Rust: Implement await expression using SatisfiesConstraint module

rust/tools/builtins/await.rs

@@ -1,7 +0,0 @@
-use std::future::Future;
-
-fn await_type_matching<T1, T2: Future<Output = T1>>(x: T2) -> T1 {
-    panic!(
-        "This function exists only in order to implement type inference for `.await` expressions."
-    );
-}