Assertion "Ptr must be a pointer to Val type!"' failed

With rust 0.6, compiling the following code

```
fn main() -> () {
  let ref y = 5;
  let z = &y;
}
```

produces

```
rustc: src/llvm/lib/VMCore/Instructions.cpp:1062: void llvm::StoreInst::AssertOK(): Assertion `getOperand(0)->getType() == cast<PointerType>(getOperand(1)->getType())->getElementType() && "Ptr must be a pointer to Val type!"' failed.
```
