If you haven't toyed with Rust since late summer when Lifetime elision[1] landed, it's very worth revisiting. That feature made writing out lifetime notations unnecessary in 87% of the standard library. It's made things a lot more pleasant. There's still plenty of room for IDEs and editors to help out, of course, but the language itself is making great strides in usability as it matures.
[1] https://github.com/rust-lang/rfcs/blob/704f0060176418659698e...
Incidentally, the 87% number is a bit misleading. Before the Lifetime Elision RFC, a limited kind of elision was already allowed (when a function borrowed a value but didn't return a borrowed value). The 87% number was the number of lifetime annotations that were still required even with that limited rule that could be removed with the new rule. When taking all kinds of elision into consideration, the number in the standard library is closer to 95%. (many of the remaining cases in the standard library involve the implementation of collections)
In practice, that means that the vast, vast majority of borrowed references don't require explicit lifetime annotations, and that is pretty close to 100% in "application" code built on top of abstractions.
I'm not sure if anyone has done much work to narrow this divide. There are some COQ IDEs out there now, but I'm not sure how effective they are in relieving cognitive burdens while programming.
The irony of the situation is that languages like Rust and Haskell provide a lot of static type feedback that theoretically would make their IDEs very powerful. However, in order for that to really happen, IDE concerns have to be considered very early in the language design process. As a result, we see the tooling crowns going to languages like Dart, whose "type system" is basically designed to make tooling possible (and secondly, for the early detection of errors).
I tried to revive as much information as I could from my days in Visual Studio, but if you have additional feedback, I'm sure he'd be very interested to hear it! Obvious caveats about it being a long-term goal, no immediate plans to tackle it, larsberg is on Servo so what does he know, etc. :-)
Rust's type system doesn't really seem to be there yet: there are just "wrong programs" and "right programs" with not much in between. Gradual typing on the other hand works very well here.
This suggests to me that the most anti-sloppy languages like Rust would benefit the most from sloppy input inference techniques. Has anyone been working on developer tools to make writing Rust code easier? (Lifetime management is the obvious new language feature to target.)
[1] http://groups.csail.mit.edu/uid/other-pubs/sloppy-programmin... (pdf), or less-detailed: http://groups.csail.mit.edu/uid/projects/keyword-commands/in...