Fence instruction incorrectly typed inside measurement calibration

[mhodson-rigetti]

Pre-Report Checklist

• I am running the latest versions of pyQuil and the Forest SDK
• I checked to make sure that this bug has not already been reported

Issue Description and reproduction recipe

With pyquil==4.14.0 the following occurs:

from pyquil import Program
from pyquil.quilbase import Gate

program = Program("""
FENCE
DEFCAL TEST 1:
    FENCE 0
DEFCAL MEASURE 0 addr:
    FENCE 0
""")

print("Instruction (top level):")

instruction = program.instructions[0]
print(f"instruction = {instruction}")

fence_is_gate = isinstance(instruction, Gate)
print(f"fence_is_gate = {fence_is_gate}")

print()

calibration = program.calibrations[0]

print("Instruction (inside gate calibration):")

instruction = calibration.instructions[0]
print(f"instruction = {instruction}")

fence_is_gate = isinstance(instruction, Gate)
print(f"fence_is_gate = {fence_is_gate}")

print()

calibration = program.measure_calibrations[0]

print("Instruction (inside measurement calibration):")

instruction = calibration.instructions[0]
print(f"instruction = {instruction}")

fence_is_gate = isinstance(instruction, Gate)
print(f"fence_is_gate = {fence_is_gate}")

print()

Erroneous output

Instruction (top level):
instruction = FENCE
fence_is_gate = False

Instruction (inside gate calibration):
instruction = FENCE
fence_is_gate = False

Instruction (inside measurement calibration):
instruction = Fence(Fence { qubits: [Fixed(0)] })
fence_is_gate = True

The FENCE instruction, when embedded in a measurement calibration, comes through with some sort of malformed type which makes it equivalent to a Gate, but then if you treat it as such of course the relevant members are missing.

I am unsure if this is an issue in the pyquil inheritance from quil-py or deeper in the Rust bindings?