diff --git a/src/test/compile-fail/associated-types/cache/chrono-scan.rs b/src/test/compile-fail/associated-types/cache/chrono-scan.rs
new file mode 100644
index 0000000000000..a753527ea53d5
--- /dev/null
+++ b/src/test/compile-fail/associated-types/cache/chrono-scan.rs
@@ -0,0 +1,39 @@
+// Copyright 2012-2015 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.
+
+#![feature(rustc_attrs)]
+#![allow(warnings)]
+
+pub type ParseResult<T> = Result<T, ()>;
+
+pub enum Item<'a> {     Literal(&'a str),
+ }
+
+pub fn colon_or_space(s: &str) -> ParseResult<&str> {
+    unimplemented!()
+}
+
+pub fn timezone_offset_zulu<F>(s: &str, colon: F) -> ParseResult<(&str, i32)>
+        where F: FnMut(&str) -> ParseResult<&str> {
+    unimplemented!()
+}
+
+pub fn parse<'a, I>(mut s: &str, items: I) -> ParseResult<()>
+        where I: Iterator<Item=Item<'a>> {
+    macro_rules! try_consume {
+        ($e:expr) => ({ let (s_, v) = try!($e); s = s_; v })
+    }
+    let offset = try_consume!(timezone_offset_zulu(s.trim_left(), colon_or_space));
+    let offset = try_consume!(timezone_offset_zulu(s.trim_left(), colon_or_space));
+    Ok(())
+}
+
+#[rustc_error]
+fn main() { } //~ ERROR compilation successful
diff --git a/src/test/compile-fail/associated-types/cache/elision.rs b/src/test/compile-fail/associated-types/cache/elision.rs
new file mode 100644
index 0000000000000..d1117328c8657
--- /dev/null
+++ b/src/test/compile-fail/associated-types/cache/elision.rs
@@ -0,0 +1,34 @@
+// Copyright 2014 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.
+
+#![feature(rustc_attrs)]
+#![allow(warnings)]
+
+// Check that you are allowed to implement using elision but write
+// trait without elision (a bug in this cropped up during
+// bootstrapping, so this is a regression test).
+
+pub struct SplitWhitespace<'a> {
+    x: &'a u8
+}
+
+pub trait UnicodeStr {
+    fn split_whitespace<'a>(&'a self) -> SplitWhitespace<'a>;
+}
+
+impl UnicodeStr for str {
+    #[inline]
+    fn split_whitespace(&self) -> SplitWhitespace {
+        unimplemented!()
+    }
+}
+
+#[rustc_error]
+fn main() { } //~ ERROR compilation successful
diff --git a/src/test/run-pass/project-cache-issue-31849.rs b/src/test/run-pass/project-cache-issue-31849.rs
new file mode 100644
index 0000000000000..d03424b2b2b7a
--- /dev/null
+++ b/src/test/run-pass/project-cache-issue-31849.rs
@@ -0,0 +1,75 @@
+// 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.
+
+// Regression test for #31849: the problem here was actually a performance
+// cliff, but I'm adding the test for reference.
+
+pub trait Upcast<T> {
+    fn upcast(self) -> T;
+}
+
+impl<S1, S2, T1, T2> Upcast<(T1, T2)> for (S1,S2)
+    where S1: Upcast<T1>,
+          S2: Upcast<T2>,
+{
+    fn upcast(self) -> (T1, T2) { (self.0.upcast(), self.1.upcast()) }
+}
+
+impl Upcast<()> for ()
+{
+    fn upcast(self) -> () { () }
+}
+
+pub trait ToStatic {
+    type Static: 'static;
+    fn to_static(self) -> Self::Static where Self: Sized;
+}
+
+impl<T, U> ToStatic for (T, U)
+    where T: ToStatic,
+          U: ToStatic
+{
+    type Static = (T::Static, U::Static);
+    fn to_static(self) -> Self::Static { (self.0.to_static(), self.1.to_static()) }
+}
+
+impl ToStatic for ()
+{
+    type Static = ();
+    fn to_static(self) -> () { () }
+}
+
+
+trait Factory {
+    type Output;
+    fn build(&self) -> Self::Output;
+}
+
+impl<S,T> Factory for (S, T)
+    where S: Factory,
+          T: Factory,
+          S::Output: ToStatic,
+          <S::Output as ToStatic>::Static: Upcast<S::Output>,
+{
+    type Output = (S::Output, T::Output);
+    fn build(&self) -> Self::Output { (self.0.build().to_static().upcast(), self.1.build()) }
+}
+
+impl Factory for () {
+    type Output = ();
+    fn build(&self) -> Self::Output { () }
+}
+
+fn main() {
+    // More parens, more time.
+    let it = ((((((((((),()),()),()),()),()),()),()),()),());
+    it.build();
+}
+