From 876f04d5edfbc26038c1addd0af4364351186759 Mon Sep 17 00:00:00 2001
From: Ding Xiang Fei <dingxiangfei2009@protonmail.ch>
Date: Sun, 2 Jan 2022 23:21:14 +0800
Subject: [PATCH 1/7] refine scopes
Co-authored-by: Felix S <pnkfelix@pnkfx.org>
---
Cargo.lock | 1 +
compiler/rustc_middle/src/middle/region.rs | 33 ++++
compiler/rustc_passes/Cargo.toml | 1 +
compiler/rustc_passes/src/region.rs | 156 +++++++++++++++++-
...age_markers.main.RemoveStorageMarkers.diff | 3 +-
.../async-await/issue-64130-4-async-move.rs | 11 +-
.../issue-64130-4-async-move.stderr | 16 +-
7 files changed, 199 insertions(+), 22 deletions(-)
diff --git a/Cargo.lock b/Cargo.lock
index 0f344dc920e57..dfe35e20a4bcb 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -4134,6 +4134,7 @@ dependencies = [
"rustc_session",
"rustc_span",
"rustc_target",
+ "smallvec",
"tracing",
]
diff --git a/compiler/rustc_middle/src/middle/region.rs b/compiler/rustc_middle/src/middle/region.rs
index 75dd223d014d4..6d25dac689aea 100644
--- a/compiler/rustc_middle/src/middle/region.rs
+++ b/compiler/rustc_middle/src/middle/region.rs
@@ -234,6 +234,8 @@ pub struct ScopeTree {
/// escape into 'static and should have no local cleanup scope.
rvalue_scopes: FxHashMap<hir::ItemLocalId, Option<Scope>>,
+ eager_scopes: FxHashMap<hir::ItemLocalId, Scope>,
+
/// If there are any `yield` nested within a scope, this map
/// stores the `Span` of the last one and its index in the
/// postorder of the Visitor traversal on the HIR.
@@ -358,6 +360,32 @@ impl ScopeTree {
self.rvalue_scopes.insert(var, lifetime);
}
+ pub fn record_local_access_scope(&mut self, var: hir::ItemLocalId, proposed_lifetime: Scope) {
+ debug!("record_local_access_scope(sub={:?}, sup={:?})", var, proposed_lifetime);
+ let mut id = Scope { id: var, data: ScopeData::Node };
+
+ while let Some(&(p, _)) = self.parent_map.get(&id) {
+ match p.data {
+ ScopeData::Destruction => return,
+ _ => id = p,
+ }
+ if id == proposed_lifetime {
+ // proposed lifetime outlives the destruction lifetime
+ self.record_rvalue_scope(var, Some(proposed_lifetime));
+ return;
+ }
+ }
+ }
+
+ pub fn record_eager_scope(&mut self, var: hir::ItemLocalId, proposed_lifetime: Scope) {
+ if let Some(destruction) = self.temporary_scope(var) {
+ if self.is_subscope_of(destruction, proposed_lifetime) {
+ return;
+ }
+ }
+ self.eager_scopes.insert(var, proposed_lifetime);
+ }
+
/// Returns the narrowest scope that encloses `id`, if any.
pub fn opt_encl_scope(&self, id: Scope) -> Option<Scope> {
self.parent_map.get(&id).cloned().map(|(p, _)| p)
@@ -393,6 +421,9 @@ impl ScopeTree {
}
_ => id = p,
}
+ if let Some(&eager_scope) = self.eager_scopes.get(&id.item_local_id()) {
+ return Some(eager_scope);
+ }
}
debug!("temporary_scope({:?}) = None", expr_id);
@@ -444,6 +475,7 @@ impl<'a> HashStable<StableHashingContext<'a>> for ScopeTree {
ref var_map,
ref destruction_scopes,
ref rvalue_scopes,
+ ref eager_scopes,
ref yield_in_scope,
} = *self;
@@ -456,6 +488,7 @@ impl<'a> HashStable<StableHashingContext<'a>> for ScopeTree {
var_map.hash_stable(hcx, hasher);
destruction_scopes.hash_stable(hcx, hasher);
rvalue_scopes.hash_stable(hcx, hasher);
+ eager_scopes.hash_stable(hcx, hasher);
yield_in_scope.hash_stable(hcx, hasher);
}
}
