type_safety

Anonymous (anonymous@undisclosed.example.com) — 2025-04-03T13:08:43+00:00

2024/09/01 12:39		current
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	- Change the contract of methods to state that default values are covariant, rather than contravariant. To be precise, that the default value of a parameter in a sub-class must be of the same concrete type as the default value in the parent, or a sub-type of it, regardless of the parameter's declared type. This would invalidate a non-trivial amount of existing code, so would need to be introduced in a major version, probably with a deprecation period.		- Change the contract of methods to state that default values are covariant, rather than contravariant. To be precise, that the default value of a parameter in a sub-class must be of the same concrete type as the default value in the parent, or a sub-type of it, regardless of the parameter's declared type. This would invalidate a non-trivial amount of existing code, so would need to be introduced in a major version, probably with a deprecation period.
	- Limit the expressions allowed to those where ''default'' can be safely substituted for any type (i.e. where it can be analysed as of type ''mixed''). In practice, this means conditional expressions where ''default'' is used unchanged as the result, such as <php>$condition ? 'explicit value' : default</php>. This probably requires a different implementation, where ''default'' is compiled as a placeholder value which triggers the function call to act as though no value was passed.		- Limit the expressions allowed to those where ''default'' can be safely substituted for any type (i.e. where it can be analysed as of type ''mixed''). In practice, this means conditional expressions where ''default'' is used unchanged as the result, such as <php>$condition ? 'explicit value' : default</php>. This probably requires a different implementation, where ''default'' is compiled as a placeholder value which triggers the function call to act as though no value was passed.
-	- Limit use further, to only using ''default'' as a stand-alone token to skip a parameter. This is essentially what was proposed and declined in [[skipparams]].	+	- Limit use further, to only using ''default'' as a stand-alone token to skip a parameter. This is essentially what was proposed and declined in [[rfc/skipparams\|Stas Malyshev's "Skipping optional parameters for functions" RFC]].

	This RFC currently proposes option 1.		This RFC currently proposes option 1.

PHP Wiki - rfc:default_expression

type_safety