Add assertion for TextSized impls

Author: CAD97

src/traits.rs

@@ -34,3 +34,23 @@ impl TextSized for char {
         (self.len_utf8() as u32).into()
     }
 }
+
+// assertion shape from static_assertions::assert_impl_all!
+const _: fn() = || {
+    use std::borrow::Cow;
+
+    fn assert_impl<T: TextSized>() {}
+
+    assert_impl::<&String>();
+    assert_impl::<&Cow<str>>();
+
+    struct StringLike {}
+    impl Deref for StringLike {
+        type Target = str;
+        fn deref(&self) -> &str {
+            unreachable!()
+        }
+    }
+
+    assert_impl::<&StringLike>();
+};