimplemented, |
| OutputTypeParameterMismatch( |
| ty::PolyTraitRef<'tcx>, |
| ty::PolyTraitRef<'tcx>, |
| ty::error::TypeError<'tcx>, |
| ), |
| TraitNotObjectSafe(DefId), |
| ConstEvalFailure(ErrorHandled), |
| Overflow, |
| } |
| |
| /// When performing resolution, it is typically the case that there |
| /// can be one of three outcomes: |
| /// |
| /// - `Ok(Some(r))`: success occurred with result `r` |
| /// - `Ok(None)`: could not definitely determine anything, usually due |
| /// to inconclusive type inference. |
| /// - `Err(e)`: error `e` occurred |
| pub type SelectionResult<'tcx, T> = Result<Option<T>, SelectionError<'tcx>>; |
| |
| /// Given the successful resolution of an obligation, the `Vtable` |
| /// indicates where the vtable comes from. Note that while we call this |
| /// a "vtable", it does not necessarily indicate dynamic dispatch at |
| /// runtime. `Vtable` instances just tell the compiler where to find |
| /// methods, but in generic code those methods are typically statically |
| /// dispatched -- only when an object is constructed is a `Vtable` |
| /// instance reified into an actual vtable. |
| /// |
| /// For example, the vtable may be tied to a specific impl (case A), |
| /// or it may be relative to some bound that is in scope (case B). |
| /// |
| /// ``` |
| /// impl<T:Clone> Clone<T> for Option<T> { ... } // Impl_1 |
| /// impl<T:Clone> Clone<T> for Box<T> { ... } // Impl_2 |
| /// impl Clone for int { ... } // Impl_3 |
| /// |
| /// fn foo<T:Clone>(concrete: Option<Box<int>>, |
| /// param: T, |
| /// mixed: Option<T>) { |
| /// |
| /// // Case A: Vtable points at a specific impl. Only possible when |
| /// // type is concretely known. If the impl itself has bounded |
| /// // type parameters, Vtable will carry resolutions for those as well: |
| /// concrete.clone(); // Vtable(Impl_1, [Vtable(Impl_2, [Vtable(Impl_3)])]) |
| /// |
| /// // Case B: Vtable must be provided by caller. This applies when |
| /// // type is a type parameter. |
| /// param.clone(); // VtableParam |
| /// |
| /// // Case C: A mix of cases A and B. |
| /// mixed.clone(); // Vtable(Impl_1, [VtableParam]) |
| /// } |
| /// ``` |
| /// |
| /// ### The type parameter `N` |
| /// |
| /// See explanation on `VtableImplData`. |
| #[derive(Clone, PartialEq, Eq, RustcEncodable, RustcDecodable, HashStable, TypeFoldable)] |
| pub enum Vtable<'tcx, N> { |
| /// Vtable identifying a particular impl. |
| VtableImpl(VtableImplData<'tcx, N>), |
| |
| /// Vtable for auto trait implementations. |
| /// This carries the information and nested obligations with regards |
| /// to an auto implementation for a trait `Trait`. The nested obligations |
| /// ensure the trait implementation holds for all the constituent types. |
| VtableAutoImpl(VtableAutoImplData<N>), |
| |
| /// Successful resolution to an obligation provided by the caller |
| /// for some type parameter. The `Vec<N>` represents the |
| /// obligations incurred from normalizing the where-clause (if |
| /// any). |
| VtableParam(Vec<N>), |
| |
| /// Virtual calls through an object. |
| VtableObject(VtableObjectData<'tcx, N>), |
| |
| /// Successful resolution for a builtin trait. |
| VtableBuiltin(VtableBuiltinData<N>), |
| |
| /// Vtable automatically generated for a closure. The `DefId` is the ID |
| /// of the closure expression. This is a `VtableImpl` in spirit, but the |
| /// impl is generated by the compiler and does not appear in the source. |
