GeezerVison

Summary

This is the deferred override half requested in #9756 (comment). The generator-supported corrections have been split into #9795, an independent PR to merge first. Both branches are based directly on main.

• Add an explicit text_signature attribute for legacy signatures that the generator cannot express.
• Apply it to the 21 str/bytes/bytearray search and prefix/suffix methods with nested optional groups, and to _csv.reader, writer, and register_dialect.
• Validate overrides against actual binding metadata at compile time: parameter count, requiredness, receiver markers, kinds, keyword names, and known flattened binders. CSV's documented keyword dialect requires a matching optional positional parameter plus an actual keyword collector.
• Keep the ordinary FromArgs derives, metadata, converters, dispatch, and CSV's delayed validation unchanged. The previous py_optional_group and DefaultRepr::OptionalGroup implementation is removed.

This stays draft for the final text-signature phase. The supported override grammar is intentionally narrow: positional parameters, /, literal defaults, **kwargs, and nested trailing optional groups. Ordinary symbolic/default corrections continue to use the generator.

Validation

At final head 4f745ac05:

• Configured commit hooks passed.
• Full workspace Rust tests and doctests passed: 1,549 passed and 20 ignored across their reported groups. This includes compilation of all 24 override annotations and the four real compile-fail rustdoc cases.
• C-API tests passed: 149 passed, 2 ignored.
• Strict workspace/all-target and separate C-API Clippy passed.
• Release build passed.
• Signature and CSV snippets passed on RustPython and CPython 3.15.1; both selected RustPython pytest cases passed.
• test_str test_bytes test_inspect test_csv passed: all 4 files, 992 tests run, 77 skipped.
• Both split branches merge cleanly and preserve all original Python test statements across the two PRs.

All native checks used a clean rebuild of every workspace package. No source fix or additional push was needed after publication. GitHub CI is tracked separately; its final results are not claimed here.

AI assistance

Split, override implementation, review, and validation were performed with Codex. Original grouped-signature and CSV binding regressions are preserved; the CSV invalid-name error-text regression moved with its runtime fix to the independent generated-signature PR.