Rework variable references detection in macro

spec/ameba/rule/useless_assign_spec.cr

@@ -851,6 +851,22 @@ module Ameba::Rule
         )
         subject.catch(s).should_not be_valid
       end
+
+      it "doesn't report if assignment is referenced in a macro below" do
+        s = Source.new %(
+          class Foo
+            def foo
+              a = 1
+              macro_call
+            end
+
+            macro macro_call
+              puts a
+            end
+          end
+        )
+        subject.catch(s).should be_valid
+      end
     end
 
     context "uninitialized" do

src/ameba/ast/scope.cr

@@ -19,9 +19,6 @@ module Ameba::AST
     # The actual AST node that represents a current scope.
     getter node : Crystal::ASTNode
 
-    # Macro literals in current scope
-    getter macro_literals = [] of Crystal::MacroLiteral
-
     delegate to_s, to: node
     delegate location, to: node
 

src/ameba/ast/variabling/variable.cr

@@ -117,7 +117,7 @@ module Ameba::AST
     # false if not.
     def used_in_macro?(scope = @scope)
       scope.inner_scopes.each do |inner_scope|
-        return true if inner_scope.macro_literals.any? { |literal| literal.value.includes?(name) }
+        return true if MacroLiteralFinder.new(inner_scope.node).references? node
       end
       return true if (outer_scope = scope.outer_scope) && used_in_macro?(outer_scope)
       false
@@ -142,5 +142,25 @@ module Ameba::AST
         node.name == @node.name &&
         node.location == @node.location
     end
+
+    private class MacroLiteralFinder < Crystal::Visitor
+      @macro_literals = [] of Crystal::MacroLiteral
+
+      def initialize(node)
+        node.accept self
+      end
+
+      def references?(node : Crystal::Var)
+        @macro_literals.any? { |literal| literal.value.includes? node.name }
+      end
+
+      def visit(node : Crystal::ASTNode)
+        true
+      end
+
+      def visit(node : Crystal::MacroLiteral)
+        @macro_literals << node
+      end
+    end
   end
 end

src/ameba/ast/visitors/scope_visitor.cr

@@ -127,11 +127,6 @@ module Ameba::AST
       end
     end
 
-    # :nodoc:
-    def visit(node : Crystal::MacroLiteral)
-      @current_scope.macro_literals << node
-    end
-
     # :nodoc:
     def visit(node : Crystal::Call)
       return true unless node.name == "super" && node.args.empty?