`Hash#delete` should return the deleted value; fix #4133

src/hash.c

@@ -460,7 +460,7 @@ sg_del(mrb_state *mrb, seglist *t, mrb_value key, mrb_value *vp)
       }
       key2 = seg->e[i].key;
       if (!mrb_undef_p(key2) && sg_hash_equal(mrb, t, key, key2)) {
-        if (vp) *vp = key2;
+        if (vp) *vp = seg->e[i].val;
         seg->e[i].key = mrb_undef_value();
         t->size--;
         return TRUE;

test/t/hash.rb

@@ -82,12 +82,12 @@ assert('Hash#default_proc', '15.2.13.4.7') do
 end
 
 assert('Hash#delete', '15.2.13.4.8') do
-  a = { 'abc' => 'abc' }
-  b = { 'abc' => 'abc' }
+  a = { 'abc' => 'ABC' }
+  b = { 'abc' => 'ABC' }
   b_tmp_1 = false
   b_tmp_2 = false
 
-  a.delete('abc')
+  assert_equal 'ABC', a.delete('abc')
   b.delete('abc') do |k|
     b_tmp_1 = true
   end