[Truffle] Kernel#to_s and Kernel#inspect are different.

We should use Rubinius's definition instead of our own, but there are some parts there we don't support yet and I decided to defer working on them.

Author: nirvdrum

truffle/src/main/java/org/jruby/truffle/nodes/core/KernelNodes.java

@@ -2231,7 +2231,7 @@ public String toHexString(RubyBignum value) {
 
     }
 
-    @CoreMethod(names = {"to_s", "inspect"})
+    @CoreMethod(names = "to_s")
     public abstract static class ToSNode extends CoreMethodNode {
 
         @Child private ClassNode classNode;

truffle/src/main/ruby/jruby/truffle/core/shims.rb

@@ -184,4 +184,21 @@ def rindex(obj)
 
     index
   end
+end
+
+module Kernel
+  def inspect
+    ivars = instance_variables
+
+    return to_s if ivars.empty?
+
+    prefix = "#<#{self.class}:0x#{self.object_id.to_s(16)}"
+
+    parts = []
+    ivars.each do |var|
+      parts << "#{var}=#{instance_variable_get(var).inspect}"
+    end
+
+    "#{prefix} #{parts.join(', ')}>"
+  end
 end