| //! Trait Resolution. See the [rustc dev guide] for more information on how this works. |
| //! |
| //! [rustc dev guide]: https://rustc-dev-guide.rust-lang.org/traits/resolution.html |
| |
| mod chalk; |
| pub mod query; |
| pub mod select; |
| pub mod specialization_graph; |
| mod structural_impls; |
| |
| use crate::infer::canonical::Canonical; |
| use crate::mir::abstract_const::NotConstEvaluatable; |
| use crate::ty::subst::SubstsRef; |
| use crate::ty::{self, AdtKind, Ty, TyCtxt}; |
| |
| use rustc_errors::{Applicability, DiagnosticBuilder}; |
| use rustc_hir as hir; |
| use rustc_hir::def_id::DefId; |
| use rustc_hir::Constness; |
| use rustc_span::symbol::Symbol; |
| use rustc_span::{Span, DUMMY_SP}; |
| use smallvec::SmallVec; |
| |
| use std::borrow::Cow; |
| use std::fmt; |
| use std::ops::Deref; |
| use std::rc::Rc; |
| |
| pub use self::select::{EvaluationCache, EvaluationResult, OverflowError, SelectionCache}; |
| |
| pub type CanonicalChalkEnvironmentAndGoal<'tcx> = Canonical<'tcx, ChalkEnvironmentAndGoal<'tcx>>; |
| |
| pub use self::ObligationCauseCode::*; |
| |
| pub use self::chalk::{ChalkEnvironmentAndGoal, RustInterner as ChalkRustInterner}; |
| |
| /// 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 auto traits 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. |
| /// |
| /// As the happy path does not care about this struct, storing this on the heap |
| /// ends up increasing performance. |
| /// |
| /// We do not want to intern this as there are a lot of obligation causes which |
| /// only live for a short period of time. |
| #[derive(Clone, PartialEq, Eq, Hash, Lift)] |
| pub struct ObligationCause<'tcx> { |
| /// `None` for `ObligationCause::dummy`, `Some` otherwise. |
| data: Option<Rc<ObligationCauseData<'tcx>>>, |
| } |
| |
| const DUMMY_OBLIGATION_CAUSE_DATA: ObligationCauseData<'static> = |
| ObligationCauseData { span: DUMMY_SP, body_id: hir::CRATE_HIR_ID, code: MiscObligation }; |
| |
| // Correctly format `ObligationCause::dummy`. |
| impl<'tcx> fmt::Debug for ObligationCause<'tcx> { |
| fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { |
| ObligationCauseData::fmt(self, f) |
| } |
| } |
| |
| impl Deref for ObligationCause<'tcx> { |
| type Target = ObligationCauseData<'tcx>; |
| |
| #[inline(always)] |
| fn deref(&self) -> &Self::Target { |
| self.data.as_deref().unwrap_or(&DUMMY_OBLIGATION_CAUSE_DATA) |
| } |
| } |
| |
| #[derive(Clone, Debug, PartialEq, Eq, Hash, Lift)] |
| pub struct ObligationCauseData<'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 { data: Some(Rc::new(ObligationCauseData { span, body_id, code })) } |
| } |
| |
| pub fn misc(span: Span, body_id: hir::HirId) -> ObligationCause<'tcx> { |
| ObligationCause::new(span, body_id, MiscObligation) |
| } |
| |
| pub fn dummy_with_span(span: Span) -> ObligationCause<'tcx> { |
| ObligationCause::new(span, hir::CRATE_HIR_ID, MiscObligation) |
| } |
| |
| #[inline(always)] |
| pub fn dummy() -> ObligationCause<'tcx> { |
| ObligationCause { data: None } |
| } |
| |
| pub fn make_mut(&mut self) -> &mut ObligationCauseData<'tcx> { |
| Rc::make_mut(self.data.get_or_insert_with(|| Rc::new(DUMMY_OBLIGATION_CAUSE_DATA))) |
| } |
| |
| pub fn span(&self, tcx: TyCtxt<'tcx>) -> Span { |
| match self.code { |
| ObligationCauseCode::CompareImplMethodObligation { .. } |
| | ObligationCauseCode::MainFunctionType |
| | ObligationCauseCode::StartFunctionType => { |
