PEP 3107 and stronger typing (note: probably a newbie question)

[kaens]

On 6/20/07, Diez B. Roggisch <deets at nospam.web.de> wrote:

> That is exactly the problem - there is no "some more" static typing.
> There is static typing - or not. You can't have it "just a bit".

Couldn't a language be made so that if you declared a variable like, say:

string foo = "I'm a string"

it would be a string, and always a string, and if you declared a variable like

foo = "i'm a dynamic variable"

it would be considered dynamic?

This doesn't seem like it would be too hard to add in to a language
that already had dynamic typing (But then again, I am inexperienced -
although interested in - language design).

It seems to me like this could be really useful, but I'm not aware of
any language implementing something like this.