Merge pull request #430 from crystal-ameba/fix-issue-429

Report unused type declarations in `Lint/UselessAssign` rule

spec/ameba/ast/visitors/flow_expression_visitor_spec.cr

@@ -1,8 +1,6 @@
 require "../../../spec_helper"
 
 module Ameba::AST
-  source = Source.new ""
-
   describe FlowExpressionVisitor do
     it "creates an expression for return" do
       rule = FlowExpressionRule.new

src/ameba/ast/scope.cr

@@ -186,9 +186,19 @@ module Ameba::AST
       node.is_a?(Crystal::Def)
     end
 
+    # Returns `true` if current scope is a class, `false` otherwise.
+    def class_def?
+      node.is_a?(Crystal::ClassDef)
+    end
+
+    # Returns `true` if current scope is a module, `false` otherwise.
+    def module_def?
+      node.is_a?(Crystal::ModuleDef)
+    end
+
     # Returns `true` if this scope is a top level scope, `false` otherwise.
     def top_level?
-      outer_scope.nil? || type_definition?
+      outer_scope.nil?
     end
 
     # Returns `true` if var is an argument in current scope, `false` otherwise.

src/ameba/ast/variabling/assignment.cr

@@ -32,9 +32,7 @@ module Ameba::AST
       return unless scope = @variable.scope
 
       @branch = Branch.of(@node, scope)
-      @referenced = true if @variable.special? ||
+      @referenced = true if @variable.special? || referenced_in_loop?
-                            @variable.scope.type_definition? ||
-                            referenced_in_loop?
     end
 
     def referenced_in_loop?

src/ameba/ast/visitors/scope_visitor.cr

@@ -170,22 +170,29 @@ module Ameba::AST
 
     # :nodoc:
     def visit(node : Crystal::Call)
-      case
+      scope = @current_scope
-      when @current_scope.def?
-        if node.name.in?(SPECIAL_NODE_NAMES) && node.args.empty?
-          @current_scope.arguments.each do |arg|
-            variable = arg.variable
 
-            ref = variable.reference(variable.node, @current_scope)
+      case
-            ref.explicit = false
+      when scope.top_level? && record_macro?(node)         then return false
-          end
+      when scope.type_definition? && record_macro?(node)   then return false
+      when scope.type_definition? && accessor_macro?(node) then return false
+      when scope.def? && special_node?(node)
+        scope.arguments.each do |arg|
+          variable = arg.variable
+
+          ref = variable.reference(variable.node, scope)
+          ref.explicit = false
         end
-        true
-      when @current_scope.top_level? && record_macro?(node)
-        false
-      else
-        true
       end
+      true
+    end
+
+    private def special_node?(node)
+      node.name.in?(SPECIAL_NODE_NAMES) && node.args.empty?
+    end
+
+    private def accessor_macro?(node)
+      node.name.matches? /^(class_)?(getter[?!]?|setter|property[?!]?)$/
     end
 
     private def record_macro?(node)

src/ameba/rule/lint/useless_assign.cr

@@ -24,10 +24,12 @@ module Ameba::Rule::Lint
   # ```
   # Lint/UselessAssign:
   #   Enabled: true
+  #   ExcludeTypeDeclarations: false
   # ```
   class UselessAssign < Base
     properties do
       description "Disallows useless variable assignments"
+      exclude_type_declarations false
     end
 
     MSG = "Useless assignment to variable `%s`"
@@ -39,7 +41,7 @@ module Ameba::Rule::Lint
     def test(source, node, scope : AST::Scope)
       scope.variables.each do |var|
         next if var.ignored? || var.used_in_macro? || var.captured_by_block?
-        next if scope.assigns_type_dec?(var.name)
+        next if exclude_type_declarations? && scope.assigns_type_dec?(var.name)
 
         var.assignments.each do |assign|
           next if assign.referenced?