From e5b779f6ea78b93ef2f8e5f599728e8346e467b3 Mon Sep 17 00:00:00 2001
From: Moody Salem <moody.salem@gmail.com>
Date: Sat, 9 May 2020 14:19:28 -0400
Subject: [PATCH] Fix reliability of error checking

---
 src/entities/trade.ts | 6 +++---
 src/errors.ts         | 4 ++++
 2 files changed, 7 insertions(+), 3 deletions(-)

diff --git a/src/entities/trade.ts b/src/entities/trade.ts
index 0ed8f224c..3355261bf 100644
--- a/src/entities/trade.ts
+++ b/src/entities/trade.ts
@@ -8,7 +8,6 @@ import { Price } from './fractions/price'
 import { Percent } from './fractions/percent'
 import { Token } from 'entities/token'
 import { sortedInsert } from '../utils'
-import { InsufficientReservesError, InsufficientInputAmountError } from '../errors'
 
 function getSlippage(midPrice: Price, inputAmount: TokenAmount, outputAmount: TokenAmount): Percent {
   const exactQuote = midPrice.raw.multiply(inputAmount.raw)
@@ -143,7 +142,8 @@ export class Trade {
       try {
         ;[amountOut] = pair.getOutputAmount(amountIn)
       } catch (error) {
-        if (error instanceof InsufficientInputAmountError) {
+        // input too low
+        if (error.isInsufficientInputAmountError) {
           continue
         }
         throw error
@@ -211,7 +211,7 @@ export class Trade {
         ;[amountIn] = pair.getInputAmount(amountOut)
       } catch (error) {
         // not enough liquidity in this pair
-        if (error instanceof InsufficientReservesError) {
+        if (error.isInsufficientReservesError) {
           continue
         }
         throw error
diff --git a/src/errors.ts b/src/errors.ts
index 72e54a552..9edab47f9 100644
--- a/src/errors.ts
+++ b/src/errors.ts
@@ -2,6 +2,8 @@
 const CAN_SET_PROTOTYPE = 'setPrototypeOf' in Object
 
 export class InsufficientReservesError extends Error {
+  public readonly isInsufficientReservesError: true = true
+
   public constructor() {
     super()
     this.name = this.constructor.name
@@ -10,6 +12,8 @@ export class InsufficientReservesError extends Error {
 }
 
 export class InsufficientInputAmountError extends Error {
+  public readonly isInsufficientInputAmountError: true = true
+
   public constructor() {
     super()
     this.name = this.constructor.name