Rollup merge of #41061 - arielb1:parent-lock, r=eddyb

cstore: return an immutable borrow from `visible_parent_map`

This prevents an ICE when `visible_parent_map` is called multiple times, for example when an item referenced in an impl signature is imported from an  `extern crate` statement occurs within an impl.

Fixes #41053.

r? @eddyb

2 files changed, 41 insertions, 0 deletions

diff --git a/src/test/run-pass/auxiliary/issue_41053.rs b/src/test/run-pass/auxiliary/issue_41053.rs
new file mode 100644
index 00000000000..68e92b10429
--- /dev/null
+++ b/src/test/run-pass/auxiliary/issue_41053.rs
@@ -0,0 +1,11 @@
+// Copyright 2017 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.
+
+pub struct Test;
diff --git a/src/test/run-pass/issue-41053.rs b/src/test/run-pass/issue-41053.rs
new file mode 100644
index 00000000000..769d841e364
--- /dev/null
+++ b/src/test/run-pass/issue-41053.rs
@@ -0,0 +1,30 @@
+// Copyright 2017 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.
+
+// aux-build:issue_41053.rs
+
+pub trait Trait { fn foo(&self) {} }
+
+pub struct Foo;
+
+impl Iterator for Foo {
+    type Item = Box<Trait>;
+    fn next(&mut self) -> Option<Box<Trait>> {
+        extern crate issue_41053;
+        impl ::Trait for issue_41053::Test {
+            fn foo(&self) {}
+        }
+        Some(Box::new(issue_41053::Test))
+    }
+}
+
+fn main() {
+    Foo.next().unwrap().foo();
+}