Calling into a C func shouldn't fast path when forwarding

When we forward calls to C functions if the callsite is a forwarding
site it might not always be a splat, so we can't use the fast path.

Fixes:

[ruby-core:118418]

1 files changed, 15 insertions, 0 deletions

diff --git a/bootstraptest/test_method.rb b/bootstraptest/test_method.rb
index 846d8e36a9..a5ea35dd4b 100644
--- a/bootstraptest/test_method.rb
+++ b/bootstraptest/test_method.rb
@@ -1344,3 +1344,18 @@ assert_equal 'ok', %q{
 
   C.new.foo
 }
+
+assert_equal 'ok', %q{
+  class C
+    def initialize(a)
+    end
+  end
+
+  def foo(...)
+    C.new(...)
+    :ok
+  end
+
+  foo(*["bar"])
+  foo("baz")
+}