Mark yields after visiting subexpressions. Never ignore yields for scopes in bindings.

src/test/run-pass/generator/borrow-in-yield-expr.rs

@@ -1,21 +0,0 @@
-// Copyright 2017 The Rust Project Developers. See the COPYRIGHT
-// file at the top-level directory of this distribution and at
-// http://rust-lang.org/COPYRIGHT.
-//
-// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
-// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
-// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
-// option. This file may not be copied, modified, or distributed
-// except according to those terms.
-
-#![feature(generators, generator_trait, conservative_impl_trait)]
-
-use std::ops::Generator;
-
-fn bar(baz: String) -> impl Generator<Yield=(), Return=()> {
-    move || {
-        yield drop(&baz);
-    }
-}
-
-fn main() {}