diff --git a/compiler/rustc_passes/Cargo.toml b/compiler/rustc_passes/Cargo.toml
index 39e578bce7ef6..1ed7c26f056f7 100644
--- a/compiler/rustc_passes/Cargo.toml
+++ b/compiler/rustc_passes/Cargo.toml
@@ -5,6 +5,7 @@ edition = "2021"
[dependencies]
tracing = "0.1"
+smallvec = { version = "1.6.1", features = ["union", "may_dangle"] }
rustc_middle = { path = "../rustc_middle" }
rustc_attr = { path = "../rustc_attr" }
rustc_data_structures = { path = "../rustc_data_structures" }
diff --git a/compiler/rustc_passes/src/region.rs b/compiler/rustc_passes/src/region.rs
index fdf93e5893247..f2e712f262f1d 100644
--- a/compiler/rustc_passes/src/region.rs
+++ b/compiler/rustc_passes/src/region.rs
@@ -18,6 +18,7 @@ use rustc_middle::ty::query::Providers;
use rustc_middle::ty::TyCtxt;
use rustc_span::source_map;
use rustc_span::Span;
+use smallvec::SmallVec;
use std::mem;
@@ -203,6 +204,106 @@ fn resolve_stmt<'tcx>(visitor: &mut RegionResolutionVisitor<'tcx>, stmt: &'tcx h
visitor.cx.parent = prev_parent;
}
+fn mark_local_terminating_scopes<'tcx>(expr: &'tcx hir::Expr<'tcx>) -> FxHashSet<hir::ItemLocalId> {
+ struct LocalAccessResolutionVisitor<'a> {
+ locals: &'a mut FxHashSet<hir::ItemLocalId>,
+ }
+ impl<'a> LocalAccessResolutionVisitor<'a> {
+ fn probe<'b>(&mut self, expr: &'b Expr<'b>) {
+ if self.locals.contains(&expr.hir_id.local_id) {
+ return;
+ }
+ let mut nested_expr = expr;
+ let mut ops = SmallVec::<[_; 4]>::new();
+ enum OpTy {
+ Ref,
+ Deref,
+ Project,
+ Local,
+ }
+ loop {
+ match nested_expr.kind {
+ hir::ExprKind::Path(hir::QPath::Resolved(
+ _,
+ hir::Path { res: hir::def::Res::Local(_), .. },
+ )) => {
+ ops.push((nested_expr, OpTy::Local));
+ break;
+ }
+ hir::ExprKind::AddrOf(_, _, subexpr) => {
+ ops.push((nested_expr, OpTy::Ref));
+ nested_expr = subexpr;
+ }
+ hir::ExprKind::Unary(hir::UnOp::Deref, subexpr) => {
+ ops.push((nested_expr, OpTy::Deref));
+ nested_expr = subexpr;
+ }
+ hir::ExprKind::Field(subexpr, _) => {
+ ops.push((nested_expr, OpTy::Project));
+ nested_expr = subexpr;
+ }
+ hir::ExprKind::Index(subexpr, idxexpr) => {
+ ops.push((nested_expr, OpTy::Project));
+ nested_expr = subexpr;
+ intravisit::walk_expr(self, idxexpr);
+ }
+ _ => {
+ drop(ops);
+ intravisit::walk_expr(self, expr);
+ return;
+ }
+ }
+ }
+ let mut ref_level = SmallVec::<[_; 4]>::new();
+ let mut ops_iter = ops.into_iter().rev();
+ ops_iter.next().unwrap();
+ for (expr, op) in ops_iter {
+ match op {
+ OpTy::Ref => {
+ ref_level.push(expr);
+ }
+ OpTy::Deref => {
+ if let Some(ref_expr) = ref_level.pop() {
+ self.locals.insert(ref_expr.hir_id.local_id);
+ }
+ }
+ OpTy::Project => {
+ ref_level.clear();
+ }
+ OpTy::Local => {
+ panic!("unexpected encounter of Local")
+ }
+ }
+ }
+ self.locals.insert(expr.hir_id.local_id);
+ }
+ }
+ impl<'a, 'b> Visitor<'a> for LocalAccessResolutionVisitor<'b> {
+ type Map = intravisit::ErasedMap<'a>;
+ fn nested_visit_map(&mut self) -> NestedVisitorMap<Self::Map> {
+ NestedVisitorMap::None
+ }
+ fn visit_expr(&mut self, expr: &'a Expr<'a>) {
+ match expr.kind {
+ hir::ExprKind::AddrOf(..)
+ | hir::ExprKind::Unary(hir::UnOp::Deref, _)
+ | hir::ExprKind::Field(..)
+ | hir::ExprKind::Index(..)
+ | hir::ExprKind::Path(..) => self.probe(expr),
+ hir::ExprKind::Block(..)
+ | hir::ExprKind::Closure(..)
