feat: expose latest answer on static a token

Makefile

@@ -35,4 +35,5 @@ coverage :; forge coverage --report lcov && \
 download :; cast etherscan-source --chain ${chain} -d src/etherscan/${chain}_${address} ${address}
 git-diff :
 	@mkdir -p diffs
+	@npx prettier ${before} ${after} --write
 	@printf '%s\n%s\n%s\n' "\`\`\`diff" "$$(git diff --no-index --diff-algorithm=patience --ignore-space-at-eol ${before} ${after})" "\`\`\`" > diffs/${out}.md

src/periphery/contracts/static-a-token/README.md

@@ -36,3 +36,19 @@ For this project, the security procedures applied/being finished are:
 
 - The test suite of the codebase itself.
 - Certora audit/property checking for all the dynamics of the `stataToken`, including respecting all the specs of [EIP-4626](https://eips.ethereum.org/EIPS/eip-4626).
+
+## Upgrade Notes Umbrella
+
+- Interface inheritance has been changed so that `IStaticATokenLM` implements `IERC4626`, making it easier for integrators to work with the interface.
+- The static A tokens are given a `rescuable`, which can be used by the ACL admin to rescue tokens locked to the contract.
+- Permit params have been excluded from the METADEPOSIT_TYPEHASH as they are not necessary. Even if someone were to frontrun the permit via mempool observation the permit is wrapped in a `try..catch` to prevent griefing attacks.
+- The static a token not implements pausability, which allows the ACL admin to pause all transfers.
+
+The storage layout diff was generated via:
+```
+git checkout main
+forge inspect src/periphery/contracts/static-a-token/StaticATokenLM.sol:StaticATokenLM storage-layout --pretty > reports/StaticATokenStorageBefore.md
+git checkout project-a
+forge inspect src/periphery/contracts/static-a-token/StaticATokenLM.sol:StaticATokenLM storage-layout --pretty > reports/StaticATokenStorageAfter.md
+make git-diff before=reports/StaticATokenStorageBefore.md after=reports/StaticATokenStorageAfter.md out=StaticATokenStorageDiff
+```

src/periphery/contracts/static-a-token/StaticATokenLM.sol

@@ -2,6 +2,8 @@
 pragma solidity ^0.8.10;
 
 import {IPool} from '../../../core/contracts/interfaces/IPool.sol';
+import {IPoolAddressesProvider} from '../../../core/contracts/interfaces/IPoolAddressesProvider.sol';
+import {IAaveOracle} from '../../../core/contracts/interfaces/IAaveOracle.sol';
 import {DataTypes, ReserveConfiguration} from '../../../core/contracts/protocol/libraries/configuration/ReserveConfiguration.sol';
 import {WadRayMath} from '../../../core/contracts/protocol/libraries/math/WadRayMath.sol';
 import {MathUtils} from '../../../core/contracts/protocol/libraries/math/MathUtils.sol';
@@ -55,6 +57,7 @@ contract StaticATokenLM is
   uint256 public constant STATIC__ATOKEN_LM_REVISION = 3;
 
   IPool public immutable POOL;
+  IPoolAddressesProvider immutable POOL_ADDRESSES_PROVIDER;
   IRewardsController public immutable INCENTIVES_CONTROLLER;
 
   IERC20 internal _aToken;
@@ -67,6 +70,7 @@ contract StaticATokenLM is
     _disableInitializers();
     POOL = pool;
     INCENTIVES_CONTROLLER = rewardsController;
+    POOL_ADDRESSES_PROVIDER = pool.ADDRESSES_PROVIDER();
   }
 
   modifier onlyPauseGuardian() {
@@ -75,7 +79,7 @@ contract StaticATokenLM is
   }
 
   function canPause(address actor) public view returns (bool) {
-    return IACLManager(POOL.ADDRESSES_PROVIDER().getACLManager()).isEmergencyAdmin(actor);
+    return IACLManager(POOL_ADDRESSES_PROVIDER.getACLManager()).isEmergencyAdmin(actor);
   }
 
