diff --git a/src/librustc_data_structures/obligation_forest/mod.rs b/src/librustc_data_structures/obligation_forest/mod.rs
index 094c1cec31a..f159857e744 100644
--- a/src/librustc_data_structures/obligation_forest/mod.rs
+++ b/src/librustc_data_structures/obligation_forest/mod.rs
@@ -65,6 +65,12 @@ pub enum ProcessResult<O, E> {
Error(E),
}
+#[derive(Clone, Copy, PartialEq, Eq, Hash, Debug)]
+struct ObligationTreeId(usize);
+
+type ObligationTreeIdGenerator =
+ ::std::iter::Map<::std::ops::RangeFrom<usize>, fn(usize) -> ObligationTreeId>;
+
pub struct ObligationForest<O: ForestObligation> {
/// The list of obligations. In between calls to
/// `process_obligations`, this list only contains nodes in the
@@ -79,11 +85,25 @@ pub struct ObligationForest<O: ForestObligation> {
/// at a higher index than its parent. This is needed by the
/// backtrace iterator (which uses `split_at`).
nodes: Vec<Node<O>>,
+
/// A cache of predicates that have been successfully completed.
done_cache: FxHashSet<O::Predicate>,
+
/// An cache of the nodes in `nodes`, indexed by predicate.
waiting_cache: FxHashMap<O::Predicate, NodeIndex>,
+
scratch: Option<Vec<usize>>,
+
+ obligation_tree_id_generator: ObligationTreeIdGenerator,
+
+ /// Per tree error cache. This is used to deduplicate errors,
+ /// which is necessary to avoid trait resolution overflow in
+ /// some cases.
+ ///
+ /// See [this][details] for details.
+ ///
+ /// [details]: https://github.com/rust-lang/rust/pull/53255#issuecomment-421184780
+ error_cache: FxHashMap<ObligationTreeId, FxHashSet<O::Predicate>>,
}
#[derive(Debug)]
@@ -99,6 +119,9 @@ struct Node<O> {
/// Obligations that depend on this obligation for their
/// completion. They must all be in a non-pending state.
dependents: Vec<NodeIndex>,
+
+ /// Identifier of the obligation tree to which this node belongs.
+ obligation_tree_id: ObligationTreeId,
}
/// The state of one node in some tree within the forest. This
@@ -165,6 +188,8 @@ impl<O: ForestObligation> ObligationForest<O> {
done_cache: FxHashSet(),
waiting_cache: FxHashMap(),
scratch: Some(vec![]),
+ obligation_tree_id_generator: (0..).map(|i| ObligationTreeId(i)),
+ error_cache: FxHashMap(),
}
}
@@ -214,9 +239,29 @@ impl<O: ForestObligation> ObligationForest<O> {
Entry::Vacant(v) => {
debug!("register_obligation_at({:?}, {:?}) - ok, new index is {}",
obligation, parent, self.nodes.len());
- v.insert(NodeIndex::new(self.nodes.len()));
- self.nodes.push(Node::new(parent, obligation));
- Ok(())
+
+ let obligation_tree_id = match parent {
+ Some(p) => {
+ let parent_node = &self.nodes[p.get()];
+ parent_node.obligation_tree_id
+ }
+ None => self.obligation_tree_id_generator.next().unwrap()
+ };
+
+ let already_failed =
+ parent.is_some()
+ && self.error_cache
+ .get(&obligation_tree_id)
+ .map(|errors| errors.contains(obligation.as_predicate()))
+ .unwrap_or(false);
+
+ if already_failed {
+ Err(())
+ } else {
+ v.insert(NodeIndex::new(self.nodes.len()));
+ self.nodes.push(Node::new(parent, obligation, obligation_tree_id));
+ Ok(())
+ }
}
}
}
@@ -251,6 +296,15 @@ impl<O: ForestObligation> ObligationForest<O> {
.collect()
}
+ fn insert_into_error_cache(&mut self, node_index: usize) {
+ let node = &self.nodes[node_index];
+
+ self.error_cache
+ .entry(node.obligation_tree_id)
+ .or_insert_with(|| FxHashSet())
+ .insert(node.obligation.as_predicate().clone());
+ }
+
/// Perform a pass through the obligation list. This must
/// be called in a loop until `outcome.stalled` is false.