+ | hir::ExprKind::ConstBlock(..) => {}
+ _ => intravisit::walk_expr(self, expr),
+ }
+ }
+ }
+ let mut locals = Default::default();
+ let mut resolution_visitor = LocalAccessResolutionVisitor { locals: &mut locals };
+ resolution_visitor.visit_expr(expr);
+ // visitor.terminating_scopes.extend(locals.iter().copied());
+ locals
+}
+
fn resolve_expr<'tcx>(visitor: &mut RegionResolutionVisitor<'tcx>, expr: &'tcx hir::Expr<'tcx>) {
debug!("resolve_expr - pre-increment {} expr = {:?}", visitor.expr_and_pat_count, expr);
@@ -396,7 +497,15 @@ fn resolve_expr<'tcx>(visitor: &mut RegionResolutionVisitor<'tcx>, expr: &'tcx h
let expr_cx = visitor.cx;
visitor.enter_scope(Scope { id: then.hir_id.local_id, data: ScopeData::IfThen });
visitor.cx.var_parent = visitor.cx.parent;
- visitor.visit_expr(cond);
+ {
+ visitor.visit_expr(cond);
+ let lifetime = Scope { id: cond.hir_id.local_id, data: ScopeData::Node };
+ for local in mark_local_terminating_scopes(cond) {
+ if local != cond.hir_id.local_id {
+ visitor.scope_tree.record_local_access_scope(local, lifetime);
+ }
+ }
+ }
visitor.visit_expr(then);
visitor.cx = expr_cx;
visitor.visit_expr(otherwise);
@@ -406,11 +515,39 @@ fn resolve_expr<'tcx>(visitor: &mut RegionResolutionVisitor<'tcx>, expr: &'tcx h
let expr_cx = visitor.cx;
visitor.enter_scope(Scope { id: then.hir_id.local_id, data: ScopeData::IfThen });
visitor.cx.var_parent = visitor.cx.parent;
- visitor.visit_expr(cond);
+ {
+ visitor.visit_expr(cond);
+ let lifetime = Scope { id: cond.hir_id.local_id, data: ScopeData::Node };
+ for local in mark_local_terminating_scopes(cond) {
+ if local != cond.hir_id.local_id {
+ visitor.scope_tree.record_local_access_scope(local, lifetime);
+ }
+ }
+ }
visitor.visit_expr(then);
visitor.cx = expr_cx;
}
+ hir::ExprKind::Match(subexpr, arms, _) => {
+ visitor.visit_expr(subexpr);
+ let lifetime = Scope { id: subexpr.hir_id.local_id, data: ScopeData::Node };
+ for local in mark_local_terminating_scopes(subexpr) {
+ if local != subexpr.hir_id.local_id {
+ visitor.scope_tree.record_local_access_scope(local, lifetime);
+ }
+ }
+ walk_list!(visitor, visit_arm, arms);
+ }
+
+ hir::ExprKind::Index(subexpr, idxexpr) => {
+ visitor.visit_expr(subexpr);
+ visitor.visit_expr(idxexpr);
+ visitor.scope_tree.record_eager_scope(
+ idxexpr.hir_id.local_id,
+ Scope { id: expr.hir_id.local_id, data: ScopeData::Node },
+ );
+ }
+
_ => intravisit::walk_expr(visitor, expr),
}
@@ -683,10 +820,17 @@ fn resolve_local<'tcx>(
visitor.scope_tree.record_rvalue_scope(expr.hir_id.local_id, blk_scope);
match expr.kind {
- hir::ExprKind::AddrOf(_, _, ref subexpr)
- | hir::ExprKind::Unary(hir::UnOp::Deref, ref subexpr)
- | hir::ExprKind::Field(ref subexpr, _)
- | hir::ExprKind::Index(ref subexpr, _) => {
+ hir::ExprKind::AddrOf(_, _, subexpr)
+ | hir::ExprKind::Unary(hir::UnOp::Deref, subexpr)
+ | hir::ExprKind::Field(subexpr, _)
+ | hir::ExprKind::Index(subexpr, _) => {
+ if let hir::ExprKind::Path(hir::QPath::Resolved(
+ _,
+ hir::Path { res: hir::def::Res::Local(_), .. },
+ )) = &subexpr.kind
+ {
+ return;
+ }
expr = &subexpr;
}
_ => {
diff --git a/src/test/mir-opt/remove_storage_markers.main.RemoveStorageMarkers.diff b/src/test/mir-opt/remove_storage_markers.main.RemoveStorageMarkers.diff
