[MLton] space leak

[Stephen Weeks]

> Has anyone else noticed a major slowdown in self-compiles?  I'm seeing
> upwards on 99% GC time for passes after defunctorize.  I've watched things
> with -verbose 3, and the IL sizes don't seem to be off.

The self compiles that I ran last night with clean sources completed
in roughly 670s, which is normal these days.  There haven't been any
commits of note today, so it looks likely the problem is on your end.
Maybe you can try with clean sources to see what's up.