Enum rustc_trait_selection::traits::wf::Elaborate

enum Elaborate {
    All,
    None,
}

Controls whether we “elaborate” supertraits and so forth on the WF predicates. This is a kind of hack to address #43784. The underlying problem in that issue was a trait structure like:

trait Foo: Copy { }
trait Bar: Foo { }
impl<T: Bar> Foo for T { }
impl<T> Bar for T { }

Here, in the Foo impl, we will check that T: Copy holds – but we decide that this is true because T: Bar is in the where-clauses (and we can elaborate that to include T: Copy). This wouldn’t be a problem, except that when we check the Bar impl, we decide that T: Foo must hold because of the Foo impl. And so nowhere did we check that T: Copy holds!

To resolve this, we elaborate the WF requirements that must be proven when checking impls. This means that (e.g.) the impl Bar for T will be forced to prove not only that T: Foo but also T: Copy (which it won’t be able to do, because there is no Copy impl for T).

Variants

All

None

Trait Implementations

impl Clone for Elaborate

fn clone(&self) -> Elaborate

Returns a copy of the value.

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

Performs copy-assignment from source.

impl Debug for Elaborate

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

Formats the value using the given formatter.

impl PartialEq<Elaborate> for Elaborate

fn eq(&self, other: &Elaborate) -> bool

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

fn ne(&self, other: &Rhs) -> bool

This method tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl Copy for Elaborate

impl Eq for Elaborate

impl StructuralEq for Elaborate

impl StructuralPartialEq for Elaborate

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: 1 byte

Size for each variant:

• All: 0 bytes
• None: 0 bytes