Reject ERC20uRWA forced transfer to self

[PramodTKodag]

Fixes #244

Problem

ERC20uRWA.forcedTransfer(from, to, amount) does not reject from == to. In that case _update(from, to, amount) moves no tokens, but the frozen-balance adjustment runs first:

uint256 currentFrozen = frozen(from);
uint256 newBalance;
unchecked { newBalance = balanceOf(from) - amount; }
if (currentFrozen > newBalance) {
    _setFrozen(from, newBalance);
}

So a self-directed forced transfer leaves the balance unchanged while lowering the frozen amount — an implicit, unauthorized unfreeze. This is most relevant when the enforcer and freezer permissions are held by different entities: an enforcer could reduce frozen balances without holding the freezer role, breaking the intended separation of duties (also noted for the ERC-7943 reference implementation in ethereum/ERCs#1778).

Example: balanceOf(alice) = 100, frozen(alice) = 100. Calling forcedTransfer(alice, alice, 100) results in frozen(alice) = 0 with the balance untouched.

Fix

Reject the degenerate self-transfer by reverting with the existing ERC7943CannotTransfer(from, to, amount) error before any state changes:

require(from != to, ERC7943CannotTransfer(from, to, amount));

Scope

This PR addresses point 1 of #244 (the self-forced-transfer edge case), which is a contained correctness/security fix. Points 2–4 in that issue (the setFrozenTokens balance cap, the canSend/canReceive vs canTransact interface split, and canTransfer semantics) are interface/semantic decisions and are intentionally left out of this PR for the maintainers to decide separately.

PR Checklist

• Tests — added a regression test asserting forcedTransfer(holder, holder, ...) reverts and leaves the frozen balance untouched; full ERC20uRWA suite passes (40 passing).
• Documentation — added a CHANGELOG.md entry and an explanatory code comment.

Summary by CodeRabbit

• Bug Fixes

  • Forced transfers now correctly reject attempts to send tokens to the same address, preventing frozen balances from being reduced without any token movement.
  • Self-directed forced transfers now fail with a clear error and leave balances unchanged.

• Tests

  • Added coverage to verify same-address forced transfers revert as expected and preserve frozen token balances.

• Documentation

  • Updated the changelog with the latest behavior change.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro

Run ID: ae3c6842-4247-45df-9a9c-43d8136e19da

📥 Commits

Reviewing files that changed from the base of the PR and between f7e5f08 and 12aa589.

📒 Files selected for processing (3)

• CHANGELOG.md
• contracts/token/ERC20/extensions/ERC20uRWA.sol
• test/token/ERC20/extensions/ERC20uRWA.test.js

---

Walkthrough

ERC20uRWA now rejects forcedTransfer when the sender and recipient are the same address. A regression test covers the revert and frozen-balance state, and the changelog records the change.

Changes

ERC20uRWA self-forced-transfer guard

Layer / File(s)	Summary
Self-transfer check in forcedTransfer contracts/token/ERC20/extensions/ERC20uRWA.sol	forcedTransfer now rejects calls where from equals to before adjusting frozen balances or moving tokens.
Regression test and release note test/token/ERC20/extensions/ERC20uRWA.test.js, CHANGELOG.md	A new test asserts the self-transfer revert and unchanged frozen balance, and the changelog records the new guard.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~10 minutes

Poem

A rabbit hopped and twitched its nose,
“No self-transfer!” the carrot prose.
🐰 Frozen bits stay snug and neat,
When sender meets receiver’s seat.
Hop-hop, the guard is яс?—no, just complete!

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly and concisely describes the main change: rejecting self forced transfers in ERC20uRWA.
Linked Issues check	✅ Passed	The PR implements the reported self-forced-transfer fix from #244 and uses the existing ERC7943CannotTransfer error as requested.
Out of Scope Changes check	✅ Passed	The changelog, code comment, and regression test are all directly related to the self-transfer fix and stay within scope.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.

_{✏️ Tip: You can configure your own custom pre-merge checks in the settings.}

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

---

Thanks for using CodeRabbit! It's free for OSS, and your support helps us grow. If you like it, consider giving us a shout-out.

❤️ Share

• X
• Mastodon
• Reddit
• LinkedIn

_{Comment @coderabbitai help to get the list of available commands.}