feat(vm): Module/Class residual surface — const_get/const_defined? paths, const_missing, included_modules, remove_class_variable

[tannevaled]

Horodate: 2026-08-09 21:12 CEST

Completes the residual Module/Class reflection surface toward MRI 3.4/4.0, verified against ruby 4.0.5.

What's implemented

• Module#const_get / #const_defined? — reworked to MRI semantics:
  • accept a String, Symbol or #to_str-coercible name;
  • resolve scoped "A::B" paths and a leading "::" toplevel qualifier;
  • honour the inherit flag (default true, coerced to boolean) — inherit searches the ancestor chain and, for a first segment, falls back to the toplevel; inherit=false consults only the receiver's own table;
  • reject malformed names (NameError "wrong constant name", incl. empty/successive :: segments) and scoping into a non-module (TypeError "… does not refer to class/module");
  • const_get routes an unresolved name through #const_missing; const_defined? reports a pending autoload as defined without triggering the require.
• Module#const_missing — default hook raising NameError (omitting the Object:: prefix at the toplevel, per MRI), carrying the name so NameError#name reports it. The :: scope operator now fires the hook, so user overrides (including a private_class_method :const_missing) apply.
• Module#included_modules — the modules (includes + prepends, transitively) in the ancestor chain, excluding the receiver.
• Module#remove_class_variable — removes a class variable defined directly on the receiver and returns its value; NameError on a malformed or absent name.

Deferred (blocked by separate, pre-existing bugs — out of this scope)

• const_source_location — needs per-constant source-location tracking threaded through constant assignment (invasive; no location is stored today).
• const_get/const_defined? "searches the superclass chain" via a module mixed into Object at the toplevel, and const_defined? "special cases Object" — blocked by top-level Kernel#include not including into Object (Object.include?(M) is false; M is absent from subclasses' ancestors).
• remove_class_variable "returns the value …" spec — blocked by Module#dup not copying class variables.
• const_defined? EUC-JP-encoded constant name — encoding edge.

Verification

• ruby/spec core/module deltas: const_get 26→42, const_defined? 19→29, const_missing 1→5, included_modules 0→1, remove_class_variable 5→7.
• ruby/spec ratchet: 12284 passing (was floor 12216); FLOOR bumped to 12254 (N-30).
• GOWORK=off go test ./... — pass (exit 0), no regressions.
• Whole-package coverage gate (-coverpkg all internal/...): every added/touched function (incl. modified scopedConst, NameError#name) is 100%; the non-100% list is exactly the pre-existing tolerated partials.
• gofmt clean; go vet ./internal/vm/ clean.

New table-driven tests in internal/vm/module_residuals_test.go.

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