Struct rustc_trait_selection::traits::Obligation

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pub struct Obligation<'tcx, T> {
    pub cause: ObligationCause<'tcx>,
    pub param_env: ParamEnv<'tcx>,
    pub predicate: T,
    pub recursion_depth: usize,
}
Expand description

An Obligation represents some trait reference (e.g., i32: Eq) for which the “impl_source” must be found. The process of finding an “impl_source” is called “resolving” the Obligation. This process consists of either identifying an impl (e.g., impl Eq for i32) that satisfies the obligation, or else finding a bound that is in scope. The eventual result is usually a Selection (defined below).

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§cause: ObligationCause<'tcx>

The reason we have to prove this thing.

§param_env: ParamEnv<'tcx>

The environment in which we should prove this thing.

§predicate: T

The thing we are trying to prove.

§recursion_depth: usize

If we started proving this as a result of trying to prove something else, track the total depth to ensure termination. If this goes over a certain threshold, we abort compilation – in such cases, we can not say whether or not the predicate holds for certain. Stupid halting problem; such a drag.

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impl<'tcx> Obligation<'tcx, Predicate<'tcx>>

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pub fn flip_polarity( &self, tcx: TyCtxt<'tcx>, ) -> Option<Obligation<'tcx, Predicate<'tcx>>>

Flips the polarity of the inner predicate.

Given T: Trait predicate it returns T: !Trait and given T: !Trait returns T: Trait.

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impl<'tcx> Obligation<'tcx, Binder<TyCtxt<'tcx>, TraitPredicate<TyCtxt<'tcx>>>>

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pub fn derived_cause( &self, variant: impl FnOnce(DerivedCause<'tcx>) -> ObligationCauseCode<'tcx>, ) -> ObligationCause<'tcx>

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impl<'tcx, O> Obligation<'tcx, O>

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pub fn new( tcx: TyCtxt<'tcx>, cause: ObligationCause<'tcx>, param_env: ParamEnv<'tcx>, predicate: impl Upcast<TyCtxt<'tcx>, O>, ) -> Obligation<'tcx, O>

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pub fn set_depth_from_parent(&mut self, parent_depth: usize)

We often create nested obligations without setting the correct depth.

To deal with this evaluate and fulfill explicitly update the depth of nested obligations using this function.

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pub fn with_depth( tcx: TyCtxt<'tcx>, cause: ObligationCause<'tcx>, recursion_depth: usize, param_env: ParamEnv<'tcx>, predicate: impl Upcast<TyCtxt<'tcx>, O>, ) -> Obligation<'tcx, O>

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pub fn misc( tcx: TyCtxt<'tcx>, span: Span, body_id: LocalDefId, param_env: ParamEnv<'tcx>, trait_ref: impl Upcast<TyCtxt<'tcx>, O>, ) -> Obligation<'tcx, O>

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pub fn with<P>( &self, tcx: TyCtxt<'tcx>, value: impl Upcast<TyCtxt<'tcx>, P>, ) -> Obligation<'tcx, P>

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impl<'tcx> Obligation<'tcx, Binder<TyCtxt<'tcx>, TraitPredicate<TyCtxt<'tcx>>>>

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pub fn polarity(&self) -> PredicatePolarity

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pub fn self_ty(&self) -> Binder<TyCtxt<'tcx>, Ty<'tcx>>

Trait Implementations§

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impl<'tcx, T> Clone for Obligation<'tcx, T>
where T: Clone,

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fn clone(&self) -> Obligation<'tcx, T>

Returns a copy of the value. Read more
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fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source. Read more
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impl<'tcx, O> Debug for Obligation<'tcx, O>
where O: Debug,

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fn fmt(&self, f: &mut Formatter<'_>) -> Result<(), Error>

Formats the value using the given formatter. Read more
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impl<'tcx> Elaboratable<TyCtxt<'tcx>> for Obligation<'tcx, Predicate<'tcx>>

For Obligation, a sub-obligation is combined with the current obligation’s param-env and cause code.

