Struct rustc_mir::borrow_check::nll::type_check::relate_tys::TypeRelating

struct TypeRelating<'cx, 'bccx: 'cx, 'gcx: 'tcx, 'tcx: 'bccx> {
    infcx: &'cx InferCtxt<'cx, 'gcx, 'tcx>,
    ambient_variance: Variance,
    a_scopes: Vec<BoundRegionScope>,
    b_scopes: Vec<BoundRegionScope>,
    locations: Locations,
    borrowck_context: Option<&'cx mut BorrowCheckContext<'bccx, 'tcx>>,
    canonical_var_values: IndexVec<CanonicalVar, Option<Kind<'tcx>>>,
}

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

this crate is being loaded from the sysroot, an unstable location; did you mean to load this crate from crates.io via Cargo.toml instead?

Fields

infcx: &'cx InferCtxt<'cx, 'gcx, 'tcx>

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

this crate is being loaded from the sysroot, an unstable location; did you mean to load this crate from crates.io via Cargo.toml instead?

ambient_variance: Variance

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

this crate is being loaded from the sysroot, an unstable location; did you mean to load this crate from crates.io via Cargo.toml instead?

How are we relating a and b?

• covariant means a <: b
• contravariant means b <: a
• invariant means `a == b
• bivariant means that it doesn't matter

a_scopes: Vec<BoundRegionScope>

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

this crate is being loaded from the sysroot, an unstable location; did you mean to load this crate from crates.io via Cargo.toml instead?

When we pass through a set of binders (e.g., when looking into a fn type), we push a new bound region scope onto here. This will contain the instantiated region for each region in those binders. When we then encounter a ReLateBound(d, br), we can use the debruijn index d to find the right scope, and then bound region name br to find the specific instantiation from within that scope. See replace_bound_region.

This field stores the instantiations for late-bound regions in the a type.

b_scopes: Vec<BoundRegionScope>

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

this crate is being loaded from the sysroot, an unstable location; did you mean to load this crate from crates.io via Cargo.toml instead?

Same as a_scopes, but for the b type.

locations: Locations

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

this crate is being loaded from the sysroot, an unstable location; did you mean to load this crate from crates.io via Cargo.toml instead?

Where (and why) is this relation taking place?

borrowck_context: Option<&'cx mut BorrowCheckContext<'bccx, 'tcx>>

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

this crate is being loaded from the sysroot, an unstable location; did you mean to load this crate from crates.io via Cargo.toml instead?

This will be Some when we are running the type check as part of NLL, and None if we are running a "sanity check".

canonical_var_values: IndexVec<CanonicalVar, Option<Kind<'tcx>>>

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

this crate is being loaded from the sysroot, an unstable location; did you mean to load this crate from crates.io via Cargo.toml instead?

As we execute, the type on the LHS may come from a canonical source. In that case, we will sometimes find a constraint like ?0 = B, where B is a type from the RHS. The first time we find that, we simply record B (and the list of scopes that tells us how to interpret B). The next time we encounter ?0, then, we can read this value out and use it.

One problem: these variables may be in some other universe, how can we enforce that? I guess I could add some kind of "minimum universe constraint" that we can feed to the NLL checker. --> also, we know this doesn't happen

Methods

impl<'cx, 'bccx, 'gcx, 'tcx> TypeRelating<'cx, 'bccx, 'gcx, 'tcx>

fn new(     infcx: &'cx InferCtxt<'cx, 'gcx, 'tcx>,     ambient_variance: Variance,     locations: Locations,     borrowck_context: Option<&'cx mut BorrowCheckContext<'bccx, 'tcx>>,     canonical_var_infos: CanonicalVarInfos<'tcx> ) -> Self

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

this crate is being loaded from the sysroot, an unstable location; did you mean to load this crate from crates.io via Cargo.toml instead?

fn ambient_covariance(&self) -> bool

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

this crate is being loaded from the sysroot, an unstable location; did you mean to load this crate from crates.io via Cargo.toml instead?

fn ambient_contravariance(&self) -> bool

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

this crate is being loaded from the sysroot, an unstable location; did you mean to load this crate from crates.io via Cargo.toml instead?

fn create_scope(     &mut self,     value: &Binder<impl TypeFoldable<'tcx>>,     universally_quantified: UniversallyQuantified ) -> BoundRegionScope

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

this crate is being loaded from the sysroot, an unstable location; did you mean to load this crate from crates.io via Cargo.toml instead?

fn lookup_bound_region(     debruijn: DebruijnIndex,     br: &BoundRegion,     first_free_index: DebruijnIndex,     scopes: &[BoundRegionScope] ) -> RegionVid

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

this crate is being loaded from the sysroot, an unstable location; did you mean to load this crate from crates.io via Cargo.toml instead?

