Prevent disabling of UnneededDisableDirective rule

spec/ameba/rule/unneded_disable_directive_spec.cr

@@ -65,6 +65,15 @@ module Ameba::Rule
       s.errors.last.message.should contain "Rule3"
     end
 
+    it "fails if there is disabled UnneededDisableDirective" do
+      s = Source.new %Q(
+        # ameba:disable #{UnneededDisableDirective.class_name}
+        a = 1
+      ), "source.cr"
+      s.error UnneededDisableDirective.new, 3, 1, "Alarm!", :disabled
+      subject.catch(s).should_not be_valid
+    end
+
     it "reports error, location and message" do
       s = Source.new %Q(
         # ameba:disable Rule1, Rule2

src/ameba/inline_comments.cr

@@ -32,6 +32,7 @@ module Ameba
     # ```
     #
     def location_disabled?(location, rule)
+      return false if Rule::SPECIAL.includes?(rule)
       return false unless line_number = location.try &.line_number.try &.- 1
       return false unless line = lines[line_number]?
 

src/ameba/rule/base.cr

@@ -1,4 +1,9 @@
 module Ameba::Rule
+  SPECIAL = [
+    Syntax.class_name,
+    UnneededDisableDirective.class_name,
+  ]
+
   # Represents a base of all rules. In other words, all rules
   # inherits from this struct:
   #

src/ameba/rule/unneeded_disable_directive.cr

@@ -9,7 +9,7 @@ module Ameba::Rule
   # end
   # ```
   #
-  # as the predicate name is correct and comment directive does not
+  # as the predicate name is correct and the comment directive does not
   # have any effect, the snippet should be written as the following:
   #
   # ```
@@ -39,11 +39,11 @@ module Ameba::Rule
       return unless directive[:action] == "disable"
 
       directive[:rules].reject do |rule_name|
-        any = source.errors.any? do |error|
+        source.errors.any? do |error|
           error.rule.name == rule_name &&
             error.disabled? &&
             error.location.try(&.line_number) == location.line_number
-        end
+        end && rule_name != self.name
       end
     end
   end