Support keyword splatting nil

nil is treated similarly to the empty hash in this case, passing
no keywords and not calling any conversion methods.

Fixes [Bug #20064]

Co-authored-by: Nobuyoshi Nakada <nobu@ruby-lang.org>

1 files changed, 3 insertions, 1 deletions

diff --git a/vm.c b/vm.c
index 37d631116a..a2a17f8fe7 100644
--- a/vm.c
+++ b/vm.c
@@ -3666,7 +3666,9 @@ kwmerge_i(VALUE key, VALUE value, VALUE hash)
 static VALUE
 m_core_hash_merge_kwd(VALUE recv, VALUE hash, VALUE kw)
 {
-    REWIND_CFP(hash = core_hash_merge_kwd(hash, kw));
+    if (!NIL_P(kw)) {
+        REWIND_CFP(hash = core_hash_merge_kwd(hash, kw));
+    }
     return hash;
 }