[perl #125574] repr trait on a class definition after a forward declaration doesn't take affect

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# New Ticket Created by  Rob Hoelz 
# Please include the string:  [perl #125574]
# in the subject line of all future correspondence about this issue. 
# <URL: https://rt.perl.org/Ticket/Display.html?id=125574 >


See the attached test script.

If I forward declare a class, like so:

    class Foo { ... }

...and define the class later on, in addition to using the repr trait:

    class Foo is repr('CPointer') { ... }

...the repr trait takes no effect.  If this is the intended behavior, a warning 
or error should probably be emitted.
use Test;

plan 1;

class Foo { ... }

class Foo is repr('CPointer') {
}

is Foo.REPR, 'CPointer';