[Select] Document how values are compared (#17912)

docs/pages/api/select.md

@@ -41,7 +41,7 @@ You can learn more about the difference by [reading this guide](/guides/minimizi
 | <span class="prop-name">open</span> | <span class="prop-type">bool</span> |  | Control `select` open state. You can only use it when the `native` prop is `false` (default). |
 | <span class="prop-name">renderValue</span> | <span class="prop-type">func</span> |  | Render the selected value. You can only use it when the `native` prop is `false` (default).<br><br>**Signature:**<br>`function(value: any) => ReactElement`<br>*value:* The `value` provided to the component. |
 | <span class="prop-name">SelectDisplayProps</span> | <span class="prop-type">object</span> |  | Props applied to the clickable div element. |
-| <span class="prop-name">value</span> | <span class="prop-type">any</span> |  | The input value. Providing an empty string will select no options. This prop is required when the `native` prop is `false` (default). Set to an empty string `''` if you don't want any of the available options to be selected. |
+| <span class="prop-name">value</span> | <span class="prop-type">any</span> |  | The input value. Providing an empty string will select no options. This prop is required when the `native` prop is `false` (default). Set to an empty string `''` if you don't want any of the available options to be selected.<br>If the value is an object it must have reference equality with the option in order to be selected. If the value is not an object, the string representation must match with the string representation of the option in order to be selected. |
 | <span class="prop-name">variant</span> | <span class="prop-type">'standard'<br>&#124;&nbsp;'outlined'<br>&#124;&nbsp;'filled'</span> | <span class="prop-default">'standard'</span> | The variant to use. |
 
 The `ref` is forwarded to the root element.

packages/material-ui/src/Select/Select.js

@@ -191,6 +191,9 @@ Select.propTypes = {
    * The input value. Providing an empty string will select no options.
    * This prop is required when the `native` prop is `false` (default).
    * Set to an empty string `''` if you don't want any of the available options to be selected.
+   *
+   * If the value is an object it must have reference equality with the option in order to be selected.
+   * If the value is not an object, the string representation must match with the string representation of the option in order to be selected.
    */
   value: PropTypes.any,
   /**