Hmm, interesting. Do you know how much of that is in the core Perl (as Ovid is using the term "core"… perl.exe itself, no modules), and how much is done by fields.pm and friends?

If it's mostly done by the modules, then I don't see a problem with there being multiple ways of hooking into my Foo $x. TIMTOWTDI after all.

It's built into the perl executable itself:

BEGIN { %Foo::FIELDS = qw(a 1 b 1) };
my Foo $x = {};
$x->{c} = 1; # compile-time error
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fields.pm just populates the field hash

Dave.

Interesting. I guess this explains the limitation with Lexical::Types where it allows you to define, say, my Str $x to do something else other than check $x is a blessed Str object (and I've started to explore that possibility using Lexical::TypeTiny), but still requires there to be a Str package defined. I guess Perl needs that package to exist so that it can look for %FIELDS.

toby döt ink