Edit report at https://bugs.php.net/bug.php?id=76311&edit=1
ID: 76311
Updated by: git@php.net
Reported by: Andy_Schmidt at HM-Software dot com
Summary: __construct/__destruct must not have return types
-Status: Verified
+Status: Closed
Type: Documentation Problem
Package: Class/Object related
PHP Version: 7.2.5
Assigned To: cmb
Block user comment: N
Private report: N
New Comment:
Automatic comment on behalf of cmb69
Revision: https://github.com/php/doc-en/commit/3926279f825d418fdd2e7079968507d8b0c62b7d
Log: Fix #76311: __construct/__destruct must not have return types
Previous Comments:
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[2021-08-27 10:54:33] cmb@php.net
Actually, this discussion happend in the meantime[1], and while
declaring the return type of __clone() as void, the notion of
declaring return types for __construct() and __destruct() has been
declined for reasons[2].
This has been documented the magic methods[3]:
| If type declarations are used in the definition of a magic
| method, they must be identical to the signature described in this
| document. Otherwise, a fatal error is emitted. Prior to PHP 8.0.0,
| no diagnostic was emitted.
This doesn't properly cater to __construct() and __destruct(),
though.
[1] <https://externals.io/message/109542>
[2] <https://externals.io/message/109542#109638>
[3] <https://www.php.net/manual/en/language.oop5.magic.php>
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[2018-05-08 20:55:11] cmb@php.net
> I can't tell what ambiguity they're talking about, but I suspect> it doesn't apply to PHP since return types are invariant.
It seems to me this âambiguityâ is actually what this discussion
is about: if no return type annotation/declaration would be given,
should return statements be checked, or not? In my opinion, it
does not make much sense, though, to make a constructor special so
that only a None/void return type annotation/declaration would be
accepted, rather than to make a constructor special by not
allowing to specify any return type annotation/declaration, in the
first place.
FWIW: JavaScript's constructor functions are a notable exception
to the no return type, since new Foo may return a Bar.
Anyhow, I don't think it is useful to have a lengthy discussion
here; the internals mailing list would be more suitable.
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[2018-05-08 17:27:51] requinix@php.net
> using a syntax that resembles that of normal methods is besides the point.
Hmm, okay, poor choice of words there, but what I'm trying to say is that for these three
methods return types do not make sense. Because there are no return values. Not in the sense of
"this function isn't returning a value" but more "this function is incapable of
using return values in the first place".
Other languages:
C# and Java don't have types.
> class Example { public Example() { } }
Python 3 does support a return type on __init__ but for reasons I don't quite understand.
https://www.python.org/dev/peps/pep-0484/#id13> (Note that the return type of __init__ ought to be annotated with -> None. The reason for
> this is subtle. If> __init__ assumed a return annotation of -> None, would that mean that an argument-less,
> un-annotated __init__ method> should still be type-checked? Rather than leaving this ambiguous or introducing an exception to
> the exception, we> simply say that __init__ ought to have a return annotation; the default behavior is thus the
> same as for other> methods.)
I can't tell what ambiguity they're talking about, but I suspect it doesn't apply to
PHP since return types are invariant.
(There's also __new__ but that's more of a factory method than a constructor.)
Meanwhile Ruby has constructors but no return types, and Perl has return types but no constructors.
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[2018-05-08 17:08:08] requinix@php.net
https://www.google.com/search?q=why+dont+constructors+have+return+types
This isn't about method signatures. This is about what constructors, destructors, and cloning
represent. The fact that PHP allows you to specify their behavior using a syntax that resembles that
of normal methods is besides the point.
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[2018-05-08 17:05:14] Andy_Schmidt at HM-Software dot com
I understand that some methods had always implicitly disallowed return values before there had been
a syntax to do so explicitly. The hard syntax error certainly was proper before 7.1.
However, this is 2018. Why would we still force occasional PHP users from having to memorize the
signature for each and every magic method?
Now that "void" is a type hint, it seems that an author writing self-documenting code (for
the benefit of less-versed coworkers) should not be penalized with run-time errors for explicitly
defining VOID?
I respectfully suggest that with 7.1 and higher, the message category
"... cannot declare a return type"
should simply recognize the now-available type "void" as being a perfectly expression of
the implicit rule!
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