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fn predicate(&self) -> Predicate<'tcx>

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fn child(&self, clause: Clause<'tcx>) -> Obligation<'tcx, Predicate<'tcx>>

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fn child_with_derived_cause( &self, clause: Clause<'tcx>, span: Span, parent_trait_pred: Binder<TyCtxt<'tcx>, TraitPredicate<TyCtxt<'tcx>>>, index: usize, ) -> Obligation<'tcx, Predicate<'tcx>>

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impl<'tcx, P> From<Obligation<'tcx, P>> for Goal<TyCtxt<'tcx>, P>

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fn from(value: Obligation<'tcx, P>) -> Goal<TyCtxt<'tcx>, P>

Converts to this type from the input type.
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impl<T> Hash for Obligation<'_, T>
where T: Hash,

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fn hash<H>(&self, state: &mut H)
where H: Hasher,

Feeds this value into the given Hasher. Read more
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fn hash_slice<H>(data: &[Self], state: &mut H)
where H: Hasher, Self: Sized,

Feeds a slice of this type into the given Hasher. Read more
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impl<'tcx, T> PartialEq for Obligation<'tcx, T>
where T: PartialEq,

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fn eq(&self, other: &Obligation<'tcx, T>) -> bool

Tests for self and other values to be equal, and is used by ==.
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fn ne(&self, other: &Rhs) -> bool

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.
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impl<'tcx, O> TypeFoldable<TyCtxt<'tcx>> for Obligation<'tcx, O>
where O: TypeFoldable<TyCtxt<'tcx>>,

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fn try_fold_with<F>( self, folder: &mut F, ) -> Result<Obligation<'tcx, O>, <F as FallibleTypeFolder<TyCtxt<'tcx>>>::Error>
where F: FallibleTypeFolder<TyCtxt<'tcx>>,

The entry point for folding. To fold a value t with a folder f call: t.try_fold_with(f). Read more
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fn fold_with<F>(self, folder: &mut F) -> Self
where F: TypeFolder<I>,

A convenient alternative to try_fold_with for use with infallible folders. Do not override this method, to ensure coherence with try_fold_with.
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impl<'tcx, O> TypeVisitable<TyCtxt<'tcx>> for Obligation<'tcx, O>
where O: TypeVisitable<TyCtxt<'tcx>>,

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fn visit_with<V>( &self, visitor: &mut V, ) -> <V as TypeVisitor<TyCtxt<'tcx>>>::Result
where V: TypeVisitor<TyCtxt<'tcx>>,

The entry point for visiting. To visit a value t with a visitor v call: t.visit_with(v). Read more
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impl<T> Eq for Obligation<'_, T>
where T: Eq,

Auto Trait Implementations§

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impl<'tcx, T> Freeze for Obligation<'tcx, T>
where T: Freeze,

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impl<'tcx, T> !RefUnwindSafe for Obligation<'tcx, T>

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impl<'tcx, T> !Send for Obligation<'tcx, T>

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impl<'tcx, T> !Sync for Obligation<'tcx, T>

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impl<'tcx, T> Unpin for Obligation<'tcx, T>
where T: Unpin,

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impl<'tcx, T> !UnwindSafe for Obligation<'tcx, T>

Blanket Implementations§

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impl<T> Aligned for T

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const ALIGN: Alignment = _

Alignment of Self.
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impl<T> Any for T
where T: 'static + ?Sized,

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fn type_id(&self) -> TypeId

Gets the TypeId of self. Read more
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impl<T> AnyEq for T
where T: Any + PartialEq,

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fn equals(&self, other: &(dyn Any + 'static)) -> bool

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fn as_any(&self) -> &(dyn Any + 'static)

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impl<T> Borrow<T> for T
where T: ?Sized,

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fn borrow(&self) -> &T

Immutably borrows from an owned value. Read more
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impl<T> BorrowMut<T> for T
where T: ?Sized,

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fn borrow_mut(&mut self) -> &mut T

Mutably borrows from an owned value. Read more
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impl<T> CloneToUninit for T
where T: Clone,

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unsafe fn clone_to_uninit(&self, dst: *mut T)

🔬This is a nightly-only experimental API. (clone_to_uninit)
Performs copy-assignment from self to dst. Read more
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impl<T, R> CollectAndApply<T, R> for T

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fn collect_and_apply<I, F>(iter: I, f: F) -> R
where I: Iterator<Item = T>, F: FnOnce(&[T]) -> R,

Equivalent to f(&iter.collect::<Vec<_>>()).

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type Output = R

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impl<Q, K> Equivalent<K> for Q
where Q: Eq + ?Sized, K: Borrow<Q> + ?Sized,

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fn equivalent(&self, key: &K) -> bool

Checks if this value is equivalent to the given key. Read more
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impl<Q, K> Equivalent<K> for Q
where Q: Eq + ?Sized, K: Borrow<Q> + ?Sized,

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fn equivalent(&self, key: &K) -> bool

Checks if this value is equivalent to the given key. Read more
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impl<Q, K> Equivalent<K> for Q
where Q: Eq + ?Sized, K: Borrow<Q> + ?Sized,

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fn equivalent(&self, key: &K) -> bool

Compare self to key and return true if they are equal.
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impl<T> Filterable for T

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fn filterable( self, filter_name: &'static str, ) -> RequestFilterDataProvider<T, fn(_: DataRequest<'_>) -> bool>

Creates a filterable data provider with the given name for debugging. Read more
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impl<T> From<T> for T

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fn from(t: T) -> T

Returns the argument unchanged.

