refactor SafeMath rich errors and use them in staking libs

packages/utils/src/safe_math_revert_errors.ts

@@ -1,16 +1,23 @@
 import { BigNumber } from './configured_bignumber';
 import { RevertError } from './revert_error';
 
-export enum SafeMathErrorCodes {
-    Uint256AdditionOverflow,
-    Uint256MultiplicationOverflow,
-    Uint256SubtractionUnderflow,
-    Uint256DivisionByZero,
+// tslint:disable:max-classes-per-file
+
+export enum BinopErrorCodes {
+    AdditionOverflow,
+    MultiplicationOverflow,
+    SubtractionUnderflow,
+    DivisionByZero,
 }
 
-export class SafeMathError extends RevertError {
-    constructor(error?: SafeMathErrorCodes, a?: BigNumber, b?: BigNumber) {
-        super('SafeMathError', 'SafeMathError(uint8 error, uint256 a, uint256 b)', {
+export enum DowncastErrorCodes {
+    ValueTooLargeToDowncastToUint64,
+    ValueTooLargeToDowncastToUint96,
+}
+
+export class Uint256BinopError extends RevertError {
+    constructor(error?: BinopErrorCodes, a?: BigNumber, b?: BigNumber) {
+        super('Uint256BinopError', 'Uint256BinopError(uint8 error, uint256 a, uint256 b)', {
             error,
             a,
             b,
@@ -18,4 +25,38 @@ export class SafeMathError extends RevertError {
     }
 }
 
-RevertError.registerType(SafeMathError);
+export class Uint96BinopError extends RevertError {
+    constructor(error?: BinopErrorCodes, a?: BigNumber, b?: BigNumber) {
+        super('Uint96BinopError', 'Uint96BinopError(uint8 error, uint96 a, uint96 b)', {
+            error,
+            a,
+            b,
+        });
+    }
+}
+
+export class Uint64BinopError extends RevertError {
+    constructor(error?: BinopErrorCodes, a?: BigNumber, b?: BigNumber) {
+        super('Uint64BinopError', 'Uint64BinopError(uint8 error, uint64 a, uint64 b)', {
+            error,
+            a,
+            b,
+        });
+    }
+}
+
+export class Uint256DowncastError extends RevertError {
+    constructor(error?: DowncastErrorCodes, a?: BigNumber) {
+        super('Uint256DowncastError', 'Uint256DowncastError(uint8 error, uint256 a)', {
+            error,
+            a,
+        });
+    }
+}
+
+const types = [Uint256BinopError, Uint96BinopError, Uint64BinopError, Uint256DowncastError];
+
+// Register the types we've defined.
+for (const type of types) {
+    RevertError.registerType(type);
+}