Emit a performance warning when a class reached max variations

[Feature #19538]

This new `peformance` warning category is disabled by default.
It needs to be specifically enabled via `-W:performance` or `Warning[:performance] = true`

2 files changed, 22 insertions, 5 deletions

diff --git a/test/ruby/test_object.rb b/test/ruby/test_object.rb
index 26256b80db..a34fc7813a 100644
--- a/test/ruby/test_object.rb
+++ b/test/ruby/test_object.rb
@@ -422,6 +422,18 @@ class TestObject < Test::Unit::TestCase
     assert_equal(1+3+5+7+9, n)
   end
 
+  def test_max_shape_variation_with_performance_warnings
+    assert_in_out_err([], <<-INPUT, %w(), /Maximum shapes variations \(8\) reached by Foo, instance variables accesses will be slower\.$/)
+      $VERBOSE = true
+      Warning[:performance] = true
+
+      class Foo; end
+      10.times do |i|
+        Foo.new.instance_variable_set(:"@a\#{i}", nil)
+      end
+    INPUT
+  end
+
   def test_redefine_method_under_verbose
     assert_in_out_err([], <<-INPUT, %w(2), /warning: method redefined; discarding old foo$/)
       $VERBOSE = true
diff --git a/test/ruby/test_rubyoptions.rb b/test/ruby/test_rubyoptions.rb
index 6aacb80d2f..4c2dc31240 100644
--- a/test/ruby/test_rubyoptions.rb
+++ b/test/ruby/test_rubyoptions.rb
@@ -99,19 +99,24 @@ class TestRubyOptions < Test::Unit::TestCase
     assert_in_out_err(%w(-W:no-deprecated -e) + ['p Warning[:deprecated]'], "", %w(false), [])
     assert_in_out_err(%w(-W:experimental -e) + ['p Warning[:experimental]'], "", %w(true), [])
     assert_in_out_err(%w(-W:no-experimental -e) + ['p Warning[:experimental]'], "", %w(false), [])
+    assert_in_out_err(%w(-W -e) + ['p Warning[:performance]'], "", %w(false), [])
+    assert_in_out_err(%w(-W:performance -e) + ['p Warning[:performance]'], "", %w(true), [])
     assert_in_out_err(%w(-W:qux), "", [], /unknown warning category: `qux'/)
     assert_in_out_err(%w(-w -e) + ['p Warning[:deprecated]'], "", %w(true), [])
     assert_in_out_err(%w(-W -e) + ['p Warning[:deprecated]'], "", %w(true), [])
     assert_in_out_err(%w(-We) + ['p Warning[:deprecated]'], "", %w(true), [])
     assert_in_out_err(%w(-e) + ['p Warning[:deprecated]'], "", %w(false), [])
-    code = 'puts "#{$VERBOSE}:#{Warning[:deprecated]}:#{Warning[:experimental]}"'
+    assert_in_out_err(%w(-w -e) + ['p Warning[:performance]'], "", %w(false), [])
+    assert_in_out_err(%w(-W -e) + ['p Warning[:performance]'], "", %w(false), [])
+    code = 'puts "#{$VERBOSE}:#{Warning[:deprecated]}:#{Warning[:experimental]}:#{Warning[:performance]}"'
     Tempfile.create(["test_ruby_test_rubyoption", ".rb"]) do |t|
       t.puts code
       t.close
-      assert_in_out_err(["-r#{t.path}", '-e', code], "", %w(false:false:true false:false:true), [])
-      assert_in_out_err(["-r#{t.path}", '-w', '-e', code], "", %w(true:true:true true:true:true), [])
-      assert_in_out_err(["-r#{t.path}", '-W:deprecated', '-e', code], "", %w(false:true:true false:true:true), [])
-      assert_in_out_err(["-r#{t.path}", '-W:no-experimental', '-e', code], "", %w(false:false:false false:false:false), [])
+      assert_in_out_err(["-r#{t.path}", '-e', code], "", %w(false:false:true:false false:false:true:false), [])
+      assert_in_out_err(["-r#{t.path}", '-w', '-e', code], "", %w(true:true:true:false true:true:true:false), [])
+      assert_in_out_err(["-r#{t.path}", '-W:deprecated', '-e', code], "", %w(false:true:true:false false:true:true:false), [])
+      assert_in_out_err(["-r#{t.path}", '-W:no-experimental', '-e', code], "", %w(false:false:false:false false:false:false:false), [])
+      assert_in_out_err(["-r#{t.path}", '-W:performance', '-e', code], "", %w(false:false:true:true false:false:true:true), [])
     end
   ensure
     ENV['RUBYOPT'] = save_rubyopt