Unused argument rule (#52)

* Unused argument rule

* IgnoreDefs, IgnoreBlocks, IgnoreProcs parameters

* Implicit reference by super keyworkd

* Handle macro arguments

spec/ameba/ast/variabling/argument_spec.cr

@@ -0,0 +1,40 @@
+require "../../../spec_helper"
+
+module Ameba::AST
+  describe Argument do
+    arg = Crystal::Arg.new "a"
+    scope = Scope.new as_node "foo = 1"
+    variable = Variable.new(Crystal::Var.new("foo"), scope)
+
+    describe "#initialize" do
+      it "creates a new argument" do
+        argument = Argument.new(arg, variable)
+        argument.node.should_not be_nil
+      end
+    end
+
+    describe "delegation" do
+      it "delegates location to node" do
+        argument = Argument.new(arg, variable)
+        argument.location.should eq arg.location
+      end
+
+      it "delegates to_s to node" do
+        argument = Argument.new(arg, variable)
+        argument.to_s.should eq arg.to_s
+      end
+    end
+
+    describe "#ignored?" do
+      it "is true if arg starts with _" do
+        argument = Argument.new(Crystal::Arg.new("_a"), variable)
+        argument.ignored?.should be_true
+      end
+
+      it "is false otherwise" do
+        argument = Argument.new(arg, variable)
+        argument.ignored?.should be_false
+      end
+    end
+  end
+end