types: unnecessary code inside removeZeroCoins adding extra runtime and less readability

[odeke-em]

Summary of Bug

Noticed while auditing cosmos/gaia that if we examine the code inside

cosmos-sdk/types/coin.go

Lines 782 to 803 in 8cce748

	func removeZeroCoins(coins Coins) Coins {
	for i := 0; i < len(coins); i++ {
	if coins[i].IsZero() {
	break
	} else if i == len(coins)-1 {
	return coins
	}
	}
	var result []Coin
	if len(coins) > 0 {
	result = make([]Coin, 0, len(coins)-1)
	}
	for _, coin := range coins {
	if !coin.IsZero() {
	result = append(result, coin)
	}
	}
	return result
	}

we can see that the first for loop of code tries to check if at least one coin is zero then exit else if at the end return. However in the next loop, it performs the iteration and checks for coins that are non-zero which thereby renders the prior loop useless.

Suggestion

Simply remove the first loop and the other unnecessary checks then only add coins that are non-zero

func removeZeroCoins(coins Coins) Coins {
	nonZeros := make([]Coin, 0, len(coins))

	for _, coin := range coins {
		if !coin.IsZero() {
			nonZeros = append(nonZeros, coin)
		}
	}

	return nonZeros
}

/cc @elias-orijtech

[tac0turtle]

want to submit a pr?

[odeke-em]

Sure @tac0turtle I've mailed PR #13967 though ideally on a code binge we open a bunch of issues firstly then we shall mail fixes :-)