encoding.c (enc_set_index): raise instead of rb_bug() for non-encoding capable objects

* Add spec.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@64172 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

1 files changed, 9 insertions, 0 deletions

diff --git a/spec/ruby/optional/capi/encoding_spec.rb b/spec/ruby/optional/capi/encoding_spec.rb
index dc1019e8ae..7661f2b68b 100644
--- a/spec/ruby/optional/capi/encoding_spec.rb
+++ b/spec/ruby/optional/capi/encoding_spec.rb
@@ -30,6 +30,15 @@ describe :rb_enc_set_index, shared: true do
     result = @s.send(@method, str, 1)
     result.first.should == result.last
   end
+
+  ruby_version_is "2.6" do
+    it "raises an ArgumentError for a non-encoding capable object" do
+      obj = Object.new
+      -> {
+        result = @s.send(@method, obj, 1)
+      }.should raise_error(ArgumentError, "cannot set encoding on non-encoding capable object")
+    end
+  end
 end
 
 describe "C-API Encoding function" do