Check coroutine upvars and resume ty in dtorck constraint

Author: compiler-errors

compiler/rustc_trait_selection/src/traits/query/dropck_outlives.rs

@@ -344,9 +344,14 @@ pub fn dtorck_constraint_for_ty_inner<'tcx>(
             let args = args.as_coroutine();
 
             // While we conservatively assume that all coroutines require drop
-            // to avoid query cycles during MIR building, we can check the actual
-            // witness during borrowck to avoid unnecessary liveness constraints.
-            if args.witness().needs_drop(tcx, tcx.erase_regions(typing_env)) {
+            // to avoid query cycles during MIR building, we can be more precise
+            // here and check the specific components of the coroutines. This
+            // includes the witness types, upvars, *and* the resume ty.
+            let typing_env = tcx.erase_regions(typing_env);
+            let needs_drop = args.witness().needs_drop(tcx, typing_env)
+                || args.upvar_tys().iter().any(|ty| ty.needs_drop(tcx, typing_env))
+                || args.resume_ty().needs_drop(tcx, typing_env);
+            if needs_drop {
                 constraints.outlives.extend(args.upvar_tys().iter().map(ty::GenericArg::from));
                 constraints.outlives.push(args.resume_ty().into());
             }

tests/ui/async-await/drop-live-upvar.rs

@@ -0,0 +1,23 @@
+//@ edition: 2018
+// Regression test for <https://github.com/rust-lang/rust/issues/144155>.
+
+struct NeedsDrop<'a>(&'a Vec<i32>);
+
+async fn await_point() {}
+
+impl Drop for NeedsDrop<'_> {
+    fn drop(&mut self) {}
+}
+
+fn foo() {
+    let v = vec![1, 2, 3];
+    let x = NeedsDrop(&v);
+    let c = async {
+        std::future::ready(()).await;
+        drop(x);
+    };
+    drop(v);
+    //~^ ERROR cannot move out of `v` because it is borrowed
+}
+
+fn main() {}

tests/ui/async-await/drop-live-upvar.stderr

@@ -0,0 +1,22 @@
+error[E0505]: cannot move out of `v` because it is borrowed
+  --> $DIR/drop-live-upvar.rs:19:10
+   |
+LL |     let v = vec![1, 2, 3];
+   |         - binding `v` declared here
+LL |     let x = NeedsDrop(&v);
+   |                       -- borrow of `v` occurs here
+...
+LL |     drop(v);
+   |          ^ move out of `v` occurs here
+LL |
+LL | }
+   | - borrow might be used here, when `c` is dropped and runs the destructor for coroutine
+   |
+help: consider cloning the value if the performance cost is acceptable
+   |
+LL |     let x = NeedsDrop(&v.clone());
+   |                         ++++++++
+
+error: aborting due to 1 previous error
+
+For more information about this error, try `rustc --explain E0505`.