Fix RuntimeError on () as a method arg or hash splat value

lib/typeprof/core/ast/call.rb

@@ -37,7 +37,7 @@ def initialize(raw_node, recv, mid, mid_code_range, raw_args, last_arg, raw_bloc
               @splat_flags << false
             end
           end
-          @positional_args = args.map {|arg| arg ? AST.create_node(arg, lenv) : DummyNilNode.new(code_range, lenv) }
+          @positional_args = args.map {|arg| arg ? AST.create_node(arg, lenv) : nil }
 
           kw = @positional_args.last
           if kw.is_a?(TypeProf::Core::AST::HashNode) && kw.keywords
@@ -119,7 +119,7 @@ def install0(genv)
           keyword_args = forward_a_args.keywords
         else
           positional_args = @positional_args.map do |arg|
-            if arg.is_a?(DummyNilNode)
+            if arg.nil?
               @lenv.get_var(:"*anonymous_rest")
             else
               arg.install(genv)

lib/typeprof/core/ast/value.rb

@@ -275,7 +275,7 @@ def initialize(raw_node, lenv, keywords)
             if raw_elem.value
               @vals << AST.create_node(raw_elem.value, lenv)
             else
-              @vals << DummyNilNode.new(code_range, lenv)
+              @vals << nil
             end
             @splat = true
           else
@@ -306,7 +306,7 @@ def install0(genv)
               all_symbol_keys = false
             end
           else
-            if val.is_a?(DummyNilNode)
+            if val.nil?
               h = @lenv.get_var(:"**anonymous_keyword")
             else
               h = val.install(genv)

scenario/misc/parens.rb

@@ -15,16 +15,49 @@ def with_default(x = ())
   x
 end
 
+def in_array
+  [()]
+end
+
+def in_condition
+  if (); 1; end
+end
+
+def take_arg(x); x; end
+
+def empty_as_arg
+  take_arg(())
+end
+
+def empty_as_splat_arg
+  take_arg(*())
+end
+
+def empty_as_kw_splat
+  { **() }
+end
+
 grouping
 nested
 empty
 with_default
 with_default(1)
+in_array
+in_condition
+empty_as_arg
+empty_as_splat_arg
+empty_as_kw_splat
 
 ## assert
 class Object
   def grouping: -> Integer
   def nested: -> Integer
   def empty: -> nil
   def with_default: (?Integer?) -> Integer?
+  def in_array: -> [nil]
+  def in_condition: -> Integer?
+  def take_arg: (nil) -> nil
+  def empty_as_arg: -> nil
+  def empty_as_splat_arg: -> nil
+  def empty_as_kw_splat: -> Hash[untyped, untyped]
 end