check that all used EVC addresses are the same

Author: haythemsellami

TODO

@@ -9,8 +9,6 @@
 * ConstantSum: incorporate price multipliers in quote methods
 * natspec
 * permit2 instead of regular approval: measure gas savings
-* in constructor, check the two vaults have the correct EVC() return value
-  * maybe even that they were created by the EVK factory?
 ? a really small swap could fail because deposit() results in 0 shares, which EVK fails on. call convertToShares() first? Seems like overkill
 ? pause guardian
 ? how should aggregators find instances

src/MaglevBase.sol

@@ -27,6 +27,7 @@ abstract contract MaglevBase is IMaglevBase, EVCUtil {
     error BadFee();
     error InsufficientReserves();
     error InsufficientCash();
+    error DifferentEVC();
 
     modifier nonReentrant() {
         require(locked == 0, Locked());
@@ -48,6 +49,10 @@ abstract contract MaglevBase is IMaglevBase, EVCUtil {
     constructor(BaseParams memory params) EVCUtil(params.evc) {
         require(params.fee < 1e18, BadFee());
 
+        address vault0Evc = IEVault(params.vault0).EVC();
+        require(vault0Evc == IEVault(params.vault1).EVC(), DifferentEVC());
+        require(vault0Evc == params.evc, DifferentEVC());
+
         vault0 = params.vault0;
         vault1 = params.vault1;
         asset0 = IEVault(vault0).asset();