1 files changed, 78 insertions, 0 deletions
diff --git a/tests/ui/generator/size-moved-locals.rs b/tests/ui/generator/size-moved-locals.rs
new file mode 100644
index 000000000..601a31418
--- /dev/null
+++ b/tests/ui/generator/size-moved-locals.rs
@@ -0,0 +1,78 @@
+// run-pass
+// Test that we don't duplicate storage for a variable that is moved to another
+// binding. This used to happen in the presence of unwind and drop edges (see
+// `complex` below.)
+//
+// The exact sizes here can change (we'd like to know when they do). What we
+// don't want to see is the `complex` generator size being upwards of 2048 bytes
+// (which would indicate it is reserving space for two copies of Foo.)
+//
+// See issue #59123 for a full explanation.
+
+// edition:2018
+// ignore-wasm32 issue #62807
+// ignore-asmjs issue #62807
+// needs-unwind Size of Closures change on panic=abort
+
+#![feature(generators, generator_trait)]
+
+use std::ops::Generator;
+
+const FOO_SIZE: usize = 1024;
+struct Foo(#[allow(unused_tuple_struct_fields)] [u8; FOO_SIZE]);
+
+impl Drop for Foo {
+    fn drop(&mut self) {}
+}
+
+fn move_before_yield() -> impl Generator<Yield = (), Return = ()> {
+    static || {
+        let first = Foo([0; FOO_SIZE]);
+        let _second = first;
+        yield;
+        // _second dropped here
+    }
+}
+
+fn noop() {}
+
+fn move_before_yield_with_noop() -> impl Generator<Yield = (), Return = ()> {
+    static || {
+        let first = Foo([0; FOO_SIZE]);
+        noop();
+        let _second = first;
+        yield;
+        // _second dropped here
+    }
+}
+
+// Today we don't have NRVO (we allocate space for both `first` and `second`,)
+// but we can overlap `first` with `_third`.
+fn overlap_move_points() -> impl Generator<Yield = (), Return = ()> {
+    static || {
+        let first = Foo([0; FOO_SIZE]);
+        yield;
+        let second = first;
+        yield;
+        let _third = second;
+        yield;
+    }
+}
+
+fn overlap_x_and_y() -> impl Generator<Yield = (), Return = ()> {
+    static || {
+        let x = Foo([0; FOO_SIZE]);
+        yield;
+        drop(x);
+        let y = Foo([0; FOO_SIZE]);
+        yield;
+        drop(y);
+    }
+}
+
+fn main() {
+    assert_eq!(1025, std::mem::size_of_val(&move_before_yield()));
+    assert_eq!(1026, std::mem::size_of_val(&move_before_yield_with_noop()));
+    assert_eq!(2051, std::mem::size_of_val(&overlap_move_points()));
+    assert_eq!(1026, std::mem::size_of_val(&overlap_x_and_y()));
+}