rfc:intersection_types

Differences

This shows you the differences between two versions of the page.

Link to this comparison view

Both sides previous revisionPrevious revision
Next revision
Previous revision
Last revisionBoth sides next revision
rfc:intersection_types [2016/04/27 17:28] levimrfc:intersection_types [2016/04/28 14:26] – Add note about missing implementation for mixing unions and intersections levim
Line 3: Line 3:
   * Date: 2016-04-27   * Date: 2016-04-27
   * Author: Levi Morrison <levim@php.net>   * Author: Levi Morrison <levim@php.net>
-  * Status: Draft+  * Status: Under Discussion
   * First Published at: http://wiki.php.net/rfc/intersection_types   * First Published at: http://wiki.php.net/rfc/intersection_types
  
Line 12: Line 12:
 Intersection types allow the programmer to write multiple type declarations for a parameter or return value. The value must satisfy all of the declared types. Each type is separated by ampersand (''&''). Intersection types allow the programmer to write multiple type declarations for a parameter or return value. The value must satisfy all of the declared types. Each type is separated by ampersand (''&'').
  
-Here is a practical example:+Here is a practical example. Given this definition:
  
 <PHP> <PHP>
Line 27: Line 27:
     }     }
 } }
 +</PHP>
  
-// Fatal error: Uncaught TypeError: Argument 1 passed to RecordsToList() must be Countable and Traversable, array given, called in %s on line %d +This will error ([[https://3v4l.org/qCeXi/rfc#rfc-multi-types|see on 3v4l.org]]): 
-echo RecordsToHtml(["Lennon", "McCartney", "Starr", "Harrison"]);+<PHP> 
 +// Argument 1 passed to RecordsToList() must be Countable and Traversable, array given 
 +echo RecordsToList(["Lennon", "McCartney", "Starr", "Harrison"]); 
 +</PHP>
  
-// Fine+This works correctly ([[https://3v4l.org/7GvqN/rfc#rfc-multi-types|see on 3v4l]]): 
-echo RecordsToHtml(new ArrayObject(["Lennon", "McCartney", "Starr", "Harrison"]));+<PHP> 
 +echo RecordsToList(new ArrayObject(["Lennon", "McCartney", "Starr", "Harrison"]));
 // Output: // Output:
 // <ol> // <ol>
Line 40: Line 45:
 //     <li>Harrison</li> //     <li>Harrison</li>
 // </ol> // </ol>
- 
 </PHP> </PHP>
  
-Note that if [[rfc:union_types|Union Types]] are also accepted then something like this will be possible, allowing for an array or an object that satisfies both constraints:+Note that if [[rfc:union_types|Union Types]] are also accepted then something like this will be possible((The experimental patch provided by Joe and Bob currently does not support mixing unions and intersections)), allowing for an array or an object that satisfies both Countable and Traversable:
 <PHP> <PHP>
 function RecordsToList(Array | (Countable & Traversable) $input): String { function RecordsToList(Array | (Countable & Traversable) $input): String {
Line 58: Line 62:
 } }
 </PHP> </PHP>
 +
 +When union and intersection types are in the same expression they must be grouped with parenthesis (demonstrated above). The following is invalid:
 +
 +<PHP>
 +function RecordsToList(Array | Countable & Traversable $input): String {
 +    // ...
 +}
 +</PHP>
 +
  
 ===== Backward Incompatible Changes ===== ===== Backward Incompatible Changes =====
Line 77: Line 90:
  
 ===== References ===== ===== References =====
-Original announcement on Mailing List of rationale for this feature: http://news.php.net/php.internals/92252+  * Original announcement on Mailing List of rationale for this feature: http://news.php.net/php.internals/92252 
 +  * Announcement for discussion phase: http://news.php.net/php.internals/92857
  
rfc/intersection_types.txt · Last modified: 2017/09/22 13:28 by 127.0.0.1