| VtableClosure(VtableClosureData<'tcx, N>), |
| |
| /// Same as above, but for a function pointer type with the given signature. |
| VtableFnPointer(VtableFnPointerData<'tcx, N>), |
| |
| /// Vtable automatically generated for a generator. |
| VtableGenerator(VtableGeneratorData<'tcx, N>), |
| |
| /// Vtable for a trait alias. |
| VtableTraitAlias(VtableTraitAliasData<'tcx, N>), |
| } |
| |
| impl<'tcx, N> Vtable<'tcx, N> { |
| pub fn nested_obligations(self) -> Vec<N> { |
| match self { |
| VtableImpl(i) => i.nested, |
| VtableParam(n) => n, |
| VtableBuiltin(i) => i.nested, |
| VtableAutoImpl(d) => d.nested, |
| VtableClosure(c) => c.nested, |
| VtableGenerator(c) => c.nested, |
| VtableObject(d) => d.nested, |
| VtableFnPointer(d) => d.nested, |
| VtableTraitAlias(d) => d.nested, |
| } |
| } |
| |
| pub fn borrow_nested_obligations(&self) -> &[N] { |
| match &self { |
| VtableImpl(i) => &i.nested[..], |
| VtableParam(n) => &n[..], |
| VtableBuiltin(i) => &i.nested[..], |
| VtableAutoImpl(d) => &d.nested[..], |
| VtableClosure(c) => &c.nested[..], |
| VtableGenerator(c) => &c.nested[..], |
| VtableObject(d) => &d.nested[..], |
| VtableFnPointer(d) => &d.nested[..], |
| VtableTraitAlias(d) => &d.nested[..], |
| } |
| } |
| |
| pub fn map<M, F>(self, f: F) -> Vtable<'tcx, M> |
| where |
| F: FnMut(N) -> M, |
| { |
| match self { |
| VtableImpl(i) => VtableImpl(VtableImplData { |
| impl_def_id: i.impl_def_id, |
| substs: i.substs, |
| nested: i.nested.into_iter().map(f).collect(), |
| }), |
| VtableParam(n) => VtableParam(n.into_iter().map(f).collect()), |
| VtableBuiltin(i) => { |
| VtableBuiltin(VtableBuiltinData { nested: i.nested.into_iter().map(f).collect() }) |
| } |
| VtableObject(o) => VtableObject(VtableObjectData { |
| upcast_trait_ref: o.upcast_trait_ref, |
| vtable_base: o.vtable_base, |
| nested: o.nested.into_iter().map(f).collect(), |
| }), |
| VtableAutoImpl(d) => VtableAutoImpl(VtableAutoImplData { |
| trait_def_id: d.trait_def_id, |
| nested: d.nested.into_iter().map(f).collect(), |
| }), |
| VtableClosure(c) => VtableClosure(VtableClosureData { |
| closure_def_id: c.closure_def_id, |
| substs: c.substs, |
| nested: c.nested.into_iter().map(f).collect(), |
| }), |
| VtableGenerator(c) => VtableGenerator(VtableGeneratorData { |
| generator_def_id: c.generator_def_id, |
| substs: c.substs, |
| nested: c.nested.into_iter().map(f).collect(), |
| }), |
| VtableFnPointer(p) => VtableFnPointer(VtableFnPointerData { |
| fn_ty: p.fn_ty, |
| nested: p.nested.into_iter().map(f).collect(), |
| }), |
| VtableTraitAlias(d) => VtableTraitAlias(VtableTraitAliasData { |
| alias_def_id: d.alias_def_id, |
| substs: d.substs, |
| nested: d.nested.into_iter().map(f).collect(), |
| }), |
| } |
| } |
| } |
| |
| /// Identifies a particular impl in the source, along with a set of |
| /// substitutions from the impl's type/lifetime parameters. The |
| /// `nested` vector corresponds to the nested obligations attached to |
| /// the impl's type parameters. |
| /// |
| /// The type parameter `N` indicates the type used for "nested |
| /// obligations" that are required by the impl. During type-check, this |
| /// is `Obligation`, as one might expect. During codegen, however, this |
| /// is `()`, because codegen only requires a shallow resolution of an |
| /// impl, and nested obligations are satisfied later. |
| #[derive(Clone, PartialEq, Eq, RustcEncodable, RustcDecodable, HashStable, TypeFoldable)] |
