Support of Crystal::UnitializedVar

spec/ameba/rule/useless_assign_spec.cr

@@ -852,5 +852,33 @@ module Ameba::Rule
         subject.catch(s).should_not be_valid
       end
     end
+
+    context "uninitialized" do
+      it "reports if uninitialized assignment is not referenced at a top level" do
+        s = Source.new %(
+          a = uninitialized U
+        )
+        subject.catch(s).should_not be_valid
+      end
+
+      it "reports if uninitialized assignment is not referenced in a method" do
+        s = Source.new %(
+          def foo
+            a = uninitialized U
+          end
+        )
+        subject.catch(s).should_not be_valid
+      end
+
+      it "doesn't report if uninitialized assignment is referenced" do
+        s = Source.new %(
+          def foo
+            a = uninitialized U
+            a
+          end
+        )
+        subject.catch(s).should be_valid
+      end
+    end
   end
 end

src/ameba/ast/visitors/scope_visitor.cr

@@ -81,7 +81,7 @@ module Ameba::AST
     @current_assign : Crystal::ASTNode?
 
     # :nodoc:
-    def visit(node : Crystal::Assign | Crystal::OpAssign | Crystal::MultiAssign)
+    def visit(node : Crystal::Assign | Crystal::OpAssign | Crystal::MultiAssign | Crystal::UninitializedVar)
       @current_assign = node
     end
 
@@ -89,12 +89,21 @@ module Ameba::AST
     def end_visit(node : Crystal::Assign | Crystal::OpAssign)
       @current_scope.assign_variable(node.target)
       @current_assign = nil
+      on_scope_end(node) if @current_scope.eql?(node)
     end
 
     # :nodoc:
     def end_visit(node : Crystal::MultiAssign)
       node.targets.each { |target| @current_scope.assign_variable(target) }
       @current_assign = nil
+      on_scope_end(node) if @current_scope.eql?(node)
+    end
+
+    # :nodoc:
+    def end_visit(node : Crystal::UninitializedVar)
+      @current_scope.assign_variable(node.var)
+      @current_assign = nil
+      on_scope_end(node) if @current_scope.eql?(node)
     end
 
     # :nodoc: