rfc:scalar_type_hinting_with_cast

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rfc:scalar_type_hinting_with_cast [2014/07/14 18:58]
ajf Made booleans strict
rfc:scalar_type_hinting_with_cast [2021/09/09 06:07] (current)
heiglandreas Fixed a typo in the First Published at URL
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 ====== Request for Comments: Scalar Type Hinting With Casts ====== ====== Request for Comments: Scalar Type Hinting With Casts ======
-  * Version: 0.1.6 +  * Version: 0.1.9.1 
-  * Date: 2012-07-03 (latest update 2014-07-14)+  * Date: 2012-07-03 (reopened 2014-07-13, latest update 2014-09-14, withdrawn 2014-09-15)
   * Author: Anthony Ferrara <ircmaxell@php.net> (original)   * Author: Anthony Ferrara <ircmaxell@php.net> (original)
   * Contributors: Andrea Faulds <ajf@ajf.me> (current maintainer)   * Contributors: Andrea Faulds <ajf@ajf.me> (current maintainer)
-  * Status: Under Discussion (previously Withdrawn) +  * Status: Withdrawn (previously Withdrawn then reopened
-  * First Published at: http://wiki.php.net/rfc/scalar_type_hinting_with_casts+  * First Published at: http://wiki.php.net/rfc/scalar_type_hinting_with_cast
  
 ===== Introduction ===== ===== Introduction =====
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 This RFC discusses a method of adding scalar type hints to PHP while attempting to embrace the dynamic nature of PHP variables.  This means that passing a type that does not exactly match the hinted type will cause a cast to happen. This cast will only succeed if the argument can be cleanly converted to the requested type. If it cannot be converted without significant data-loss, an //E_RECOVERABLE_ERROR// will be raised. This RFC discusses a method of adding scalar type hints to PHP while attempting to embrace the dynamic nature of PHP variables.  This means that passing a type that does not exactly match the hinted type will cause a cast to happen. This cast will only succeed if the argument can be cleanly converted to the requested type. If it cannot be converted without significant data-loss, an //E_RECOVERABLE_ERROR// will be raised.
  
-For consistency, this patch attempts to largely follow //zend_parse_parameters()// for the validation rules, but disallows lossy conversion from float to int (1.5 -> int generates an error) and non-well-formed numeric values for float or int ('123abc' is an error). Since v0.1.6, booleans are handled strictly, also a departure from zpp.+For consistency, this patch attempts to largely follow //zend_parse_parameters()// for the validation rules, but disallows lossy conversion from float to int (1.5 -> int generates an error) and non-well-formed numeric values for float or int ('123abc' is an error). Since v0.1.6, booleans are handled strictly, and since v0.1.9, booleans are not accepted for int, float, numeric and string, also departures from zpp 
 + 
 +=== Rationale for this proposal compared to others === 
 + 
 +Other options for scalar type hints have been proposed. The most obvious other two are strict type hinting, where no casting is done and if the value is the wrong type, it errors (much like the non-scalar type hints), and type casting, where values are simply casted using the implicit casting rules with no failure cases (but sometimes emitting notices). 
 + 
 +The problems with strict type hinting are twofold. Firstly, PHP's types can change somewhat unpredictably. For example, dividing one integer by another may result in a float when the the divisor is not a factor, and existing code may be poorly written and not guaranteed to return the types you'd expect. Secondly, while PHP's non-scalar types have always been quite strict and not been juggled, PHP's scalar types are routinely casted implictly, juggled, and are expected to do so, because of PHP's designed-for-the-web nature where numeric values are likely to start life in string form (from //$_GET// etc.). To break from this convention would be rather "un-PHP-like"; PHP has always juggled its scalar types, and PHP's internal (zend_parse_parameters-using, at least) functions have always had implict casting. 
 + 
 +The other main option, simply type casting, also has problems. This way, there is no real error prevention (E_NOTICE is not a safeguard, it is a message in a log file, and in production it is not even that) and unsafe casts can happen with data being lost. Being able to pass "foobar" as an argument which is expected to be an integer doesn't really make sense and would probably be a source of problems. It's also not actually consistent, despite what it first appears, with the behaviour of zend_parse_parameters for internal functions; zend_parse_parameters actually fails in many cases, and a lot of internal functions will bail out and return NULL when it does. 
 + 
 +On the other hand, this RFC tries to strike a balance between strict typing and mere type casting. It casts, making sure PHP's type shifting won't break things and keeping with PHP's traditional type casting and juggling nature, which is useful when dealing with the web, but prevents conversions causing data loss, reducing the likelihood of causing bugs and making it more likely bugs will be caught. In this way we feel the RFC combines the best parts of both proposals, providing both validation and type conversion.
  
