🔧 Replace mypy with ty

[denialhaag]

Description

This PR replaces mypy with ty.

Checklist:

• The pull request only contains commits that are focused and relevant to this change.
• I have added appropriate tests that cover the new/changed functionality.
• I have updated the documentation to reflect these changes.
• I have added entries to the changelog for any noteworthy additions, changes, fixes, or removals.
• I have added migration instructions to the upgrade guide (if needed).
• The changes follow the project's style guidelines and introduce no new warnings.
• The changes are fully tested and pass the CI checks.
• I have reviewed my own code changes.

[coderabbitai]

📝 Walkthrough

Walkthrough

Migrate static typing from mypy to Ty: enable Ty in CI, replace pre-commit mypy hook with a local ty-check hook, add Ty config and dependency, and update code/tests with type-import adjustments, signature changes, and type-ignore annotations to satisfy Ty.

Changes

Cohort / File(s)	Summary
CI & Tooling \.github/workflows/ci.yml, \.pre-commit-config.yaml, pyproject.toml, CHANGELOG.md	Enable ty in CI (enable-ty: true, disable mypy), add ty dev dependency and [tool.ty.*] config, replace pre-commit mypy hook with local ty-check (uv run ty check), and record changelog entry.
Typing imports & small annotations src/mqt/predictor/hellinger/utils.py, src/mqt/predictor/reward.py, src/mqt/predictor/ml/helper.py, src/mqt/predictor/utils.py	Adjust TYPE_CHECKING import origins, small type annotation refinements, and add targeted # type: ignore[...] to silence Ty where needed (no runtime changes).
RL parsing / signatures src/mqt/predictor/rl/parsing.py, src/mqt/predictor/rl/predictor.py, src/mqt/predictor/rl/predictorenv.py	Change return/type annotations and signatures: Gate and Target typing moves to TYPE_CHECKING; postprocess_vf2postlayout now returns ApplyLayout; compile_as_predicted accepts `QuantumCircuit
Predictor ML typing & error handling src/mqt/predictor/ml/predictor.py, src/mqt/predictor/ml/helper.py	Add type: ignore annotations on QuantumCircuit.from_qasm_file calls, replace assertion-based unreachable with NotImplementedError, and silence specific type warnings.
Runtime pass handling & guards src/mqt/predictor/rl/helper.py, src/mqt/predictor/rl/predictorenv.py, tests/compilation/test_helper_rl.py	Remove unnecessary str() for path args, add runtime assertions/casts for transpile passes, ensure layout existence before post-processing, and construct PassManager from pass lists.
Tests — typing and data shapes tests/compilation/test_integration_further_SDKs.py, tests/compilation/test_reward.py, tests/hellinger_distance/test_estimated_hellinger_distance.py	Update test signatures/fixtures to new typed shapes (e.g., dict[PassType, list[Action]]), add runtime isinstance checks for passes/actions, convert list-based data to NumPy arrays, and add targeted ty: ignore where necessary.

Sequence Diagram(s)

(Skipped — changes are tooling migration and scattered typing/signature updates, not a new multi-component runtime control flow.)

Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~25 minutes

Possibly related PRs

• 🔧 Enable ty for type checking qcec#775 — same migration enabling ty in CI, replacing mypy with ty-check hook, and adding Ty config.
• 🚨 Enable Astral's type checker ty core#1333 — matching repository-level changes to enable Ty and add Ty configuration/dev dependency.
• 🔧 Fix ty configuration qcec#784 — related pre-commit adjustments introducing a local ty-check hook.

Suggested labels

documentation

Poem

🐇
I hopped through types and CI light,
swapped mypy cape for Ty tonight.
Imports nudged and tests made new,
linting tuned — a tidy view.
Carrots for builds that pass just right! 🍃

🚥 Pre-merge checks | ✅ 3

✅ Passed checks (3 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly and concisely summarizes the main change: replacing mypy with ty as the type checker.
Docstring Coverage	✅ Passed	Docstring coverage is 90.91% which is sufficient. The required threshold is 80.00%.
Description check	✅ Passed	The pull request provides a brief description of replacing mypy with ty, includes a comprehensive checklist with most items checked, but lacks detailed context about motivation, rationale, or dependencies.

