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NexusERC20 is an upgradeable ERC20 token designed for Tokenized RWAs OFT. Unlike ERC20Plus which embeds allowlist and pause logic directly, NexusERC20 delegates these checks to a shared NexusERC20Guard contract — one guard serving multiple tokens.

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Comparison with ERC20Plus

FeatureERC20PlusNexusERC20
Allowlist (3-mode)InlineDelegated to NexusERC20Guard
PauseGlobal (inline)Per-token via guard (PauseByID, keyed by uint160(token))
Fund recoveryYesYes
ERC20Permit (EIP-2612)YesYes
RBAC mint/burnYesYes
Guard contractN/AShared across tokens
UpgradeableYes (EIP-7201)Yes (EIP-7201)

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NexusERC20

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Roles

bytes32 public constant MINTER_ROLE = keccak256("MINTER_ROLE");
bytes32 public constant BURNER_ROLE = keccak256("BURNER_ROLE");
When used with Tokenized RWAs OFT, the burner-minter address (which can be the NexusERC20 itself or a separate contract) must be granted both roles. Nexus calls mint/burn via configurable function selectors.

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Guard Checks

Every transfer, transferFrom, and burn call goes through the guard: 
guard.checkTransfer(address(this), msg.sender, _from, _to, _amount);
The guard enforces:
  1. Pause — _assertNotPaused(uint160(_token)), keyed by the token’s address
  2. Allowlist — _assertAllowlisted() for caller, sender, and recipient (non-zero addresses)
mint does not enforce checks — funds cannot be debited from a non-allowlisted address or when the contract is paused, so restricting inflows is unnecessary.

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Fund Recovery

Same as ERC20Plus — addresses holding DEFAULT_ADMIN_ROLE can transfer tokens from non-allowlisted addresses: 
function recoverFunds(address _from, address _to, uint256 _amount) public;
Reverts with CannotRecoverFromAllowlisted if _from is allowlisted.

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ERC20Permit (EIP-2612)

Built-in gasless approvals, identical to ERC20Plus.

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NexusERC20Guard

A single upgradeable guard shared by all NexusERC20 tokens on the same chain.

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What It Does

The guard combines two concerns:
  • AllowlistRBACUpgradeable — Three-mode allowlist (Open / Blacklist / Whitelist) with the same behavior as Stablecoin OFT’s allowlist
  • PauseByIDRBACUpgradeable — Per-token pause using uint160(tokenAddress) as the pause ID

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Initialization

function initialize(address _initialAdmin) public initializer;
Initializes with AllowlistMode.Open (no transfer restrictions).

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Roles

RoleSourceUsed For
DEFAULT_ADMIN_ROLEAccessControl2StepUpgradeableAdmin transfer, set allowlist mode
BLACKLISTER_ROLEAllowlistRBACUpgradeableBlacklist addresses
WHITELISTER_ROLEAllowlistRBACUpgradeableWhitelist addresses
PAUSER_ROLEPauseByIDRBACUpgradeablesetDefaultPaused (when pausing), setPaused (when effectively pausing by token address as ID)
UNPAUSER_ROLEPauseByIDRBACUpgradeablesetDefaultPaused (when unpausing), setPaused (when effectively unpausing or no-op)

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Allowlist Modes

ModeBehavior
OpenNo restrictions
BlacklistBlock specific addresses
WhitelistAllow only specific addresses
Mode transitions do not clear existing lists. Both lists support paginated enumeration via getBlacklist(offset, limit) and getWhitelist(offset, limit).

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Next Steps