 ===== Proposal ===== ===== Proposal =====
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 ==== Engine Changes ==== ==== Engine Changes ====
  
-The current implementation introduces four new reserved words: //int//, //float//, //bool// and //string//. These were not previously reserved, because casting is a special case in the lexer.+The current implementation introduces five new reserved words: //int//, //float//, //bool////string// and //numeric//. These were not previously reserved, because casting is a special case in the lexer.
  
 If this causes a problem, it would be possible to revert to the previous implementation, where the parser still detects the type hints as object type hints and the compiler (zend_compile.c) then detects the exact value for the type hint, changing the stored hint from IS_OBJECT to the proper type (freeing the string). If this causes a problem, it would be possible to revert to the previous implementation, where the parser still detects the type hints as object type hints and the compiler (zend_compile.c) then detects the exact value for the type hint, changing the stored hint from IS_OBJECT to the proper type (freeing the string).
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 ==== Syntax ==== ==== Syntax ====
  
-Four new type hints are introduced with this patch:+Five new type hints are introduced with this patch:
  
   * //int// - Matching integers only   * //int// - Matching integers only
   * //float// - Matching floating point numbers   * //float// - Matching floating point numbers
 +  * //numeric// - Matching integers and floating point numbers (to allow polymorphic functions dealing with numbers)
   * //bool// - Matching boolean parameters only   * //bool// - Matching boolean parameters only
   * //string// - Matching strings only   * //string// - Matching strings only
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 ==== Conversion Rules ==== ==== Conversion Rules ====
  
-Conversion is allowed only if data-loss does not happen. There are a few exceptions (objects using <nowiki>__toString</nowiki>, strings containing leading numerics, etc). Here's a table of examples. +Conversion is allowed only if data-loss does not happen. There are a few exceptions (objects using <nowiki>__toString</nowiki>, etc.). Here's a table of examples. 
  
   * //fail// indicates an E_RECOVERABLE_ERROR   * //fail// indicates an E_RECOVERABLE_ERROR
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   * //notice// indicates an E_NOTICE and a conversion   * //notice// indicates an E_NOTICE and a conversion
  
