Fix [Bug #20246]: Don't set next_head_exact if a capture is called (#9897)

Author: makenowjust

regcomp.c

@@ -3395,7 +3395,7 @@ next_setup(Node* node, Node* next_node, regex_t* reg)
   }
   else if (type == NT_ENCLOSE) {
     EncloseNode* en = NENCLOSE(node);
-    if (en->type == ENCLOSE_MEMORY) {
+    if (en->type == ENCLOSE_MEMORY && !IS_ENCLOSE_CALLED(en)) {
       node = en->target;
       goto retry;
     }

test/ruby/test_regexp.rb

@@ -2045,6 +2045,11 @@ def test_bug_20212 # [Bug #20212]
     100.times.each { assert(regex.match?(string)) }
   end
 
+  def test_bug_20246 # [Bug #20246]
+    assert_equal '1.2.3', '1.2.3'[/(\d+)(\.\g<1>){2}/]
+    assert_equal '1.2.3', '1.2.3'[/((?:\d|foo|bar)+)(\.\g<1>){2}/]
+  end
+
   def test_linear_time_p
     assert_send [Regexp, :linear_time?, /a/]
     assert_send [Regexp, :linear_time?, 'a']