D const design rationale

[Martin Howe]

After reading the articles by Walter referred to recently, I'm less confused 
that I was, but would still appreciate some further explanation.

So should "const foo bar = baz" be an error if foo is a value type, on the 
basis that one should be using "invariant" or maybe final? It it safe to 
have two things const/invariant that become identical depending on type?

And does "final" exist *solely* so that you can approximate "invariant" for 
objects as well as for structs and scalars? I can see its use when you want 
something to be invariant but with the stipulation that it must exist in 
memory and have an address. In which case, why have final vs invariant at 
all, rather than having final be, for example, "weak invariant" or "stored 
invariant" or something like that? From here, final just looks 
*semantically* like "a poor man's invariant".