| pub struct VtableImplData<'tcx, N> { |
| pub impl_def_id: DefId, |
| pub substs: SubstsRef<'tcx>, |
| pub nested: Vec<N>, |
| } |
| |
| #[derive(Clone, PartialEq, Eq, RustcEncodable, RustcDecodable, HashStable, TypeFoldable)] |
| pub struct VtableGeneratorData<'tcx, N> { |
| pub generator_def_id: DefId, |
| pub substs: SubstsRef<'tcx>, |
| /// Nested obligations. This can be non-empty if the generator |
| /// signature contains associated types. |
| pub nested: Vec<N>, |
| } |
| |
| #[derive(Clone, PartialEq, Eq, RustcEncodable, RustcDecodable, HashStable, TypeFoldable)] |
| pub struct VtableClosureData<'tcx, N> { |
| pub closure_def_id: DefId, |
| pub substs: SubstsRef<'tcx>, |
| /// Nested obligations. This can be non-empty if the closure |
| /// signature contains associated types. |
| pub nested: Vec<N>, |
| } |
| |
| #[derive(Clone, PartialEq, Eq, RustcEncodable, RustcDecodable, HashStable, TypeFoldable)] |
| pub struct VtableAutoImplData<N> { |
| pub trait_def_id: DefId, |
| pub nested: Vec<N>, |
| } |
| |
| #[derive(Clone, PartialEq, Eq, RustcEncodable, RustcDecodable, HashStable, TypeFoldable)] |
| pub struct VtableBuiltinData<N> { |
| pub nested: Vec<N>, |
| } |
| |
| /// A vtable for some object-safe trait `Foo` automatically derived |
| /// for the object type `Foo`. |
| #[derive(PartialEq, Eq, Clone, RustcEncodable, RustcDecodable, HashStable, TypeFoldable)] |
| pub struct VtableObjectData<'tcx, N> { |
| /// `Foo` upcast to the obligation trait. This will be some supertrait of `Foo`. |
| pub upcast_trait_ref: ty::PolyTraitRef<'tcx>, |
| |
| /// The vtable is formed by concatenating together the method lists of |
| /// the base object trait and all supertraits; this is the start of |
| /// `upcast_trait_ref`'s methods in that vtable. |
| pub vtable_base: usize, |
| |
| pub nested: Vec<N>, |
| } |
| |
| #[derive(Clone, PartialEq, Eq, RustcEncodable, RustcDecodable, HashStable, TypeFoldable)] |
| pub struct VtableFnPointerData<'tcx, N> { |
| pub fn_ty: Ty<'tcx>, |
| pub nested: Vec<N>, |
| } |
| |
| #[derive(Clone, PartialEq, Eq, RustcEncodable, RustcDecodable, HashStable, TypeFoldable)] |
| pub struct VtableTraitAliasData<'tcx, N> { |
| pub alias_def_id: DefId, |
| pub substs: SubstsRef<'tcx>, |
| pub nested: Vec<N>, |
| } |
| |
| #[derive(Clone, Debug, PartialEq, Eq, Hash, HashStable)] |
| pub enum ObjectSafetyViolation { |
| /// `Self: Sized` declared on the trait. |
| SizedSelf(SmallVec<[Span; 1]>), |
| |
| /// Supertrait reference references `Self` an in illegal location |
| /// (e.g., `trait Foo : Bar<Self>`). |
| SupertraitSelf(SmallVec<[Span; 1]>), |
| |
| /// Method has something illegal. |
| Method(ast::Name, MethodViolationCode, Span), |
| |
| /// Associated const. |
| AssocConst(ast::Name, Span), |
| } |
| |
| impl ObjectSafetyViolation { |
| pub fn error_msg(&self) -> Cow<'static, str> { |
| match *self { |
| ObjectSafetyViolation::SizedSelf(_) => "it requires `Self: Sized`".into(), |
| ObjectSafetyViolation::SupertraitSelf(ref spans) => { |
| if spans.iter().any(|sp| *sp != DUMMY_SP) { |
| "it uses `Self` as a type parameter in this".into() |
| } else { |
| "it cannot use `Self` as a type parameter in a supertrait or `where`-clause" |
| .into() |
| } |
| } |
| ObjectSafetyViolation::Method(name, MethodViolationCode::StaticMethod(_), _) => { |
| format!("associated function `{}` has no `self` parameter", name).into() |
