rfc:prototype_checks

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rfc:prototype_checks [2011/09/19 11:18] – colderrfc:prototype_checks [2014/04/08 22:52] – Inactive levim
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-====== Request for Comments: How to write RFCs ======+====== Request for Comments: Prototype checks ======
   * Version: 1.0   * Version: 1.0
   * Date: 2011-09-19   * Date: 2011-09-19
   * Author: Etienne Kneuss <colder@php.net>   * Author: Etienne Kneuss <colder@php.net>
-  * Status: Under Discussion+  * Status: Inactive
   * First Published at: http://wiki.php.net/rfc/prototype_checks   * First Published at: http://wiki.php.net/rfc/prototype_checks
  
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 ==== Implementing abstract method ==== ==== Implementing abstract method ====
 +=== Normal methods ===
 The prototype is checked with current normal rules (see Current rules). Any mismatch with current rules generates a FATAL error. The prototype is checked with current normal rules (see Current rules). Any mismatch with current rules generates a FATAL error.
 +=== Constructors ===
 +  * In 5.3: No checks are performed
 +  * In 5.4: The prototype is checked with current normal rules (see Current rules). Any mismatch with current rules generates a FATAL error.
  
 ==== Implementing interface method ==== ==== Implementing interface method ====
 +=== All Methods ===
 The prototype is checked with current normal rules (see Current rules). Any mismatch with current rules generates a FATAL error. The prototype is checked with current normal rules (see Current rules). Any mismatch with current rules generates a FATAL error.
  
-==== Overriding existing method ==== 
  
 +==== Overriding concrete method ====
 +=== Normal methods ===
 The prototype is checked with current normal rules (see Current rules). Any mismatch with current rules generates a STRICT error. The prototype is checked with current normal rules (see Current rules). Any mismatch with current rules generates a STRICT error.
 +=== Constructors ===
 +No checks are performed.
  
 +==== Overriding abstract method ====
 +Scenario:
 +
 +  abstract class ParentAbs {
 +      abstract public function foo($a);
 +  }
 +  abstract class SubAbs extends ParentAbs {
 +      abstract public function foo($a);
 +  }
 +  
 +NOT allowed, always result in a fatal error even if the prototypes are compatible.
 +
 +==== Overriding interface method ====
 +Scenario:
 +
 +  interface ParentIface {
 +      function foo($a);
 +  }
 +  interface SubIface extends ParentIface {
 +      function foo($a);
 +  }
 +  
 +NOT allowed, always result in a fatal error even if the prototypes are compatible.
 +
 +  
 ===== Current rules ===== ===== Current rules =====
  
-This part specifies what is currently considered as a compatible signature: 
 ==== Allowed ==== ==== Allowed ====
 +This part specifies what is currently considered as valid signature modifications:
 +
 === Adding new optional arguments === === Adding new optional arguments ===
  
   function foo($a)   function foo($a)
-becomes+is compatible with, in a sub class:
   function foo($a, $b = 42)   function foo($a, $b = 42)
  
Line 40: Line 72:
  
   function foo($a)   function foo($a)
-becomes+is compatible with, in a sub class:
   function &foo($a)   function &foo($a)
  
 +==== Mismatch ====
 +This part specifies what is currently considered as invalid signature modifications:
 +
 +=== Strenghtening the type hint ===
 +Given:
 +  class A {}
 +  class B extends A{}
 +
 +  function foo(A $a)
 +is imcompatible with, in a sub class:
 +  function foo(B $a)
 +
 +=== Removing a return by ref ===
 +
 +  function &foo()
 +is imcompatible with, in a sub class:
 +  function foo()
 +
 +
 +=== Adding a mandatory argument ===
 +
 +  function foo()
 +is imcompatible with, in a sub class:
 +  function foo($a)
 +
 +==== Mismatch but theoretically compatible ====
 +
 +This part specifies what is currently considered as invalid modifications, despite being theoretically sound:
 +
 +=== Removing the type hint ===
 +
 +  function foo(Array $a)
 +is currently imcompatible with, in a sub class:
 +  function foo($a)
 +
 +=== Weakening the type hint ===
 +Given:
 +  class A {}
 +  class B extends A{}
 +
 +  function foo(B $a)
 +is currently imcompatible with, in a sub class:
 +  function foo(A $a)
 +
 +=== Arg no longer by ref ===
 +
 +  function foo(&$a)
 +is currently imcompatible with, in a sub class:
 +  function foo($a)
 +
 +
 +=== Requiring less arguments ===
 +
 +  function foo($a)
 +is currently imcompatible with, in a sub class:
 +  function foo()
 +
 +
 +===== Topics worth discussing =====
 +
 +==== Allow more theoretically valid modifications ====
 +
 +We have three wrong errors for modifications that should be accepted. Some of those might require more sophisticated checks than others, so not all might be worth including.
 +
 +==== Clarify the constructor problem ====
 +Constructors can be seen as pseudo-static methods, for this reason, the same checks for normal methods do not always apply for constructors.
 +
 +It is however unclear whether we really want, for constructors, to be more strict (and how strict) if they are defined via an abstract class. So:
 +
 +  - Do we really want that check to be performed on 5.4 for constructors coming from abstract methods
 +  - Do we really want the mismatch to result in a FATAL error (potential BC break coming from 5.3 where no checks were done)
 +
 +
 +==== Similar prototypes from different interfaces ====
 +It would be better to allow multiple interfaces to define the same intersection of prototype. It is currently not allowed in any case.
 +
 +For example:
  
 +  interface A {
 +    function apply($a, $b);
 +    // ...
 +  }
 +  
 +  interface B {
 +     function apply($a, $b);
 +     // ...
 +  }
 +  
 +  class C implements A, B { .. }
  
 +This is currently not allowed, but there is no reason why it shouldn't be.
rfc/prototype_checks.txt · Last modified: 2017/09/22 13:28 by 127.0.0.1

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