Enum rustc::traits::Reveal [] [src]

pub enum Reveal {
    UserFacing,
    All,
}
🔬 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?

Depending on the stage of compilation, we want projection to be more or less conservative.

Variants

🔬 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?

At type-checking time, we refuse to project any associated type that is marked default. Non-default ("final") types are always projected. This is necessary in general for soundness of specialization. However, we could allow projections in fully-monomorphic cases. We choose not to, because we prefer for default type to force the type definition to be treated abstractly by any consumers of the impl. Concretely, that means that the following example will fail to compile:

trait Assoc {
    type Output;
}

impl<T> Assoc for T {
    default type Output = bool;
}

fn main() {
    let <() as Assoc>::Output = true;
}
🔬 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?

At trans time, all monomorphic projections will succeed. Also, impl Trait is normalized to the concrete type, which has to be already collected by type-checking.

NOTE: As impl Trait's concrete type should never be observable directly by the user, Reveal::All should not be used by checks which may expose type equality or type contents to the user. There are some exceptions, e.g. around OIBITS and transmute-checking, which expose some details, but not the whole concrete type of the impl Trait.

Trait Implementations

impl<'tcx> HashStable<StableHashingContext<'tcx>> for Reveal
[src]

[src]

🔬 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?

impl Debug for Reveal
[src]

[src]

Formats the value using the given formatter.

impl Copy for Reveal
[src]

impl Clone for Reveal
[src]

[src]

Returns a copy of the value. Read more

1.0.0
[src]

Performs copy-assignment from source. Read more

impl PartialEq for Reveal
[src]

[src]

This method tests for self and other values to be equal, and is used by ==. Read more

1.0.0
[src]

This method tests for !=.

impl Eq for Reveal
[src]

impl Hash for Reveal
[src]

[src]

Feeds this value into the given [Hasher]. Read more

1.3.0
[src]

Feeds a slice of this type into the given [Hasher]. Read more