Add exception support in `Range#first`.

Closes: https://github.com/ruby/ruby/pull/2163

1 files changed, 3 insertions, 0 deletions

diff --git a/range.c b/range.c
index 4180a663aa..03ca38d611 100644
--- a/range.c
+++ b/range.c
@@ -1012,6 +1012,9 @@ range_first(int argc, VALUE *argv, VALUE range)
 {
     VALUE n, ary[2];
 
+    if (NIL_P(RANGE_BEG(range))) {
+        rb_raise(rb_eRangeError, "cannot get the first element of beginless range");
+    }
     if (argc == 0) return RANGE_BEG(range);
 
     rb_scan_args(argc, argv, "1", &n);