Handle not()

lib/syntax_tree/node.rb

@@ -8168,7 +8168,7 @@ def deconstruct_keys(keys)
   #     not value
   #
   class Not < Node
-    # [untyped] the statement on which to operate
+    # [nil | untyped] the statement on which to operate
     attr_reader :statement
 
     # [boolean] whether or not parentheses were used
@@ -8205,7 +8205,7 @@ def deconstruct_keys(keys)
 
     def format(q)
       q.text(parentheses ? "not(" : "not ")
-      q.format(statement)
+      q.format(statement) if statement
       q.text(")") if parentheses
     end
   end

lib/syntax_tree/parser.rb

@@ -2837,19 +2837,17 @@ def on_unary(operator, statement)
         # parentheses they don't get reported as a paren node for some reason.
 
         beginning = find_token(Kw, "not")
-        ending = statement
+        ending = statement || beginning
+        parentheses = source[beginning.location.end_char] == "("
 
-        range = beginning.location.end_char...statement.location.start_char
-        paren = source[range].include?("(")
-
-        if paren
+        if parentheses
           find_token(LParen)
           ending = find_token(RParen)
         end
 
         Not.new(
           statement: statement,
-          parentheses: paren,
+          parentheses: parentheses,
           location: beginning.location.to(ending.location)
         )
       else

test/fixtures/not.rb

@@ -1,4 +1,10 @@
 %
+not()
+%
+not ()
+%
 not foo
 %
 not(foo)
+%
+not (foo)