Do not report unneeded disable directive if directive is used one line above

spec/ameba/rule/unneded_disable_directive_spec.cr

@@ -18,7 +18,16 @@ module Ameba::Rule
       subject.catch(s).should be_valid
     end
 
-    it "passes if there is disable directive and it is needed" do
+    it "doesn't report if there is disable directive and it is needed" do
+      s = Source.new %Q(
+        # ameba:disable #{NamedRule.name}
+        a = 1
+      )
+      s.error NamedRule.new, 3, 9, "Useless assignment", :disabled
+      subject.catch(s).should be_valid
+    end
+
+    it "passes if there is inline disable directive and it is needed" do
       s = Source.new %Q(
         a = 1 # ameba:disable #{NamedRule.name}
       )

spec/spec_helper.cr

@@ -72,7 +72,7 @@ module Ameba
     def failure_message(source)
       String.build do |str|
         str << "Source expected to be valid, but there are errors:\n\n"
-        source.errors.each do |e|
+        source.errors.reject(&.disabled?).each do |e|
           str << "  * #{e.rule.name}: #{e.message}\n"
         end
       end

src/ameba/inline_comments.cr

@@ -70,6 +70,13 @@ module Ameba
       end
     end
 
+    # Returns true if the line at the given `line_number` is a comment.
+    def comment?(line_number : Int32)
+      if line = lines[line_number]?
+        comment?(line)
+      end
+    end
+
     private def comment?(line)
       return true if line.lstrip.starts_with? '#'
     end

src/ameba/rule/unneeded_disable_directive.cr

@@ -43,9 +43,18 @@ module Ameba::Rule
         source.errors.any? do |error|
           error.rule.name == rule_name &&
             error.disabled? &&
-            error.location.try(&.line_number) == location.line_number
+            error_at_location?(source, error, location)
         end && rule_name != self.name
       end
     end
+
+    private def error_at_location?(source, error, location)
+      return false unless error_line_number = error.location.try(&.line_number)
+
+      error_line_number == location.line_number ||
+        ((prev_line_number = error_line_number - 1) &&
+          prev_line_number == location.line_number &&
+          source.comment?(prev_line_number - 1))
+    end
   end
 end