| tcx.sess.source_map().guess_head_span(self.span) |
| } |
| ObligationCauseCode::MatchExpressionArm(box MatchExpressionArmCause { |
| arm_span, |
| .. |
| }) => arm_span, |
| _ => self.span, |
| } |
| } |
| } |
| |
| #[derive(Clone, Debug, PartialEq, Eq, Hash, Lift)] |
| pub struct UnifyReceiverContext<'tcx> { |
| pub assoc_item: ty::AssocItem, |
| pub param_env: ty::ParamEnv<'tcx>, |
| pub substs: SubstsRef<'tcx>, |
| } |
| |
| #[derive(Clone, Debug, PartialEq, Eq, Hash, Lift)] |
| 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(Option<Span>), |
| /// Return type must be `Sized`. |
| SizedReturnType, |
| /// Yield type must be `Sized`. |
| SizedYieldType, |
| /// Inline asm operand type must be `Sized`. |
| InlineAsmSized, |
| /// `[T, ..n]` implies that `T` must be `Copy`. |
| /// If the function in the array repeat expression is a `const fn`, |
| /// display a help message suggesting to move the function call to a |
| /// new `const` item while saying that `T` doesn't implement `Copy`. |
| RepeatVec(bool), |
| |
| /// Types of fields (other than the last, except for packed structs) in a struct must be sized. |
| FieldSized { |
| adt_kind: AdtKind, |
| span: Span, |
| last: bool, |
| }, |
| |
| /// Constant expressions must be sized. |
| ConstSized, |
| |
| /// `static` items must have `Sync` type. |
| SharedStatic, |
| |
| BuiltinDerivedObligation(DerivedObligationCause<'tcx>), |
| |
| ImplDerivedObligation(DerivedObligationCause<'tcx>), |
| |
| DerivedObligation(DerivedObligationCause<'tcx>), |
| |
| /// Error derived when matching traits/impls; see ObligationCause for more details |
| CompareImplConstObligation, |
| |
| /// Error derived when matching traits/impls; see ObligationCause for more details |
| CompareImplMethodObligation { |
| item_name: Symbol, |
| impl_item_def_id: DefId, |
| trait_item_def_id: DefId, |
| }, |
| |
| /// Error derived when matching traits/impls; see ObligationCause for more details |
| CompareImplTypeObligation { |
| item_name: Symbol, |
| 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, |
| |
| UnifyReceiver(Box<UnifyReceiverContext<'tcx>>), |
| |
| /// `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, |
| |
| /// If `X` is the concrete type of an opaque type `impl Y`, then `X` must implement `Y` |
| OpaqueType, |
| } |
| |
| 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) |
| | DerivedObligation(cause) = base_cause |
| { |
| base_cause = &cause.parent_code; |
| } |
| base_cause |
| } |
| } |
| |
| // `ObligationCauseCode` is used a lot. Make sure it doesn't unintentionally get bigger. |
| #[cfg(all(target_arch = "x86_64", target_pointer_width = "64"))] |
| static_assert_size!(ObligationCauseCode<'_>, 40); |
| |
| #[derive(Copy, Clone, Debug, PartialEq, Eq, Hash)] |
| pub enum StatementAsExpression { |
| CorrectType, |
| NeedsBoxing, |
| } |
| |
| impl<'tcx> ty::Lift<'tcx> for StatementAsExpression { |
| type Lifted = StatementAsExpression; |
| fn lift_to_tcx(self, _tcx: TyCtxt<'tcx>) -> Option<StatementAsExpression> { |
| Some(self) |
| } |
| } |
| |
| #[derive(Clone, Debug, PartialEq, Eq, Hash, Lift)] |
| pub struct MatchExpressionArmCause<'tcx> { |
| pub arm_span: Span, |
| pub scrut_span: Span, |
| pub semi_span: Option<(Span, StatementAsExpression)>, |
| pub source: hir::MatchSource, |
| pub prior_arms: Vec<Span>, |
| pub last_ty: Ty<'tcx>, |
| pub scrut_hir_id: hir::HirId, |
| pub opt_suggest_box_span: Option<Span>, |
| } |
