Remove stale Float constants and add a constant drift test

core/float.rbs

@@ -1222,8 +1222,6 @@ Float::EPSILON: Float
 #
 Float::INFINITY: Float
 
-Float::Infinity: Float
-
 # <!-- rdoc-file=numeric.c -->
 # The number of base digits for the `double` data type.
 #
@@ -1292,25 +1290,3 @@ Float::NAN: Float
 # decimal.
 #
 Float::RADIX: Integer
-
-# Deprecated, do not use.
-#
-# Represents the rounding mode for floating point addition at the start time.
-#
-# Usually defaults to 1, rounding to the nearest number.
-#
-# Other modes include:
-#
-# -1
-# :   Indeterminable
-# 0
-# :   Rounding towards zero
-# 1
-# :   Rounding to the nearest number
-# 2
-# :   Rounding towards positive infinity
-# 3
-# :   Rounding towards negative infinity
-#
-#
-Float::ROUNDS: Integer

test/stdlib/Float_test.rb

@@ -1,5 +1,59 @@
 require_relative "test_helper"
 
+class FloatSingletonTest < Test::Unit::TestCase
+  include TestHelper
+
+  testing 'singleton(::Float)'
+
+  def test_DIG
+    assert_const_type 'Integer', 'Float::DIG'
+  end
+
+  def test_EPSILON
+    assert_const_type 'Float', 'Float::EPSILON'
+  end
+
+  def test_INFINITY
+    assert_const_type 'Float', 'Float::INFINITY'
+  end
+
+  def test_MANT_DIG
+    assert_const_type 'Integer', 'Float::MANT_DIG'
+  end
+
+  def test_MAX
+    assert_const_type 'Float', 'Float::MAX'
+  end
+
+  def test_MAX_10_EXP
+    assert_const_type 'Integer', 'Float::MAX_10_EXP'
+  end
+
+  def test_MAX_EXP
+    assert_const_type 'Integer', 'Float::MAX_EXP'
+  end
+
+  def test_MIN
+    assert_const_type 'Float', 'Float::MIN'
+  end
+
+  def test_MIN_10_EXP
+    assert_const_type 'Integer', 'Float::MIN_10_EXP'
+  end
+
+  def test_MIN_EXP
+    assert_const_type 'Integer', 'Float::MIN_EXP'
+  end
+
+  def test_NAN
+    assert_const_type 'Float', 'Float::NAN'
+  end
+
+  def test_RADIX
+    assert_const_type 'Integer', 'Float::RADIX'
+  end
+end
+
 class FloatTest < StdlibTest
   target Float
 

test/stdlib/constant_drift_test.rb

@@ -0,0 +1,77 @@
+require_relative "test_helper"
+
+# Guards against "constant drift" between the RBS core signatures and the actual
+# runtime, in both directions:
+#
+# *   a constant declared in RBS but no longer defined by Ruby (e.g.
+#     `Float::ROUNDS`, removed in Ruby 3.0), and
+# *   a constant defined by Ruby but missing from RBS.
+#
+# Only platform- and build-invariant core classes are hard-gated here. Classes
+# whose constant set legitimately varies by OS or build options (`Process`,
+# `Socket`, `Errno`, `Signal`, `File::Constants`, `RbConfig`, `Etc`, ...) are
+# intentionally excluded: their RBS declarations cannot match any single
+# platform's runtime. `Object`/`BasicObject`/`Kernel` are excluded too, since
+# every top-level class shows up under `Object.constants`.
+class ConstantDriftTest < Test::Unit::TestCase
+  # Platform/build-invariant core classes and modules whose declared constant
+  # set must match the runtime exactly.
+  HARD_GATE = [
+    Float, Integer, Numeric, Rational, Complex,
+    Math, Comparable,
+    String, Symbol,
+    Array, Hash, Range, Struct,
+    NilClass, TrueClass, FalseClass
+  ].freeze
+
+  # Known, intentional exceptions keyed by "::Name" => [:CONST, ...]. Use this
+  # for build- or platform-conditional constants (and `private_constant`s) that
+  # are legitimately undeclared, so the gate stays green across CI platforms
+  # without being weakened elsewhere.
+  SKIP = {
+    # Defined only when Ruby is built with GMP (USE_GMP): present on the Linux
+    # CI build, absent on e.g. macOS.
+    "::Integer" => [:GMP_VERSION]
+  }.freeze
+
+  def env
+    StdlibTest::DEFAULT_ENV
+  end
+
+  # Constants declared directly under `type_name` in the loaded RBS environment
+  # (plain constants plus nested classes/modules and their aliases), matching
+  # what `Module#constants(false)` returns at runtime.
+  def rbs_constants(type_name)
+    prefix = "#{type_name}::"
+    names = []
+    [env.constant_decls, env.class_decls, env.class_alias_decls].each do |store|
+      store.each_key do |tn|
+        s = tn.to_s
+        next unless s.start_with?(prefix)
+
+        rest = s.delete_prefix(prefix)
+        names << rest.to_sym unless rest.include?("::")
+      end
+    end
+    names.uniq.sort
+  end
+
+  HARD_GATE.each do |klass|
+    define_method(:"test_no_constant_drift_#{klass.name.gsub("::", "_")}") do
+      type_name = "::#{klass.name}"
+      skip = SKIP[type_name] || []
+      runtime = (klass.constants(false) - skip).sort
+      declared = (rbs_constants(type_name) - skip).sort
+
+      stale = declared - runtime
+      missing = runtime - declared
+
+      assert_empty stale,
+        "RBS declares #{type_name} constants that no longer exist at runtime: #{stale.inspect}. " \
+        "Remove them from the signature (or add to ConstantDriftTest::SKIP if intentional)."
+      assert_empty missing,
+        "Runtime defines #{type_name} constants missing from RBS: #{missing.inspect}. " \
+        "Add them to the signature (or add to ConstantDriftTest::SKIP if intentional)."
+    end
+  end
+end