[RFC] type safe trees

[Richard Kenner]

    We really need front-end specific data structures, lowered to a common
    representation (I suspect gimple).  It would even solve the current
    Kenner thread, though he may disagree.  

I don't see how it would "solve" the current thread since that's what
the Ada front end already does!  It has a quite complex internal
representation that's basically a very heavily annotated (well over
100 fields and flags) parse tree.

That tree is then converted node-for-node to a GCC tree that is essentially
GENERIC with a very small number of additional nodes.  Then it's brought
down to GIMPLE.

But a tremendous amount of care is taken during this process to be
sure that all the trees are precisely type-correct.  Ada may well actually
be the only front end that does this.