Ah, that reminds me. A feature I"ve always wanted in rustc is to have better linking of tests to the code they test. Let me try to remember what I had planned...

One thing I wanted was to have "hashtags", so you could put #foo into a test and #foo into the code to link them, and we would report an error if there was a #foo that appeared either only in the code or only in tests.

But I"m wondering now if we could start to compute code coverage reports and maybe even generate a kind of index. Have to think on that one.