Support indirect-object method dispatch used by Set::IntSpan

Bắt đầu bằng cách chạy test tập trung của Set::IntSpan trong t/real_set.t, đặc biệt là các lệnh gọi gián tiếp quanh dòng 22, trên cả hai backend JVM và interpreter. Theo dõi cách parser/compiler xử lý các lệnh gọi này và so sánh với công việc liên quan đến parser trong các issue #1166 và #1314. Được coi là hoàn tất khi cả bốn dạng đều dispatch chính xác, đã bổ sung độ bao phủ hồi quy và toàn bộ test suite gồm 1.947 test đều vượt qua.

Summary

Set::IntSpan 1.19 fails one upstream test under PerlOnJava because valid Perl indirect-object method syntax is resolved as a call to a nonexistent main:: subroutine.

Reproduction

Run the normal Set::IntSpan 1.19 test suite. The focused failure is t/real_set.t, which contains calls such as:

my $set_2 = union $set "1-5,8-9";
my $set_3 = union $set $set_2;
my $set_4 = union $set +[1, 5, 2, 8, 9, 1, 3, 4, 9];

These are valid Perl indirect-object method calls. The union method is implemented by Set::IntSpan and is used through the object in $set.

Expected result

System Perl passes the complete upstream suite:

• 20 test files
• 1,947 tests
• t/real_set.t passes all 4 tests

Actual result

PerlOnJava runs the first real_set.t operation successfully, then fails at the next indirect method call:

1..4
#real_set
#real_set:  union set -> -
ok 1
Undefined subroutine &main::union called at t/real_set.t line 22.

The archived CPAN run records:

Failed 1/20 test programs. 0/1944 subtests failed.

The focused t/real_set.t failure reproduces on both the JVM and interpreter backends.

Likely root cause

The parser/compiler recognizes the first form, union $set, sufficiently to execute the empty-set case, but does not consistently preserve the indirect-object method dispatch when additional arguments follow. It emits or resolves union as an ordinary bareword subroutine call in the main package instead of dispatching it as a method on $set.

This is a pure-Perl parser/runtime compatibility issue. Set::IntSpan contains no XS, C, XSLoader, DynaLoader, or FFI dependency, and the failure is independent of services or platform prerequisites.

Acceptance criteria

• All indirect-object method forms used by Set::IntSpan t/real_set.t dispatch to the object method on both backends.
• Set::IntSpan 1.19 passes all 1,947 upstream tests on JVM and interpreter backends.
• Add project-owned regression coverage for an indirect method call with no extra argument, a string argument, an object argument, and an array-reference argument.
• Preserve existing parsing behavior for ordinary bareword subroutine calls and malformed syntax.

Evidence

• CPAN run: 20260918-141920-96054
• Distribution: Set-IntSpan-1.19
• Failing test: t/real_set.t, line 22 (union $set "1-5,8-9")
• System Perl: PASS, 20 files / 1,947 tests
• PerlOnJava: FAIL, 1 file; the run reached 1,944 tests before aborting
• JVM and interpreter: focused failure reproduced

Related issues

• #1166 tracks valid fully-qualified indirect-object constructor forms. It covers a related parser area, but not this unqualified indirect-object method dispatch form.
• #1314 tracks bareword filehandle method dispatch used by Expect. It is related at the method-dispatch level, but this failure involves a normal Perl object and does not depend on filehandle or IO behavior.

This issue should be coordinated with those parser/runtime fixes, while retaining Set::IntSpan as independent regression coverage.