renumber regions in the generator interior

Fixes #47189.

src/test/ui/nll/generator-distinct-lifetime.rs

@@ -0,0 +1,38 @@
+// 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, nll)]
+
+// Test for issue #47189. Here, both `s` and `t` are live for the
+// generator's lifetime, but within the generator they have distinct
+// lifetimes.
+//
+// Currently, we accept this code (with NLL enabled) since `x` is only
+// borrowed once at a time -- though whether we should is not entirely
+// obvious to me (the borrows are live over a yield, but then they are
+// re-borrowing borrowed content, etc). Maybe I just haven't had
+// enough coffee today, but I'm not entirely sure at this moment what
+// effect a `suspend` should have on existing borrows. -nmatsakis
+
+fn foo(x: &mut u32) {
+    move || {
+        let s = &mut *x;
+        yield;
+        *s += 1;
+
+        let t = &mut *x;
+        yield;
+        *t += 1;
+    };
+}
+
+fn main() {
+    foo(&mut 0);
+}