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impl<T> Instrument for T

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fn instrument(self, span: Span) -> Instrumented<Self>

Instruments this type with the provided Span, returning an Instrumented wrapper. Read more
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fn in_current_span(self) -> Instrumented<Self>

Instruments this type with the current Span, returning an Instrumented wrapper. Read more
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impl<T, U> Into<U> for T
where U: From<T>,

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fn into(self) -> U

Calls U::from(self).

That is, this conversion is whatever the implementation of From<T> for U chooses to do.

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impl<T> IntoEither for T

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fn into_either(self, into_left: bool) -> Either<Self, Self>

Converts self into a Left variant of Either<Self, Self> if into_left is true. Converts self into a Right variant of Either<Self, Self> otherwise. Read more
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fn into_either_with<F>(self, into_left: F) -> Either<Self, Self>
where F: FnOnce(&Self) -> bool,

Converts self into a Left variant of Either<Self, Self> if into_left(&self) returns true. Converts self into a Right variant of Either<Self, Self> otherwise. Read more
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impl<P> IntoQueryParam<P> for P

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impl<'tcx, T> IsSuggestable<'tcx> for T
where T: TypeVisitable<TyCtxt<'tcx>> + TypeFoldable<TyCtxt<'tcx>>,

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fn is_suggestable(self, tcx: TyCtxt<'tcx>, infer_suggestable: bool) -> bool

Whether this makes sense to suggest in a diagnostic. Read more
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fn make_suggestable( self, tcx: TyCtxt<'tcx>, infer_suggestable: bool, placeholder: Option<Ty<'tcx>>, ) -> Option<T>

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type Error = !

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impl<T> Same for T

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type Output = T

Should always be Self
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where T: Clone,

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The resulting type after obtaining ownership.
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type Error = Infallible

The type returned in the event of a conversion error.
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Performs the conversion.
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where U: TryFrom<T>,

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type Error = <U as TryFrom<T>>::Error

The type returned in the event of a conversion error.
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Performs the conversion.
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where I: Interner, T: TypeVisitable<I>,

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fn has_type_flags(&self, flags: TypeFlags) -> bool

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fn has_vars_bound_at_or_above(&self, binder: DebruijnIndex) -> bool

Returns true if self has any late-bound regions that are either bound by binder or bound by some binder outside of binder. If binder is ty::INNERMOST, this indicates whether there are any late-bound regions that appear free.
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fn error_reported(&self) -> Result<(), <I as Interner>::ErrorGuaranteed>

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fn has_vars_bound_above(&self, binder: DebruijnIndex) -> bool

Returns true if this type has any regions that escape binder (and hence are not bound by it).
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fn has_escaping_bound_vars(&self) -> bool

Return true if this type has regions that are not a part of the type. For example, for<'a> fn(&'a i32) return false, while fn(&'a i32) would return true. The latter can occur when traversing through the former. Read more
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fn has_non_region_param(&self) -> bool

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fn has_infer_regions(&self) -> bool

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fn has_infer_types(&self) -> bool

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fn has_non_region_infer(&self) -> bool

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fn has_infer(&self) -> bool

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fn has_non_region_placeholders(&self) -> bool

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fn has_param(&self) -> bool

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fn has_free_regions(&self) -> bool

“Free” regions in this context means that it has any region that is not (a) erased or (b) late-bound.
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True if there are any un-erased free regions.
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Indicates whether this value references only ‘global’ generic parameters that are the same regardless of what fn we are in. This is used for caching.
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True if there are any late-bound regions
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True if there are any late-bound non-region variables
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True if there are any bound variables
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Indicates whether this value still has parameters/placeholders/inference variables which could be replaced later, in a way that would change the results of impl specialization.
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where Tcx: DepContext,

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default fn from_cycle_error( tcx: Tcx, cycle_error: &CycleError, _guar: ErrorGuaranteed, ) -> T

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where S: Into<Dispatch>,

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Note: Unable to compute type layout, possibly due to this type having generic parameters. Layout can only be computed for concrete, fully-instantiated types.