packmap operation keeps duplicate entries

[Slava0135]

Current Behavior

packmap keeps duplicate keys (and entries)
behavior might be considered undefined, though its probably better to copy C# implementation

[
  {
    "type": "Map",
    "value": [
      {
        "key": {
          "type": "Integer",
          "value": "1"
        },
        "value": {
          "type": "Integer",
          "value": "1"
        }
      },
      {
        "key": {
          "type": "Integer",
          "value": "1"
        },
        "value": {
          "type": "Integer",
          "value": "1"
        }
      }
    ]
  }
]

Expected Behavior

C# results:

[
  {
    "type": "Map",
    "value": [
      {
        "key": {
          "type": "Integer",
          "value": "1"
        },
        "value": {
          "type": "Integer",
          "value": "1"
        }
      }
    ]
  }
]

Possible Solution

Steps to Reproduce

1. ./bin/neo-go vm
2. loadbase64 ERERERK+
3. run

Your Environment

• Version of the product used: master (a924253)

[AnnaShaleva]

Wow, a really unexpected bug! Sure, it should be aligned with C# implementation. They use an ordered dictionary for the internal Map item implementation, so the bug is legit.
https://github.com/neo-project/neo/blob/3f2f78c1fcf71ea51f2c40c3a0e67062ac390aed/src/Neo.VM/JumpTable/JumpTable.Compound.cs#L45
https://github.com/neo-project/neo/blob/3f2f78c1fcf71ea51f2c40c3a0e67062ac390aed/src/Neo.VM/Types/Map.cs#L63

[roman-khimov]

And it's a map, it can't have duplicate keys, one key --- one value.