I think the idea is to give an error when there is absolutely no way that variable could have been initialised when it's read, i.e. cases like this:
int x;
h(x);
The point is not to solve the Halting Problem, but to catch code that is so obviously wrong that no programmer would deliberately write it (unless they were testing the compiler's reaction.)
If so, "that should always be a compile error. Period.” is IMO a poor way to express that idea.
On top of that, the C compilers I know more or less have that, as they give warnings for basically cases where Java (with its stricter rules) would refuse to compile equivalent code, and have a flag that turns warnings into errors.
