Improve search_ribs in resolve

[catamorphism]

As per comment: don't use a while loop, and try caching.

[pcwalton]

I don't think this is backwards incompatible.

[graydon]

just a bug, removing milestone/nomination.

[huonw]

Triage: fixme is still there (looks like the while loop could at least be converted to a for, but that's not a fundamental change).

[steveklabnik]

There is no more search_rlibs, and poking around, I couldn't figure out what this might be talking about.

$ git grep -C 10 rlibs | grep while
src/librustc/metadata/loader.rs-//! is a rustc-defined file format (currently just an ar archive) while a dylib

I'm thinking this one can be closed.

[steveklabnik]

Wow, it's ribs not rlibs. The fixme is still there:

rust/src/librustc/middle/resolve.rs

Line 3612 in e2273d9

// FIXME #4950: This should not use a while loop.

[steveklabnik]

Update: this code is now in

rust/src/librustc_resolve/lib.rs

Lines 1742 to 1758 in 216f664

	/// Searches the current set of local scopes and
	/// applies translations for closures.
	fn search_ribs(&self,
	ribs: &[Rib],
	name: Name,
	span: Span)
	-> Option<DefLike> {
	// FIXME #4950: Try caching?
	for (i, rib) in ribs.iter().enumerate().rev() {
	if let Some(def_like) = rib.bindings.get(&name).cloned() {
	return self.upvarify(&ribs[i + 1..], def_like, span);
	}
	}
	None
	}

and the while loop has been fixed.

Caching FIXME is still there.

[gereeter]

search_ribs and the FIXME seem to both be gone. Should this be closed?

[alexcrichton]

Yay!