[Fix #3120] Fix #new visibility modifier scopes (#3126)

Blocks passed to {Class,Module,Struct}.new create a new scope, in a
similar way to Klass.class_eval.

CHANGELOG.md

@@ -5,6 +5,7 @@
 ### Bug fixes
 
 * [#3114](https://github.com/bbatsov/rubocop/issues/3114): Fix alignment `end` when auto-correcting `Style/EmptyElse`. ([@rrosenblum][])
+* [#3120](https://github.com/bbatsov/rubocop/issues/3120): Fix `Lint/UselessAccessModifier` reporting useless access modifiers inside {Class,Module,Struct}.new blocks. ([@owst][])
 
 ## 0.40.0 (2016-05-09)
 

lib/rubocop/cop/lint/useless_access_modifier.rb

@@ -68,7 +68,7 @@ def on_module(node)
         end
 
         def on_block(node)
-          return unless class_or_instance_eval?(node)
+          return unless instance_eval_or_new_call?(node)
 
           check_node(node.children[2]) # block body
         end
@@ -95,6 +95,10 @@ def on_sclass(node)
           (block (send _ {:class_eval :instance_eval}) ...)
         PATTERN
 
+        def_node_matcher :class_or_module_or_struct_new_call?, <<-PATTERN
+          (block (send (const nil {:Class :Module :Struct}) :new ...) ...)
+        PATTERN
+
         def check_node(node)
           return if node.nil?
 
@@ -143,7 +147,12 @@ def method_definition?(child)
 
         def start_of_new_scope?(child)
           child.module_type? || child.class_type? ||
-            child.sclass_type? || class_or_instance_eval?(child)
+            child.sclass_type? || instance_eval_or_new_call?(child)
+        end
+
+        def instance_eval_or_new_call?(child)
+          class_or_instance_eval?(child) ||
+            class_or_module_or_struct_new_call?(child)
         end
       end
     end

spec/rubocop/cop/lint/useless_access_modifier_spec.rb

@@ -603,6 +603,26 @@
     end
   end
 
+  shared_examples 'def in new block' do |klass, modifier|
+    it "doesn't register an offense if a method is defined in #{klass}.new" do
+      src = ["#{klass}.new do",
+             "  #{modifier}",
+             '  def foo',
+             '  end',
+             'end']
+      inspect_source(cop, src)
+      expect(cop.offenses).to be_empty
+    end
+
+    it "registers an offense if no method is defined in #{klass}.new" do
+      src = ["#{klass}.new do",
+             "  #{modifier}",
+             'end']
+      inspect_source(cop, src)
+      expect(cop.offenses.size).to eq(1)
+    end
+  end
+
   shared_examples 'method defined using instance_eval' do |modifier|
     it "doesn't register an offense if a method is defined" do
       src = ['A.instance_eval do',
@@ -709,6 +729,12 @@
     it_behaves_like('method defined using instance_eval', modifier)
   end
 
+  %w(Class Module Struct).each do |klass|
+    %w(protected private).each do |modifier|
+      it_behaves_like('def in new block', klass, modifier)
+    end
+  end
+
   %w(module class).each do |keyword|
     it_behaves_like('at the top of the body', keyword)
     it_behaves_like('non-repeated visibility modifiers', keyword)