From: Ian Jackson <ijackson@chiark.greenend.org.uk>
Date: Mon, 5 Jun 2023 18:16:21 +0000 (+0100)
Subject: assertc
X-Git-Url: http://www.chiark.greenend.org.uk/ucgi/~ian/git?a=commitdiff_plain;h=1afb95548ec4cd6c85475a16e1ea61295bfcba4f;p=rust-experiments.git

assertc
---

diff --git a/src/main.rs b/src/main.rs
index 959fa1b..9123cea 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -26,6 +26,8 @@ impl HasPseudoMethods for Frog {
     // table.  I'm not sure if that's needed.
     fn get_caster(&self, tp: TypeId) -> Option<&'static dyn Any> {
         if tp == TypeId::of::<&'static dyn HasFeet>() {
+            fn assert_static<X: 'static>(_: X) { }
+            let _ = |x: Box<dyn HasFeet + '_>| assert_static(x);
             static CASTER: fn(&dyn HasPseudoMethods) -> &dyn HasFeet = |self_| {
                 let self_: &dyn Any = Downcast::as_any(self_);
                 let self_: &Frog = self_.downcast_ref().unwrap();