-^ value                   ^ string ^ float  ^ int    ^ boolean‡^ array ^ +^ value                   ^ string ^ float  ^ int    ^ numeric ^ boolean‡^ array ^ 
-^ true (boolean)          | pass   | pass   | pass   | pass    | fail  | +^ true (boolean)          | fail   | fail   | fail   | fail    | pass    | fail  | 
-^ false (boolean)         pass   | pass   | pass   | pass    | fail  | +^ false (boolean)         fail   | fail   | fail   | fail    | pass    | fail  | 
-^ 0 (integer)             | pass   | pass   | pass   | fail    | fail  | +^ NULL (NULL)             | fail   | fail   | fail   | fail    | fail    | fail  | 
-^ 1 (integer)             | pass   | pass   | pass   | fail    | fail  | +^ 0 (integer)             | pass   | pass   | pass   | pass    | fail    | fail  | 
-^ 12 (integer)            | pass   | pass   | pass   | fail    | fail  | +^ 1 (integer)             | pass   | pass   | pass   | pass    | fail    | fail  | 
-^ 12 (double)             | pass   | pass   | pass   | fail    | fail  | +^ 12 (integer)            | pass   | pass   | pass   | pass    | fail    | fail  | 
-^ 12.34 (double)          | pass   | pass   | fail   | fail    | fail  | +^ 12 (double)             | pass   | pass   | pass   | pass    | fail    | fail  | 
-^ 'true' (string)         | pass   | fail   | fail   | fail    | fail  | +^ 12.34 (double)          | pass   | pass   | fail   | pass    | fail    | fail  | 
-^ 'false' (string)        | pass   | fail   | fail   | fail    | fail  | +^ 'true' (string)         | pass   | fail   | fail   | fail    | fail    | fail  | 
-^ '0' (string)            | pass   | pass   | pass   | fail    | fail  | +^ 'false' (string)        | pass   | fail   | fail   | fail    | fail    | fail  | 
-^ '1' (string)            | pass   | pass   | pass   | fail    | fail  | +^ '0' (string)            | pass   | pass   | pass   | pass    | fail    | fail  | 
-^ '12' (string)           | pass   | pass   | pass   | fail    | fail  | +^ '1' (string)            | pass   | pass   | pass   | pass    | fail    | fail  | 
-^ '12abc' (string)        | pass   | fail   | fail   | fail    | fail  | +^ '12' (string)           | pass   | pass   | pass   | pass    | fail    | fail  | 
-^ '12.0' (string)         | pass   | pass   | pass   | fail    | fail  | +^ '12abc' (string)        | pass   | fail   | fail   | fail    | fail    | fail  | 
-^ '12.34' (string)        | pass   | pass   | fail   | fail    | fail  | +^ '12.0' (string)         | pass   | pass   | pass   | pass    | fail    | fail  | 
-^ 'foo' (string)          | pass   | fail   | fail   | fail    | fail  | +^ '12.34' (string)        | pass   | pass   | fail   | pass    | fail    | fail  | 
-^ array () (array)        | fail   | fail   | fail   | fail    | pass  | +^ 'foo' (string)          | pass   | fail   | fail   | fail    | fail    | fail  | 
-^ array (0 => 12) (array) | fail   | fail   | fail   | fail    | pass  | +^ array () (array)        | fail   | fail   | fail   | fail    | fail    | pass  | 
-^ NULL (NULL)             | pass   | pass   | pass   | fail    | fail  | +^ array (0 => 12) (array) | fail   | fail   | fail   | fail    | fail    | pass  | 
-^ %%''%% (string)         | pass   | fail   | fail   | fail    | fail  | +^ %%''%% (string)         | pass   | fail   | fail   | fail    | fail    | fail  | 
-^ 1 (resource)            | fail   | fail   | fail   | fail    | fail  | +^ 1 (resource)            | fail   | fail   | fail   | fail    | fail    | fail  | 
-^ StdClass                | fail   | fail*  | fail*  | fail†   | fail  | +^ StdClass                | fail   | fail*  | fail*  | fail*   | fail†   | fail  | 
-^ implementing __toString | pass   | fail*  | fail*  | fail†   | fail  |+^ implementing __toString | pass   | fail*  | fail*  | fail*   | fail†   | fail  |
  
 <nowiki>*</nowiki>actually //notice// in patch as it stands due to behaviour of default object casting handler <nowiki>*</nowiki>actually //notice// in patch as it stands due to behaviour of default object casting handler
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 ==== Errors ==== ==== Errors ====
  
-If a provided hint does not match at all ("foo" passed to an //int// hint), an //E_RECOVERABLE_ERROR// is raised. This includes non-well-formed numerics passed to an //int// or //float// hinted parameter, unlike zend_parse_parameters which would simply raise an //E_NOTICE//.+If a provided hint does not match at all ("foo" passed to an //int// hint), an //E_RECOVERABLE_ERROR// is raised. This includes non-well-formed numerics passed to an //int////float// or //numeric// hinted parameter, unlike zend_parse_parameters which would simply raise an //E_NOTICE//.
  
