Enum rustc_trait_selection::traits::BuiltinImplSource

pub enum BuiltinImplSource {
    Misc,
    Object {
        vtable_base: usize,
    },
    TraitUpcasting {
        vtable_vptr_slot: Option<usize>,
    },
    TupleUnsizing,
}

Variants

Misc

Some builtin impl we don’t need to differentiate. This should be used unless more specific information is necessary.

Object

Fields

vtable_base: usize

A builtin impl for trait objects.

The vtable is formed by concatenating together the method lists of the base object trait and all supertraits, pointers to supertrait vtable will be provided when necessary; this is the start of upcast_trait_ref’s methods in that vtable.

TraitUpcasting

Fields

vtable_vptr_slot: Option<usize>

The vtable is formed by concatenating together the method lists of the base object trait and all supertraits, pointers to supertrait vtable will be provided when necessary; this is the position of upcast_trait_ref’s vtable within that vtable.

TupleUnsizing

Unsizing a tuple like (A, B, ..., X) to (A, B, ..., Y) if X unsizes to Y.

This needs to be a separate variant as it is still unstable and we need to emit a feature error when using it on stable.

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: 16 bytes

Size for each variant:

• Misc: 0 bytes
• Object: 16 bytes
• TraitUpcasting: 16 bytes
• TupleUnsizing: 0 bytes