adding checks to ensure denoms are sorted

x/bank/types/balance.go

@@ -34,6 +34,11 @@ func (b Balance) Validate() error {
 	if err != nil {
 		return err
 	}
+
+	var prevDenom string
+	if !b.Coins.Empty() {
+		prevDenom = b.Coins[0].Denom
+	}
 	seenDenoms := make(map[string]bool)
 
 	// NOTE: we perform a custom validation since the coins.Validate function
@@ -47,16 +52,18 @@ func (b Balance) Validate() error {
 			return err
 		}
 
+		if coin.Denom < prevDenom {
+			return fmt.Errorf("denomination %s is not sorted", coin.Denom)
+		}
+
 		if coin.IsNegative() {
 			return fmt.Errorf("coin %s amount is cannot be negative", coin.Denom)
 		}
 
 		seenDenoms[coin.Denom] = true
+		prevDenom = coin.Denom
 	}
 
-	// sort the coins post validation
-	b.Coins = b.Coins.Sort()
-
 	return nil
 }
 

x/bank/types/balance_test.go

@@ -64,6 +64,18 @@ func TestBalanceValidate(t *testing.T) {
 			},
 			true,
 		},
+		{
+			"unsorted coins",
+			bank.Balance{
+				Address: "cosmos1yq8lgssgxlx9smjhes6ryjasmqmd3ts2559g0t",
+				Coins: sdk.Coins{
+					sdk.NewInt64Coin("atom", 2),
+					sdk.NewInt64Coin("zatom", 2),
+					sdk.NewInt64Coin("batom", 12),
+				},
+			},
+			true,
+		},
 	}
 
 	for _, tc := range testCases {