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The Basics
Id: 67731
Status: resolved
Priority: 0/
Queue: Moose

Owner: Nobody in particular
Requestors: michael [...]

Bug Information
Severity: Important
Broken in: 2.0001
Fixed in: 2.0300-TRIAL

Subject: Union types reports spurious parent types
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After reading the documentation of Moose::Meta::TypeConstraint::Union, I believe I have found a nasty error. If you have a type constraint hierarchy: Defined Value Str Num Int ClassName RoleName This means that anything a Num constraint matches, is always matched by any of its parents, i.e. Value and Defined. Generally, any constraint will always match any value that has been matched by any of its children. The same is stated in Moose::Manual::Types: A subtype is defined in terms of a parent type and a constraint. Any constraints defined by the parent(s) will be checked first, followed by constraints defined by the subtype. A value must pass all of these checks to be valid for the subtype. Looking in the documentation of Moose::Meta::TypeConstraint::Union, it states something very different: $constraint->is_a_type_of($type_name_or_object) This returns true if any of the member type constraints return true for the is_a_type_of method. $constraint->is_subtype_of This returns true if any of the member type constraints return true for the is_a_subtype_of method. The word "any" (occuring twice above) should be replaced with "all". Also, the code behaves as written. I've written the test attached to illustrate the issue. (Run on Ubuntu 9.x, perl 5.10.0.)
Subject: union_subtype.t
Download union_subtype.t
text/x-perl 1.7k
#!perl use Test::More; use Moose; use Moose::Util::TypeConstraints 'find_type_constraint'; use Moose::Meta::TypeConstraint::Union; my($item, $int, $classname, $num) = map {find_type_constraint($_)} qw{Item Int ClassName Num}; ok($int->is_subtype_of($item), 'Int is subtype of Item'); ok($classname->is_subtype_of($item), 'ClassName is subtype of Item'); ok((not $int->is_subtype_of($classname)), 'Int is not subtype of ClassName'); ok((not $classname->is_subtype_of($int)), 'ClassName is not subtype of Int'); my $union = Moose::Meta::TypeConstraint::Union->new( type_constraints => [$int, $classname] ); my @domain_values = qw{85439 Moose::Meta::TypeConstraint}; ok($union->constraint->($_), "Composite accepts \"$_\".") for @domain_values; diag "Finished warming up. All the tests above should pass."; diag "Now to the tests that fail because of the bug reported."; diag "Any proper parent type should pass all the following tests:"; for(@{$union->parents}) { my $type_con = find_type_constraint($_); diag "Testing parent: $_"; ok($type_con->constraint->($_), "Parent accepts \"$_\".") for @domain_values; } diag "In other words, a union type can't rely on being type of all the types used:"; diag "In this case, \$union should be a subtype of Item, Defined, Value and Str:"; ok($union->is_subtype_of(find_type_constraint($_)), "Union is subtype of $_") for qw{Item Defined Value Str}; diag "But not a subtype of Num:"; ok((not $union->is_subtype_of(find_type_constraint($_))), "Union is not subtype of $_") for qw{Num Int ClassName}; diag "And definately not a type of Int or ClassName:"; ok((not $union->is_a_type_of(find_type_constraint($_))), "Union is not type of $_") for qw{Int ClassName}; done_testing;
From: michael [...]
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One note: The test script attached has a number of tests that passes where it may seem as if I expect them to fail. If you need me to point to the tests that fail due to this issue, let me know.
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I think your analysis is correct. Since this would break a documented API, we won't be changing it until the next major release (2.02), which is likely to come out in July.

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