| |
| #[derive(Clone, Debug, PartialEq, Eq, Hash)] |
| pub struct IfExpressionCause { |
| pub then: Span, |
| pub else_sp: Span, |
| pub outer: Option<Span>, |
| pub semicolon: Option<(Span, StatementAsExpression)>, |
| pub opt_suggest_box_span: Option<Span>, |
| } |
| |
| #[derive(Clone, Debug, PartialEq, Eq, Hash, Lift)] |
| 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>>, |
| } |
| |
| #[derive(Clone, Debug, TypeFoldable, Lift)] |
| pub enum SelectionError<'tcx> { |
| Unimplemented, |
| OutputTypeParameterMismatch( |
| ty::PolyTraitRef<'tcx>, |
| ty::PolyTraitRef<'tcx>, |
| ty::error::TypeError<'tcx>, |
| ), |
| TraitNotObjectSafe(DefId), |
| NotConstEvaluatable(NotConstEvaluatable), |
| 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 `ImplSource` |
| /// indicates where the impl comes from. |
| /// |
| /// For example, the obligation may be satisfied by 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 i32 { ... } // Impl_3 |
| /// |
| /// fn foo<T: Clone>(concrete: Option<Box<i32>>, 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 A: ImplSource points at a specific impl. Only possible when |
| /// // type is concretely known. If the impl itself has bounded |
| /// // type parameters, ImplSource will carry resolutions for those as well: |
| /// concrete.clone(); // ImplSource(Impl_1, [ImplSource(Impl_2, [ImplSource(Impl_3)])]) |
| /// |
| /// // Case B: ImplSource must be provided by caller. This applies when |
| /// // type is a type parameter. |
| /// param.clone(); // ImplSource::Param |
| /// |
| /// // Case C: A mix of cases A and B. |
| /// mixed.clone(); // ImplSource(Impl_1, [ImplSource::Param]) |
| /// } |
| /// ``` |
| /// |
| /// ### The type parameter `N` |
| /// |
| /// See explanation on `ImplSourceUserDefinedData`. |
| #[derive(Clone, PartialEq, Eq, TyEncodable, TyDecodable, HashStable, TypeFoldable, Lift)] |
| pub enum ImplSource<'tcx, N> { |
| /// ImplSource identifying a particular impl. |
| UserDefined(ImplSourceUserDefinedData<'tcx, N>), |
| |
| /// ImplSource 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. |
| AutoImpl(ImplSourceAutoImplData<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). |
| Param(Vec<N>, Constness), |
| |
| /// Virtual calls through an object. |
| Object(ImplSourceObjectData<'tcx, N>), |
| |
| /// Successful resolution for a builtin trait. |
| Builtin(ImplSourceBuiltinData<N>), |
| |
| /// ImplSource automatically generated for a closure. The `DefId` is the ID |
| /// of the closure expression. This is a `ImplSource::UserDefined` in spirit, but the |
| /// impl is generated by the compiler and does not appear in the source. |
| Closure(ImplSourceClosureData<'tcx, N>), |
| |
| /// Same as above, but for a function pointer type with the given signature. |
| FnPointer(ImplSourceFnPointerData<'tcx, N>), |
| |
| /// ImplSource for a builtin `DeterminantKind` trait implementation. |
| DiscriminantKind(ImplSourceDiscriminantKindData), |
| |
| /// ImplSource for a builtin `Pointee` trait implementation. |
| Pointee(ImplSourcePointeeData), |
| |
| /// ImplSource automatically generated for a generator. |
| Generator(ImplSourceGeneratorData<'tcx, N>), |
| |
| /// ImplSource for a trait alias. |
| TraitAlias(ImplSourceTraitAliasData<'tcx, N>), |
| } |
| |
| impl<'tcx, N> ImplSource<'tcx, N> { |
| pub fn nested_obligations(self) -> Vec<N> { |
| match self { |
| ImplSource::UserDefined(i) => i.nested, |
