Use do yeet () and do yeet _ instead of None? and Err(_)? in compiler

This prevents breakage when `?` no longer skews inference.

compiler/rustc_infer/src/lib.rs

@@ -27,6 +27,7 @@
 #![feature(iterator_try_collect)]
 #![cfg_attr(bootstrap, feature(min_specialization))]
 #![feature(try_blocks)]
+#![feature(yeet_expr)]
 #![recursion_limit = "512"] // For rustdoc
 
 #[macro_use]