Auto merge of #93165 - eholk:disable-generator-drop-tracking, r=nikomatsakis

Disable drop range tracking in generators

Generator drop tracking caused an ICE for generators involving the Never type (Issue #93161). Since this breaks a test case with miri, we temporarily disable drop tracking so miri is unblocked while we properly fix the issue.

Author: bors

compiler/rustc_typeck/src/check/generator_interior.rs

@@ -22,6 +22,11 @@ use tracing::debug;
 
 mod drop_ranges;
 
+// FIXME(eholk): This flag is here to give a quick way to disable drop tracking in case we find
+// unexpected breakages while it's still new. It should be removed before too long. For example,
+// see #93161.
+const ENABLE_DROP_TRACKING: bool = false;
+
 struct InteriorVisitor<'a, 'tcx> {
     fcx: &'a FnCtxt<'a, 'tcx>,
     types: FxIndexSet<ty::GeneratorInteriorTypeCause<'tcx>>,
@@ -77,7 +82,10 @@ impl<'a, 'tcx> InteriorVisitor<'a, 'tcx> {
                                 yield_data.expr_and_pat_count, self.expr_count, source_span
                             );
 
-                            if self.drop_ranges.is_dropped_at(hir_id, yield_data.expr_and_pat_count)
+                            if ENABLE_DROP_TRACKING
+                                && self
+                                    .drop_ranges
+                                    .is_dropped_at(hir_id, yield_data.expr_and_pat_count)
                             {
                                 debug!("value is dropped at yield point; not recording");
                                 return false;

src/test/ui/async-await/async-fn-nonsend.rs

@@ -1,6 +1,10 @@
 // edition:2018
 // compile-flags: --crate-type lib
 
+// FIXME(eholk): temporarily disabled while drop range tracking is disabled
+// (see generator_interior.rs:27)
+// ignore-test
+
 use std::{cell::RefCell, fmt::Debug, rc::Rc};
 
 fn non_sync() -> impl Debug {

src/test/ui/async-await/unresolved_type_param.rs

@@ -3,6 +3,10 @@
 // (rather than give a general error message)
 // edition:2018
 
+// FIXME(eholk): temporarily disabled while drop range tracking is disabled
+// (see generator_interior.rs:27)
+// ignore-test
+
 async fn bar<T>() -> () {}
 
 async fn foo() {

src/test/ui/generator/drop-control-flow.rs

@@ -1,5 +1,9 @@
 // build-pass
 
+// FIXME(eholk): temporarily disabled while drop range tracking is disabled
+// (see generator_interior.rs:27)
+// ignore-test
+
 // A test to ensure generators capture values that were conditionally dropped,
 // and also that values that are dropped along all paths to a yield do not get
 // included in the generator type.

src/test/ui/generator/issue-57478.rs

@@ -1,5 +1,9 @@
 // check-pass
 
+// FIXME(eholk): temporarily disabled while drop range tracking is disabled
+// (see generator_interior.rs:27)
+// ignore-test
+
 #![feature(negative_impls, generators)]
 
 struct Foo;

src/test/ui/generator/issue-93161.rs

@@ -0,0 +1,93 @@
+// edition:2021
+// run-pass
+
+#![feature(never_type)]
+
+use std::future::Future;
+
+// See if we can run a basic `async fn`
+pub async fn foo(x: &u32, y: u32) -> u32 {
+    let y = &y;
+    let z = 9;
+    let z = &z;
+    let y = async { *y + *z }.await;
+    let a = 10;
+    let a = &a;
+    *x + y + *a
+}
+
+async fn add(x: u32, y: u32) -> u32 {
+    let a = async { x + y };
+    a.await
+}
+
+async fn build_aggregate(a: u32, b: u32, c: u32, d: u32) -> u32 {
+    let x = (add(a, b).await, add(c, d).await);
+    x.0 + x.1
+}
+
+enum Never {}
+fn never() -> Never {
+    panic!()
+}
+
+async fn includes_never(crash: bool, x: u32) -> u32 {
+    let mut result = async { x * x }.await;
+    if !crash {
+        return result;
+    }
+    #[allow(unused)]
+    let bad = never();
+    result *= async { x + x }.await;
+    drop(bad);
+    result
+}
+
+async fn partial_init(x: u32) -> u32 {
+    #[allow(unreachable_code)]
+    let _x: (String, !) = (String::new(), return async { x + x }.await);
+}
+
+async fn read_exact(_from: &mut &[u8], _to: &mut [u8]) -> Option<()> {
+    Some(())
+}
+
+async fn hello_world() {
+    let data = [0u8; 1];
+    let mut reader = &data[..];
+
+    let mut marker = [0u8; 1];
+    read_exact(&mut reader, &mut marker).await.unwrap();
+}
+
+fn run_fut<T>(fut: impl Future<Output = T>) -> T {
+    use std::sync::Arc;
+    use std::task::{Context, Poll, Wake, Waker};
+
+    struct MyWaker;
+    impl Wake for MyWaker {
+        fn wake(self: Arc<Self>) {
+            unimplemented!()
+        }
+    }
+
+    let waker = Waker::from(Arc::new(MyWaker));
+    let mut context = Context::from_waker(&waker);
+
+    let mut pinned = Box::pin(fut);
+    loop {
+        match pinned.as_mut().poll(&mut context) {
+            Poll::Pending => continue,
+            Poll::Ready(v) => return v,
+        }
+    }
+}
+
+fn main() {
+    let x = 5;
+    assert_eq!(run_fut(foo(&x, 7)), 31);
+    assert_eq!(run_fut(build_aggregate(1, 2, 3, 4)), 10);
+    assert_eq!(run_fut(includes_never(false, 4)), 16);
+    assert_eq!(run_fut(partial_init(4)), 8);
+    run_fut(hello_world());
+}

src/test/ui/generator/partial-drop.rs

@@ -1,3 +1,7 @@
+// FIXME(eholk): temporarily disabled while drop range tracking is disabled
+// (see generator_interior.rs:27)
+// ignore-test
+
 #![feature(negative_impls, generators)]
 
 struct Foo;