index 2dfc94f21868e..124017463d06a 100644
--- a/src/test/mir-opt/remove_storage_markers.main.RemoveStorageMarkers.diff
+++ b/src/test/mir-opt/remove_storage_markers.main.RemoveStorageMarkers.diff
@@ -71,7 +71,6 @@
- StorageDead(_13); // scope 3 at $DIR/remove_storage_markers.rs:9:16: 9:17
_6 = const (); // scope 3 at $DIR/remove_storage_markers.rs:8:20: 10:6
- StorageDead(_12); // scope 2 at $DIR/remove_storage_markers.rs:10:5: 10:6
-- StorageDead(_9); // scope 2 at $DIR/remove_storage_markers.rs:10:5: 10:6
- StorageDead(_7); // scope 2 at $DIR/remove_storage_markers.rs:10:5: 10:6
- StorageDead(_6); // scope 2 at $DIR/remove_storage_markers.rs:10:5: 10:6
_5 = const (); // scope 2 at $DIR/remove_storage_markers.rs:8:5: 10:6
@@ -80,7 +79,6 @@
bb3: {
_0 = const (); // scope 2 at $DIR/remove_storage_markers.rs:8:5: 10:6
-- StorageDead(_9); // scope 2 at $DIR/remove_storage_markers.rs:10:5: 10:6
- StorageDead(_7); // scope 2 at $DIR/remove_storage_markers.rs:10:5: 10:6
- StorageDead(_6); // scope 2 at $DIR/remove_storage_markers.rs:10:5: 10:6
- StorageDead(_4); // scope 1 at $DIR/remove_storage_markers.rs:10:5: 10:6
@@ -91,6 +89,7 @@
bb4: {
- StorageDead(_14); // scope 5 at $DIR/remove_storage_markers.rs:8:14: 8:19
+- StorageDead(_9); // scope 2 at $DIR/remove_storage_markers.rs:8:18: 8:19
- StorageDead(_8); // scope 2 at $DIR/remove_storage_markers.rs:8:18: 8:19
_10 = discriminant(_7); // scope 2 at $DIR/remove_storage_markers.rs:8:14: 8:19
switchInt(move _10) -> [0_isize: bb3, otherwise: bb2]; // scope 2 at $DIR/remove_storage_markers.rs:8:14: 8:19
diff --git a/src/test/ui/async-await/issue-64130-4-async-move.rs b/src/test/ui/async-await/issue-64130-4-async-move.rs
index 2538f34351e5a..e74c740f893f3 100644
--- a/src/test/ui/async-await/issue-64130-4-async-move.rs
+++ b/src/test/ui/async-await/issue-64130-4-async-move.rs
@@ -10,16 +10,15 @@ impl Client {
}
}
-async fn get() { }
+async fn get() {}
pub fn foo() -> impl Future + Send {
- //~^ ERROR future cannot be sent between threads safely
- let client = Client(Box::new(true));
- async move {
- match client.status() {
+ async {
+ //~^ ERROR future cannot be sent between threads safely
+ match Client(Box::new(true)).status() {
200 => {
let _x = get().await;
- },
+ }
_ => (),
}
}
diff --git a/src/test/ui/async-await/issue-64130-4-async-move.stderr b/src/test/ui/async-await/issue-64130-4-async-move.stderr
index d631e6dc7f7e9..0eeed986cd7eb 100644
--- a/src/test/ui/async-await/issue-64130-4-async-move.stderr
+++ b/src/test/ui/async-await/issue-64130-4-async-move.stderr
@@ -6,21 +6,21 @@ LL | pub fn foo() -> impl Future + Send {
|
= help: the trait `Sync` is not implemented for `(dyn Any + Send + 'static)`
note: future is not `Send` as this value is used across an await
- --> $DIR/issue-64130-4-async-move.rs:21:31
+ --> $DIR/issue-64130-4-async-move.rs:20:31
|
-LL | match client.status() {
- | ------ has type `&Client` which is not `Send`
+LL | match Client(Box::new(true)).status() {
+ | ---------------------- has type `&Client` which is not `Send`
LL | 200 => {
LL | let _x = get().await;
- | ^^^^^^ await occurs here, with `client` maybe used later
+ | ^^^^^^ await occurs here, with `Client(Box::new(true))` maybe used later
...