| } |
| ObjectSafetyViolation::Method( |
| name, |
| MethodViolationCode::ReferencesSelfInput(_), |
| DUMMY_SP, |
| ) => format!("method `{}` references the `Self` type in its parameters", name).into(), |
| ObjectSafetyViolation::Method(name, MethodViolationCode::ReferencesSelfInput(_), _) => { |
| format!("method `{}` references the `Self` type in this parameter", name).into() |
| } |
| ObjectSafetyViolation::Method(name, MethodViolationCode::ReferencesSelfOutput, _) => { |
| format!("method `{}` references the `Self` type in its return type", name).into() |
| } |
| ObjectSafetyViolation::Method( |
| name, |
| MethodViolationCode::WhereClauseReferencesSelf, |
| _, |
| ) => { |
| format!("method `{}` references the `Self` type in its `where` clause", name).into() |
| } |
| ObjectSafetyViolation::Method(name, MethodViolationCode::Generic, _) => { |
| format!("method `{}` has generic type parameters", name).into() |
| } |
| ObjectSafetyViolation::Method(name, MethodViolationCode::UndispatchableReceiver, _) => { |
| format!("method `{}`'s `self` parameter cannot be dispatched on", name).into() |
| } |
| ObjectSafetyViolation::AssocConst(name, DUMMY_SP) => { |
| format!("it contains associated `const` `{}`", name).into() |
| } |
| ObjectSafetyViolation::AssocConst(..) => "it contains this associated `const`".into(), |
| } |
| } |
| |
| pub fn solution(&self) -> Option<(String, Option<(String, Span)>)> { |
| Some(match *self { |
| ObjectSafetyViolation::SizedSelf(_) | ObjectSafetyViolation::SupertraitSelf(_) => { |
| return None; |
| } |
| ObjectSafetyViolation::Method(name, MethodViolationCode::StaticMethod(sugg), _) => ( |
| format!( |
| "consider turning `{}` into a method by giving it a `&self` argument or \ |
| constraining it so it does not apply to trait objects", |
| name |
| ), |
| sugg.map(|(sugg, sp)| (sugg.to_string(), sp)), |
| ), |
| ObjectSafetyViolation::Method( |
| name, |
| MethodViolationCode::UndispatchableReceiver, |
| span, |
| ) => ( |
| format!("consider changing method `{}`'s `self` parameter to be `&self`", name), |
| Some(("&Self".to_string(), span)), |
| ), |
| ObjectSafetyViolation::AssocConst(name, _) |
| | ObjectSafetyViolation::Method(name, ..) => { |
| (format!("consider moving `{}` to another trait", name), None) |
| } |
| }) |
| } |
| |
| pub fn spans(&self) -> SmallVec<[Span; 1]> { |
| // When `span` comes from a separate crate, it'll be `DUMMY_SP`. Treat it as `None` so |
| // diagnostics use a `note` instead of a `span_label`. |
| match self { |
| ObjectSafetyViolation::SupertraitSelf(spans) |
| | ObjectSafetyViolation::SizedSelf(spans) => spans.clone(), |
| ObjectSafetyViolation::AssocConst(_, span) |
| | ObjectSafetyViolation::Method(_, _, span) |
| if *span != DUMMY_SP => |
| { |
| smallvec![*span] |
| } |
| _ => smallvec![], |
| } |
| } |
| } |
| |
| /// Reasons a method might not be object-safe. |
| #[derive(Copy, Clone, Debug, PartialEq, Eq, Hash, HashStable)] |
| pub enum MethodViolationCode { |
| /// e.g., `fn foo()` |
| StaticMethod(Option<(&'static str, Span)>), |
| |
| /// e.g., `fn foo(&self, x: Self)` |
| ReferencesSelfInput(usize), |
| |
| /// e.g., `fn foo(&self) -> Self` |
| ReferencesSelfOutput, |
| |
| /// e.g., `fn foo(&self) where Self: Clone` |
| WhereClauseReferencesSelf, |
| |
| /// e.g., `fn foo<A>()` |
| Generic, |
| |
| /// the method's receiver (`self` argument) can't be dispatched on |
| UndispatchableReceiver, |
| } |