Lifetime in rustc_hir::hir - Rust
Description: A lifetime. The valid field combinations are non-obvious and not all combinations are possible. The following example shows some of them. See also the comments on `LifetimeKind` and `LifetimeSource`.

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## Lifetime

# Struct Lifetime

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    #[repr(align(4))]pub struct Lifetime {
        pub hir_id: HirId,
        pub ident: Ident,
        pub kind: LifetimeKind,
        pub source: LifetimeSource,
        pub syntax: LifetimeSyntax,
    }

Expand description

A lifetime. The valid field combinations are non-obvious and not all combinations are possible. The following example shows some of them. See also the comments on `LifetimeKind` and `LifetimeSource`.

    #[repr(C)]
    struct S<'a>(&'a u32);       // res=Param, name='a, source=Reference, syntax=ExplicitBound
    unsafe extern "C" {
        fn f1(s: S);             // res=Param, name='_, source=Path, syntax=Implicit
        fn f2(s: S<'_>);         // res=Param, name='_, source=Path, syntax=ExplicitAnonymous
        fn f3<'a>(s: S<'a>);     // res=Param, name='a, source=Path, syntax=ExplicitBound
    }

    struct St<'a> { x: &'a u32 } // res=Param, name='a, source=Reference, syntax=ExplicitBound
    fn f() {
        _ = St { x: &0 };        // res=Infer, name='_, source=Path, syntax=Implicit
        _ = St::<'_> { x: &0 };  // res=Infer, name='_, source=Path, syntax=ExplicitAnonymous
    }

    struct Name<'a>(&'a str);    // res=Param,  name='a, source=Reference, syntax=ExplicitBound
    const A: Name = Name("a");   // res=Static, name='_, source=Path, syntax=Implicit
    const B: &str = "";          // res=Static, name='_, source=Reference, syntax=Implicit
    static C: &'_ str = "";      // res=Static, name='_, source=Reference, syntax=ExplicitAnonymous
    static D: &'static str = ""; // res=Static, name='static, source=Reference, syntax=ExplicitBound

    trait Tr {}
    fn tr(_: Box<dyn Tr>) {}     // res=ImplicitObjectLifetimeDefault, name='_, source=Other, syntax=Implicit

    fn capture_outlives<'a>() ->
        impl FnOnce() + 'a       // res=Param, ident='a, source=OutlivesBound, syntax=ExplicitBound
    {
        || {}
    }

    fn capture_precise<'a>() ->
        impl FnOnce() + use<'a>  // res=Param, ident='a, source=PreciseCapturing, syntax=ExplicitBound
    {
        || {}
    }

    // (commented out because these cases trigger errors)
    // struct S1<'a>(&'a str);   // res=Param, name='a, source=Reference, syntax=ExplicitBound
    // struct S2(S1);            // res=Error, name='_, source=Path, syntax=Implicit
    // struct S3(S1<'_>);        // res=Error, name='_, source=Path, syntax=ExplicitAnonymous
    // struct S4(S1<'a>);        // res=Error, name='a, source=Path, syntax=ExplicitBound

Some combinations that cannot occur are `LifetimeSyntax::Implicit` with `LifetimeSource::OutlivesBound` or `LifetimeSource::PreciseCapturing` — there’s no way to “elide” these lifetimes.

## Fields§

§`hir_id: HirId`§`ident: Ident`

Either a named lifetime definition (e.g. `'a`, `'static`) or an anonymous lifetime (`'_`, either explicitly written, or inserted for things like `&type`).

§`kind: LifetimeKind`

Semantics of this lifetime.

§`source: LifetimeSource`

The context in which the lifetime occurred. See `Lifetime::suggestion` for example use.

§`syntax: LifetimeSyntax`

The syntax that the user used to declare this lifetime. See `Lifetime::suggestion` for example use.

## Implementations§

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### impl Lifetime

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#### pub fn new( hir_id: HirId, ident: Ident, kind: LifetimeKind, source: LifetimeSource, syntax: LifetimeSyntax, ) -> Lifetime

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#### pub fn is_elided(&self) -> bool

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#### pub fn is_anonymous(&self) -> bool

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#### pub fn is_implicit(&self) -> bool

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#### pub fn is_static(&self) -> bool

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#### pub fn suggestion(&self, new_lifetime: &str) -> (Span, String)

## Trait Implementations§

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### impl Clone for Lifetime

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#### fn clone(&self) -> Lifetime

Returns a duplicate of the value. Read more
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#### fn clone_from(&mut self, source: &Self)

Performs copy-assignment from `source`. Read more
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### impl Copy for Lifetime

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### impl Debug for Lifetime

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#### fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter. Read more
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### impl Display for Lifetime

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#### fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter. Read more
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### impl StableHash for Lifetime

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#### fn stable_hash<__Hcx: StableHashCtxt>( &self, __hcx: &mut __Hcx, __hasher: &mut StableHasher, )

## Auto Trait Implementations§

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### impl DynSend for Lifetime

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### impl DynSync for Lifetime

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### impl Freeze for Lifetime

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### impl RefUnwindSafe for Lifetime