LL | }
- | - `client` is later dropped here
+ | - `Client(Box::new(true))` is later dropped here
help: consider moving this into a `let` binding to create a shorter lived borrow
- --> $DIR/issue-64130-4-async-move.rs:19:15
+ --> $DIR/issue-64130-4-async-move.rs:18:15
|
-LL | match client.status() {
- | ^^^^^^^^^^^^^^^
+LL | match Client(Box::new(true)).status() {
+ | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
error: aborting due to previous error
From bc114c47affc43338d59bd93fea9c3d3128f7b7c Mon Sep 17 00:00:00 2001
From: Ding Xiang Fei <dingxiangfei2009@protonmail.ch>
Date: Mon, 3 Jan 2022 12:10:02 +0800
Subject: [PATCH 2/7] tests from the relevant issue trackers
---
.../issue-69663-lingering-local-borrows.rs | 51 +++++++++++++++++++
.../refined-region-for-local-accesses.rs | 32 ++++++++++++
2 files changed, 83 insertions(+)
create mode 100644 src/test/ui/async-await/issue-69663-lingering-local-borrows.rs
create mode 100644 src/test/ui/generator/refined-region-for-local-accesses.rs
diff --git a/src/test/ui/async-await/issue-69663-lingering-local-borrows.rs b/src/test/ui/async-await/issue-69663-lingering-local-borrows.rs
new file mode 100644
index 0000000000000..9c77a1fc0266e
--- /dev/null
+++ b/src/test/ui/async-await/issue-69663-lingering-local-borrows.rs
@@ -0,0 +1,51 @@
+// edition:2018
+// run-pass
+
+use std::ops::Index;
+
+/// A `Send + !Sync` for demonstration purposes.
+struct Banana(*mut ());
+unsafe impl Send for Banana {}
+
+impl Banana {
+ /// Make a static mutable reference to Banana for convenience purposes.
+ ///
+ /// Any potential unsoundness here is not super relevant to the issue at hand.
+ fn new() -> &'static mut Banana {
+ static mut BANANA: Banana = Banana(std::ptr::null_mut());
+ unsafe { &mut BANANA }
+ }
+}
+
+// Peach is still Send (because `impl Send for &mut T where T: Send`)
+struct Peach<'a>(&'a mut Banana);
+
+impl<'a> std::ops::Index<usize> for Peach<'a> {
+ type Output = ();
+ fn index(&self, _: usize) -> &() {
+ &()
+ }
+}
+
+async fn baz(_: &()) {}
+
+async fn bar() {
+ let peach = Peach(Banana::new());
+ let r = &*peach.index(0);
+ baz(r).await;
+ peach.index(0); // make sure peach is retained across yield point
+}
+
+async fn bat() {
+ let peach = Peach(Banana::new());
+ let r = &peach[0];
+ baz(r).await;
+ peach[0]; // make sure peach is retained across yield point
+}
+
+fn assert_send<T: Send>(_: T) {}
+
+pub fn main() {
+ assert_send(bar());
+ assert_send(bat());
+}
diff --git a/src/test/ui/generator/refined-region-for-local-accesses.rs b/src/test/ui/generator/refined-region-for-local-accesses.rs
new file mode 100644
index 0000000000000..340408f3eca89
--- /dev/null
+++ b/src/test/ui/generator/refined-region-for-local-accesses.rs
@@ -0,0 +1,32 @@
+// edition:2018
+// run-pass
+#![feature(generators, generator_trait, negative_impls)]
+
+fn assert_send<T: Send>(_: T) {}
+
+struct Client;
+
+impl Client {
+ fn status(&self) -> i16 {
+ 200
+ }
+}
+
+impl !Sync for Client {}
+
+fn status(_: &Client) -> i16 {
+ 200
+}
+
+fn main() {
+ let g = || {
+ let x = Client;
+ match status(&x) {
+ _ => yield,
+ }
+ match (&*&x).status() {
+ _ => yield,
+ }
+ };
+ assert_send(g);
+}
From 4097274050dc5c9c74019b8589f76381c328d11d Mon Sep 17 00:00:00 2001
From: Ding Xiang Fei <dingxiangfei2009@protonmail.ch>
Date: Mon, 3 Jan 2022 12:48:47 +0800
Subject: [PATCH 3/7] comments about the workings
---
compiler/rustc_middle/src/middle/region.rs | 9 +++++++++
compiler/rustc_passes/src/region.rs | 12 +++++++++++-
2 files changed, 20 insertions(+), 1 deletion(-)
diff --git a/compiler/rustc_middle/src/middle/region.rs b/compiler/rustc_middle/src/middle/region.rs
index 6d25dac689aea..6323dad57daf3 100644
--- a/compiler/rustc_middle/src/middle/region.rs
+++ b/compiler/rustc_middle/src/middle/region.rs
@@ -234,6 +234,13 @@ pub struct ScopeTree {
/// escape into 'static and should have no local cleanup scope.
rvalue_scopes: FxHashMap<hir::ItemLocalId, Option<Scope>>,
+ /// Sometimes destruction scopes are too overarching in the sense that
+ /// all temporaries are dropped while it may be the case that
+ /// only a subset of temporaries is requested to be dropped.
+ /// For instance, `x[y.z()]` indexing operation can discard the temporaries
+ /// generated in evaluating `y.z()`.
