[Bug #19549] Check for variables to be interpolated

Merged: https://github.com/ruby/ruby/pull/7615

parse.y

@@ -5432,24 +5432,10 @@ string_dend	: tSTRING_DEND
                 | END_OF_INPUT
                 ;
 
-string_dvar	: tGVAR
+string_dvar	: nonlocal_var
                     {
                     /*%%%*/
-                        $$ = NEW_GVAR($1, &@$);
+                        if (!($$ = gettable(p, $1, &@$))) $$ = NEW_BEGIN(0, &@$);
-                    /*% %*/
-                    /*% ripper: var_ref!($1) %*/
-                    }
-                | tIVAR
-                    {
-                    /*%%%*/
-                        $$ = NEW_IVAR($1, &@$);
-                    /*% %*/
-                    /*% ripper: var_ref!($1) %*/
-                    }
-                | tCVAR
-                    {
-                    /*%%%*/
-                        $$ = NEW_CVAR($1, &@$);
                     /*% %*/
                     /*% ripper: var_ref!($1) %*/
                     }

test/ruby/test_parse.rb

@@ -1443,6 +1443,11 @@ x = __ENCODING__
     assert_equal(expected, obj.arg)
   end
 
+  def test_ungettable_gvar
+    assert_syntax_error('$01234', /not valid to get/)
+    assert_syntax_error('"#$01234"', /not valid to get/)
+  end
+
 =begin
   def test_past_scope_variable
     assert_warning(/past scope/) {catch {|tag| eval("BEGIN{throw tag}; tap {a = 1}; a")}}