Geo::Coordinates::OSGB 2.20 fails on constant hash-reference dereferences

Bắt đầu với jperl t/02-known.t và jperl --interpreter t/02-known.t, sau đó kiểm tra Geo::Coordinates::OSGB.pm cùng với cách JVM và trình thông dịch xử lý việc dereference các tham chiếu hash hằng. Sử dụng các test bị ảnh hưởng, bao gồm t/02-known.t, t/03-format.t, t/05-random.t, t/06-osgb-grid-to-ll.t, t/06-osgb-ll-to-grid.t, t/08-out_of_range.t và t/13-edge-and-at-sea.t. Hoàn thành khi một regression test tập trung bao quát việc dereference exists và array, cả hai backend đều vượt qua toàn bộ 360 upstream test, đồng thời các biến thông thường và kiểu trả về hằng vẫn được giữ nguyên.

Summary

Geo::Coordinates::OSGB v2.20 fails most of its upstream test suite under PerlOnJava when code dereferences the hash reference returned by a use constant declaration:

use constant ELLIPSOIDS => { ... };
my $shape = ...;
my ($a, $b, $f, $e2) = @{ ELLIPSOIDS->{$shape} };

This was observed in CPAN random tester run 20260914-160652-26153.

Reproduction

The upstream suite passes completely under system Perl:

• 10 test programs
• 360 tests
• all tests successful

Under PerlOnJava, the failure reproduces on both execution backends. Focused reproductions are:

jperl t/02-known.t
jperl --interpreter t/02-known.t

Observed failures

JVM backend:

Global symbol "@ELLIPSOIDS" requires explicit package name (did you forget to declare "my @ELLIPSOIDS"?)

The error is reported from Geo::Coordinates::OSGB.pm at the ELLIPSOIDS->{$shape} dereference.

Interpreter backend:

Can't use string ("0") as a HASH ref while "strict refs" in use

The affected upstream programs include:

• t/02-known.t
• t/03-format.t
• t/05-random.t
• t/06-osgb-grid-to-ll.t
• t/06-osgb-ll-to-grid.t
• t/08-out_of_range.t
• t/13-edge-and-at-sea.t

Some tests that do not exercise the affected coordinate-conversion paths pass, including t/01-load.t, t/04-parsing.t, and t/07-maps.t.

Expected behavior

Perl treats the value declared by use constant ELLIPSOIDS => { ... } as a hash reference. The expression ELLIPSOIDS->{$shape} must resolve the constant value and perform a normal hash lookup under both PerlOnJava backends, matching system Perl.

Technical evidence and diagnosis

The distribution is pure Perl and has no XS, native-library, network, display, or platform-specific prerequisite involved in the failing tests. System Perl passes all 360 upstream tests, while PerlOnJava fails deterministically during compilation/execution on both backends.

The relevant source contains:

use constant ELLIPSOIDS => {
    WGS84  => [ ... ],
    ETRS89 => [ ... ],
    GRS80  => [ ... ],
    OSGB36 => [ ... ],
};

and repeatedly uses expressions such as:

exists ELLIPSOIDS->{$shape}
@{ ELLIPSOIDS->{$shape} }

The JVM frontend appears to parse the bareword constant as a package variable and performs strict-vars validation against an array symbol named @ELLIPSOIDS. The interpreter instead evaluates the constant call incorrectly and attempts to dereference the string value "0" as a hash reference. This suggests a shared semantic gap in constant subroutine resolution or bareword/hash-dereference handling, with backend-specific failure paths.

Acceptance criteria

• All 10 upstream test programs and 360 tests pass on the JVM backend.
• The same suite passes on the interpreter backend.
• Add a project-owned focused regression test for hash-reference constants used through bareword dereference syntax, including exists CONSTANT->{key} and @{ CONSTANT->{key} } cases.
• Preserve behavior for ordinary package variables and other constant return types.

Environment

• PerlOnJava CPAN run: 20260914-160652-26153
• Distribution: Geo-Coordinates-OSGB-2.20
• System Perl: full upstream suite passes
• Affected backends: JVM and interpreter