[jiro-by-nori]

Pathname instances answer every unmodeled selector with a named Unsupported — including selectors no Ruby defines — because the prelude carries a blanket method_missing plus a respond_to_missing? that answers true for anything. An invented name therefore looked like an honest gap instead of the NoMethodError CRuby raises, a real unmodeled method (realpath, stat, …) lost its own name behind one generic reason, and respond_to? was a wrong value. This is the instance-side twin of #29 (class side, PR #146) and the sibling of #27 (File/IO instance methods, fixed in #28).

Fixes #147.

What changes

Pathname is a prelude class, but CRuby ships it as part of the language, so its surface is now generated like a builtin's:

• scripts/gen_cruby_names.rb lists Pathname in FOLD, so crubyMethodNames, crubySingletonNames and crubyNamespaceConstants carry its real selectors. It also loads pathname.rb: the booted pathname.so answers require "pathname", so a plain require would be a no-op and the snapshot would miss the methods the .rb half adds (find, rmtree, Pathname.mktmpdir). Those are real methods a program that required pathname can call, so they must gate, not raise.
• prelude/prelude.rb: method_missing and respond_to_missing? are deleted; a miss is an ordinary lookup miss and dispatchMiss classifies it (a real name declines as unmodeled method Pathname#…, an invented one raises CRuby's byte-exact NoMethodError).
• Pathname#path is protected in CRuby, so it is modeled as protected: p.path raises the protected-method NoMethodError, p.send(:path) answers.
• include Comparable is removed: CRuby's Pathname is not Comparable, so <, > and between? are NoMethodError rather than answers.
• The checker's copied projection grows (the conservative direction): nativeInstanceNames gains the Pathname selectors, nativeQueryRows gains Pathname's ===/to_s (required by query_covered), and instance_covered needs maxRecDepth 4000 to walk the larger list.
• New regression case difftest/corpus/regressions/pathname-instance-surface pins the whole surface; docs/testing.md's reproducer count goes 219 → 224 (it was already stale by four).

Behaviour, model vs CRuby 4.0.5

to_s: "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/a/b"                               inspect: "#<Pathname:/a/b>"
basename: "b"                              dirname: "/a"
extname: ".rb"                             sub: "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/a/z"
eq: true                                   eql: true
spaceship: -1                              to_path: "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/a/b"
send_path: "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/a/b"
path: NoMethodError: protected method 'path' called for an instance of Pathname
miss: NoMethodError: undefined method 'zzz_does_not_exist' for an instance of Pathname
respond_zzz: false                         respond_basename: true
lt / between / clamp: NoMethodError: undefined method '<'/'between?'/'clamp' for an instance of Pathname

bin/ruby-lean --compare reports AGREE on that program. Real unmodeled selectors now decline by name — verified for 38 of them (realpath, stat, lstat, children, each_child, readlink, chmod, mkdir, rmdir, delete, unlink, rename, expand_path, relative_path_from, cleanpath, absolute?, relative?, root?, parent, sub_ext, entries, find, rmtree, size, read, write, open, each_line, atime, ctime, mtime, birthtime, utime, world_readable?, zero?, split, fnmatch?, ascend, descend, each_filename), each answering unmodeled method Pathname#<name>. Without the pathname.rb load, find and rmtree raised NoMethodError for methods CRuby has.

Test plan

make gen-check        fresh
make lint             no offenses (rubocop, ruff, shellcheck, actionlint)
make lean             ok
make books            1405 jobs, ok
make metatheory       ok
make soundness        SOUNDNESS CHECK PASSED  (corpus accepted.txt unchanged)
make conformance      CONFORMANCE OK — 1287 programs: agree 1087, disagree 0,
                      sut_unsupported 194, i.e. exactly the recorded baseline;
                      regressions tier 224 cases, 223 held, 0 disagree
make comparator       ok
make book-checks      ok
make feature-loading  ok
make difftest-test    ok, coverage baseline holds
make desugar-unit emitter-unit   ok
make docs             ok
make check-not-weakened          CHECKS NOT WEAKENED

Also bin/ruby-lean --compare on the program above (agrees) and per-selector probes for the 38 unmodeled names and the invented one.

Notes for review

• The first commit is Locate FastPower's Power instance and result Array instead of pinning their ids (fixes #53) #136's fix (FastPower pinned heap object ids), included verbatim because this prelude change shifts the boot heap. Drop it when rebasing if Locate FastPower's Power instance and result Array instead of pinning their ids (fixes #53) #136 has landed first.
• Class-side dispatch reads the CRuby name tables: a real unmodeled File/Dir/Pathname method gates, an invented one is a NoMethodError #146 fixes the same defect for the class side and touches the same generated tables; whichever lands second needs make gen regenerated, which is mechanical.
• Pathname#empty? still answers String#empty? instead of asking the filesystem; that is Pathname#empty? answers String#empty? instead of asking the filesystem, so it is a wrong answer #91 (PR Pathname#empty? asks the filesystem, not the path String (fixes #91) #92), deliberately untouched here.
• The code and this description were written by Jiro, an autonomous agent, on behalf of @sam-xif.