Struct rustc::infer::outlives::obligations::TypeOutlives

pub struct TypeOutlives<'cx, 'gcx: 'tcx, 'tcx: 'cx, D> where
    D: TypeOutlivesDelegate<'tcx>,  {
    delegate: D,
    tcx: TyCtxt<'cx, 'gcx, 'tcx>,
    region_bound_pairs: &'cx [(Region<'tcx>, GenericKind<'tcx>)],
    implicit_region_bound: Option<Region<'tcx>>,
    param_env: ParamEnv<'tcx>,
}

🔬 This is a nightly-only experimental API. (rustc_private)

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The TypeOutlives struct has the job of "lowering" a T: 'a obligation into a series of 'a: 'b constraints and "verifys", as described on the module comment. The final constraints are emitted via a "delegate" of type D -- this is usually the infcx, which accrues them into the region_obligations code, but for NLL we use something else.

Fields

delegate: D

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tcx: TyCtxt<'cx, 'gcx, 'tcx>

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region_bound_pairs: &'cx [(Region<'tcx>, GenericKind<'tcx>)]

🔬 This is a nightly-only experimental API. (rustc_private)

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implicit_region_bound: Option<Region<'tcx>>

🔬 This is a nightly-only experimental API. (rustc_private)

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param_env: ParamEnv<'tcx>

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Methods

impl<'cx, 'gcx, 'tcx, D> TypeOutlives<'cx, 'gcx, 'tcx, D> where     D: TypeOutlivesDelegate<'tcx>,

pub fn new(     delegate: D,     tcx: TyCtxt<'cx, 'gcx, 'tcx>,     region_bound_pairs: &'cx [(Region<'tcx>, GenericKind<'tcx>)],     implicit_region_bound: Option<Region<'tcx>>,     param_env: ParamEnv<'tcx> ) -> Self

🔬 This is a nightly-only experimental API. (rustc_private)

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pub fn type_must_outlive(     &mut self,     origin: SubregionOrigin<'tcx>,     ty: Ty<'tcx>,     region: Region<'tcx> )

🔬 This is a nightly-only experimental API. (rustc_private)

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Adds constraints to inference such that T: 'a holds (or reports an error if it cannot).

Parameters

• origin, the reason we need this constraint
• ty, the type T
• region, the region 'a

fn components_must_outlive(     &mut self,     origin: SubregionOrigin<'tcx>,     components: Vec<Component<'tcx>>,     region: Region<'tcx> )

🔬 This is a nightly-only experimental API. (rustc_private)

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fn param_ty_must_outlive(     &mut self,     origin: SubregionOrigin<'tcx>,     region: Region<'tcx>,     param_ty: ParamTy )

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fn projection_must_outlive(     &mut self,     origin: SubregionOrigin<'tcx>,     region: Region<'tcx>,     projection_ty: ProjectionTy<'tcx> )

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fn type_bound(&self, ty: Ty<'tcx>) -> VerifyBound<'tcx>

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fn param_bound(&self, param_ty: ParamTy) -> VerifyBound<'tcx>

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Important traits for Vec<u8>

impl Write for Vec<u8>

fn projection_declared_bounds(     &self,     projection_ty: ProjectionTy<'tcx> ) -> Vec<Region<'tcx>>

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fn projection_bound(     &self,     declared_bounds: Vec<Region<'tcx>>,     projection_ty: ProjectionTy<'tcx> ) -> VerifyBound<'tcx>

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fn recursive_type_bound(&self, ty: Ty<'tcx>) -> VerifyBound<'tcx>

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Important traits for Vec<u8>

impl Write for Vec<u8>

fn declared_generic_bounds_from_env(     &self,     generic: GenericKind<'tcx> ) -> Vec<Region<'tcx>>

🔬 This is a nightly-only experimental API. (rustc_private)

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Important traits for Vec<u8>

impl Write for Vec<u8>

fn declared_projection_bounds_from_trait(     &self,     projection_ty: ProjectionTy<'tcx> ) -> Vec<Region<'tcx>>

🔬 This is a nightly-only experimental API. (rustc_private)

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Given a projection like <T as Foo<'x>>::Bar, returns any bounds declared in the trait definition. For example, if the trait were

trait Foo<'a> {
    type Bar: 'a;
}

then this function would return 'x. This is subject to the limitations around higher-ranked bounds described in region_bounds_declared_on_associated_item.

Important traits for Vec<u8>

impl Write for Vec<u8>

fn region_bounds_declared_on_associated_item(     &self,     assoc_item_def_id: DefId ) -> Vec<Region<'tcx>>

🔬 This is a nightly-only experimental API. (rustc_private)

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Given the def-id of an associated item, returns any region bounds attached to that associated item from the trait definition.

For example:

trait Foo<'a> {
    type Bar: 'a;
}

If we were given the def-id of Foo::Bar, we would return 'a. You could then apply the substitutions from the projection to convert this into your namespace. This also works if the user writes where <Self as Foo<'a>>::Bar: 'a on the trait. In fact, it works by searching for just such a where-clause.

It will not, however, work for higher-ranked bounds like:

trait Foo<'a, 'b>
where for<'x> <Self as Foo<'x, 'b>>::Bar: 'x
{
    type Bar;
}

This is for simplicity, and because we are not really smart enough to cope with such bounds anywhere.

Important traits for Vec<u8>

impl Write for Vec<u8>

fn collect_outlives_from_predicate_list<I, P>(     &self,     ty: Ty<'tcx>,     predicates: I ) -> Vec<Region<'tcx>> where     I: IntoIterator<Item = P>,     P: AsRef<Predicate<'tcx>>,

🔬 This is a nightly-only experimental API. (rustc_private)

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Searches through a predicate list for a predicate T: 'a.

Careful: does not elaborate predicates, and just uses == when comparing ty for equality, so ty must be something that does not involve inference variables and where you otherwise want a precise match.