@function __index-by-aggregator($result, $value, $key, $args...) {
  @return __set($result, $key, $value);
}

@function __index-by($arguments...) {
  $function: __create-aggregator("__index-by-aggregator");

  @return __exec($function, $arguments...);
}

/// Creates a map composed of keys generated from the results of running
/// each element of `$collection` through `$iteratee`. The corresponding value
/// of each key is the last element responsible for generating the key. The
/// iteratee function is bound to `$this-arg` and invoked with three arguments;
/// (value, index|key, collection).
///
/// If a property name is provided for `$predicate` the created `_property`
/// style callback returns the property value of the given element.
///
/// If a value is also provided for `$this-arg` the created `_matches-property`
/// style callback returns `true` for elements that have a matching property
/// value, else `false`.
///
/// If a map is provided for `$predicate` the created `_matches` style
/// callback returns `true` for elements that have the properties of the given
/// object, else `false`.
///
///
/// @access public
/// @group Collection
/// @param {List|Map|string} $collection The collection to iterate over.
/// @param {Function|Map|string} $iteratee [_identity] - The function invoked
///  per iteration.
/// @param {*} $this-arg [null] - The `_this` binding of `$iteratee`.
/// @returns {Map} Returns the composed aggregate object.
/// @example scss
/// // todo

@function _index-by($args...) {
  @return call(get-function("__index-by"), $args...);
}