src/vs/platform/contextkey/common/contextkey.ts/ContextKeyRegexExpr/equals
class ContextKeyRegexExpr:	public equals(other: ContextKeyExpression): boolean {
		if (other.type === this.type) {
			const thisSource = this.regexp ? this.regexp.source : '';
			const otherSource = other.regexp ? other.regexp.source : '';
			return (this.key === other.key && thisSource === otherSource);
		}
		return false;
	}