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### impl Send for Lifetime

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### impl Sync for Lifetime

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### impl Unpin for Lifetime

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### impl UnsafeUnpin for Lifetime

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### impl UnwindSafe for Lifetime

## Blanket Implementations§

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### impl<T> Aligned for T

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#### const ALIGN: Alignment

Alignment of `Self`.
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### impl<T> Any for T
where T: 'static + ?Sized,

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#### fn type_id(&self) -> TypeId

Gets the `TypeId` of `self`. Read more
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### impl<'tcx, T> ArenaAllocatable<'tcx, IsCopy> for T
where T: Copy,

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#### fn allocate_on(self, arena: &'tcx Arena<'tcx>) -> &'tcx mut T

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#### fn allocate_from_iter( arena: &'tcx Arena<'tcx>, iter: impl IntoIterator<Item = T>, ) -> &'tcx mut [T]

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### impl<T> Borrow<T> for T
where T: ?Sized,

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#### fn borrow(&self) -> &T

Immutably borrows from an owned value. Read more
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### impl<T> BorrowMut<T> for T
where T: ?Sized,

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#### fn borrow_mut(&mut self) -> &mut T

Mutably borrows from an owned value. Read more
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### impl<T> CloneToUninit for T
where T: Clone,

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#### unsafe fn clone_to_uninit(&self, dest: *mut u8)

🔬This is a nightly-only experimental API. (`clone_to_uninit`)
Performs copy-assignment from `self` to `dest`. Read more
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### impl<T> DynClone for T
where T: Clone,

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#### fn __clone_box(&self, _: Private) -> *mut ()

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### impl<T> ErasedDestructor for T
where T: 'static,

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### impl<T> From<T> for T

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#### fn from(t: T) -> T

Returns the argument unchanged.

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### impl<T> Instrument for T

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#### fn instrument(self, span: Span) -> Instrumented<Self>

Instruments this type with the provided `Span`, returning an `Instrumented` wrapper. Read more
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#### fn in_current_span(self) -> Instrumented<Self>

Instruments this type with the current `Span`, returning an `Instrumented` wrapper. Read more
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### impl<T, U> Into<U> for T
where U: From<T>,

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#### fn into(self) -> U

Calls `U::from(self)`.

That is, this conversion is whatever the implementation of `From<T> for U` chooses to do.

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### impl<T> IntoEither for T

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#### fn into_either(self, into_left: bool) -> Either<Self, Self>

Converts `self` into a `Left` variant of `Either<Self, Self>` if `into_left` is `true`. Converts `self` into a `Right` variant of `Either<Self, Self>` otherwise. Read more
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#### fn into_either_with<F>(self, into_left: F) -> Either<Self, Self>
where F: FnOnce(&Self) -> bool,

Converts `self` into a `Left` variant of `Either<Self, Self>` if `into_left(&self)` returns `true`. Converts `self` into a `Right` variant of `Either<Self, Self>` otherwise. Read more
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### impl<T> Pointable for T

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#### const ALIGN: usize

The alignment of pointer.
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#### type Init = T

The type for initializers.
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#### unsafe fn init(init: <T as Pointable>::Init) -> usize

Initializes a with the given initializer. Read more
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#### unsafe fn deref<'a>(ptr: usize) -> &'a T

Dereferences the given pointer. Read more
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#### unsafe fn deref_mut<'a>(ptr: usize) -> &'a mut T

Mutably dereferences the given pointer. Read more
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#### unsafe fn drop(ptr: usize)

Drops the object pointed to by the given pointer. Read more
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### impl<T> Same for T

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#### type Output = T

Should always be `Self`
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### impl<T> ToOwned for T
where T: Clone,

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#### type Owned = T

The resulting type after obtaining ownership.
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#### fn to_owned(&self) -> T

Creates owned data from borrowed data, usually by cloning. Read more
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#### fn clone_into(&self, target: &mut T)

Uses borrowed data to replace owned data, usually by cloning. Read more
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### impl<T> ToString for T
where T: Display + ?Sized,

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#### fn to_string(&self) -> String

Converts the given value to a `String`. Read more
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### impl<T, U> TryFrom<U> for T
where U: Into<T>,

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#### type Error = Infallible

The type returned in the event of a conversion error.
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#### fn try_from(value: U) -> Result<T, <T as TryFrom<U>>::Error>

Performs the conversion.
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### impl<T, U> TryInto<U> for T
where U: TryFrom<T>,

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#### type Error = <U as TryFrom<T>>::Error

The type returned in the event of a conversion error.
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#### fn try_into(self) -> Result<U, <U as TryFrom<T>>::Error>

Performs the conversion.
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### impl<V, T> VZip<V> for T
where V: MultiLane<T>,

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#### fn vzip(self) -> V

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### impl<T> WithSubscriber for T

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#### fn with_subscriber<S>(self, subscriber: S) -> WithDispatch<Self>
where S: Into<Dispatch>,

Attaches the provided `Subscriber` to this type, returning a `WithDispatch` wrapper. Read more
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#### fn with_current_subscriber(self) -> WithDispatch<Self>

Attaches the current default `Subscriber` to this type, returning a `WithDispatch` wrapper. Read more

## 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: 28 bytes