refactor(collections): add UintValueEncoder and use Uint for wei store

[expertdicer]

Abstract

• Closes [bug] The IntKeyEncoder.Encode function panics if the input math.Int is nil or negative.  #2491

collections.IntValueEncoder used to delegate to IntKeyEncoder, which panics on negative or nil sdkmath.Int values. That was misleading for signed state (e.g. wei block deltas) and unsafe for callers that expected a general signed int encoder.

This PR splits signed value encoding from unsigned fixed-width encoding: IntValueEncoder now marshals signed sdkmath.Int, a new UintValueEncoder keeps the existing 32-byte big-endian format for non-negative persisted state, and weiStore is typed as sdkmath.Uint. eth.SignedIntValueEncoder is removed in favor of the generic collections encoder.

[gemini-code-assist]

Code Review

This pull request refactors the weiStore balance tracking in the bank keeper to use sdkmath.Uint instead of sdkmath.Int, introducing a new UintValueEncoder in the x/collections module. It also removes the custom SignedIntValueEncoder from the eth package, standardizing on collections.IntValueEncoder. The review identified two issues: a potential nil pointer dereference in setWeiStoreBalance due to the order of conditions in an equality check, and a potential slice bounds out of range panic in encodeFixedWidthUnsignedBigEndian if the big integer exceeds 256 bits.

[gemini-code-assist]

In setWeiStoreBalance, there is a potential nil pointer dereference panic at line 294:

if weiStoreBalPre.Eq(newStoreBal) || newStoreBal == nil {

If newStoreBal is nil (which can happen when setNibiBalanceFromWei is called with a nil wei balance), weiStoreBalPre.Eq(newStoreBal) is evaluated first. Since newStoreBal is nil, calling Eq on it will dereference a nil pointer and panic.

To fix this, the nil check newStoreBal == nil must be placed before weiStoreBalPre.Eq(newStoreBal) to leverage short-circuit evaluation:

if newStoreBal == nil || weiStoreBalPre.Eq(newStoreBal) {

[gemini-code-assist]

If i is larger than 256 bits, len(be) will exceed maxIntKeyLen (32). This will cause maxIntKeyLen - len(be) to be negative, resulting in a cryptic runtime slice bounds out of range panic when slicing padded.

Adding an explicit overflow check with a clear panic message improves robustness and makes debugging much easier.

func encodeFixedWidthUnsignedBigEndian(i *big.Int) []byte {
	be := i.Bytes()
	if len(be) > maxIntKeyLen {
		panic(fmt.Sprintf("value overflows max bit length of %d bits", sdkmath.MaxBitLen))
	}
	padded := make([]byte, maxIntKeyLen)
	copy(padded[maxIntKeyLen-len(be):], be)
	return padded
}

[codecov]

Codecov Report

❌ Patch coverage is 75.67568% with 9 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
x/collections/value_encoder.go	67.85%	7 Missing and 2 partials ⚠️

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