 ==== Defaults ==== ==== Defaults ====
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 === NULL defaults (nullable hints) === === NULL defaults (nullable hints) ===
  
-Normally, scalar typehints are non-nullable and NULL is casted like any other valueHowever, if the default value for a scalar typehint is NULL, the typehint is considered nullableThis means that while values of other types would be casted, NULL will not, e.g.: +The scalar types can be nullable just like any other typeIf a parameter does not have a default value of NULL, then NULL is not a permitted valueIf it does have a default value of NULL, and is therefore nullablethen the value NULL is accepted and will not be casted.
- +
-<code php> +
-function foo(int $a) { var_dump($a);+
-function bar(int $a = NULL) { var_dump($a);+
- +
-foo(NULL); // int(0) +
-bar(NULL); // NULL +
-</code>+
  
 ==== References ==== ==== References ====
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   * //int convert_to_{type}_safe_ex(zval <nowiki>**</nowiki>ptr)// - Separate zval if not a reference, and convert to {type}. Return indicates clean conversion (FAILURE indicates unclean conversion).   * //int convert_to_{type}_safe_ex(zval <nowiki>**</nowiki>ptr)// - Separate zval if not a reference, and convert to {type}. Return indicates clean conversion (FAILURE indicates unclean conversion).
  
-These functions pairs exist for //long//, //double//, //string// and //boolean//.+These functions pairs exist for //long//, //double//, //string////boolean// and //numeric//.
  
 ==== New Methods ==== ==== New Methods ====
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   * //isBool()// - boolean to determine if parameter is type-hinted as a boolean.   * //isBool()// - boolean to determine if parameter is type-hinted as a boolean.
   * //isString()// - boolean to determine if parameter is type-hinted as a string.   * //isString()// - boolean to determine if parameter is type-hinted as a string.
 +  * //isNumeric()// - boolean to determine if parameter is type-hinted as numeric.
  
 ==== Patch ==== ==== Patch ====
  
-The modifications necessary to implement this feature exist on the [[https://github.com/TazeTSchnitzel/php-src/tree/scalar_type_hints|scalar_type_hints branch of Andrea's GitHub fork]] (forked from the [[https://github.com/ircmaxell/php-src/tree/scalar_type_hints|branch on ircmaxell's GitHub fork]]). It is still a work-in-progress, and should be considered unstable at this time.+The modifications necessary to implement this feature exist on the [[https://github.com/TazeTSchnitzel/php-src/tree/scalar_type_hints|scalar_type_hints branch of Andrea's GitHub fork]] (forked from the [[https://github.com/ircmaxell/php-src/tree/scalar_type_hints|branch on ircmaxell's GitHub fork]]). It is stable to the best of Andrea's knowledgewith its tests passing and it breaking no known tests on her machine nor Travis.
  
 ===== Possible Changes ===== ===== Possible Changes =====
 +
 +For points I'm unsure on, this section lists possible future changes to the RFC.
  
 ==== Float to Int Casting Rules ==== ==== Float to Int Casting Rules ====
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 Both the author of this RFC (Anthony) and the current maintainer (Andrea) are yet to settle on one specific option. Both the author of this RFC (Anthony) and the current maintainer (Andrea) are yet to settle on one specific option.
-==== Handling of "123abc" for int and float ====+==== Handling of "123abc" for intfloat and numeric ====
  
