Anonymous functions which are a key in a hash will get the line number of the hash declaration.

[schwern]

Here's an example.

#line 15
my $hash = {
    over    => 'under',
    left    => 'right',
    key     => func() {
        return __LINE__;
    },
    foo     => "bar",
    up      => "down",
};

is $hash->{key}->(), 19;
is __LINE__, 26;

It doesn't matter how many hash pairs come before the function, it will always return 16. The function thinks it starts on the same line as the hash.

This has been a problem since at least v20090424. This does not appear to be a mistake on our part, but something wrong with the compiler / Devel::Declare.

This a particular problem in classes which use Moose.

has foo =>
    is => 'rw',
    default => method() {
        return $self->bar + 23;
    };

[schwern]

Wrapping the function in a do block fixes the problem. Unfortunately we have no way of doing that.

[schwern]

Function::Parameters doesn't have this problem. It uses the keyword plugin API instead of Devel::Declare. It might be more prudent to adapt it to Method::Signatures. That would mean raising the minimum requirement to 5.14.