_{✏️ Tip: You can configure your own custom pre-merge checks in the settings.}

✨ Finishing touches

• 📝 Generate docstrings

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[coderabbitai]

Actionable comments posted: 4

🤖 Fix all issues with AI agents

In `@src/mqt/predictor/ml/helper.py`:
- Around line 121-123: The call site uses qc.count_ops() (returns a
Counter/Mapping-like object) and currently silences the type mismatch with a
ty-ignore; update the signature of dict_to_featurevector to accept a
Mapping[str, int] (or collections.abc.Mapping) instead of a concrete dict so it
directly accepts ops_list without casting, remove the ty: ignore in the call,
and add any needed typing import (Mapping) and adjust internal code in
dict_to_featurevector to treat the input as a mapping of str->int.

In `@src/mqt/predictor/rl/predictorenv.py`:
- Around line 17-18: Remove the unused noqa marker on the import of TketBasePass
in predictorenv.py: delete the trailing "# noqa: PLC2701" from the line
importing pytket._tket.passes.BasePass (aliased as TketBasePass) so the import
is a plain statement alongside the QiskitBasePass import; ensure no other noqa
markers are added for TketBasePass or QiskitBasePass.

In `@tests/compilation/test_integration_further_SDKs.py`:
- Line 42: The parameter annotation for available_actions_dict is wrong: replace
dict[str, list[Action]] with dict[PassType, list[Action]] wherever used (e.g.,
in test_bqskit_o2_action and the other test functions that accept
available_actions_dict) so the type matches the fixture returning keys of type
PassType; update the function signatures (and any related type hints) to use
PassType as the dict key type and ensure PassType is imported where needed.

In `@tests/hellinger_distance/test_estimated_hellinger_distance.py`:
- Around line 254-258: The test uses rng.integers(0, 10) which can produce 0 and
generates 1‑D feature arrays; change to a deterministic positive sample count
(e.g. set random_int = 5) and construct X_train as a 2‑D array (e.g.
rng.random((random_int, n_features))) while keeping y_train as a 1‑D array of
length random_int so TrainingData(X_train=..., y_train=...) provides a non-empty
2‑D feature matrix compatible with RandomForestRegressor and avoids spurious
failures when checking device count.

[coderabbitai]

Actionable comments posted: 2

🤖 Fix all issues with AI agents

In `@src/mqt/predictor/rl/predictorenv.py`:
- Around line 19-20: Remove the no-op conditional that checks "if
sys.version_info >= (3, 11) and TYPE_CHECKING:  # pragma: no cover" in
predictorenv.py; delete that entire empty block (the conditional and its "pass")
so there is no dead code left behind, keeping imports and other logic intact.

In `@tests/compilation/test_integration_further_SDKs.py`:
- Line 20: The import line "from pytket._tket.passes import BasePass as
TketBasePass" contains an unnecessary "# noqa: PLC2701" directive; remove that
trailing noqa comment so the import is clean and linter warnings about unused
noqa are resolved—edit the import statement that defines TketBasePass to drop
the "# noqa: PLC2701" suffix.

♻️ Duplicate comments (1)

src/mqt/predictor/rl/predictorenv.py (1)

17-17: Remove unused noqa directive.

Static analysis flags # noqa: PLC2701 as unused on this import.

🧹 Proposed fix

-from pytket._tket.passes import BasePass as TketBasePass  # noqa: PLC2701
+from pytket._tket.passes import BasePass as TketBasePass

[codecov]

Codecov Report

❌ Patch coverage is 85.18519% with 4 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
src/mqt/predictor/ml/predictor.py	60.0%	2 Missing ⚠️
src/mqt/predictor/rl/predictorenv.py	88.8%	2 Missing ⚠️

📢 Thoughts on this report? Let us know!

[coderabbitai]

Actionable comments posted: 1

🤖 Fix all issues with AI agents

In `@src/mqt/predictor/ml/predictor.py`:
- Line 179: The call to QuantumCircuit.from_qasm_file(filename) uses a
type-check suppression; instead normalize the argument by converting filename to
a string (e.g., use str(filename) or filename.as_posix()) before passing it and
remove the "# ty: ignore" comment; update the call site where
QuantumCircuit.from_qasm_file is invoked so it passes str(filename) (or
filename.as_posix()) to satisfy the type checker and keep the call readable.

♻️ Duplicate comments (2)

src/mqt/predictor/ml/predictor.py (2)

356-356: Same type-ignore concern as above.
Consider converting the Path to str here as well to avoid suppression.

---

466-468: Same type-ignore concern as above.
Converting the Path to str avoids the ignore and keeps the call type-safe.

[burgholzer]

This looks reasonable 👍🏻 thanks 🙏