| ImplSource::Param(n, _) => n, |
| ImplSource::Builtin(i) => i.nested, |
| ImplSource::AutoImpl(d) => d.nested, |
| ImplSource::Closure(c) => c.nested, |
| ImplSource::Generator(c) => c.nested, |
| ImplSource::Object(d) => d.nested, |
| ImplSource::FnPointer(d) => d.nested, |
| ImplSource::DiscriminantKind(ImplSourceDiscriminantKindData) |
| | ImplSource::Pointee(ImplSourcePointeeData) => Vec::new(), |
| ImplSource::TraitAlias(d) => d.nested, |
| } |
| } |
| |
| pub fn borrow_nested_obligations(&self) -> &[N] { |
| match &self { |
| ImplSource::UserDefined(i) => &i.nested[..], |
| ImplSource::Param(n, _) => &n[..], |
| ImplSource::Builtin(i) => &i.nested[..], |
| ImplSource::AutoImpl(d) => &d.nested[..], |
| ImplSource::Closure(c) => &c.nested[..], |
| ImplSource::Generator(c) => &c.nested[..], |
| ImplSource::Object(d) => &d.nested[..], |
| ImplSource::FnPointer(d) => &d.nested[..], |
| ImplSource::DiscriminantKind(ImplSourceDiscriminantKindData) |
| | ImplSource::Pointee(ImplSourcePointeeData) => &[], |
| ImplSource::TraitAlias(d) => &d.nested[..], |
| } |
| } |
| |
| pub fn map<M, F>(self, f: F) -> ImplSource<'tcx, M> |
| where |
| F: FnMut(N) -> M, |
| { |
| match self { |
| ImplSource::UserDefined(i) => ImplSource::UserDefined(ImplSourceUserDefinedData { |
| impl_def_id: i.impl_def_id, |
| substs: i.substs, |
| nested: i.nested.into_iter().map(f).collect(), |
| }), |
| ImplSource::Param(n, ct) => ImplSource::Param(n.into_iter().map(f).collect(), ct), |
| ImplSource::Builtin(i) => ImplSource::Builtin(ImplSourceBuiltinData { |
| nested: i.nested.into_iter().map(f).collect(), |
| }), |
| ImplSource::Object(o) => ImplSource::Object(ImplSourceObjectData { |
| upcast_trait_ref: o.upcast_trait_ref, |
| vtable_base: o.vtable_base, |
| nested: o.nested.into_iter().map(f).collect(), |
| }), |
| ImplSource::AutoImpl(d) => ImplSource::AutoImpl(ImplSourceAutoImplData { |
| trait_def_id: d.trait_def_id, |
| nested: d.nested.into_iter().map(f).collect(), |
| }), |
| ImplSource::Closure(c) => ImplSource::Closure(ImplSourceClosureData { |
| closure_def_id: c.closure_def_id, |
| substs: c.substs, |
| nested: c.nested.into_iter().map(f).collect(), |
| }), |
| ImplSource::Generator(c) => ImplSource::Generator(ImplSourceGeneratorData { |
| generator_def_id: c.generator_def_id, |
| substs: c.substs, |
| nested: c.nested.into_iter().map(f).collect(), |
| }), |
| ImplSource::FnPointer(p) => ImplSource::FnPointer(ImplSourceFnPointerData { |
| fn_ty: p.fn_ty, |
| nested: p.nested.into_iter().map(f).collect(), |
| }), |
| ImplSource::DiscriminantKind(ImplSourceDiscriminantKindData) => { |
| ImplSource::DiscriminantKind(ImplSourceDiscriminantKindData) |
| } |
| ImplSource::Pointee(ImplSourcePointeeData) => { |
| ImplSource::Pointee(ImplSourcePointeeData) |
| } |
| ImplSource::TraitAlias(d) => ImplSource::TraitAlias(ImplSourceTraitAliasData { |
| 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, TyEncodable, TyDecodable, HashStable, TypeFoldable, Lift)] |
| pub struct ImplSourceUserDefinedData<'tcx, N> { |
| pub impl_def_id: DefId, |
| pub substs: SubstsRef<'tcx>, |
| pub nested: Vec<N>, |
| } |
| |
| #[derive(Clone, PartialEq, Eq, TyEncodable, TyDecodable, HashStable, TypeFoldable, Lift)] |
| pub struct ImplSourceGeneratorData<'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, TyEncodable, TyDecodable, HashStable, TypeFoldable, Lift)] |
