This hack was added in 6ab1f05.
I don't know what change allowed removing the hack, but that commit
added a test (which I presume covered the hack's behavior), and all
tests are passing with this change. So, I think it should be good.

Inherent associated types *are* supported, just unstable.

This currently calls `std` a "crate" in one part of the message and a
"module" in another part. The next commits fix this so it says "crate"
in both places.

This allows simplifying a lot of code. It also fixes a subtle bug,
exemplified by the test output changes.

Now that `res` is used directly, it seems the conditional is
unnecessary.

I'm still not sure why this hack works so seemingly well.

These closures were quite complex and part of a quite complex function.
The fact that they are closures makes mistakes likely when refactoring.
For example, earlier, I meant to use `resolved`, an argument of the
closure, but I instead typed `res`, which captured a local variable and
caused a subtle bug that led to a confusing test failure.

Extracting them as functions makes the code easier to understand and
refactor.