FEATURE: Destructuring Patterns and Alternatives

Purpose

Support array and object destructuring in as bindings, bind absent members as null, and backtrack through ?// alternatives when a pattern or subsequent expression fails.

Behavior

• Array patterns bind positional elements and use null for missing positions.
• Object patterns bind named fields and nested patterns.
• Alternative patterns try later alternatives when an earlier binding fails.
• Variables introduced by successful alternatives remain available to the following filter.
• Errors from the final alternative propagate as runtime errors.

Programmatic Acceptance

=== AC func-004-conformance ===
Intent: The authoritative corpus slice covering destructuring patterns and alternative bindings executes and passes.
Suite: scoped
Requires: executable=python3; scope=test

import json import os import subprocess import sys

select = r"\?//| as \{" result = subprocess.run( [sys.executable, "sources/run_conformance.py", "--select", select, "--json"], capture_output=True, text=True, env={**os.environ, "JQ": f"{os.getcwd()}/jq"}, ) print(result.stdout) print(result.stderr, file=sys.stderr) report = json.loads(result.stdout) summary = report["summary"] assert sum(summary.values()) > 0 assert summary["fail"] == 0 assert summary["error"] == 0 assert result.returncode == 0 === END AC func-004-conformance ===

User Acceptance

• None.

Guardrails

• Preserve lexical scope and generator backtracking.
• Do not silently convert a final alternative error into a successful value.