Merge #43: impl WriteBase32 for Vec<u5> show cannot fail

cc50e7d `impl WriteBase32 for Vec<u5>` show cannot fail (John Ericson)

Pull request description:

  Use void::Void, which in uninhabited, to do this.

ACKs for top commit:
  apoelstra:
    utACK cc50e7d
  tcharding:
    ACK cc50e7d

Tree-SHA512: 809b001c57a985677ea7e077eca77be964d283474c83dcc10232c4d003711b3c17a84e17381eca5341b7867a44f879806b31140b1430b48ab505a0c965ee6e49

src/lib.rs

@@ -71,7 +71,7 @@ use alloc::borrow::Cow;
 #[cfg(any(feature = "std", test))]
 use std::borrow::Cow;
 
-use core::{fmt, mem};
+use core::{convert::Infallible, fmt, mem};
 
 /// Integer in the range `0..32`
 #[derive(PartialEq, Eq, Debug, Copy, Clone, Default, PartialOrd, Ord, Hash)]
@@ -232,7 +232,7 @@ pub trait FromBase32: Sized {
 }
 
 impl WriteBase32 for Vec<u5> {
-    type Err = ();
+    type Err = Infallible;
 
     fn write(&mut self, data: &[u5]) -> Result<(), Self::Err> {
         self.extend_from_slice(data);