---

yaml
---
r: 224520
b: refs/heads/beta
c: 99043dd
h: refs/heads/master
v: v3

Author: Gankra

[refs]

@@ -23,7 +23,7 @@ refs/tags/0.9: 36870b185fc5f5486636d4515f0e22677493f225
 refs/tags/0.10: ac33f2b15782272ae348dbd7b14b8257b2148b5a
 refs/tags/0.11.0: e1247cb1d0d681be034adb4b558b5a0c0d5720f9
 refs/tags/0.12.0: f0c419429ef30723ceaf6b42f9b5a2aeb5d2e2d1
-refs/heads/beta: 5f6e0abe27aa6632f95492ad8864d8084c1bacef
+refs/heads/beta: 99043dde9dd2d0507ad2e3cda65b9d3e9244f13f
 refs/tags/1.0.0-alpha: e42bd6d93a1d3433c486200587f8f9e12590a4d7
 refs/heads/tmp: 938f5d7af401e2d8238522fed4a612943b6e77fd
 refs/tags/1.0.0-alpha.2: 4c705f6bc559886632d3871b04f58aab093bfa2f

branches/beta/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.