Support instance method returning instance type

Author: tompng

lib/repl_type_completor/types.rb

@@ -332,6 +332,8 @@ def self.from_rbs_type(return_type, self_type, extra_vars = {})
         self_type.transform do |type|
           if type.is_a?(SingletonType) && type.module_or_class.is_a?(Class)
             InstanceType.new type.module_or_class
+          elsif type.is_a?(InstanceType)
+            InstanceType.new type.klass
           else
             OBJECT
           end

test/repl_type_completor/test_type_analyze.rb

@@ -719,5 +719,10 @@ def test_rbs_untyped_function
       # Proc#call `(?) -> untyped` is RBS::Types::UntypedFunction
       assert_call('proc{}.call; 1.', include: Integer)
     end
+
+    def test_rbs_instance_type
+      assert_call('Thread.start{}.', include: Thread)
+      assert_call('"".encode("utf-8").', include: String)
+    end
   end
 end