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Date: Wed, 25 Nov 2020 09:00:58 +0000
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Subject: Re: [PHP-DEV] List of attributes
From: rowan.collins@gmail.com (Rowan Tommins)

On 24/11/2020 23:09, Theodore Brown wrote:
> That's not necessarily the case for nested attributes. A developer
> may want to declare that an attribute constructor takes a single
> attribute with a particular type as one of its arguments.


I'm still not sure what the use case for such an attribute constructor 
would be. Your example with "CustomError" seemed to be abusing nested 
attributes as a way to get a value object into a static declaration; and 
all the examples I've seen of nested attributes/annotations "in the 
wild" are wrapping a list of attributes in some kind of container.


> Moreover, re-purposing the syntax for function
> calls or class instantiation is likely to cause confusion, since it
> looks like the code is doing something other than what it actually
> does (and of course it would prevent ever extending constant
> expressions to support function calls or class instantiation).

Then maybe we should make it *be* instantiation. The example you gave 
earlier, of CustomError, would be just as useful outside attributes, 
e.g. in a property initialiser, so perhaps what we need for that use 
case is not nested attributes at all, but the ability to create some 
subset of objects ("structs"?) inside static contexts.

That can be entirely parallel to a feature that lets you wrap a list of 
attributes inside another attribute, and does some recursive magic with 
reflection to let you delay calling their constructors.

Regards,

-- 
Rowan Tommins (né Collins)
[IMSoP]