From 7e22ad3d4b8644b6f3bce442d9ea20a1765c9989 Mon Sep 17 00:00:00 2001
From: Mark Hodson <58451176+mhodson-rigetti@users.noreply.github.com>
Date: Fri, 7 Jul 2023 08:24:14 +0930
Subject: [PATCH] fix:`Program.copy_everything_except_instructions()` no longer
 adds declarations to the instructions property (#1612)

* Reverse RC23 change set (code only, not the test).

* Fix: Program.declarations is a view on Program.instructions and should not be copied.

This alternate solution makes the test that was developed for #1596 pass, where previously it failed. This should resolve both #1596 and #1611.

* Fix: the shallow copy() method needs to copy the declarations
---
 pyquil/api/_rewrite_arithmetic.py  | 3 +--
 pyquil/quil.py                     | 6 ++----
 test/unit/test_quantum_computer.py | 4 +++-
 3 files changed, 6 insertions(+), 7 deletions(-)

diff --git a/pyquil/api/_rewrite_arithmetic.py b/pyquil/api/_rewrite_arithmetic.py
index fe2cea3b8..fc674dc1f 100644
--- a/pyquil/api/_rewrite_arithmetic.py
+++ b/pyquil/api/_rewrite_arithmetic.py
@@ -138,8 +138,7 @@ def expr_mref(expr: object) -> MemoryReference:
                 # so we divide by 8...
                 expr = str(Div(inst.scale, 8))
                 updated.inst(SetScale(inst.frame, expr_mref(expr)))
-        # Program.copy_everything_except_instructions persists DECLARE statements
-        elif not isinstance(inst, Declare):
+        else:
             updated.inst(inst)
 
     if mref_idx > 0:
diff --git a/pyquil/quil.py b/pyquil/quil.py
index ab3df733d..e11c89634 100644
--- a/pyquil/quil.py
+++ b/pyquil/quil.py
@@ -183,9 +183,6 @@ def copy_everything_except_instructions(self) -> "Program":
         """
         new_prog = Program()
         new_prog._calibrations = self.calibrations.copy()
-        for declaration in self.declarations.values():
-            new_prog.inst(declaration)
-        new_prog._declarations = self._declarations.copy()
         new_prog._waveforms = self.waveforms.copy()
         new_prog._defined_gates = self._defined_gates.copy()
         new_prog._frames = self.frames.copy()
@@ -203,8 +200,9 @@ def copy(self) -> "Program":
 
         :return: a new Program
         """
-        new_prog = self.copy_everything_except_instructions()
+        new_prog = self.copy_everything_except_instructions()  # and declarations, which is a view
         new_prog._instructions = self._instructions.copy()
+        new_prog._declarations = self._declarations.copy()
         return new_prog
 
     @property
diff --git a/test/unit/test_quantum_computer.py b/test/unit/test_quantum_computer.py
index dfb09275e..1d78a7a57 100644
--- a/test/unit/test_quantum_computer.py
+++ b/test/unit/test_quantum_computer.py
@@ -834,7 +834,7 @@ def test_qc_expectation_on_qvm(client_configuration: QCSClient, dummy_compiler:
 
 def test_undeclared_memory_region(client_configuration: QCSClient, dummy_compiler: DummyCompiler):
     """
-    Fix for https://github.com/rigetti/pyquil/issues/1596
+    Test for https://github.com/rigetti/pyquil/issues/1596
     """
     program = Program(
         """
@@ -847,6 +847,8 @@ def test_undeclared_memory_region(client_configuration: QCSClient, dummy_compile
 """
     )
     program = program.copy_everything_except_instructions()
+    assert len(program.instructions) == 0  # the purpose of copy_everything_except_instructions()
+    assert len(program.declarations) == 0  # this is a view on the instructions member; must be consistent
     qc = QuantumComputer(name="testy!", qam=QVM(client_configuration=client_configuration), compiler=dummy_compiler)
     executable = qc.compiler.native_quil_to_executable(program)
     qc.run(executable)