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5.4 Notes

Generalized back-end notion provides dynamic retargeting? (for byte code)

The current node type annotations seem to be somewhat unsatisfactory, since we lose information when we do a THE on a continuation that already has uses, or when we convert a let where the actual result continuation has other uses.

But the case with THE isn’t really all that bad, since the test of whether there are any uses happens before conversion of the argument, thus THE loses information only when there are uses outside of the declared form. The LET case may not be a big deal either.

Note also that losing user assertions isn’t really all that bad, since it won’t damage system integrity. At worst, it will cause a bug to go undetected. More likely, it will just cause the error to be signaled in a different place (and possibly in a less informative way). Of course, there is an efficiency hit for losing type information, but if it only happens in strange cases, then this isn’t a big deal.