Only `'static` is permitted within type bounds (causes ICE: Cannot relate bound region)

[nikomatsakis]

Once we can declare lifetime parameters, there is no reason not to permit them in type bounds. Also, I am not entirely sure if the way we are handling them is correct/sound. I've tagged places where such bounds appear with FIXMEs so that I can look into them later.

---

Example:

trait Iterable<'a> {
    fn my_iter(&'a self);
}

fn foo<'a, C: Iterable<'a>>(c: C) {
    c.my_iter();
}

fn main() { }

5121.rs:6:5: 6:6 error: internal compiler error: Cannot relate bound region: ReLateBound(12, BrNamed(syntax::ast::DefId{crate: 0u32, node: 21u32}, a)) <= ReInfer(1)
This message reflects a bug in the Rust compiler. 
We would appreciate a bug report: https://github.com/mozilla/rust/wiki/HOWTO-submit-a-Rust-bug-report
5121.rs:6     c.my_iter();
              ^
task 'rustc' failed at 'explicit failure', /home/huon/rust/src/libsyntax/diagnostic.rs:41
task '<main>' failed at 'explicit failure', /home/huon/rust/src/librustc/lib.rs:440

---

pnkfelix: I am adding a checklist to the bottom of this bug, where the unchecked issues represent problems that still remain unfixed (and the entire list of issues were closed as duplicates of this ticket).

• ICE using trait lifetime in a method definition #10391
• Internal compiler error passing an iterator as a parameter. #10467
• Cannot relate bound region: ReInfer(53) <= ReLateBound(284, ... #10841
• ICE: Cannot relate bound region #10868
• ICE: Cannot relate bound region #11016
• ICE: Cannot relate bound region #11446
• ICE when trying to parameterize on ebml::writer::Encoder #11881
• ICE when compiling function w/ Iterator with lifetime constraint #12008
• ICE using struct MyStruct<'a, 'b> { x: &'a MyTrait<'b>,} #12851
• type parameter bounds can't use already defined lifetimes #5715
• Owned trait objects are erroneously permitted to contain references #11971
• ICE on trait method with type parameter bounded by trait with lifetime parameter #12856
• lifetime variables in type bounds not properly enforced #12857

[nikomatsakis]

see also #5715

[emberian]

@nikomatsakis this going to land in time for 0.7? I really hope so, it's really obnoxious.

[emberian]

(Also, 'self is allowed too, I think)

[brson]

Bumping from 0.7

[bblum]

I ran into this when trying to devise a too-clever interface for select2 that would let me avoid code duplication, but it would not let me use non-static borrowed pointers. https://gist.github.com/bblum/6042762

[nikomatsakis]

This will be the final part of #4846. Turns out that this is not so simple as I originally thought (but also not horribly scary or complex). I'll put up a blog post soon (and link it here) describing my proposal.

[nikomatsakis]

See http://smallcultfollowing.com/babysteps/blog/2013/10/29/intermingled-parameter-lists/ for a detailed write-up of the changes I propose to fix this.