internal compiler error by using a string slice in pattern match

[StephanvanSchaik]

Attempting to get a string slice in a pattern when pattern matching yields the following: "error: internal compiler error: ident only path should have been covered already." As an example, do consider the following code:
http://is.gd/cuYVtu

struct Test(String);

fn main() {
    let x = Test(format!("foo"));
    let Test(&desc[..]) = x;
}

I expected a less serious error, as this was by accident, I intended to do something different. The version I am using is: rustc 1.0.0-dev (ecf8c64 2015-03-21) (built 2015-03-22).