to check.
For large, complicated programs, it becomes useful to put some things in `RefCell`s to make things
-simpler. For example, a lot of the maps in [the `ctxt` struct][ctxt] in the Rust compiler internals
+simpler. For example, a lot of the maps in the `ctxt` struct in the Rust compiler internals
are inside this wrapper. These are only modified once (during creation, which is not right after
initialization) or a couple of times in well-separated places. However, since this struct is
pervasively used everywhere, juggling mutable and immutable pointers would be hard (perhaps
[cell-mod]: ../std/cell/
[cell]: ../std/cell/struct.Cell.html
[refcell]: ../std/cell/struct.RefCell.html
-[ctxt]: ../rustc/middle/ty/struct.ctxt.html
# Synchronous types