noreturn branch tag

[kddnewton]

Hello! I am hoping for a noreturn branch flag feature that will indicate to steep that if a branch is taken, control flow does not return to the caller. For example:

# @rbs noreturn
def raise_error(node)
  # ...
end

def compile(node)
  case node
  when Foo
    compile_foo(node)
  when Bar
    compile_bar(node)
  else
    raise_error(node)
  end
end

Currently this will union the types of compile_foo, compile_bar, and raise_error. I am hoping to have it ignore the return type of raise_error instead. (Note I do see that some methods use a return type of bot for this purpose, but I figured I'd check since noreturn is in other systems.)