Moose won't do coersion unless you request it, so, at the least, you would need:

has file => ( isa => 'ExistingFile', is => 'ro', required => 1, coerce
+ => 1 );

[download]

However, that doesn't work for me either, complaining:

You cannot coerce an attribute (file) unless its type (ExistingFile) h
+as a coercion at /tmp/test.pl line 26

[download]

Apparently, coersion is not inherited by subtypes by design, so you will need to duplicate the coersion.

subtype 'ExistingFile' =>
    as 'AFile' =>
    where { say "In subtype where clause: $_[0]"; -f $_[0] },
    message { "$_[0] does not exist" };

coerce  'ExistingFile' =>
    from 'Str' =>
    via { file($_) };

has file => ( isa => 'ExistingFile', is => 'ro', required => 1, coerce
+ => 1 );

[download]

Note: You can reduce the code duplicationg using:

for my $ftype (qw/ AFile ExistingFile /) {
    coerce  $ftype =>
        from 'Str' =>
        via { file($_) };
}

[download]

Good Day,
    Dean

In reply to Re: Moose: Problems subtyping a coerced subtype by duelafn
in thread Moose: Problems subtyping a coerced subtype by BaldManTom

Title:
Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
to format your post, it's "PerlMonks-approved HTML":


  • Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!
  • Titles consisting of a single word are discouraged, and in most cases are disallowed outright.
  • Read Where should I post X? if you're not absolutely sure you're posting in the right place.
  • Please read these before you post! —
  • Posts may use any of the Perl Monks Approved HTML tags:
    a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr
  • You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)
            For:     Use:
    & &amp;
    < &lt;
    > &gt;
    [ &#91;
    ] &#93;
  • Link using PerlMonks shortcuts! What shortcuts can I use for linking?
  • See Writeup Formatting Tips and other pages linked from there for more info.