From 8c28284e51cbfc141939dde5dc3998383d0082e5 Mon Sep 17 00:00:00 2001
From: Niko Matsakis <niko@alum.mit.edu>
Date: Tue, 3 Mar 2015 19:27:50 -0500
Subject: When generating WF criteria, do not visit the same type more than
 once. Fixes an infinite stack overflow (#23003).

---
 .../compile-fail/traits-issue-23003-overflow.rs    | 38 +++++++++++++++++++++
 src/test/run-pass/traits-issue-23003.rs            | 39 ++++++++++++++++++++++
 2 files changed, 77 insertions(+)
 create mode 100644 src/test/compile-fail/traits-issue-23003-overflow.rs
 create mode 100644 src/test/run-pass/traits-issue-23003.rs

(limited to 'src/test')

diff --git a/src/test/compile-fail/traits-issue-23003-overflow.rs b/src/test/compile-fail/traits-issue-23003-overflow.rs
new file mode 100644
index 00000000000..ea41775f310
--- /dev/null
+++ b/src/test/compile-fail/traits-issue-23003-overflow.rs
@@ -0,0 +1,38 @@
+// 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.
+
+// A variant of traits-issue-23003 in which an infinite series of
+// types are required. This currently creates an overflow. This test
+// is included to ensure that some controlled failure, at least,
+// results -- but it might be that we should adjust the rules somewhat
+// to make this legal. -nmatsakis
+
+use std::marker::PhantomData;
+
+trait Async {
+    type Cancel;
+}
+
+struct Receipt<A:Async> {
+    marker: PhantomData<A>,
+}
+
+struct Complete<B> {
+    core: Option<B>,
+}
+
+impl<B> Async for Complete<B> {
+    type Cancel = Receipt<Complete<Option<B>>>;
+}
+
+fn foo(r: Receipt<Complete<()>>) { }
+//~^ ERROR overflow
+
+fn main() { }
diff --git a/src/test/run-pass/traits-issue-23003.rs b/src/test/run-pass/traits-issue-23003.rs
new file mode 100644
index 00000000000..37b13d319aa
--- /dev/null
+++ b/src/test/run-pass/traits-issue-23003.rs
@@ -0,0 +1,39 @@
+// 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.
+
+// Test stack overflow triggered by evaluating the implications. To be
+// WF, the type `Receipt<Complete>` would require that `<Complete as
+// Async>::Cancel` be WF. This normalizes to `Receipt<Complete>`
+// again, leading to an infinite cycle. Issue #23003.
+
+#![allow(dead_code)]
+#![allow(unused_variables)]
+
+use std::marker::PhantomData;
+
+trait Async {
+    type Cancel;
+}
+
+struct Receipt<A:Async> {
+    marker: PhantomData<A>,
+}
+
+struct Complete {
+    core: Option<()>,
+}
+
+impl Async for Complete {
+    type Cancel = Receipt<Complete>;
+}
+
+fn foo(r: Receipt<Complete>) { }
+
+fn main() { }
-- 
cgit 1.4.1-3-g733a5