From e244f625bebb86dbbf5f80da3a5fbcc0eca32dd1 Mon Sep 17 00:00:00 2001
From: Tyler Mandry <tmandry@gmail.com>
Date: Wed, 22 May 2019 15:17:38 -0700
Subject: [PATCH] Add test for DropAndReplace bug

---
 .../run-pass/generator/drop-and-replace.rs    | 44 +++++++++++++++++++
 1 file changed, 44 insertions(+)
 create mode 100644 src/test/run-pass/generator/drop-and-replace.rs

diff --git a/src/test/run-pass/generator/drop-and-replace.rs b/src/test/run-pass/generator/drop-and-replace.rs
new file mode 100644
index 00000000000..042e1276db5
--- /dev/null
+++ b/src/test/run-pass/generator/drop-and-replace.rs
@@ -0,0 +1,44 @@
+// Regression test for incorrect DropAndReplace behavior introduced in #60840
+// and fixed in #61373. When combined with the optimization implemented in
+// #60187, this produced incorrect code for generators when a saved local was
+// re-assigned.
+
+#![feature(generators, generator_trait)]
+
+use std::ops::{Generator, GeneratorState};
+use std::pin::Pin;
+
+#[derive(Debug, PartialEq)]
+struct Foo(i32);
+
+impl Drop for Foo {
+    fn drop(&mut self) { }
+}
+
+fn main() {
+    let mut a = || {
+        let mut x = Foo(4);
+        yield;
+        assert_eq!(x.0, 4);
+
+        // At one point this tricked our dataflow analysis into thinking `x` was
+        // StorageDead after the assignment.
+        x = Foo(5);
+        assert_eq!(x.0, 5);
+
+        {
+            let y = Foo(6);
+            yield;
+            assert_eq!(y.0, 6);
+        }
+
+        assert_eq!(x.0, 5);
+    };
+
+    loop {
+        match Pin::new(&mut a).resume() {
+            GeneratorState::Complete(()) => break,
+            _ => (),
+        }
+    }
+}