Add a test

src/test/run-pass/mir_trans_critical_edge.rs

@@ -0,0 +1,53 @@
+// Copyright 2015 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 code produces a CFG with critical edges that, if we don't
+// handle properly, will cause invalid codegen.
+
+#![feature(rustc_attrs)]
+
+enum State {
+    Both,
+    Front,
+    Back
+}
+
+pub struct Foo<A: Iterator, B: Iterator> {
+    state: State,
+    a: A,
+    b: B
+}
+
+impl<A, B> Foo<A, B>
+where A: Iterator, B: Iterator<Item=A::Item>
+{
+    // This is the function we care about
+    #[rustc_mir]
+    fn next(&mut self) -> Option<A::Item> {
+        match self.state {
+            State::Both => match self.a.next() {
+                elt @ Some(..) => elt,
+                None => {
+                    self.state = State::Back;
+                    self.b.next()
+                }
+            },
+            State::Front => self.a.next(),
+            State::Back => self.b.next(),
+        }
+    }
+}
+
+// Make sure we actually translate a version of the function
+pub fn do_stuff(mut f: Foo<Box<Iterator<Item=u32>>, Box<Iterator<Item=u32>>>) {
+    let _x = f.next();
+}
+
+fn main() {}