diff --git a/src/test/run-pass/default-ty-param-fallback/associated_type_as_default.rs b/src/test/run-pass/default-ty-param-fallback/associated_type_as_default.rs
new file mode 100644
index 0000000000000..43e92f9f1ff74
--- /dev/null
+++ b/src/test/run-pass/default-ty-param-fallback/associated_type_as_default.rs
@@ -0,0 +1,64 @@
+// 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.
+// compile-flags: --error-format=human
+
+// 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.
+//
+
+#![feature(default_type_parameter_fallback)]
+
+use std::vec::IntoIter;
+use std::iter::Sum;
+use std::slice::Iter;
+use std::ops::Add;
+
+trait Itarator: Iterator {
+    type Iten;
+    // Bug: Even though it's unambiguos, using Self::Iten dosen't work here.
+    // probably can be fixed in fn associated_path_def_to_ty.
+    fn foo<T:Default=<Self as Itarator>::Iten>(&self) -> T {
+        T::default()
+    }
+    
+    fn suma<S=<<Self as Itarator>::Iten as Add>::Output>(self) -> S
+        where Self: Sized,
+              S: Sum<<Self as Iterator>::Item>,
+    {
+        Sum::sum(self)
+    }
+}
+
+impl Itarator for IntoIter<u32> {
+    type Iten = <IntoIter<u32> as Iterator>::Item;
+}
+
+impl<'a> Itarator for Iter<'a, u32> {
+    type Iten = <Iter<'a, u32> as Iterator>::Item;
+}
+
+fn main() {
+    let x = vec![0u32];
+    {
+        let v = x.iter();
+        // Bug: if we put a cast such as `as u64`, inference fails.
+        //The usual guess is that we propagate the origin but not the default of the inference var.
+        v.suma();
+    }
+    x.clone().into_iter().suma();
+    x.into_iter().suma();
+}
diff --git a/src/test/ui/default-ty-param-fallback/elided_is_not_inferred.rs b/src/test/ui/default-ty-param-fallback/elided_is_not_inferred.rs
new file mode 100644
index 0000000000000..7efcf64e9f807
--- /dev/null
+++ b/src/test/ui/default-ty-param-fallback/elided_is_not_inferred.rs
@@ -0,0 +1,30 @@
+// 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.
+// compile-flags: --error-format=human
+
+#![feature(default_type_parameter_fallback)]
+
+struct Bar<T>(T);
+
+impl Bar<T> {
+    fn new<U, Z:Default=String>() -> Bar<Z> {
+        Bar(Z::default())
+    }
+}
+
+fn main() {
+    let _:u32 = foo::<usize>();
+    let _:Bar<u32> = Bar::new::<usize>();
+}
+
+fn foo<U:Default, T:Default=String>() -> T {
+    T::default()
+}
+
diff --git a/src/test/ui/default-ty-param-fallback/elided_is_not_inferred.stderr b/src/test/ui/default-ty-param-fallback/elided_is_not_inferred.stderr
new file mode 100644
index 0000000000000..1bb7b710ddc7f
--- /dev/null
+++ b/src/test/ui/default-ty-param-fallback/elided_is_not_inferred.stderr
@@ -0,0 +1,26 @@
+error[E0412]: cannot find type `T` in this scope
+  --> $DIR/elided_is_not_inferred.rs:16:10
+   |
+16 | impl Bar<T> {
+   |          ^ not found in this scope
+
+error[E0308]: mismatched types
+  --> $DIR/elided_is_not_inferred.rs:23:17
+   |
+23 |     let _:u32 = foo::<usize>();
+   |                 ^^^^^^^^^^^^^^ expected u32, found struct `std::string::String`
+   |
+   = note: expected type `u32`
+              found type `std::string::String`
+
+error[E0308]: mismatched types
+  --> $DIR/elided_is_not_inferred.rs:24:22
+   |
+24 |     let _:Bar<u32> = Bar::new::<usize>();
+   |                      ^^^^^^^^^^^^^^^^^^^ expected u32, found struct `std::string::String`
+   |
+   = note: expected type `Bar<u32>`
+              found type `Bar<std::string::String>`
+
+error: aborting due to 3 previous errors
+