Do not copy compare_by_identity flag for non-empty hashes in Hash.[]

It wasn't copied for empty hashes, and Hash.[] doesn't copy the
default value, so copying the compare_by_identity flag does not
make sense.

Partially Fixes [Bug #19113]

1 files changed, 16 insertions, 4 deletions

diff --git a/hash.c b/hash.c
index c9f741f2ec..40866509d1 100644
--- a/hash.c
+++ b/hash.c
@@ -1801,6 +1801,8 @@ rb_hash_initialize(int argc, VALUE *argv, VALUE hash)
     return hash;
 }
 
+static VALUE rb_hash_to_a(VALUE hash);
+
 /*
  *  call-seq:
  *    Hash[] -> new_empty_hash
@@ -1844,12 +1846,22 @@ rb_hash_s_create(int argc, VALUE *argv, VALUE klass)
     if (argc == 1) {
         tmp = rb_hash_s_try_convert(Qnil, argv[0]);
         if (!NIL_P(tmp)) {
-            hash = hash_alloc(klass);
-            hash_copy(hash, tmp);
-            return hash;
+            if (!RHASH_EMPTY_P(tmp)  && rb_hash_compare_by_id_p(tmp)) {
+                /* hash_copy for non-empty hash will copy compare_by_identity
+                   flag, but we don't want it copied. Work around by
+                   converting hash to flattened array and using that. */
+                tmp = rb_hash_to_a(tmp);
+            }
+            else {
+                hash = hash_alloc(klass);
+                hash_copy(hash, tmp);
+                return hash;
+            }
+        }
+        else {
+            tmp = rb_check_array_type(argv[0]);
         }
 
-        tmp = rb_check_array_type(argv[0]);
         if (!NIL_P(tmp)) {
             long i;