+ /// `eager_scopes` is a map from items to a region smaller than a destruction scope
+ /// so that the temporaries do not need to linger unnecessarily.
eager_scopes: FxHashMap<hir::ItemLocalId, Scope>,
/// If there are any `yield` nested within a scope, this map
@@ -380,6 +387,8 @@ impl ScopeTree {
pub fn record_eager_scope(&mut self, var: hir::ItemLocalId, proposed_lifetime: Scope) {
if let Some(destruction) = self.temporary_scope(var) {
if self.is_subscope_of(destruction, proposed_lifetime) {
+ // If the current temporary scope is already a subset of the proposed region,
+ // it is safe to keep this scope and discard the proposal.
return;
}
}
diff --git a/compiler/rustc_passes/src/region.rs b/compiler/rustc_passes/src/region.rs
index f2e712f262f1d..6f13666edbe31 100644
--- a/compiler/rustc_passes/src/region.rs
+++ b/compiler/rustc_passes/src/region.rs
@@ -221,6 +221,12 @@ fn mark_local_terminating_scopes<'tcx>(expr: &'tcx hir::Expr<'tcx>) -> FxHashSet
Project,
Local,
}
+ // Here we are looking for a chain of access to extract a place reference for
+ // a local variable.
+ // For instance, given `&*(&*x[y]).z().u`, `probe` will pick out
+ // the sub-expressions `&*x[y]` and `y` as expressions making accesses to locals.
+ // The place references generated can be discarded earlier as MIR allows,
+ // and, thus, can be assigned a smaller region.
loop {
match nested_expr.kind {
hir::ExprKind::Path(hir::QPath::Resolved(
@@ -268,6 +274,9 @@ fn mark_local_terminating_scopes<'tcx>(expr: &'tcx hir::Expr<'tcx>) -> FxHashSet
}
}
OpTy::Project => {
+ // The generated MIR produces temporaries for the each of the nested references,
+ // such as `&x`, `&&x` in `(&&&x).y` for the field access of `y`.
+ // These temporaries must stay alive even after the field access.
ref_level.clear();
}
OpTy::Local => {
@@ -290,6 +299,8 @@ fn mark_local_terminating_scopes<'tcx>(expr: &'tcx hir::Expr<'tcx>) -> FxHashSet
| hir::ExprKind::Field(..)
| hir::ExprKind::Index(..)
| hir::ExprKind::Path(..) => self.probe(expr),
+
+ // We do not probe into other function bodies or blocks.
hir::ExprKind::Block(..)
| hir::ExprKind::Closure(..)
| hir::ExprKind::ConstBlock(..) => {}
@@ -300,7 +311,6 @@ fn mark_local_terminating_scopes<'tcx>(expr: &'tcx hir::Expr<'tcx>) -> FxHashSet
let mut locals = Default::default();
let mut resolution_visitor = LocalAccessResolutionVisitor { locals: &mut locals };
resolution_visitor.visit_expr(expr);
- // visitor.terminating_scopes.extend(locals.iter().copied());
locals
}
From 906cdbfa6f65bb5c7c5e4f055b626689cc03cbf6 Mon Sep 17 00:00:00 2001
From: Ding Xiang Fei <dingxiangfei2009@protonmail.ch>
Date: Sat, 8 Jan 2022 15:31:55 +0800
Subject: [PATCH 4/7] simplify tracking and opt for build-pass testing
---
compiler/rustc_middle/src/middle/region.rs | 6 +++++-
compiler/rustc_passes/src/region.rs | 11 +++--------
.../issue-69663-lingering-local-borrows.rs | 2 +-
.../ui/generator/refined-region-for-local-accesses.rs | 2 +-
4 files changed, 10 insertions(+), 11 deletions(-)
diff --git a/compiler/rustc_middle/src/middle/region.rs b/compiler/rustc_middle/src/middle/region.rs
index 6323dad57daf3..5f9ddae5f8abc 100644
--- a/compiler/rustc_middle/src/middle/region.rs
+++ b/compiler/rustc_middle/src/middle/region.rs
@@ -368,7 +368,10 @@ impl ScopeTree {
}
pub fn record_local_access_scope(&mut self, var: hir::ItemLocalId, proposed_lifetime: Scope) {
- debug!("record_local_access_scope(sub={:?}, sup={:?})", var, proposed_lifetime);
+ debug!(
+ "record_local_access_scope(var={:?}, proposed_lifetime={:?})",
+ var, proposed_lifetime
+ );
let mut id = Scope { id: var, data: ScopeData::Node };
while let Some(&(p, _)) = self.parent_map.get(&id) {
@@ -385,6 +388,7 @@ impl ScopeTree {
}
pub fn record_eager_scope(&mut self, var: hir::ItemLocalId, proposed_lifetime: Scope) {
+ debug!("record_eager_scope(var={:?}, proposed_lifetime={:?})", var, proposed_lifetime);
if let Some(destruction) = self.temporary_scope(var) {
if self.is_subscope_of(destruction, proposed_lifetime) {
// If the current temporary scope is already a subset of the proposed region,
diff --git a/compiler/rustc_passes/src/region.rs b/compiler/rustc_passes/src/region.rs
index 6f13666edbe31..b48c3b091834c 100644
--- a/compiler/rustc_passes/src/region.rs
+++ b/compiler/rustc_passes/src/region.rs
@@ -219,7 +219,6 @@ fn mark_local_terminating_scopes<'tcx>(expr: &'tcx hir::Expr<'tcx>) -> FxHashSet
Ref,
Deref,
Project,
- Local,
}
// Here we are looking for a chain of access to extract a place reference for
// a local variable.
