---

yaml
---
r: 229032
b: refs/heads/try
c: 99043dd
h: refs/heads/master
v: v3

Author: Gankra

[refs]

@@ -1,7 +1,7 @@
 ---
 refs/heads/master: aca2057ed5fb7af3f8905b2bc01f72fa001c35c8
 refs/heads/snap-stage3: 1af31d4974e33027a68126fa5a5a3c2c6491824f
-refs/heads/try: 5f6e0abe27aa6632f95492ad8864d8084c1bacef
+refs/heads/try: 99043dde9dd2d0507ad2e3cda65b9d3e9244f13f
 refs/tags/release-0.1: 1f5c5126e96c79d22cb7862f75304136e204f105
 refs/tags/release-0.2: c870d2dffb391e14efb05aa27898f1f6333a9596
 refs/tags/release-0.3: b5f0d0f648d9a6153664837026ba1be43d3e2503

branches/try/src/doc/tarpl/exotic-sizes.md

@@ -95,10 +95,9 @@ actually possible to communicate this at the type level by returning a
 knowing that it's *statically impossible* for this value to be an `Err`, as
 this would require providing a value of type Void.
 
-In principle, Rust can do some interesting analysees and optimizations based
+In principle, Rust can do some interesting analyses and optimizations based
 on this fact. For instance, `Result<T, Void>` could be represented as just `T`,
-because the Err case doesn't actually exist. Also in principle the following
-could compile:
+because the Err case doesn't actually exist. The following *could* also compile:
 
 ```rust,ignore
 enum Void {}
@@ -111,3 +110,9 @@ let Ok(num) = res;
 
 But neither of these tricks work today, so all Void types get you today is
 the ability to be confident that certain situations are statically impossible.
+
+One final subtle detail about empty types is that raw pointers to them are
+actually valid to construct, but dereferencing them is Undefined Behaviour
+because that doesn't actually make sense. That is, you could model C's `void *`
+type with `*const Void`, but this doesn't necessarily gain anything over using
+e.g. `*const ()`, which *is* safe to randomly dereference.