Enum rustc::traits::Reveal
[−]
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pub enum Reveal { UserFacing, All, }
rustc_private
)Depending on the stage of compilation, we want projection to be more or less conservative.
Variants
UserFacing
rustc_private
)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; }
All
rustc_private
)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 Debug for Reveal
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impl Copy for Reveal
[src]
impl Clone for Reveal
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fn clone(&self) -> Reveal
Returns a copy of the value. Read more
fn clone_from(&mut self, source: &Self)
1.0.0
Performs copy-assignment from source
. Read more
impl PartialEq for Reveal
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fn eq(&self, __arg_0: &Reveal) -> bool
This method tests for self
and other
values to be equal, and is used by ==
. Read more
fn ne(&self, other: &Rhs) -> bool
1.0.0
This method tests for !=
.