rfc:scalar_type_hints
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rfc:scalar_type_hints [2015/02/01 23:41] – v0.3 - return types ajf | rfc:scalar_type_hints [2017/09/22 13:28] (current) – external edit 127.0.0.1 | ||
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====== PHP RFC: Scalar Type Hints ====== | ====== PHP RFC: Scalar Type Hints ====== | ||
- | * Version: 0.3 | + | * Version: 0.3.1 |
- | * Date: 2014-12-14 (initial draft; put Under Discussion 2014-12-31; version 0.2 created 2015-01-13) | + | * Date: 2014-12-14 (initial draft; put Under Discussion 2014-12-31; version 0.2 created 2015-01-13; withdrawn 2015-02-15) |
* Author: Andrea Faulds, ajf@ajf.me | * Author: Andrea Faulds, ajf@ajf.me | ||
- | * Status: | + | * Status: |
* First Published at: http:// | * First Published at: http:// | ||
===== Summary ===== | ===== Summary ===== | ||
- | This RFC proposes the addition of four type hints for scalar types: '' | + | This RFC proposes the addition of four type hints for scalar types: '' |
- | This RFC further proposes the addition of a new optional per-file directive, '' | + | This RFC further proposes the addition of a new optional per-file directive, '' |
With these two features, it is hoped that more correct and self-documenting PHP programs can be written. | With these two features, it is hoped that more correct and self-documenting PHP programs can be written. | ||
Line 87: | Line 87: | ||
</ | </ | ||
- | The strict type checking mode also affects extension and built-in PHP functions: | + | The directive affects all function calls in the file (or '' |
+ | |||
+ | <file php strict_mix.php> | ||
+ | <?php | ||
+ | require " | ||
+ | |||
+ | // implicitly weakly type-checked code (default) | ||
+ | $nelly = new ElePHPant(12345, | ||
+ | |||
+ | declare(strict_types=1) { | ||
+ | // explicitly strictly type-checked code | ||
+ | |||
+ | $nelly = new ElePHPant(12345, | ||
+ | // Catchable fatal error: Argument 1 passed to ElePHPant:: | ||
+ | } | ||
+ | </ | ||
+ | |||
+ | This applies equally to nested function calls, which also use the strictness setting of the file: | ||
+ | |||
+ | <file php strict_mix2.php> | ||
+ | <?php | ||
+ | require " | ||
+ | |||
+ | // implicitly weakly type-checked code (default) | ||
+ | function makeEllie() { | ||
+ | return new ElePHPant(42, | ||
+ | } | ||
+ | |||
+ | makeEllie(); | ||
+ | |||
+ | declare(strict_types=1) { | ||
+ | // explicitly strictly type-checked code | ||
+ | |||
+ | makeEllie(); | ||
+ | |||
+ | function makeEllie_strict() { | ||
+ | return new ElePHPant(42, | ||
+ | } | ||
+ | |||
+ | makeEllie_strict(); | ||
+ | } | ||
+ | |||
+ | // implicitly weakly type-checked code, again | ||
+ | |||
+ | makeEllie_strict(); | ||
+ | </ | ||
+ | |||
+ | In addition to userland functions, the strict type checking mode also affects extension and built-in PHP functions: | ||
<file php main4.php> | <file php main4.php> | ||
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</ | </ | ||
- | Scalar type hints would also work for return values: | + | Scalar type hints would also work for return values, as does strict type checking mode: |
<file php returns.php> | <file php returns.php> | ||
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var_dump(foobar()); | var_dump(foobar()); | ||
+ | |||
+ | declare(strict_types=1) { | ||
+ | function foobar2(): int { | ||
+ | return 1.0; | ||
+ | } | ||
+ | } | ||
+ | |||
+ | var_dump(foobar2()); | ||
+ | // Catchable fatal error: Return value of foobar() must be of the type integer, float returned | ||
</ | </ | ||
- | And strict | + | However, there is a key difference between parameter and return |
- | <file php returns2.php> | + | <file php returns.php> |
<?php | <?php | ||
- | declare(strict_types=1); | + | declare(strict_types=1) |
+ | function foobar3(): int { | ||
+ | return 1.0; // error, regardless of where it is called from | ||
+ | } | ||
- | function foobar(): int { | + | foobar3(); // error |
- | return 1.0; | + | |
} | } | ||
- | var_dump(foobar()); | + | foobar3(); // also error |
- | // Catchable fatal error: Return value of foobar() must be of the type integer, float returned | + | |
</ | </ | ||
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==== History ==== | ==== History ==== | ||
- | PHP has had parameter type hints for class names since PHP 5.0, arrays since PHP 5.1 and callables since PHP 5.4. These type hints allow the PHP runtime to ensure that correctly-typed arguments are passed to functions, and make function signatures more informative. Unfortunately, | + | PHP has had parameter type hints for interface and class names since PHP 5.0, arrays since PHP 5.1 and callables since PHP 5.4. These type hints allow the PHP runtime to ensure that correctly-typed arguments are passed to functions, and make function signatures more informative. Unfortunately, |
There have been some previous attempts at adding scalar type hints, such as the [[rfc: | There have been some previous attempts at adding scalar type hints, such as the [[rfc: | ||
