log (fail, 2) hits an LLVM assertion

```
fn main() {
    log (fail, 2);
}
```

Assertion failed: ((i >= FTy->getNumParams() || FTy->getParamType(i) == Args[i]->getType()) && "Calling a function with a bad signature!"), function init, file /Users/jruderman/code/rust/src/llvm/lib/VMCore/Instructions.cpp, line 274.
