What happened

After the parser refactoring in #17977, promtool check config no longer respects --enable-feature flags for PromQL experimental features (e.g. promql-experimental-functions, promql-extended-range-selectors).

Root cause

In cmd/promtool/main.go, the CheckConfig function creates a default parser with no features enabled:

// cmd/promtool/main.go:622
rulesFailed, rulesHaveErrors := checkRules(ruleFiles, lintSettings.rulesLintConfig, parser.NewParser(parser.Options{}))

Before #17977, this code path called parser.ParseExpr() which read global flags that were set earlier in main(). Now that globals are replaced with per-instance options, this call site uses a fresh parser that ignores the user's feature flags stored in promtoolParserOpts.

Expected behavior

promtool check config --enable-feature=promql-experimental-functions myconfig.yml should accept rules using experimental PromQL functions.

Actual behavior

Rules using experimental PromQL functions are rejected with parse errors, even when the corresponding --enable-feature flag is passed.

Fix

Pass promtoolParser (or accept it as a parameter) instead of parser.NewParser(parser.Options{}).