pub enum RegionClassification {



A global region is one that can be named from anywhere. There is only one, 'static.


An external region is only relevant for closures, generators, and inline consts. In that case, it refers to regions that are free in the type – basically, something bound in the surrounding context.

Consider this example:

fn foo<'a, 'b>(a: &'a u32, b: &'b u32, c: &'static u32) {
  let closure = for<'x> |x: &'x u32| { .. };
   //           ^^^^^^^ pretend this were legal syntax
   //                   for declaring a late-bound region in
   //                   a closure signature

Here, the lifetimes 'a and 'b would be external to the closure.

If we are not analyzing a closure/generator/inline-const, there are no external lifetimes.


A local lifetime is one about which we know the full set of relevant constraints (that is, relationships to other named regions). For a closure, this includes any region bound in the closure’s signature. For a fn item, this includes all regions other than global ones.

Continuing with the example from External, if we were analyzing the closure, then 'x would be local (and 'a and 'b are external). If we are analyzing the function item foo, then 'a and 'b are local (and 'x is not in scope).

Trait Implementations

Formats the value using the given formatter. Read more

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

This method tests for !=.

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Gets the TypeId of self. Read more

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Mutably borrows from an owned value. Read more

Returns the argument unchanged.

Calls U::from(self).

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

The type returned in the event of a conversion error.

Performs the conversion.

The type returned in the event of a conversion error.

Performs the conversion.


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: 1 byte

Size for each variant:

  • Global: 0 bytes
  • External: 0 bytes
  • Local: 0 bytes