 This has been changed to E_RECOVERABLE_ERROR, but should it perhaps be something softer, like E_NOTICE or E_WARNING? This has been changed to E_RECOVERABLE_ERROR, but should it perhaps be something softer, like E_NOTICE or E_WARNING?
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 foo("1a"); // E_RECOVERABLE_ERROR foo("1a"); // E_RECOVERABLE_ERROR
 foo("a"); // E_RECOVERABLE_ERROR foo("a"); // E_RECOVERABLE_ERROR
 +foo(""); // E_RECOVERABLE_ERROR
 foo(999999999999999999999999999999999999); // E_RECOVERABLE_ERROR (since it's not exactly representable by an int) foo(999999999999999999999999999999999999); // E_RECOVERABLE_ERROR (since it's not exactly representable by an int)
 +foo('999999999999999999999999999999999999'); // E_RECOVERABLE_ERROR (since it's not exactly representable by an int)
 foo(1.5); // E_RECOVERABLE_ERROR foo(1.5); // E_RECOVERABLE_ERROR
 foo(array()); // E_RECOVERABLE_ERROR foo(array()); // E_RECOVERABLE_ERROR
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 foo("1a"); // E_RECOVERABLE_ERROR foo("1a"); // E_RECOVERABLE_ERROR
 foo("a"); // E_RECOVERABLE_ERROR foo("a"); // E_RECOVERABLE_ERROR
 +foo(""); // E_RECOVERABLE_ERROR
 +foo(1.5); // float(1.5)
 +foo(array()); // E_RECOVERABLE_ERROR
 +foo(new StdClass); // E_RECOVERABLE_ERROR
 +?>
 +</file>
 +
 +==== Numeric Hints ====
 +
 +<file php numeric_hint.php>
 +<?php
 +function foo(numeric $a) {
 +    var_dump($a); 
 +}
 +foo(1); // int(1)
 +foo("1"); // int(1)
 +foo(1.0); // float(1)
 +foo("1a"); // E_RECOVERABLE_ERROR
 +foo("a"); // E_RECOVERABLE_ERROR
 +foo(""); // E_RECOVERABLE_ERROR
 foo(1.5); // float(1.5) foo(1.5); // float(1.5)
 foo(array()); // E_RECOVERABLE_ERROR foo(array()); // E_RECOVERABLE_ERROR
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 foo("1a"); // string "1a" foo("1a"); // string "1a"
 foo("a"); // string "a" foo("a"); // string "a"
 +foo(""); // string ""
 foo(1.5); // string "1.5" foo(1.5); // string "1.5"
 foo(array()); // E_RECOVERABLE_ERROR foo(array()); // E_RECOVERABLE_ERROR
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 foo("1a"); // E_RECOVERABLE_ERROR foo("1a"); // E_RECOVERABLE_ERROR
 foo("a"); // E_RECOVERABLE_ERROR foo("a"); // E_RECOVERABLE_ERROR
 +foo(""); // E_RECOVERABLE_ERROR
 foo(1.5); // E_RECOVERABLE_ERROR foo(1.5); // E_RECOVERABLE_ERROR
 foo(array()); // E_RECOVERABLE_ERROR foo(array()); // E_RECOVERABLE_ERROR
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 ?> ?>
 </file> </file>
 +
 +===== Proposed Voting Choices =====
 +
 +As this is a language change, a 2/3 majority is required. Voting started 2014-09-14 and ends 2014-09-21.
 +
 +It will be a straight Yes/No vote.
  
 ===== More Information ===== ===== More Information =====
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   * 0.1.5 - Note on NULL default values   * 0.1.5 - Note on NULL default values
   * 0.1.6 - Booleans are now strict   * 0.1.6 - Booleans are now strict
 +  * 0.1.7 - Types are now not nullable by default
 +  * 0.1.8 - Added numeric typehint
 +  * 0.1.8.1 - Overflow prevention for int hints
 +  * 0.1.9 - Booleans not accepted for int, float, numeric or string
 +  * 0.1.9.1 - Added "" to tests, patch is stable
rfc/scalar_type_hinting_with_cast.1405364299.txt.gz · Last modified: 2017/09/22 13:28 (external edit)