Auto merge of #29860 - steveklabnik:stackheapfixes, r=huonw
Auto merge of #29860 - steveklabnik:stackheapfixes, r=huonw

Fixes #29853
Fixes #29852

While these points are true, we're not going for 100% accuracy here,
this is introductory material. Changing these things would be more
confusing, but it is important to note that we're presenting an
abstraction here.

r? @huonw

graydon/rust,graydon/rust,graydon/rust,GBGamer/rust,GBGamer/rust,aidancully/rust,GBGamer/rust,aidancully/rust,GBGamer/rust,GBGamer/rust,graydon/rust,GBGamer/rust,aidancully/rust,aidancully/rust,aidancully/rust,GBGamer/rust,graydon/rust,GBGamer/rust,aidancully/rust,graydon/rust