silence warning about missing return and add assert to isError

[rainers]

tiny followup for #3074

[yebblies]

Auto-merge toggled on

[dnadlinger]

I'd rather we used a function similar to llvm_unreachable which is easy to mark up as __attribute__((noreturn))/__declspec(noreturn).

[yebblies]

I'd rather we didn't add stuff that doesn't have a translation to D.

[dnadlinger]

assert(0, msg) seems like a good D translation of that, because the semantics are actually part of the language there. (Well, actually llvm_unreachable doesn't compile to a trap in release mode, just to the respective equivalent of __builtin_unreachable but that's was not my point here. Anyway, it's a rather minor issue…)

[yebblies]

There is already an assert(0) here.

[dnadlinger]

Yes?

[yebblies]

Hmm never mind. Still, I'd rather not put and more clang/gcc/msvc extensions into the dmd source, eg I had to special case the noreturn attributes on fatal. We're abandoning C++ after all.