Avoid writing a temporary closure kind

We used to write a temporary closure kind into the inference table, but
this could lead to obligations being incorrectled resolved before
inference had completed. This result could then be cached, leading to
further trouble. This patch avoids writing any closure kind until the
computation is complete.

Fixes #34349.

1 files changed, 32 insertions, 0 deletions

diff --git a/src/test/compile-fail/issue-34349.rs b/src/test/compile-fail/issue-34349.rs
new file mode 100644
index 00000000000..591753181db
--- /dev/null
+++ b/src/test/compile-fail/issue-34349.rs
@@ -0,0 +1,32 @@
+// Copyright 2016 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.
+
+// This is a regression test for a problem encountered around upvar
+// inference and trait caching: in particular, we were entering a
+// temporary closure kind during inference, and then caching results
+// based on that temporary kind, which led to no error being reported
+// in this particular test.
+
+fn main() {
+    let inc = || {};
+    inc();
+
+    fn apply<F>(f: F) where F: Fn() {
+        f()
+    }
+
+    let mut farewell = "goodbye".to_owned();
+    let diary = || { //~ ERROR E0525
+        farewell.push_str("!!!");
+        println!("Then I screamed {}.", farewell);
+    };
+
+    apply(diary);
+}