Revert "Fix an ICE in the vtable iteration for a trait reference" The ICE fix appears to be unsound, causing a miscompilation involving `dyn Trait` and `async {}` which induces segfaults in safe Rust code. As the patch only hid an ICE, it does not seem worth the risk. This addresses the problem in rust-lang/rust#152735 but it may still merit team discussion even if this PR is merged. This reverts commit 8afd63610b0a261d3c39e24140c6a87d3bff075c, reversing changes made to 19122c03c7bea6bde1dfa5c81fca5810953d9f39.