Struct rustc_trait_selection::error_reporting::infer::sub_relations::SubRelations

pub struct SubRelations {
    map: FxHashMap<TyVid, SubId>,
    table: UnificationTableStorage<SubId>,
}

When reporting ambiguity errors, we sometimes want to treat all inference vars which are subtypes of each others as if they are equal. For this case we compute the transitive closure of our subtype obligations here.

E.g. when encountering ambiguity errors, we want to suggest specifying some method argument or to add a type annotation to a local variable. Because subtyping cannot change the shape of a type, it’s fine if the cause of the ambiguity error is only related to the suggested variable via subtyping.

Even for something like let x = returns_arg(); x.method(); the type of x is only a supertype of the argument of returns_arg. We still want to suggest specifying the type of the argument.

Fields

map: FxHashMap<TyVid, SubId>

table: UnificationTableStorage<SubId>

Implementations

impl SubRelations

fn get_id<'tcx>(&mut self, infcx: &InferCtxt<'tcx>, vid: TyVid) -> SubId

pub fn add_constraints<'tcx>( &mut self, infcx: &InferCtxt<'tcx>, obls: impl IntoIterator<Item = Predicate<'tcx>>, )

pub fn unified<'tcx>( &mut self, infcx: &InferCtxt<'tcx>, a: TyVid, b: TyVid, ) -> bool

Trait Implementations

impl Default for SubRelations

fn default() -> SubRelations

Returns the “default value” for a type.

Layout

Note: Most layout information is completely unstable and may even differ between compilations. The only exception is types with certain repr(...) attributes. Please see the Rust Reference's “Type Layout” chapter for details on type layout guarantees.

Size: 56 bytes