Version 4 of Typed Tcl

MJ - After watching Christian Gollwitzer and dkf's talks on EuroTcl I was contemplating an idea for Tcl9. A big reason of Tcl's flexibility is brought by EIAS, however this is a double edged sword.

It's slow.
It makes intellisense like tools virtually impossible.

So how about a Typed Tcl where you can define and use Tcl_Objs with a specific internal representation and conversion functions to other intreps without passing to string.

You would need to declare the value as a typed value and as soon as you play the EIAS card, you will get an error unless you make the shimmer explicit.

This has a couple of benefits.

You wont break EIAS (it just needs to be explicit) so if you use a part of Tcl which is not type aware you need to pass toString $var instead of $var
You can go fast if you have a direct intrep_type_a to intrep_type_b function defined.

This approach is complementary to the approach of speeding up Tcl by code analysis. Sometimes I will just know when I don't need EIAS but I will just need speed instead.

How could it look?

   settyped a list {a b c d}
   puts $a # error, can't use a tped Tcl_Obj as a string
   puts [toString $a] # ok $a is now untyped
   dict get $a c # error if there is no list->dict conversion
   dict get [toString $a c] # ok, EIAS

On second thought, this will require a library user to cast every returned value to an untyped Tcl value to prevent errors, so this seems to be similar to Java land Object.