Sail's assert() prints the file and line/column numbers but only if you don't add a message. I wonder if it should just always print them?

Currently the RISC-V model has this mess:

// This is all over the place:
internal_error(__FILE__, __LINE__, "should be unreachable");

val internal_error : forall ('a : Type). (string, int, string) -> 'a
function internal_error(file, line, s) = {
    assert (false, file ^ ":" ^ dec_str(line) ^ ": " ^ s);
    throw Error_internal_error()
}

It's pretty annoying to have to manually write __FILE__, __LINE__ (I think every time I've written this I copy/pasted it from somewhere else).

Also I don't know why it does a throw after assert(false). Can Sail asserts be disabled?

A built in unreachable("message") that is equivalent to assert(false, "message") would be neat too, given how many internal_error() calls we have.