@@ -233,7 +232,8 @@ fn mark_local_terminating_scopes<'tcx>(expr: &'tcx hir::Expr<'tcx>) -> FxHashSet
_,
hir::Path { res: hir::def::Res::Local(_), .. },
)) => {
- ops.push((nested_expr, OpTy::Local));
+ // We have reached the end of the access path
+ // because a local variable access is encountered
break;
}
hir::ExprKind::AddrOf(_, _, subexpr) => {
@@ -261,9 +261,7 @@ fn mark_local_terminating_scopes<'tcx>(expr: &'tcx hir::Expr<'tcx>) -> FxHashSet
}
}
let mut ref_level = SmallVec::<[_; 4]>::new();
- let mut ops_iter = ops.into_iter().rev();
- ops_iter.next().unwrap();
- for (expr, op) in ops_iter {
+ for (expr, op) in ops.into_iter().rev() {
match op {
OpTy::Ref => {
ref_level.push(expr);
@@ -279,9 +277,6 @@ fn mark_local_terminating_scopes<'tcx>(expr: &'tcx hir::Expr<'tcx>) -> FxHashSet
// These temporaries must stay alive even after the field access.
ref_level.clear();
}
- OpTy::Local => {
- panic!("unexpected encounter of Local")
- }
}
}
self.locals.insert(expr.hir_id.local_id);
diff --git a/src/test/ui/async-await/issue-69663-lingering-local-borrows.rs b/src/test/ui/async-await/issue-69663-lingering-local-borrows.rs
index 9c77a1fc0266e..7dfde370f31d8 100644
--- a/src/test/ui/async-await/issue-69663-lingering-local-borrows.rs
+++ b/src/test/ui/async-await/issue-69663-lingering-local-borrows.rs
@@ -1,5 +1,5 @@
// edition:2018
-// run-pass
+// build-pass
use std::ops::Index;
diff --git a/src/test/ui/generator/refined-region-for-local-accesses.rs b/src/test/ui/generator/refined-region-for-local-accesses.rs
index 340408f3eca89..680770a48f96a 100644
--- a/src/test/ui/generator/refined-region-for-local-accesses.rs
+++ b/src/test/ui/generator/refined-region-for-local-accesses.rs
@@ -1,5 +1,5 @@
// edition:2018
-// run-pass
+// build-pass
#![feature(generators, generator_trait, negative_impls)]
fn assert_send<T: Send>(_: T) {}
From 7cad314fc04d25ad27d5040fd7789eafadd7efb1 Mon Sep 17 00:00:00 2001
From: Ding Xiang Fei <dingxiangfei2009@protonmail.ch>
Date: Tue, 11 Jan 2022 21:57:10 +0800
Subject: [PATCH 5/7] stop descending to avoid duplicated effort
---
compiler/rustc_passes/src/region.rs | 11 ++++-------
.../ui/generator/refined-region-for-local-accesses.rs | 8 ++++++++
2 files changed, 12 insertions(+), 7 deletions(-)
diff --git a/compiler/rustc_passes/src/region.rs b/compiler/rustc_passes/src/region.rs
index b48c3b091834c..678b0c6e5e222 100644
--- a/compiler/rustc_passes/src/region.rs
+++ b/compiler/rustc_passes/src/region.rs
@@ -244,15 +244,10 @@ fn mark_local_terminating_scopes<'tcx>(expr: &'tcx hir::Expr<'tcx>) -> FxHashSet
ops.push((nested_expr, OpTy::Deref));
nested_expr = subexpr;
}
- hir::ExprKind::Field(subexpr, _) => {
+ hir::ExprKind::Field(subexpr, _) | hir::ExprKind::Index(subexpr, _) => {
ops.push((nested_expr, OpTy::Project));
nested_expr = subexpr;
}
- hir::ExprKind::Index(subexpr, idxexpr) => {
- ops.push((nested_expr, OpTy::Project));
- nested_expr = subexpr;
- intravisit::walk_expr(self, idxexpr);
- }
_ => {
drop(ops);
intravisit::walk_expr(self, expr);
@@ -296,7 +291,9 @@ fn mark_local_terminating_scopes<'tcx>(expr: &'tcx hir::Expr<'tcx>) -> FxHashSet
| hir::ExprKind::Path(..) => self.probe(expr),
// We do not probe into other function bodies or blocks.
