Fix `String#partition`

Split with the matched part when the separator matches the empty
part at the beginning.  [Bug #11014]

2 files changed, 2 insertions, 1 deletions

diff --git a/string.c b/string.c
index 2413fbf8fc..ca425e9780 100644
--- a/string.c
+++ b/string.c
@@ -9795,7 +9795,6 @@ rb_str_partition(VALUE str, VALUE sep)
 	    return rb_ary_new3(3, rb_str_dup(str), str_new_empty(str), str_new_empty(str));
 	}
 	sep = rb_str_subpat(str, sep, INT2FIX(0));
-	if (pos == 0 && RSTRING_LEN(sep) == 0) goto failed;
     }
     else {
 	pos = rb_str_index(str, sep, 0);
diff --git a/test/ruby/test_string.rb b/test/ruby/test_string.rb
index 09d099bb4a..f0b765314c 100644
--- a/test/ruby/test_string.rb
+++ b/test/ruby/test_string.rb
@@ -2567,6 +2567,8 @@ CODE
     hello = "hello"
     hello.partition("hi").map(&:upcase!)
     assert_equal("hello", hello, bug)
+
+    assert_equal(["", "", "foo"], "foo".partition(/^=*/))
   end
 
   def test_rpartition