1 files changed, 44 insertions, 0 deletions
diff --git a/src/test/ui/mir/mir_codegen_critical_edge.rs b/src/test/ui/mir/mir_codegen_critical_edge.rs
new file mode 100644
index 000000000..5c1f1c3b7
--- /dev/null
+++ b/src/test/ui/mir/mir_codegen_critical_edge.rs
@@ -0,0 +1,44 @@
+// run-pass
+#![allow(dead_code)]
+// 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
+    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 codegen a version of the function
+pub fn do_stuff(mut f: Foo<Box<dyn Iterator<Item=u32>>, Box<dyn Iterator<Item=u32>>>) {
+    let _x = f.next();
+}
+
+fn main() {}