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| rfc:closures_in_const_expr [2024/11/04 12:01] – timwolla | rfc:closures_in_const_expr [2024/11/13 13:35] (current) – Voting timwolla |
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| * Date: 2024-10-24 | * Date: 2024-10-24 |
| * Author: Tim Düsterhus (tim@tideways-gmbh.com), Volker Dusch (volker@tideways-gmbh.com) | * Author: Tim Düsterhus (tim@tideways-gmbh.com), Volker Dusch (volker@tideways-gmbh.com) |
| * Status: Under Discussion | * Status: In Voting |
| * First Published at: https://wiki.php.net/rfc/closures_in_const_expr | * First Published at: https://wiki.php.net/rfc/closures_in_const_expr |
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| If Closures are placed in constant expressions they are subject to the following constraints: | If Closures are placed in constant expressions they are subject to the following constraints: |
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| * They may not include variables from the surrounding scope using <php>use($foo, $bar)</php>, because except for constants and static variables there is no surrounding scope. This also means that short closures (arrow functions) are not supported, because they perform implicit capturing. This constraint is consistent with how variables may not be part of a constant expression. | * They may not include variables from the surrounding scope using <php>use($foo, $bar)</php>, because except for constants and possibly for default parameter values there is no surrounding scope. This also means that short closures (arrow functions) are not supported, because they perform implicit capturing. This constraint is consistent with how variables may not be part of a constant expression. |
| * They must be <php>static</php> (and thus they must not access <php>$this</php>). Semantically <php>$this</php> would only be well-defined for property default values and possibly attribute parameters, but this would require reevaluating the Closure for each object / attribute instance, which would be different to existing constant expressions which are only evaluated once. This constraint is consistent with how <php>new</php> expressions may not be used in property default values. | * They must be <php>static</php> (and thus they must not access <php>$this</php>). Semantically <php>$this</php> would only be well-defined for property default values and possibly attribute parameters, but this would require reevaluating the Closure for each object / attribute instance, which would be different to existing constant expressions which are only evaluated once. This constraint is consistent with how <php>new</php>-expressions may not be used in property default values. |
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| Both of these constraints will be verified at compile time. | Both of these constraints will be verified at compile time. |
| </PHP> | </PHP> |
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| Passing a Closure to a new expression: | Passing a Closure to a <php>new</php>-expression: |
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| <PHP> | <PHP> |
| ===== Proposed Voting Choices ===== | ===== Proposed Voting Choices ===== |
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| <doodle title="Support Closures in constant expressions as proposed?" auth="timwolla" voteType="single" closed="true" closeon="2024-06-05T08:00:00Z"> | <doodle title="Support Closures in constant expressions as proposed?" auth="timwolla" voteType="single" closed="false" closeon="2024-11-27T14:00:00Z"> |
| * Yes | * Yes |
| * No | * No |