| pub struct ImplSourceClosureData<'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, TyEncodable, TyDecodable, HashStable, TypeFoldable, Lift)] |
| pub struct ImplSourceAutoImplData<N> { |
| pub trait_def_id: DefId, |
| pub nested: Vec<N>, |
| } |
| |
| #[derive(Clone, PartialEq, Eq, TyEncodable, TyDecodable, HashStable, TypeFoldable, Lift)] |
| pub struct ImplSourceBuiltinData<N> { |
| pub nested: Vec<N>, |
| } |
| |
| #[derive(PartialEq, Eq, Clone, TyEncodable, TyDecodable, HashStable, TypeFoldable, Lift)] |
| pub struct ImplSourceObjectData<'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, TyEncodable, TyDecodable, HashStable, TypeFoldable, Lift)] |
| pub struct ImplSourceFnPointerData<'tcx, N> { |
| pub fn_ty: Ty<'tcx>, |
| pub nested: Vec<N>, |
| } |
| |
| // FIXME(@lcnr): This should be refactored and merged with other builtin vtables. |
| #[derive(Clone, Debug, PartialEq, Eq, TyEncodable, TyDecodable, HashStable)] |
| pub struct ImplSourceDiscriminantKindData; |
| |
| #[derive(Clone, Debug, PartialEq, Eq, TyEncodable, TyDecodable, HashStable)] |
| pub struct ImplSourcePointeeData; |
| |
| #[derive(Clone, PartialEq, Eq, TyEncodable, TyDecodable, HashStable, TypeFoldable, Lift)] |
| pub struct ImplSourceTraitAliasData<'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(Symbol, MethodViolationCode, Span), |
| |
| /// Associated const. |
| AssocConst(Symbol, Span), |
| |
| /// GAT |
| GAT(Symbol, 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".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(), |
| ObjectSafetyViolation::GAT(name, _) => { |
| format!("it contains the generic associated type `{}`", name).into() |
| } |
| } |
| } |
| |
| pub fn solution(&self, err: &mut DiagnosticBuilder<'_>) { |
| match *self { |
| ObjectSafetyViolation::SizedSelf(_) | ObjectSafetyViolation::SupertraitSelf(_) => {} |
| ObjectSafetyViolation::Method( |
| name, |
| MethodViolationCode::StaticMethod(sugg, self_span, has_args), |
| _, |
| ) => { |
| err.span_suggestion( |
| self_span, |
| &format!( |
| "consider turning `{}` into a method by giving it a `&self` argument", |
| name |
| ), |
| format!("&self{}", if has_args { ", " } else { "" }), |
| Applicability::MaybeIncorrect, |
| ); |
| match sugg { |
| Some((sugg, span)) => { |
| err.span_suggestion( |
| span, |
| &format!( |
| "alternatively, consider constraining `{}` so it does not apply to \ |
| trait objects", |
| name |
| ), |
| sugg.to_string(), |
| Applicability::MaybeIncorrect, |
| ); |
| } |
| None => { |
| err.help(&format!( |
| "consider turning `{}` into a method by giving it a `&self` \ |
| argument or constraining it so it does not apply to trait objects", |
| name |
| )); |
| } |
| } |
| } |
| ObjectSafetyViolation::Method( |
| name, |
| MethodViolationCode::UndispatchableReceiver, |
| span, |
| ) => { |
| err.span_suggestion( |
| span, |
| &format!( |
| "consider changing method `{}`'s `self` parameter to be `&self`", |
| name |
| ), |
| "&Self".to_string(), |
| Applicability::MachineApplicable, |
| ); |
| } |
| ObjectSafetyViolation::AssocConst(name, _) |
| | ObjectSafetyViolation::GAT(name, _) |
| | ObjectSafetyViolation::Method(name, ..) => { |
| err.help(&format!("consider moving `{}` to another trait", name)); |
| } |
| } |
| } |
| |
| 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::GAT(_, 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)>, Span, bool /* has args */), |
| |
| /// 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, |
| } |
