[tannevaled]

One more of the 27 from #799. core/objectspace/_id2ref_spec.rb goes 0 → 1 —
the whole file is that single example at 4.0, the eleven others being
ruby_version_is ""..."4.0".

gc.c calls rb_category_warn(RB_WARN_CATEGORY_DEPRECATED, "ObjectSpace._id2ref is deprecated"). The method still answers; it only says so.

⛔ The find is not the deprecation, it is the gate

Writing this meant copying the nearest precedent — iterator?, which rbgo
already deprecates. Measuring that precedent against MRI 4.0.7 first showed
it wrong in two ways, and copying it would have spread both.

One — it warns where MRI is silent.

$VERBOSE = nil; Warning[:deprecated] = true; iterator?
  rbgo  "…:13: warning: iterator? is deprecated; use block_given? instead"
  MRI   ""

MRI's deprecation_warning_enabled() wants a non-nil $VERBOSE and the
category. rbgo checked the category alone — and $VERBOSE = nil is precisely
how a program asks for that silence. All four combinations measured:

$VERBOSE	Warning[:deprecated]	MRI
nil	on	silent
false	on	warns
true	off	silent
true	on	warns

Two — the category never arrived. With a Warning.warn override installed:

module Warning; def self.warn(msg, category: nil) = $seen << [msg, category]; end
#  rbgo  [..., nil]
#  MRI   [..., :deprecated]

A handler that filters on the category saw nil. Not decoration.

Both are our code, so both are fixed here rather than filed. warnDeprecated
is MRI's gate in one place — the two-condition test, the
"<file>:<line>: warning: " head, Warning.warn with category: :deprecated —
and iterator? now goes through it.

Measured

rubydiff against MRI 4.0.7, three probe programs: AGREE on all, including
the four $VERBOSE × Warning[:deprecated] combinations and the Warning.warn
interception.

The argument check stays ahead of the warning, so ObjectSpace._id2ref with
no argument raises ArgumentError in silence — a warning emitted first would make
a plain mistake look like a deprecation. There is a test for that.

warnDeprecated: 100.0% covered.

Not done here

The full internal/vm suite was not run locally for this change: the
machine is at a 1-minute load average of 12.5, and the one run attempted hit
#895 — TestUDPSocketLoopback hanging for 38 minutes until the suite's
40-minute timeout. CI runs it on this pull request.

🤖 Generated with Claude Code