   ///@inheritdoc IInitializableStaticATokenLM
@@ -103,7 +107,7 @@ contract StaticATokenLM is
 
   /// @inheritdoc IRescuable
   function whoCanRescue() public view override returns (address) {
-    return POOL.ADDRESSES_PROVIDER().getACLAdmin();
+    return POOL_ADDRESSES_PROVIDER.getACLAdmin();
   }
 
   ///@inheritdoc IStaticATokenLM
@@ -468,6 +472,15 @@ contract StaticATokenLM is
     return _withdraw(owner, receiver, shares, 0, withdrawFromAave);
   }
 
+  ///@inheritdoc IStaticATokenLM
+  function latestAnswer() external view returns (int256) {
+    return
+      int256(
+        (IAaveOracle(POOL_ADDRESSES_PROVIDER.getPriceOracle()).getAssetPrice(_aTokenUnderlying) *
+          POOL.getReserveNormalizedIncome(_aTokenUnderlying)) / 1e27
+      );
+  }
+
   function _deposit(
     address depositor,
     address receiver,

src/periphery/contracts/static-a-token/interfaces/IStaticATokenLM.sol

@@ -219,4 +219,11 @@ interface IStaticATokenLM is IInitializableStaticATokenLM, IERC4626 {
    * @param paused boolean determining if the token should be paused or unpaused
    */
   function setPaused(bool paused) external;
+
+  /**
+   * @notice Returns the current asset price of the stataToken.
+   * The price is calculated as `underlying_price * exchangeRate`, but it's important to note that `underlying_price` is the price obtained by the aave-oracle, which means it's subject to caps and similar imposed by the aave DAO on the oracle.
+   * @return int256 the current asset price in 8 decimals.
+   */
+  function latestAnswer() external view returns (int256);
 }

tests/periphery/static-a-token/StaticATokenLM.t.sol

@@ -10,6 +10,7 @@ import {RayMathExplicitRounding} from '../../../src/periphery/contracts/librarie
 import {IStaticATokenLM} from '../../../src/periphery/contracts/static-a-token/interfaces/IStaticATokenLM.sol';
 import {SigUtils} from '../../utils/SigUtils.sol';
 import {BaseTest, TestnetERC20} from './TestBase.sol';
+import {IPool} from '../../../src/core/contracts/interfaces/IPool.sol';
 
 contract StaticATokenLMTest is BaseTest {
   using RayMathExplicitRounding for uint256;
@@ -48,6 +49,29 @@ contract StaticATokenLMTest is BaseTest {
     );
   }
 
+  function test_latestAnswer_priceShouldBeEqualOnDefaultIndex() public {
+    vm.mockCall(
+      address(POOL),
+      abi.encodeWithSelector(IPool.getReserveNormalizedIncome.selector),
+      abi.encode(1e27)
+    );
+    uint256 stataPrice = uint256(staticATokenLM.latestAnswer());
+    uint256 underlyingPrice = contracts.aaveOracle.getAssetPrice(UNDERLYING);
+    assertEq(stataPrice, underlyingPrice);
+  }
+
+  function test_latestAnswer_priceShouldReflectIndexAccrual(uint256 liquidityIndex) public {
+    liquidityIndex = bound(liquidityIndex, 1e27, 1e29);
+    vm.mockCall(
+      address(POOL),
+      abi.encodeWithSelector(IPool.getReserveNormalizedIncome.selector),
+      abi.encode(liquidityIndex)
+    );
+    uint256 stataPrice = uint256(staticATokenLM.latestAnswer());
+    uint256 underlyingPrice = contracts.aaveOracle.getAssetPrice(UNDERLYING);
+    assertEq(stataPrice, (underlyingPrice * liquidityIndex) / 1e27);
+  }
+
   function test_convertersAndPreviews() public view {
     uint128 amount = 5 ether;
     uint256 shares = staticATokenLM.convertToShares(amount);