Enum LateParamRegionKind 

pub enum LateParamRegionKind {
    Anon(u32),
    NamedAnon(u32, Symbol),
    Named(DefId),
    ClosureEnv,
}

When liberating bound regions, we map their BoundRegionKind to this as we need to track the index of anonymous regions. We otherwise end up liberating multiple bound regions to the same late-bound region.

Variants

Anon(u32)

An anonymous region parameter for a given fn (&T)

Unlike BoundRegionKind::Anon, this tracks the index of the liberated bound region.

We should ideally never liberate anonymous regions, but do so for the sake of diagnostics in FnCtxt::sig_of_closure_with_expectation.

NamedAnon(u32, Symbol)

An anonymous region parameter with a Symbol name.

Used to give late-bound regions names for things like pretty printing.

Named(DefId)

Late-bound regions that appear in the AST.

ClosureEnv

Anonymous region for the implicit env pointer parameter to a closure