Merge rust-bitcoin/rust-bitcoin#3280: Remove bool from const_assert

c71b23d81d Remove bool from cont_assert (Tobin C. Harding)

Pull request description:

  It was correctly pointed out during review of #3215 (when we made `const_assert` panic) that using a `bool` added no additional information.

  Remove the `bool` and just use unit.

ACKs for top commit:
  apoelstra:
    ACK c71b23d81d successfully ran local tests; lol sure
  Kixunil:
    ACK c71b23d81d

Tree-SHA512: be9f4f10ee7d626a082b7ae9f257b79d500824ed3c1f7327391b2ad4d67e60d7da47a14fa7ef8f99d1ea8157967b4658518cbcf1c1bfcf1d8888455f3eb96437

internals/src/macros.rs

@@ -140,12 +140,11 @@ macro_rules! debug_from_display {
 #[macro_export]
 macro_rules! const_assert {
     ($x:expr $(; $message:expr)?) => {
-        const _: bool = {
+        const _: () = {
             if !$x {
                 // We can't use formatting in const, only concating literals.
                 panic!(concat!("assertion ", stringify!($x), " failed" $(, ": ", $message)?))
             }
-            $x
         };
     }
 }