[perl #109182] where{} section triggered in signature despite param optional and not given

[via RT]

# New Ticket Created by  Paweł Pabian 
# Please include the string:  [perl #109182]
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# <URL: https://rt.perl.org:443/rt3/Ticket/Display.html?id=109182 >


$ perl6 -e 'sub foo ( :$id? where { say "I should not be here when there is no 
param passed"} ) {}; foo()'

Returns:
I should not be here when there is no param passed

$ perl6 --version
This is perl6 version 2012.01 built on parrot 3.11.0 revision RELEASE_3_11_0