diff --git a/src/test/compile-fail/issue-6458-1.rs b/src/test/compile-fail/issue-6458-1.rs
new file mode 100644
index 00000000000..a54f05ec348
--- /dev/null
+++ b/src/test/compile-fail/issue-6458-1.rs
@@ -0,0 +1,12 @@
+// Copyright 2013 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.
+
+fn foo<T>(t: T) {}
+fn main() { foo(fail!()) } //~ ERROR cannot determine a type for this expression: unconstrained type
diff --git a/src/test/compile-fail/issue-6458-2.rs b/src/test/compile-fail/issue-6458-2.rs
new file mode 100644
index 00000000000..8621b37146f
--- /dev/null
+++ b/src/test/compile-fail/issue-6458-2.rs
@@ -0,0 +1,13 @@
+// Copyright 2013 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.
+
+fn main() {
+    fmt!("%?", None); //~ ERROR: cannot determine a type for this expression: unconstrained type
+}
diff --git a/src/test/compile-fail/issue-6458-3.rs b/src/test/compile-fail/issue-6458-3.rs
new file mode 100644
index 00000000000..ac41cc11682
--- /dev/null
+++ b/src/test/compile-fail/issue-6458-3.rs
@@ -0,0 +1,15 @@
+// Copyright 2013 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.
+
+use std::cast;
+
+fn main() {
+    cast::transmute(0);  //~ ERROR: cannot determine a type for this expression: unconstrained type
+}
diff --git a/src/test/compile-fail/issue-6458-4.rs b/src/test/compile-fail/issue-6458-4.rs
new file mode 100644
index 00000000000..131d9c824b6
--- /dev/null
+++ b/src/test/compile-fail/issue-6458-4.rs
@@ -0,0 +1,17 @@
+// Copyright 2013 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.
+
+fn foo(b: bool) -> Result<bool,~str> {
+    Err(~"bar"); //~ ERROR: cannot determine a type for this expression: unconstrained type
+}
+
+fn main() {
+    foo(false);
+}
diff --git a/src/test/compile-fail/issue-6458.rs b/src/test/compile-fail/issue-6458.rs
new file mode 100644
index 00000000000..8d9c63687ff
--- /dev/null
+++ b/src/test/compile-fail/issue-6458.rs
@@ -0,0 +1,21 @@
+// Copyright 2013 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.
+
+pub struct TypeWithState<State>;
+pub struct MyState;
+
+pub fn foo<State>(_: TypeWithState<State>) {}
+
+pub fn bar() {
+   foo(TypeWithState); //~ ERROR: cannot determine a type for this expression: unconstrained type
+}
+
+fn main() {
+}