Type Alias AliasConstKind 

pub type AliasConstKind<'tcx> = AliasConstKind<TyCtxt<'tcx>>;

Aliased Type

pub enum AliasConstKind<'tcx> {
    Projection {
        def_id: DefId,
    },
    InherentSelf {
        def_id: DefId,
    },
    InherentImpl {
        def_id: DefId,
    },
    Free {
        def_id: DefId,
    },
    Anon {
        def_id: DefId,
    },
}

Variants

Projection

A projection <Type as Trait>::AssocConst

Fields

def_id: DefId

InherentSelf

An associated const in an inherent impl.

The generic args are in “Self form”, i.e. there is a single Self type parameter, followed by any GAT args on the inherent const itself.

The “impl form” args can be obtained by generating fresh vars for each of the impl params, instantiating the impl block’s Self type with the fresh vars, equating the resulting type with the Self generic argument, and using the result of what the fresh vars resolved to as the “impl form” args. Doing so without considering the extra predicates generated by the equate is a lossy operation, consider the following impl block:

impl<T> Struct<'static, T> {
    const ASSOC<A>: () = ();
}

If we have Struct::<'a, u32>::Assoc<usize>, the Self args form would be [Struct<'a, u32>, usize]. The “impl form” args would be [u32, usize], with an extra constraint generated that 'a == 'static. Disregarding this extra constraint would be wrong.

Hence, when HIR lowering wants to construct an inherent alias, it must use the “Self form” to let the trait solver do the equate and consider additional constraints.

FIXME(inherent_associated_types): This ideally ought be a list of candidate DefIds that a path could resolve to, then the trait solver does the above-written routine to figure out which exact impl to use. InherentSelf could be conceptually be thought of as corresponding to Projection where the def_id is a trait, and InherentImpl is Projection where the def_id is an impl.

Fields

def_id: DefId

InherentImpl

An associated const in an inherent impl. See [Self::InherentSelf] for a description on the difference between InherentSelf and InherentImpl.

Fields

def_id: DefId

Free

A free constant, outside an impl block.

Fields

def_id: DefId

Anon

Anonymous constant, e.g. the 1 + 2 in [u8; 1 + 2].

Fields

def_id: DefId

Layout

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