- hir::ExprKind::Block(..)
+ hir::ExprKind::If(..)
+ | hir::ExprKind::Match(..)
+ | hir::ExprKind::Block(..)
| hir::ExprKind::Closure(..)
| hir::ExprKind::ConstBlock(..) => {}
_ => intravisit::walk_expr(self, expr),
diff --git a/src/test/ui/generator/refined-region-for-local-accesses.rs b/src/test/ui/generator/refined-region-for-local-accesses.rs
index 680770a48f96a..67daf6bc6aac5 100644
--- a/src/test/ui/generator/refined-region-for-local-accesses.rs
+++ b/src/test/ui/generator/refined-region-for-local-accesses.rs
@@ -7,6 +7,10 @@ fn assert_send<T: Send>(_: T) {}
struct Client;
impl Client {
+ fn zero(&self) -> usize {
+ 0
+ }
+
fn status(&self) -> i16 {
200
}
@@ -27,6 +31,10 @@ fn main() {
match (&*&x).status() {
_ => yield,
}
+ let a = [0];
+ match a[Client.zero()] {
+ _ => yield,
+ }
};
assert_send(g);
}
From 849eb4b2bdd5a63494e5d7901b3257ce3e138d4b Mon Sep 17 00:00:00 2001
From: Ding Xiang Fei <dingxiangfei2009@protonmail.ch>
Date: Mon, 24 Jan 2022 23:27:19 +0800
Subject: [PATCH 6/7] use the new visitor api
---
compiler/rustc_passes/src/region.rs | 7 ++-----
1 file changed, 2 insertions(+), 5 deletions(-)
diff --git a/compiler/rustc_passes/src/region.rs b/compiler/rustc_passes/src/region.rs
index 678b0c6e5e222..de26585e9014e 100644
--- a/compiler/rustc_passes/src/region.rs
+++ b/compiler/rustc_passes/src/region.rs
@@ -278,10 +278,6 @@ fn mark_local_terminating_scopes<'tcx>(expr: &'tcx hir::Expr<'tcx>) -> FxHashSet
}
}
impl<'a, 'b> Visitor<'a> for LocalAccessResolutionVisitor<'b> {
- type Map = intravisit::ErasedMap<'a>;
- fn nested_visit_map(&mut self) -> NestedVisitorMap<Self::Map> {
- NestedVisitorMap::None
- }
fn visit_expr(&mut self, expr: &'a Expr<'a>) {
match expr.kind {
hir::ExprKind::AddrOf(..)
@@ -290,7 +286,8 @@ fn mark_local_terminating_scopes<'tcx>(expr: &'tcx hir::Expr<'tcx>) -> FxHashSet
| hir::ExprKind::Index(..)
| hir::ExprKind::Path(..) => self.probe(expr),
- // We do not probe into other function bodies or blocks.
+ // We do not probe into other function bodies or blocks,
+ // neither `if`s and `match`es because they will be covered in deeper visits
hir::ExprKind::If(..)
| hir::ExprKind::Match(..)
| hir::ExprKind::Block(..)
From 348584d3e2cd3feb3aa76b2dbe0bbbd8f34b971e Mon Sep 17 00:00:00 2001
From: Ding Xiang Fei <dingxiangfei2009@protonmail.ch>
Date: Thu, 10 Feb 2022 09:53:26 +0800
Subject: [PATCH 7/7] rebase and update tests
---
src/test/ui/async-await/issue-64130-4-async-move.rs | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/src/test/ui/async-await/issue-64130-4-async-move.rs b/src/test/ui/async-await/issue-64130-4-async-move.rs
index e74c740f893f3..99a3b28c5e00f 100644
--- a/src/test/ui/async-await/issue-64130-4-async-move.rs
+++ b/src/test/ui/async-await/issue-64130-4-async-move.rs
@@ -13,8 +13,8 @@ impl Client {
async fn get() {}
pub fn foo() -> impl Future + Send {
+ //~^ ERROR future cannot be sent between threads safely
async {
- //~^ ERROR future cannot be sent between threads safely
match Client(Box::new(true)).status() {
200 => {
let _x = get().await;