encoding.c (rb_enc_get_index): return -1 for non-encoding capable objects

* Clarify logic and add spec.
* Now passes test-all with the JSON fix.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@64178 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

1 files changed, 5 insertions, 0 deletions

diff --git a/spec/ruby/optional/capi/encoding_spec.rb b/spec/ruby/optional/capi/encoding_spec.rb
index 7661f2b68b..33587bf03a 100644
--- a/spec/ruby/optional/capi/encoding_spec.rb
+++ b/spec/ruby/optional/capi/encoding_spec.rb
@@ -147,6 +147,11 @@ describe "C-API Encoding function" do
     it "returns -1 as the index for immediates" do
       @s.send(@method, 1).should == -1
     end
+
+    it "returns -1 for an object without an encoding" do
+      obj = Object.new
+      @s.send(@method, obj).should == -1
+    end
   end
 
   describe "rb_enc_set_index" do