Fix drop-tracking ICE when a struct containing a field with a `Drop` impl is used across an await

Previously, drop-tracking would incorrectly assume the struct would be dropped immediately, which
was not true: when the field had a type with a manual `Drop` impl, the drop becomes observable and
has to be dropped after the await instead.

For reasons I don't understand, this also fixes another error crater popped up related to type parameters.

 #98476

1 files changed, 22 insertions, 0 deletions

diff --git a/src/test/ui/async-await/default-struct-update.rs b/src/test/ui/async-await/default-struct-update.rs
new file mode 100644
index 00000000000..64fb6280dd7
--- /dev/null
+++ b/src/test/ui/async-await/default-struct-update.rs
@@ -0,0 +1,22 @@
+// build-pass
+// edition:2018
+// compile-flags: -Zdrop-tracking=y
+
+fn main() {
+    let _ = foo();
+}
+
+async fn from_config(_: Config) {}
+
+async fn foo() {
+    from_config(Config {
+        nickname: None,
+        ..Default::default()
+    })
+    .await;
+}
+
+#[derive(Default)]
+struct Config {
+    nickname: Option<Box<u8>>,
+}