Fix Struct#hash for keyword_init: true Struct

* The return value of `vm_hash_update` was not used.

Author: eregon

CHANGELOG.md

@@ -55,6 +55,7 @@ Bug fixes:
 * Made `Kernel#caller_locations` accept a range argument, and return `nil` when appropriate.
 * Made `rb_respond_to` work with primitives (#1869, @chrisseaton).
 * Fixed issue with missing backtrace for `rescue $ERROR_INFO` (#1660).
+* Fixed `Struct#hash` for `keyword_init: true` `Struct`.
 
 Compatibility:
 

src/main/ruby/truffleruby/core/struct.rb

@@ -309,7 +309,9 @@ def hash
     val = TrufflePrimitive.vm_hash_start(CLASS_SALT)
     val = TrufflePrimitive.vm_hash_update(val, size)
     return val if Thread.detect_outermost_recursion self do
-      _attrs.each { |var| TrufflePrimitive.vm_hash_update(val, TrufflePrimitive.object_hidden_var_get(self, var).hash) }
+      _attrs.each do |var|
+        val = TrufflePrimitive.vm_hash_update(val, TrufflePrimitive.object_hidden_var_get(self, var).hash)
+      end
     end
     TrufflePrimitive.vm_hash_end(val)
   end