Separate numbered parameter scope in eval

[Feature #16432]

parse.y

@@ -12041,7 +12041,7 @@ dvar_defined_ref(struct parser_params *p, ID id, ID **vidrefp)
 	if (used) used = used->prev;
     }
 
-    if (vars == DVARS_INHERIT) {
+    if (vars == DVARS_INHERIT && !NUMPARAM_ID_P(id)) {
         return rb_dvar_defined(id, p->parent_iseq);
     }
 

test/ruby/test_syntax.rb

@@ -1450,7 +1450,13 @@ eom
       assert_valid_syntax("->{_1;#{c};->{_1};end}\n")
     end
 
-    1.times {_1}
+    1.times {
+      [
+        _1,
+        assert_equal([:a], eval("[:a].map{_1}")),
+        assert_raise(NameError) {eval("_1")},
+      ]
+    }
   end
 
   def test_value_expr_in_condition