Correctly process record declaration at a top level (#78)

spec/ameba/rule/lint/useless_assign_spec.cr

@@ -419,6 +419,35 @@ module Ameba::Rule::Lint
         )
         subject.catch(s).should be_valid
       end
+
+      it "doesn't report if this is a record declaration" do
+        s = Source.new %(
+          record Foo, foo = "foo"
+        )
+        subject.catch(s).should be_valid
+      end
+
+      it "does not report if assignment is referenced after the record declaration" do
+        s = Source.new %(
+          foo = 2
+          record Bar, foo = 3 # foo = 3 is not parsed as assignment
+          puts foo
+        )
+        subject.catch(s).should be_valid
+      end
+
+      it "reports if assignment is not referenced after the record declaration" do
+        s = Source.new %(
+          foo = 2
+          record Bar, foo = 3
+        ), "source.cr"
+        subject.catch(s).should_not be_valid
+        s.issues.size.should eq 1
+
+        issue = s.issues.first
+        issue.location.to_s.should eq "source.cr:2:11"
+        issue.message.should eq "Useless assignment to variable `foo`"
+      end
     end
 
     context "branching" do

src/ameba/ast/scope.cr

@@ -98,6 +98,11 @@ module Ameba::AST
       node.is_a? Crystal::Def
     end
 
+    # Returns true if this scope is a top level scope, false if not.
+    def top_level?
+      outer_scope.nil?
+    end
+
     # Returns true if var is an argument in current scope, false if not.
     def arg?(var)
       case current_node = node

src/ameba/ast/visitors/scope_visitor.cr

@@ -3,6 +3,9 @@ require "./base_visitor"
 module Ameba::AST
   # AST Visitor that traverses the source and constructs scopes.
   class ScopeVisitor < BaseVisitor
+    SUPER_NODE_NAME  = "super"
+    RECORD_NODE_NAME = "record"
+
     @current_scope : Scope
 
     def initialize(@rule, @source)
@@ -140,13 +143,23 @@ module Ameba::AST
 
     # :nodoc:
     def visit(node : Crystal::Call)
-      return true unless node.name == "super" && node.args.empty?
-      return true unless (scope = @current_scope).def?
-      scope.arguments.each do |arg|
-        variable = arg.variable
-        variable.reference(variable.node, scope).explicit = false
+      case @current_scope
+      when .def?
+        if node.name == SUPER_NODE_NAME && node.args.empty?
+          @current_scope.arguments.each do |arg|
+            variable = arg.variable
+            variable.reference(variable.node, @current_scope).explicit = false
+          end
+        end
+      when .top_level?
+        return false if record_macro?(node)
       end
+
       true
     end
+
+    private def record_macro?(node)
+      node.name == RECORD_NODE_NAME && node.args.first?.is_a?(Crystal::Path)
+    end
   end
 end