///
@@ -264,22 +318,15 @@ impl<O: ForestObligation> ObligationForest<O> {
let mut stalled = true;
for index in 0..self.nodes.len() {
- debug!("process_obligations: node {} == {:?}",
- index,
- self.nodes[index]);
+ debug!("process_obligations: node {} == {:?}", index, self.nodes[index]);
let result = match self.nodes[index] {
- Node { ref state, ref mut obligation, .. }
- if state.get() == NodeState::Pending =>
- {
- processor.process_obligation(obligation)
- }
+ Node { ref state, ref mut obligation, .. } if state.get() == NodeState::Pending =>
+ processor.process_obligation(obligation),
_ => continue
};
- debug!("process_obligations: node {} got result {:?}",
- index,
- result);
+ debug!("process_obligations: node {} got result {:?}", index, result);
match result {
ProcessResult::Unchanged => {
@@ -420,13 +467,13 @@ impl<O: ForestObligation> ObligationForest<O> {
}
while let Some(i) = error_stack.pop() {
- let node = &self.nodes[i];
-
- match node.state.get() {
+ match self.nodes[i].state.get() {
NodeState::Error => continue,
- _ => node.state.set(NodeState::Error)
+ _ => self.nodes[i].state.set(NodeState::Error),
}
+ let node = &self.nodes[i];
+
error_stack.extend(
node.parent.iter().chain(node.dependents.iter()).map(|x| x.get())
);
@@ -514,6 +561,7 @@ impl<O: ForestObligation> ObligationForest<O> {
self.waiting_cache.remove(self.nodes[i].obligation.as_predicate());
node_rewrites[i] = nodes_len;
dead_nodes += 1;
+ self.insert_into_error_cache(i);
}
NodeState::OnDfsStack | NodeState::Success => unreachable!()
}
@@ -587,12 +635,17 @@ impl<O: ForestObligation> ObligationForest<O> {
}
impl<O> Node<O> {
- fn new(parent: Option<NodeIndex>, obligation: O) -> Node<O> {
+ fn new(
+ parent: Option<NodeIndex>,
+ obligation: O,
+ obligation_tree_id: ObligationTreeId
+ ) -> Node<O> {
Node {
obligation,
state: Cell::new(NodeState::Pending),
parent,
dependents: vec![],
+ obligation_tree_id,
}
}
}
diff --git a/src/test/ui/issue-40827.rs b/src/test/ui/issue-40827.rs
new file mode 100644
index 00000000000..4b079ace3ca
--- /dev/null
+++ b/src/test/ui/issue-40827.rs
@@ -0,0 +1,27 @@
+// Copyright 2018 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+use std::rc::Rc;
+use std::sync::Arc;
+
+struct Foo(Arc<Bar>);
+
+enum Bar {
+ A(Rc<Foo>),
+ B(Option<Foo>),
+}
+
+fn f<T: Send>(_: T) {}
+
+fn main() {
+ f(Foo(Arc::new(Bar::B(None))));
+ //~^ ERROR E0277
+ //~| ERROR E0277
+}
diff --git a/src/test/ui/issue-40827.stderr b/src/test/ui/issue-40827.stderr
new file mode 100644
index 00000000000..dd0ebf96d19
--- /dev/null
+++ b/src/test/ui/issue-40827.stderr
@@ -0,0 +1,35 @@
+error[E0277]: `std::rc::Rc<Foo>` cannot be sent between threads safely
+ --> $DIR/issue-40827.rs:24:5
+ |
+LL | f(Foo(Arc::new(Bar::B(None))));
+ | ^ `std::rc::Rc<Foo>` cannot be sent between threads safely
+ |
+ = help: within `Bar`, the trait `std::marker::Send` is not implemented for `std::rc::Rc<Foo>`
+ = note: required because it appears within the type `Bar`
+ = note: required because of the requirements on the impl of `std::marker::Send` for `std::sync::Arc<Bar>`
+ = note: required because it appears within the type `Foo`
+note: required by `f`
+ --> $DIR/issue-40827.rs:21:1
+ |
+LL | fn f<T: Send>(_: T) {}
+ | ^^^^^^^^^^^^^^^^^^^
+
+error[E0277]: `std::rc::Rc<Foo>` cannot be shared between threads safely
+ --> $DIR/issue-40827.rs:24:5
+ |
+LL | f(Foo(Arc::new(Bar::B(None))));
+ | ^ `std::rc::Rc<Foo>` cannot be shared between threads safely
+ |
+ = help: within `Bar`, the trait `std::marker::Sync` is not implemented for `std::rc::Rc<Foo>`
+ = note: required because it appears within the type `Bar`
+ = note: required because of the requirements on the impl of `std::marker::Send` for `std::sync::Arc<Bar>`
+ = note: required because it appears within the type `Foo`
+note: required by `f`
+ --> $DIR/issue-40827.rs:21:1
+ |
+LL | fn f<T: Send>(_: T) {}
+ | ^^^^^^^^^^^^^^^^^^^
+
+error: aborting due to 2 previous errors
+
+For more information about this error, try `rustc --explain E0277`.
