move Array#recursively_flatten to ArrayOperations#flatten_helper

Author: Nicolas Laurent

src/main/java/org/truffleruby/core/CoreLibrary.java

@@ -1049,6 +1049,7 @@ public boolean isTruffleBootMainMethod(SharedMethodInfo info) {
             "/core/truffle/internal.rb",
             "/core/kernel.rb",
             "/core/lazy_rubygems.rb",
+            "/core/truffle/array_operations.rb",
             "/core/truffle/boot.rb",
             "/core/truffle/debug.rb",
             "/core/truffle/encoding_operations.rb",

src/main/ruby/truffleruby/core/array.rb

@@ -444,7 +444,7 @@ def flatten(level=-1)
     return self.dup if level == 0
 
     out = self.class.allocate # new_reserved size
-    recursively_flatten(self, out, level)
+    Truffle::ArrayOperations.flatten_helper(self, out, level)
     Primitive.infect(out, self)
     out
   end
@@ -456,7 +456,7 @@ def flatten!(level=-1)
     return nil if level == 0
 
     out = self.class.allocate # new_reserved size
-    if recursively_flatten(self, out, level)
+    if Truffle::ArrayOperations.flatten_helper(self, out, level)
       Primitive.steal_array_storage(self, out)
       return self
     end
@@ -1251,46 +1251,6 @@ def zip(*others)
     end
   end
 
-  # Helper to "recurse" through flattening. Detects recursive structures.
-  # Does not actually recurse, but uses a worklist instead.
-  def recursively_flatten(array, out, max_levels = -1)
-    modified = false
-    visited = {}.compare_by_identity
-    worklist = [[array, 0]]
-
-    until worklist.empty?
-      array, i = worklist.pop
-
-      if i == 0
-        raise ArgumentError, 'tried to flatten recursive array' if visited.key?(array)
-        if max_levels == worklist.size
-          out.concat(array)
-          next
-        end
-        visited[array] = true
-      end
-
-      size = array.size
-      while i < size
-        o = array.at i
-        tmp = Truffle::Type.rb_check_convert_type(o, Array, :to_ary)
-        if Primitive.nil? tmp
-          out << o
-        else
-          modified = true
-          worklist.push([array, i + 1], [tmp, 0])
-          break
-        end
-        i += 1
-      end
-
-      visited.delete array if i == size
-    end
-
-    modified
-  end
-  private :recursively_flatten
-
   private def sort_fallback(&block)
     # Use this instead of #dup as we want an instance of Array
     sorted = Array.new(self)

src/main/ruby/truffleruby/core/truffle/array_operations.rb

@@ -0,0 +1,50 @@
+# frozen_string_literal: true
+
+# Copyright (c) 2020 Oracle and/or its affiliates. All rights reserved. This
+# code is released under a tri EPL/GPL/LGPL license. You can use it,
+# redistribute it and/or modify it under the terms of the:
+#
+# Eclipse Public License version 2.0, or
+# GNU General Public License version 2, or
+# GNU Lesser General Public License version 2.1.
+#
+module Truffle::ArrayOperations
+  # Helper to "recurse" through flattening. Detects recursive structures.
+  # Does not actually recurse, but uses a worklist instead.
+  def self.flatten_helper(array, out, max_levels = -1)
+    modified = false
+    visited = {}.compare_by_identity
+    worklist = [[array, 0]]
+
+    until worklist.empty?
+      array, i = worklist.pop
+
+      if i == 0
+        raise ArgumentError, 'tried to flatten recursive array' if visited.key?(array)
+        if max_levels == worklist.size
+          out.concat(array)
+          next
+        end
+        visited[array] = true
+      end
+
+      size = array.size
+      while i < size
+        o = array.at i
+        tmp = Truffle::Type.rb_check_convert_type(o, Array, :to_ary)
+        if Primitive.nil? tmp
+          out << o
+        else
+          modified = true
+          worklist.push([array, i + 1], [tmp, 0])
+          break
+        end
+        i += 1
+      end
+
+      visited.delete array if i == size
+    end
+
+    modified
+  end
+end