feat: Allow pytket circuits in py expressions

.github/workflows/pull-request.yaml

@@ -52,3 +52,21 @@ jobs:
 
       - name: Run tests
         run: poetry run pytest
+
+      - name: Checkout tket2
+        uses: actions/checkout@v4
+        with:
+          name: CQCL/tket2
+          path: guppy
+
+      - name: Build tket2
+        uses: PyO3/maturin-action@v1
+        with:
+          command: build
+          sccache: 'true'
+          rust-toolchain: '1.75'
+          working-directory: tket2/tket2-py
+
+      - name: Rerun `py(...)` expression tests with tket2 installed
+        run: poetry run pytest tests/integration/test_py.py tests/error/test_py_errors.py
+

guppylang/checker/expr_checker.py

@@ -60,6 +60,7 @@
     NoneType,
     Subst,
     TupleType,
+    row_to_type,
     unify,
 )
 from guppylang.nodes import (
@@ -918,4 +919,25 @@ def python_value_to_guppy_type(
                 return None
             return TupleType(cast(list[GuppyType], tys))
         case _:
+            # Pytket conversion is an optional feature
+            try:
+                import pytket
+
+                if isinstance(v, pytket.circuit.Circuit):
+                    # We also need tket2 installed
+                    try:
+                        import tket2  # type: ignore[import-untyped]  # noqa: F401
+
+                        qubit = globals.types["Qubit"].build()
+                        return FunctionType(
+                            [qubit] * v.n_qubits, row_to_type([qubit] * v.n_qubits)
+                        )
+                    except ImportError:
+                        raise GuppyError(
+                            "Pytket compatibility requires `tket2` to be installed. "
+                            "See https://github.com/CQCL/tket2/tree/main/tket2-py",
+                            node,
+                        ) from None
+            except ImportError:
+                pass
             return None

guppylang/compiler/expr_compiler.py

@@ -1,4 +1,5 @@
 import ast
+import json
 from collections.abc import Iterator
 from contextlib import contextmanager
 from typing import Any
@@ -314,4 +315,15 @@ def python_value_to_hugr(v: Any) -> val.Value | None:
                 return None
             return val.Tuple(vs=vs)
         case _:
+            # Pytket conversion is an optional feature
+            try:
+                import pytket
+
+                if isinstance(v, pytket.circuit.Circuit):
+                    from tket2.circuit import Tk2Circuit  # type: ignore[import-untyped]
+
+                    hugr = json.loads(Tk2Circuit(v).to_hugr_json())
+                    return val.FunctionVal(hugr=hugr)
+            except ImportError:
+                pass
             return None

pyproject.toml

@@ -20,6 +20,7 @@ mypy = "^1.8.0"
 pre-commit = "^3.6.0"
 ruff = "^0.1.11"
 maturin = "^1.4.0"
+pytket = "^1.24.0"
 
 [build-system]
 requires = ["poetry-core"]

tests/error/py_errors/tket2_not_installed.py

@@ -0,0 +1,20 @@
+from pytket import Circuit
+
+from guppylang.decorator import guppy
+from guppylang.module import GuppyModule
+from guppylang.prelude.quantum import quantum, Qubit
+
+circ = Circuit(1)
+circ.H(0)
+
+module = GuppyModule("test")
+module.load(quantum)
+
+
+@guppy(module)
+def foo(q: Qubit) -> Qubit:
+    f = py(circ)
+    return f(q)
+
+
+module.compile()

tests/error/test_py_errors.py

@@ -3,12 +3,21 @@
 
 from tests.error.util import run_error_test
 
+
+try:
+    import tket2
+
+    tket2_installed = True
+except ImportError:
+    tket2_installed = False
+
+
 path = pathlib.Path(__file__).parent.resolve() / "py_errors"
 files = [
     x
     for x in path.iterdir()
     if x.is_file()
-    if x.suffix == ".py" and x.name != "__init__.py"
+    if x.suffix == ".py" and x.name not in ("__init__.py", "tket2_not_installed.py")
 ]
 
 # Turn paths into strings, otherwise pytest doesn't display the names
@@ -18,3 +27,9 @@
 @pytest.mark.parametrize("file", files)
 def test_py_errors(file, capsys):
     run_error_test(file, capsys)
+
+
+@pytest.mark.skipif(tket2_installed, reason="tket2 is installed")
+def test_tket2_not_installed(capsys):
+    path = pathlib.Path(__file__).parent.resolve() / "py_errors" / "tket2_not_installed.py"
+    run_error_test(str(path), capsys)

tests/integration/test_py.py

@@ -1,7 +1,20 @@
+import pytest
+
+from guppylang.decorator import guppy
+from guppylang.module import GuppyModule
+from guppylang.prelude.quantum import Qubit, quantum
 from tests.integration.util import py
 from tests.util import compile_guppy
 
 
+try:
+    import tket2
+
+    tket2_installed = True
+except ImportError:
+    tket2_installed = False
+
+
 def test_basic(validate):
     x = 42
 
@@ -60,3 +73,41 @@ def foo() -> int:
         return x
 
     validate(foo)
+
+
+@pytest.mark.skipif(not tket2_installed, reason="Tket2 is not installed")
+def test_pytket_single_qubit(validate):
+    from pytket import Circuit
+
+    circ = Circuit(1)
+    circ.H(0)
+
+    module = GuppyModule("test")
+    module.load(quantum)
+
+    @guppy(module)
+    def foo(q: Qubit) -> Qubit:
+        f = py(circ)
+        return f(q)
+
+    validate(module.compile())
+
+
+@pytest.mark.skipif(not tket2_installed, reason="Tket2 is not installed")
+def test_pytket_multi_qubit(validate):
+    from pytket import Circuit
+
+    circ = Circuit(3)
+    circ.CX(0, 1)
+    circ.H(2)
+    circ.T(0)
+    circ.CZ(2, 0)
+
+    module = GuppyModule("test")
+    module.load(quantum)
+
+    @guppy(module)
+    def foo(q1: Qubit, q2:Qubit, q3:Qubit) -> tuple[Qubit, Qubit, Qubit]:
+        return py(circ)(q1, q2, q3)
+
+    validate(module.compile())