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==== strict_types declare() directive ==== | ==== strict_types declare() directive ==== | ||
- | By default, all PHP files are in weak type-checking mode. A new '' | + | By default, all PHP files are in weak type-checking mode. A new '' |
- | This directive also supports the '' | + | This directive also supports the '' |
Like the '' | Like the '' | ||
- | The directive is entirely compile-time and cannot be controlled at runtime. It works by setting a flag on function | + | The directive is entirely compile-time and cannot be controlled at runtime. It works by setting a flag on the opcodes for function |
=== Parameter type hints === | === Parameter type hints === | ||
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</ | </ | ||
- | Whether or not the function being called was declared in a file that uses strict or weak type checking is entirely | + | Whether or not the function being called was declared in a file that uses strict or weak type checking is irrelevant. The type checking mode depends on the file where the function is called. |
=== Return type hints === | === Return type hints === | ||
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This doesn' | This doesn' | ||
- | When the strict type-checking mode isn't in use (which is the default), function calls behave identically to previous PHP versions. | + | When the strict type-checking mode isn't in use (which is the default), function calls to built-in and extension PHP functions |
===== Open Issues ===== | ===== Open Issues ===== | ||
- | There is currently an open issue related to naming, described below. This will probably | + | There is currently an open issue related to naming, described below. This will go to a vote. |
This RFC and patch allows the aliases '' | This RFC and patch allows the aliases '' | ||
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* Produce a different error message on strict type hint failure vs. on weak type hint failure, lest debugging be a pain. For practical reasons we may not be able to change the weak one, as it is an existing message (should we?). | * Produce a different error message on strict type hint failure vs. on weak type hint failure, lest debugging be a pain. For practical reasons we may not be able to change the weak one, as it is an existing message (should we?). | ||
- | * Return types need tests. | + | * Return types need more tests. |
===== Future Scope ===== | ===== Future Scope ===== | ||
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Because scalar type hints guarantee that a passed argument will be of a certain type within a function body (at least initially), this could be used in the Zend Engine for optimisations. For example, if a function takes two '' | Because scalar type hints guarantee that a passed argument will be of a certain type within a function body (at least initially), this could be used in the Zend Engine for optimisations. For example, if a function takes two '' | ||
- | ===== Proposed | + | In discussions around this RFC, the '' |
+ | |||
+ | Another issue that came up is PHP's lack of a typehint for numbers (which also came up with the previous Scalar Type Hinting with Cast RFC). I plan to propose a '' | ||
+ | |||
+ | ===== Vote ===== | ||
+ | |||
+ | As this is a language change, this RFC requires a 2/3 majority to pass. Voting | ||
+ | |||
+ | ==== Main ==== | ||
+ | |||
+ | This vote is for the RFC itself. | ||
+ | |||
+ | <doodle title=" | ||
+ | * Yes | ||
+ | * No | ||
+ | </ | ||
+ | |||
+ | ==== Type aliases ==== | ||
+ | |||
+ | This second vote is to solve the open issue regarding the '' | ||
+ | |||
+ | <doodle title=" | ||
+ | * Allow synonyms | ||
+ | * Reserve synonyms and produce error message when used | ||
+ | * Do not reserve | ||
+ | </ | ||
+ | |||
+ | ==== Reserve for future use ==== | ||
+ | |||
+ | This final vote is in case the RFC fails to pass. It's a 2/3 majority-required backwards compatibility-breaking language change, which is to reserve the type hint names proposed by the RFC, so that a future RFC could implement scalar type hints without requiring a backwards compatibility break. The type names reserved include the synonyms '' | ||
- | As this is a language change, this RFC requires a 2/3 majority to pass. It will be a Yes/No vote. | + | <doodle title=" |
+ | | ||
+ | * No | ||
+ | </doodle> | ||
===== Patches and Tests ===== | ===== Patches and Tests ===== | ||
- | There is a working, but incomplete | + | There is a working, but possibly buggy php-src pull request with tests here: https:// |
- | There is no language specification patch. | + | There is no language specification patch as yet. |
===== Implementation ===== | ===== Implementation ===== | ||
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===== Changelog ===== | ===== Changelog ===== | ||
+ | * v0.3.1 - Noted '' | ||
* v0.3 - Return types support | * v0.3 - Return types support | ||
* v0.2.3 - '' | * v0.2.3 - '' |
rfc/scalar_type_hints.1422834086.txt.gz · Last modified: 2017/09/22 13:28 (external edit)