Add module_function support

When `module_function` is called without arguments in a module body,
subsequent method definitions are registered as both instance methods
and singleton methods, matching Ruby's behavior.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: mame

lib/typeprof/core/ast.rb

@@ -280,6 +280,10 @@ def self.create_node(raw_node, lenv, use_result = true, allow_meta = false)
             return AttrReaderMetaNode.new(raw_node, lenv)
           when :attr_accessor
             return AttrAccessorMetaNode.new(raw_node, lenv)
+          when :module_function
+            if raw_node.arguments.nil?
+              return ModuleFunctionMetaNode.new(raw_node, lenv)
+            end
           end
         end
         CallNode.new(raw_node, lenv)

lib/typeprof/core/ast/meta.rb

@@ -146,5 +146,11 @@ def install0(genv)
         Source.new
       end
     end
+    class ModuleFunctionMetaNode < Node
+      def install0(genv)
+        @lenv.module_function = true
+        Source.new
+      end
+    end
   end
 end

lib/typeprof/core/ast/method.rb

@@ -289,6 +289,9 @@ def install0(genv)
         )
 
         @changes.add_method_def_box(genv, @lenv.cref.cpath, @singleton, @mid, f_args, @body.lenv.return_boxes)
+        if @lenv.module_function && !@singleton
+          @changes.add_method_def_box(genv, @lenv.cref.cpath, true, @mid, f_args, @body.lenv.return_boxes)
+        end
 
         Source.new(Type::Symbol.new(genv, @mid))
       end

lib/typeprof/core/env.rb

@@ -331,6 +331,7 @@ def initialize(file_context, cref, locals, return_boxes)
     end
 
     attr_reader :file_context, :cref, :locals, :return_boxes, :break_vtx, :next_boxes, :strict_const_scope
+    attr_accessor :module_function
 
     def path = @file_context&.path
     def code_range_from_node(node)

scenario/misc/module_function.rb

@@ -0,0 +1,16 @@
+## update
+module Foo
+  module_function
+
+  def bar
+    42
+  end
+end
+
+Foo.bar
+
+## assert
+module Foo
+  def bar: -> Integer
+  def self.bar: -> Integer
+end