bugfix: copy-instance was not robust enough #905
Merged
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This partially addresses one source of "nondeterminism" in quilc compilation (see #676) that was due to a violation of referential transparency.
Specifically, non destructive compilation was not non-destructive enough: compiling the same parsed-program instance twice produced two different outputs. This was because copy-instance did not copy instances of measurement deeply, resulting in different outputs from compress-qubits, with downstream consequences.
This only addresses #676 in those cases where you are not parsing the same raw text-based source everytime you compile. Or equivalently, when you are not rebuilding your
Program
object from pyquil every time.