fix result loc implicit casting optionals and error unions

```zig
pub fn openHandle(handle: i32) File {
    return File{ .handle = handle };
}

pub fn getStdErr() anyerror!File {
    return openHandle(1);
}
```
b552e68c14Andrew Kelley committed on 6/13/2019, 2:13:18 AMparentcdf14ba
1 file changedLine totals unavailable