Expand keyword-in-ref coverage for complex parser edge cases (interpreter + RVM)

[Copilot]

The existing keyword-in-ref tests covered common cases but missed several high-value parser edge paths. This update broadens coverage to ensure keyword field handling is exercised in complex and corner-case reference shapes across both execution paths.

• Interpreter coverage: complex keyword ref scenarios

  • Extended /tests/interpreter/cases/refr/keywords_in_refs.yaml with cases for:
    • future-keyword fields used as ref segments without import future.keywords
    • keyword segments inside package paths
    • keyword segments inside import paths
    • keyword segments in rule-head reference paths
    • mixed dot-keyword access plus dynamic bracket indexing

• RVM parity coverage

  • Added matching scenarios in /tests/rvm/rego/cases/chained_access.yaml so RVM exercises the same reference patterns and semantics as interpreter coverage.

• Result-shape consistency

  • Normalized expected literal formatting in YAML where needed to avoid ambiguity in string-valued array expectations.

package test
import data.catalog.if.default as kw

segment := "import"
result := input.package[segment].value
x := data.words.if.default.value
y := kw.value

[Copilot]

Pull request overview

This PR expands keyword-in-reference parsing support in the core Rego parser so that reserved keywords (and imported future keywords) can be used as dot-notation field names (e.g. input.package.format, data.words.if.default.value) without being rejected as keywords. It then adds interpreter and RVM regression tests to exercise these edge-case reference shapes and ensure execution-path parity.

Changes:

• Added Parser::parse_ref_field() to accept any TokenKind::Ident as a ref field segment after . (including keyword spellings).
• Updated ref/path/rule-head parsing to use parse_ref_field() instead of parse_var() / parse_ident() for dot segments.
• Added/extended YAML test coverage for keyword segments in refs (interpreter + RVM), including package/import paths and dynamic bracket indexing mixed with keyword dot access.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated no comments.

File	Description
src/parser.rs	Allows keyword spellings as dot-notation ref field segments by introducing parse_ref_field() and wiring it into ref/path/rule-ref parsing.
tests/rvm/rego/cases/chained_access.yaml	Adds RVM cases covering keyword segments in refs across package fields, package/import paths, rule-head refs, and mixed dot+dynamic bracket access.
tests/interpreter/cases/refr/keywords_in_refs.yaml	Adds interpreter coverage for keywords-as-field-names in dot refs, including reserved keywords and selected complex edge shapes.