Struct Lifetime

pub struct Lifetime {
    pub hir_id: HirId,
    pub ident: Ident,
    pub kind: LifetimeKind,
    pub source: LifetimeSource,
    pub syntax: LifetimeSyntax,
}

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=Named
unsafe extern "C" {
    fn f1(s: S);             // res=Param, name='_, source=Path, syntax=Hidden
    fn f2(s: S<'_>);         // res=Param, name='_, source=Path, syntax=Anonymous
    fn f3<'a>(s: S<'a>);     // res=Param, name='a, source=Path, syntax=Named
}

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

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

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

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

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

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

Some combinations that cannot occur are LifetimeSyntax::Hidden 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

impl Lifetime

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

pub fn is_elided(&self) -> bool

pub fn is_anonymous(&self) -> bool

pub fn is_syntactically_hidden(&self) -> bool

pub fn is_syntactically_anonymous(&self) -> bool

pub fn is_static(&self) -> bool

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

Trait Implementations

impl Clone for Lifetime

fn clone(&self) -> Lifetime

Returns a copy of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for Lifetime

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

Formats the value using the given formatter.

impl Display for Lifetime

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

Formats the value using the given formatter.

impl<__CTX> HashStable<__CTX> for Lifetime

where __CTX: HashStableContext,

fn hash_stable(&self, __hcx: &mut __CTX, __hasher: &mut StableHasher)

impl Copy for Lifetime

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