[Pre-RFC] Backward-compatible GATification

[voidc]

@CAD97

You could provide impl LendingIterator for <impl Iterator> by just discarding the lifetime generic, but you can't impl Iterator for <impl LendingIterator> .

This is exactly what I meant. Maybe my wording is imprecise. Given a non-lending T: Iterator a impl LendingIterator for T can be provided trivially. (i.e. non-lending iterators are a special case)

@CAD97

I seem to recall arguing that this isn't possible

At least in Closures that can return references to captured variables - #4 by CAD97, you wrote:

@CAD97

Underspecified, but I think possible, somewhat realistic given other lifetime inference rules, and potentially desirable if it allows us to reuse existing traits for the lending versions.

@quinedot

You would need elision ( Item<'_> , to be filled in by the lifetime on &mut self ) and not 'static .

Hmm, you are right. Maybe we only need "defaults" for type parameters and lifetimes are elided if not specified. Are there cases where elision would not work?