Enum rustc::hir::lowering::AnonymousLifetimeMode [−][src]
enum AnonymousLifetimeMode { CreateParameter, PassThrough, }
🔬 This is a nightly-only experimental API. (rustc_private
)
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instead?
What to do when we encounter an anonymous lifetime
reference. Anonymous lifetime references come in two flavors. You
have implicit, or fully elided, references to lifetimes, like the
one in &T
or Ref<T>
, and you have '_
lifetimes, like &'_ T
or Ref<'_, T>
. These often behave the same, but not always:
- certain usages of implicit references are deprecated, like
Ref<T>
, and we sometimes just give hard errors in those cases as well. - for object bounds there is a difference:
Box<dyn Foo>
is not the same asBox<dyn Foo + '_>
.
We describe the effects of the various modes in terms of three cases:
- Modern -- includes all uses of
'_
, but also the lifetime arg of a&
(e.g., the missing lifetime in something like&T
) - Dyn Bound -- if you have something like
Box<dyn Foo>
, there is an elided lifetime bound (Box<dyn Foo + 'X>
). These elided bounds follow special rules. Note that this only covers cases where nothing is written; the'_
inBox<dyn Foo + '_>
is a case of "modern" elision. - Deprecated -- this coverse cases like
Ref<T>
, where the lifetime parameter to ref is completely elided.Ref<'_, T>
would be the modern, non-deprecated equivalent.
Currently, the handling of lifetime elision is somewhat spread out
between HIR lowering and -- as described below -- the
resolve_lifetime
module. Often we "fallthrough" to that code by generating
an "elided" or "underscore" lifetime name. In the future, we probably want to move
everything into HIR lowering.
Variants
CreateParameter
🔬 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?
For Modern cases, create a new anonymous region parameter and reference that.
For Dyn Bound cases, pass responsibility to
resolve_lifetime
code.
For Deprecated cases, report an error.
PassThrough
🔬 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?
Pass responsibility to resolve_lifetime
code for all cases.
Trait Implementations
impl Copy for AnonymousLifetimeMode
[src]
impl Copy for AnonymousLifetimeMode
impl Clone for AnonymousLifetimeMode
[src]
impl Clone for AnonymousLifetimeMode
fn clone(&self) -> AnonymousLifetimeMode
[src]
fn clone(&self) -> AnonymousLifetimeMode
Returns a copy of the value. Read more
fn clone_from(&mut self, source: &Self)
1.0.0[src]
fn clone_from(&mut self, source: &Self)
Performs copy-assignment from source
. Read more
Auto Trait Implementations
impl Send for AnonymousLifetimeMode
impl Send for AnonymousLifetimeMode
impl Sync for AnonymousLifetimeMode
impl Sync for AnonymousLifetimeMode