diff --git a/src/test/ui/recursion/recursive-requirements.rs b/src/test/ui/recursion/recursive-requirements.rs
index 2c0f0338b2d..dd6d2f6a225 100644
--- a/src/test/ui/recursion/recursive-requirements.rs
+++ b/src/test/ui/recursion/recursive-requirements.rs
@@ -23,5 +23,7 @@ pub struct Bar {
}
fn main() {
- let _: AssertSync<Foo> = unimplemented!(); //~ ERROR E0275
+ let _: AssertSync<Foo> = unimplemented!();
+ //~^ ERROR E0277
+ //~| ERROR E0277
}
diff --git a/src/test/ui/recursion/recursive-requirements.stderr b/src/test/ui/recursion/recursive-requirements.stderr
index d9e08102ab6..8fe282505e9 100644
--- a/src/test/ui/recursion/recursive-requirements.stderr
+++ b/src/test/ui/recursion/recursive-requirements.stderr
@@ -1,15 +1,33 @@
-error[E0275]: overflow evaluating the requirement `Foo: std::marker::Sync`
+error[E0277]: `*const Bar` cannot be shared between threads safely
--> $DIR/recursive-requirements.rs:26:12
|
-LL | let _: AssertSync<Foo> = unimplemented!(); //~ ERROR E0275
- | ^^^^^^^^^^^^^^^
+LL | let _: AssertSync<Foo> = unimplemented!();
+ | ^^^^^^^^^^^^^^^ `*const Bar` cannot be shared between threads safely
|
- = help: consider adding a `#![recursion_limit="128"]` attribute to your crate
- = note: required because it appears within the type `std::marker::PhantomData<Foo>`
+ = help: within `Foo`, the trait `std::marker::Sync` is not implemented for `*const Bar`
+ = note: required because it appears within the type `Foo`
+note: required by `AssertSync`
+ --> $DIR/recursive-requirements.rs:13:1
+ |
+LL | struct AssertSync<T: Sync>(PhantomData<T>);
+ | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+error[E0277]: `*const Foo` cannot be shared between threads safely
+ --> $DIR/recursive-requirements.rs:26:12
+ |
+LL | let _: AssertSync<Foo> = unimplemented!();
+ | ^^^^^^^^^^^^^^^ `*const Foo` cannot be shared between threads safely
+ |
+ = help: within `Foo`, the trait `std::marker::Sync` is not implemented for `*const Foo`
= note: required because it appears within the type `Bar`
= note: required because it appears within the type `std::marker::PhantomData<Bar>`
= note: required because it appears within the type `Foo`
+note: required by `AssertSync`
+ --> $DIR/recursive-requirements.rs:13:1
+ |
+LL | struct AssertSync<T: Sync>(PhantomData<T>);
+ | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
-error: aborting due to previous error
+error: aborting due to 2 previous errors
-For more information about this error, try `rustc --explain E0275`.
+For more information about this error, try `rustc --explain E0277`.