null checks vs. class resolution, and translation strategy for casts

Brian Goetz brian.goetz at
Tue Apr 14 13:56:06 UTC 2020

> How it is better than a new opcode "unbox" with exactly the same semantics ?

For one, an “unbox” opcode assumes that the VM understands the fictitious relationship between the val and ref projections.  But these are language fictions; the VM sees only classes related by extension and sealing.

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