Annotate raise_qasm3_error as NoReturn

[TheGupta2012]

Problem

raise_qasm3_error always raises — every path through it ends in a raise. But it was annotated -> None, so to mypy and pylint every caller looked like it could fall through and return nothing. Eight suppressions existed only to silence that:

• # type: ignore[return] on evaluate_expression, _visit_switch_statement, extract_qasm_version, map_qasm_op_to_callable
• inconsistent-return-statements disables in validator.py, analyzer.py, maps/gates.py, maps/expressions.py

Blanket suppressions do not distinguish a function that provably raises from one that genuinely falls through, so real gaps were sitting behind them.

Change

raise_qasm3_error is annotated NoReturn, and all eight suppressions are removed. mypy and pylint then found the three functions the annotation does not cover.

A valid switch crashed. _visit_switch_statement fell off its last branch when no case matched and no default was declared, returning None into result.extend(...):

int i = 5;
switch (i) {
  case 1 { x q; }
  case 2 { z q; }
}
// TypeError: 'NoneType' object is not iterable

The spec does not require a default, so this is valid and must simply contribute no statements. The redundant not case_fulfilled guard is gone too — the loop returns as soon as a case matches, so reaching that line already means none did.

qasm_variable_type_cast fell off its branch chain rather than reporting an unsupported target type. It now raises a ValidationError naming the type and variable.

validate_return_statement fell off its void branch implicitly. It now returns None explicitly, which also lets the else arm flatten out one level of nesting.

Tests

test_switch_no_match_without_default covers the crash. 803 passed, 3 skipped.

Verified against CI's exact linters (pylint==4.0.7, astroid==4.0.4): pylint exits 0 with no messages, isort and black exit 0, mypy reports only the pre-existing tabulate stub error.

[argus-eye]

Argus review

Auto-review is off for this repo. Tick the box below to run a review on this PR.

• Trigger Argus review

Estimated cost

• Files changed: 9
• Diff lines (±): 64
• Historical avg: ~243.6k tokens · ~$0.95 · across last 10 review(s)

Tip: you can also comment @argus-eye review at any time.

[coderabbitai]

Important

Review skipped

Auto reviews are disabled on this repository. Please check the settings in the CodeRabbit UI or the .coderabbit.yaml file in this repository. To trigger a single review, invoke the @coderabbitai review command.

⚙️ Run configuration

Configuration used: Path: .coderabbit.yaml

Review profile: CHILL

Plan: Pro Plus

Run ID: db187a3c-b282-42f0-bee3-824af2e423f5

You can disable this status message by setting the reviews.review_status to false in the CodeRabbit configuration file.

Use the checkbox below for a quick retry:

• 🔍 Trigger review

---

Thanks for using CodeRabbit! It's free for OSS, and your support helps us grow. If you like it, consider giving us a shout-out.

❤️ Share

• X
• Mastodon
• Reddit
• LinkedIn

_{Comment @coderabbitai help to get the list of available commands.}

[codecov-commenter]

Codecov Report

❌ Patch coverage is 94.44444% with 1 line in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
src/pyqasm/maps/expressions.py	0.00%	1 Missing ⚠️

📢 Thoughts on this report? Let us know!