accmumulate throttles during dissolve()/mint() (#1197)

contracts/p0/RToken.sol

@@ -267,6 +267,8 @@ contract RTokenP0 is ComponentP0, ERC20PermitUpgradeable, IRToken {
     /// @custom:protected
     function mint(uint192 baskets) external exchangeRateIsValidAfter {
         require(_msgSender() == address(main.backingManager()), "not backing manager");
+        issuanceThrottle.useAvailable(totalSupply(), 0);
+        redemptionThrottle.useAvailable(totalSupply(), 0);
         _scaleUp(address(main.backingManager()), baskets);
     }
 
@@ -285,6 +287,8 @@ contract RTokenP0 is ComponentP0, ERC20PermitUpgradeable, IRToken {
     /// @custom:protected
     function dissolve(uint256 amount) external exchangeRateIsValidAfter {
         require(_msgSender() == address(main.backingManager()), "not backing manager");
+        issuanceThrottle.useAvailable(totalSupply(), 0);
+        redemptionThrottle.useAvailable(totalSupply(), 0);
         _scaleDown(_msgSender(), amount);
     }
 

contracts/p1/RToken.sol

@@ -355,7 +355,12 @@ contract RTokenP1 is ComponentP1, ERC20PermitUpgradeable, IRToken {
     // BU exchange rate cannot decrease, and it can only increase when < FIX_ONE.
     function mint(uint192 baskets) external {
         require(_msgSender() == address(backingManager), "not backing manager");
-        _scaleUp(address(backingManager), baskets, totalSupply());
+        uint256 supply = totalSupply();
+
+        // Accumulate the throttle before the supply change
+        issuanceThrottle.useAvailable(supply, 0);
+        redemptionThrottle.useAvailable(supply, 0);
+        _scaleUp(address(backingManager), baskets, supply);
     }
 
     /// Melt a quantity of RToken from the caller's account, increasing the basket rate
@@ -372,6 +377,7 @@ contract RTokenP1 is ComponentP1, ERC20PermitUpgradeable, IRToken {
         require(caller == address(furnace), "furnace only");
         _burn(caller, amtRToken);
         emit Melted(amtRToken);
+        // do not update throttles: melting is frequent and always small
     }
 
     /// Burn an amount of RToken from caller's account and scale basketsNeeded down
@@ -387,6 +393,11 @@ contract RTokenP1 is ComponentP1, ERC20PermitUpgradeable, IRToken {
     function dissolve(uint256 amount) external {
         address caller = _msgSender();
         require(caller == address(backingManager), "not backing manager");
+        uint256 supply = totalSupply();
+
+        // Accumulate the throttle before the supply change
+        issuanceThrottle.useAvailable(supply, 0);
+        redemptionThrottle.useAvailable(supply, 0);
         _scaleDown(caller, amount);
     }