Fix Performance/FixedSize false positive when count is called with a numblock

Author: dvandersluis

changelog/fix_fix_performance_fixed_size_false.md

@@ -0,0 +1 @@
+* [#494](https://github.com/rubocop/rubocop-performance/pull/494): Fix `Performance/FixedSize` false positive when `count` is called with a `numblock`. ([@dvandersluis][])

lib/rubocop/cop/performance/fixed_size.rb

@@ -75,7 +75,7 @@ def allowed_argument?(arg)
         end
 
         def allowed_parent?(node)
-          node&.type?(:casgn, :block)
+          node&.type?(:casgn, :any_block)
         end
 
         def contains_splat?(node)

spec/rubocop/cop/performance/fixed_size_spec.rb

@@ -204,6 +204,14 @@
       expect_no_offenses("#{variable}.count { |v| v == 'a' }")
     end
 
+    it 'accepts calling count with a numblock', :ruby27 do
+      expect_no_offenses("#{variable}.count { _1 == 'a' }")
+    end
+
+    it 'accepts calling count with an itblock', :ruby34 do
+      expect_no_offenses("#{variable}.count { it == 'a' }")
+    end
+
     it 'accepts calling count with a symbol proc' do
       expect_no_offenses("#{variable}.count(&:any?) ")
     end