Cleanup lifetime and pointer guides

[alan-andrade]

My main goals were:

• be clear when we talk about "references" and "pointers"
• remove Managed boxes completely and the concept of GC.

#13987

[emberian]

Don't use emphasis around here, it's distracting.

[emberian]

Thanks for doing this! Clean docs are really important.

[alan-andrade]

ready for a second review.

[emberian]

Comments from someone on IRC:

<anon>  (region pointers),
<anon>  usually introduced as (e.g. region pointers)
<anon>  (or some other latin thing)
<anon>  Therefore, the best way to explain how
<anon>  i'd drop Therefore
<anon>
<anon>  point to, instead, they
<anon>  run-on-y
<anon>  point to. Instead, they might be better
<anon>
<anon>  As an example, consider a simple struct type  Point : drop as an example
<anon>  drop many of those phrases
<anon>  im seeing a lot
<anon>  but if you really wan t one, "In the following code" or similar is better
<anon>
<anon>  In order to convert  Box<T>  into a  &T , we need to use  &* .
<anon>  might that be better broken up into the two operations?
<anon>  if it even is
<anon>  I imagine that you would first deference(whatever it is)
<anon>  then take the address of
<anon>  new users might mistakenly think of that as one operation
<anon>  and if it is, then its fine
<anon>
<anon>  the other uses for the & operator section is ehhhhh
<anon>  under borrowing and enums
<anon>  everyone might not know what tau is
<anon>  might want to put it before the code
<anon>
<anon>  if you borrow a structs or boxes to create a reference,
<anon>  that pluralization/possessivation is wrong

[ftxqxd]

GitHub won’t let me comment on it, but four lines up (line 290/197) it reads ‘Here, as before, the interior of the variable x…’. That previous section was removed, so you should probably remove the ‘as before’ part.

[alan-andrade]

ohhh, nice catch! thanks

[alan-andrade]

Ready for a third review.