Question

Take this simple test case:

#!/usr/bin/env perl

use Test::Most;
use Scalar::Util qw( reftype );

ok( 1, 'foo' );

done_testing();

Running this test gives me the following output:

Prototype mismatch: sub main::reftype: none vs ($) at /Users/olaf/perl5/perlbrew/perls/perl-5.16.2/lib/site_perl/5.16.2/Exporter.pm line 66.

There are 2 ways I can get rid of this warning.

• I can use Test::More rather than Test::Most
• I can use Test::Most but not explicitly import reftype

I’m ok with calling Scalar::Util::reftype (or even using another module), but I’m looking for a little help in debugging this issue so that I can file the appropriate bug report, since I’m not sure as to where the root cause of the warning lies.

Answer 1

Both Test::Most and Scalar::Util define functions called reftype, and the way you are calling use causes both modules to try to export their reftype functions to the calling package. Sometimes this will trigger a Subroutine ... redefined warning, but in this case Scalar::Util::reftype wants to define itself with a prototype, so the conflict is a more serious error.

Some options other than calling Scalar::Util::reftype($ref):

One. to define and use a different alias for Scalar::Util::reftype

     use Scalar::Util ();
     BEGIN { *su_reftype = *Scalar::Util::reftype; }
     print "reftype is ", su_reftype($ref), " ...";

Two. Remove reftype from the symbol table before loading Scalar::Util:

    use Test::Most;
    BEGIN { *{reftype} = '' }
    use Scalar::Util 'reftype';