rustc_errors: add a new assert for the size of PResult<()>.

Author: eddyb

compiler/rustc_errors/src/lib.rs

@@ -56,6 +56,8 @@ pub type PResult<'a, T> = Result<T, DiagnosticBuilder<'a>>;
 // `PResult` is used a lot. Make sure it doesn't unintentionally get bigger.
 // (See also the comment on `DiagnosticBuilder`'s `diagnostic` field.)
 #[cfg(all(target_arch = "x86_64", target_pointer_width = "64"))]
+rustc_data_structures::static_assert_size!(PResult<'_, ()>, 16);
+#[cfg(all(target_arch = "x86_64", target_pointer_width = "64"))]
 rustc_data_structures::static_assert_size!(PResult<'_, bool>, 24);
 
 #[derive(Debug, PartialEq, Eq, Clone, Copy, Hash, Encodable, Decodable)]