function normalizeEcmaVersionForLanguageOptions(ecmaVersion) {
	switch (ecmaVersion) {
		case 3:
			return 3;

		// void 0 = no ecmaVersion specified so use the default
		case 5:
		case void 0:
			return 5;

		default:
			if (typeof ecmaVersion === "number") {
				return ecmaVersion >= 2015 ? ecmaVersion : ecmaVersion + 2009;
			}
	}

	/*
	 * We default to the latest supported ecmaVersion for everything else.
	 * Remember, this is for languageOptions.ecmaVersion, which sets the version
	 * that is used for a number of processes inside of ESLint. It's normally
	 * safe to assume people want the latest unless otherwise specified.
	 */
	return LATEST_ECMA_VERSION;
}
Normalize ECMAScript version from the initial config into languageOptions (year)
format.
@param {any} [ecmaVersion] ECMAScript version from the initial config
@returns {number} normalized ECMAScript version