function isValidThisArg(expectedThis, thisArg, sourceCode) {
	if (!expectedThis) {
		return astUtils.isNullOrUndefined(thisArg);
	}
	return astUtils.equalTokens(expectedThis, thisArg, sourceCode);
}
Checks whether or not `thisArg` is not changed by `.call()`/`.apply()`.
@param {ASTNode|null} expectedThis The node that is the owner of the applied function.
@param {ASTNode} thisArg The node that is given to the first argument of the `.call()`/`.apply()`.
@param {SourceCode} sourceCode The ESLint source code object.
@returns {boolean} Whether or not `thisArg` is not changed by `.call()`/`.apply()`.