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Date: Wed, 3 Jul 2013 13:45:57 +0100
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Subject: New feature: sequential constructors
From: terence.copestake@gmail.com (Terence Copestake)

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Hello, all.

On one or two occasions I've encountered a problem when designing a base
class, where I wish to implement important set-up functionality in the
constructor, but am limited in how to ensure that the base constructor
functionality is unmolested whilst not restricting any inheriting classes
in their use of a constructor, as would be the case when using the final
keyword. I also don't feel 100% comfortable trusting the inheriting class
to call the parent constructor.

The idea I'm presenting for discussion here is to have some kind of
(keyword-driven?) hierarchy for constructors, whereby it's possible to have
for example sequential constructors, using syntax similar to:

... public sequential function __construct($ ...

In this scenario, constructors defined as sequential are, as the name
implies, called in sequence.

If the introduction of a new keyword is problematic, perhaps this same
behaviour could be enacted in cases where an inheriting class has a
constructor and the base class' constructor is defined as final i.e. rather
than causing an error, the final constructor is executed first, followed by
any other constructors in the hierarchy.

If this keyword is introduced, perhaps it this idea could also be expanded
to allow for sequential methods in general, which would behave similarly -
and may be a gateway to function overloading (or similar behaviour).

I'm open to people pointing out design flaws/implementation difficulties
with this; pull no punches.

Thanks.

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