Struct rustc_trait_selection::infer::region_constraints::VerifyIfEq

pub struct VerifyIfEq<'tcx> {
    pub ty: Ty<'tcx>,
    pub bound: Region<'tcx>,
}

This is a “conditional bound” that checks the result of inference and supplies a bound if it ended up being relevant. It’s used in situations like this:

fn foo<'a, 'b, T: SomeTrait<'a>>
where
   <T as SomeTrait<'a>>::Item: 'b

If we have an obligation like <T as SomeTrait<'?x>>::Item: 'c, then we don’t know yet whether it suffices to show that 'b: 'c. If '?x winds up being equal to 'a, then the where-clauses on function applies, and in that case we can show 'b: 'c. But if '?x winds up being something else, the bound isn’t relevant.

In the VerifyBound, this struct is enclosed in Binder to account for cases like

where for<'a> <T as SomeTrait<'a>::Item: 'a

The idea is that we have to find some instantiation of 'a that can make <T as SomeTrait<'a>>::Item equal to the final value of G, the generic we are checking.

fn(min) -> bool {
    exists<'a> {
        if G == K {
            B(min)
        } else {
            false
        }
    }
}

Fields

ty: Ty<'tcx>

Type which must match the generic G

bound: Region<'tcx>

Bound that applies if ty is equal.

Trait Implementations

impl<'tcx> Clone for VerifyIfEq<'tcx>

fn clone(&self) -> VerifyIfEq<'tcx>

Returns a copy of the value.

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

Performs copy-assignment from source.

impl<'tcx> Debug for VerifyIfEq<'tcx>

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

Formats the value using the given formatter.

impl<'tcx> TypeFoldable<TyCtxt<'tcx>> for VerifyIfEq<'tcx>

fn try_fold_with<__F>( self, __folder: &mut __F, ) -> Result<VerifyIfEq<'tcx>, <__F as FallibleTypeFolder<TyCtxt<'tcx>>>::Error>

where __F: FallibleTypeFolder<TyCtxt<'tcx>>,

The entry point for folding. To fold a value t with a folder f call: t.try_fold_with(f).

fn fold_with<F>(self, folder: &mut F) -> Self

where F: TypeFolder<I>,

A convenient alternative to try_fold_with for use with infallible folders. Do not override this method, to ensure coherence with try_fold_with.

impl<'tcx> TypeVisitable<TyCtxt<'tcx>> for VerifyIfEq<'tcx>

fn visit_with<__V>( &self, __visitor: &mut __V, ) -> <__V as TypeVisitor<TyCtxt<'tcx>>>::Result

where __V: TypeVisitor<TyCtxt<'tcx>>,

The entry point for visiting. To visit a value t with a visitor v call: t.visit_with(v).

impl<'tcx> Copy for VerifyIfEq<'tcx>

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: 16 bytes