rfc:fetch_property_in_const_expressions

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rfc:fetch_property_in_const_expressions [2022/06/23 11:05] – Link ilutovrfc:fetch_property_in_const_expressions [2022/07/18 21:57] (current) – Move to implemented ilutov
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   * Date: 2022-05-27   * Date: 2022-05-27
   * Author: Ilija Tovilo <ilutov@php.net>   * Author: Ilija Tovilo <ilutov@php.net>
-  * Status: Under discussion+  * Status: Implemented
   * Proposed Version: PHP 8.2   * Proposed Version: PHP 8.2
   * Implementation: https://github.com/php/php-src/pull/8625   * Implementation: https://github.com/php/php-src/pull/8625
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 class A {} class A {}
  
-// Warning: Undefined property: A::$c+// Warning: Undefined property: E::$c
 const C = E::Foo->c; // NULL const C = E::Foo->c; // NULL
 // Note that this will change to an error in PHP 9 https://wiki.php.net/rfc/undefined_property_error_promotion // Note that this will change to an error in PHP 9 https://wiki.php.net/rfc/undefined_property_error_promotion
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   - Order of evaluation   - Order of evaluation
-  - Cache invalidation+  - Caching of constant expression values 
 + 
 +Once we have a solution for these two problems we can extend support of ''->'' in constant expressions to all objects.
  
 ==== Order of evaluation ==== ==== Order of evaluation ====
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 </blockquote> </blockquote>
  
-The ''->'' suffers from the same problem as it may invoke the ''%%__get%%'' magic method with arbitrary side-effects. I incorrectly assumed this wasn't possible because ''%%__get%%'' can only be invoked in combination with ''new'' (as enums don't allow ''%%__get%%'') which are disallowed in these contexts. This assumption was incorrect though as the LHS of the ''->'' operator might be another constant which might be an object.+The ''->'' operator suffers from the same problem as it may invoke the ''%%__get%%'' magic method with arbitrary side-effects. I incorrectly assumed this wasn't possible because ''%%__get%%'' can only be invoked in combination with ''new'' (as enums don't allow ''%%__get%%'') which are disallowed in these contexts. This assumption was incorrect though as the LHS of the ''->'' operator might be another constant which might be an object.
  
 <PHP> <PHP>
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 [1] Ref-counted values consist of non-interned strings, arrays, resources and objects. [1] Ref-counted values consist of non-interned strings, arrays, resources and objects.
  
-==== Allow all ''readonly'' properties ====+==== Allow all readonly properties ====
  
-It was suggested that, instead of restricting ''->'' to be used on all non-enums to restrict access to just non-''readonly'' properties. Unfortunately, this doesn't solve the caching problem described above as ''readonly'' properties can be initialized after object construction and thus becomes non-pure.+It was suggested that instead of restricting ''->'' to be used on all non-enums to restrict access to just non-''readonly'' properties. Unfortunately, this doesn't solve the caching problem described above as ''readonly'' properties can be initialized after object construction and thus becomes non-pure. The enum ''name'' and ''value'' properties are automatically initialized by the engine and thus are truly immutable.
  
 <PHP> <PHP>
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 ===== Vote ===== ===== Vote =====
  
-Voting opened on xxx and closes on xxx.+Voting opened on 2022-07-01 and closes on 2022-07-15.
  
 <doodle title="Add support for fetching properties of enums in constant expressions?" auth="ilutov" voteType="single" closed="true"> <doodle title="Add support for fetching properties of enums in constant expressions?" auth="ilutov" voteType="single" closed="true">
rfc/fetch_property_in_const_expressions.1655982328.txt.gz · Last modified: 2022/06/23 11:05 by ilutov

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