When we encounter binders during the type traversal, we record the value to substitute for each of the things contained in that binder. (This will be either a universal placeholder or an existential inference variable.) Given the debruijn index debruijn (and name br) of some binder we have now encountered, this routine finds the value that we instantiated the region with; to do so, it indexes backwards into the list of ambient scopes scopes.

fn replace_bound_region(     &self,     universal_regions: &UniversalRegions<'tcx>,     r: Region<'tcx>,     first_free_index: DebruijnIndex,     scopes: &[BoundRegionScope] ) -> RegionVid

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

this crate is being loaded from the sysroot, an unstable location; did you mean to load this crate from crates.io via Cargo.toml instead?

If r is a bound region, find the scope in which it is bound (from scopes) and return the value that we instantiated it with. Otherwise just return r.

fn push_outlives(&mut self, sup: RegionVid, sub: RegionVid)

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

this crate is being loaded from the sysroot, an unstable location; did you mean to load this crate from crates.io via Cargo.toml instead?

Push a new outlives requirement into our output set of constraints.

fn relate_var(     &mut self,     var: CanonicalVar,     b_kind: Kind<'tcx> ) -> RelateResult<'tcx, Kind<'tcx>>

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

this crate is being loaded from the sysroot, an unstable location; did you mean to load this crate from crates.io via Cargo.toml instead?

When we encounter a canonical variable var in the output, equate it with kind. If the variable has been previously equated, then equate it again.

fn generalize_value(&self, kind: Kind<'tcx>) -> Kind<'tcx>

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

this crate is being loaded from the sysroot, an unstable location; did you mean to load this crate from crates.io via Cargo.toml instead?

Trait Implementations

impl<'cx, 'bccx, 'gcx, 'tcx> TypeRelation<'cx, 'gcx, 'tcx> for TypeRelating<'cx, 'bccx, 'gcx, 'tcx>

fn tcx(&self) -> TyCtxt<'cx, 'gcx, 'tcx>

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

this crate is being loaded from the sysroot, an unstable location; did you mean to load this crate from crates.io via Cargo.toml instead?

fn tag(&self) -> &'static str

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

this crate is being loaded from the sysroot, an unstable location; did you mean to load this crate from crates.io via Cargo.toml instead?

Returns a static string we can use for printouts.

fn a_is_expected(&self) -> bool

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

this crate is being loaded from the sysroot, an unstable location; did you mean to load this crate from crates.io via Cargo.toml instead?

Returns true if the value a is the "expected" type in the relation. Just affects error messages.

fn relate_with_variance<T: Relate<'tcx>>(     &mut self,     variance: Variance,     a: &T,     b: &T ) -> RelateResult<'tcx, T>

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

this crate is being loaded from the sysroot, an unstable location; did you mean to load this crate from crates.io via Cargo.toml instead?

Switch variance for the purpose of relating a and b.

fn tys(&mut self, a: Ty<'tcx>, b: Ty<'tcx>) -> RelateResult<'tcx, Ty<'tcx>>

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

this crate is being loaded from the sysroot, an unstable location; did you mean to load this crate from crates.io via Cargo.toml instead?

fn regions(     &mut self,     a: Region<'tcx>,     b: Region<'tcx> ) -> RelateResult<'tcx, Region<'tcx>>

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

this crate is being loaded from the sysroot, an unstable location; did you mean to load this crate from crates.io via Cargo.toml instead?

fn binders<T>(     &mut self,     a: &Binder<T>,     b: &Binder<T> ) -> RelateResult<'tcx, Binder<T>> where     T: Relate<'tcx>,

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

this crate is being loaded from the sysroot, an unstable location; did you mean to load this crate from crates.io via Cargo.toml instead?

fn with_cause<F, R>(&mut self, _cause: Cause, f: F) -> R where     F: FnOnce(&mut Self) -> R,

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

this crate is being loaded from the sysroot, an unstable location; did you mean to load this crate from crates.io via Cargo.toml instead?

fn relate<T>(&mut self, a: &T, b: &T) -> Result<T, TypeError<'tcx>> where     T: Relate<'tcx>,

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

this crate is being loaded from the sysroot, an unstable location; did you mean to load this crate from crates.io via Cargo.toml instead?

Generic relation routine suitable for most anything.

fn relate_item_substs(     &mut self,     item_def_id: DefId,     a_subst: &'tcx List<Kind<'tcx>>,     b_subst: &'tcx List<Kind<'tcx>> ) -> Result<&'tcx List<Kind<'tcx>>, TypeError<'tcx>>

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

this crate is being loaded from the sysroot, an unstable location; did you mean to load this crate from crates.io via Cargo.toml instead?

Relate the two substitutions for the given item. The default is to look up the variance for the item and proceed accordingly.