refactor refund logic

Co-authored-by: lightclient <[email protected]>

core/state_transition.go

@@ -510,18 +510,8 @@ func (st *stateTransition) execute() (*ExecutionResult, error) {
 		ret, st.gasRemaining, vmerr = st.evm.Call(sender, st.to(), msg.Data, st.gasRemaining, value)
 	}
 
-	var gasRefund uint64
-	if !rules.IsLondon {
-		// Before EIP-3529: refunds were capped to gasUsed / 2
-		gasRefund = st.refundAmount(params.RefundQuotient)
-	} else {
-		// After EIP-3529: refunds are capped to gasUsed / 5
-		gasRefund = st.refundAmount(params.RefundQuotientEIP3529)
-	}
-
-	if st.evm.Config.Tracer != nil && st.evm.Config.Tracer.OnGasChange != nil && gasRefund > 0 {
-		st.evm.Config.Tracer.OnGasChange(st.gasRemaining, st.gasRemaining+gasRefund, tracing.GasChangeTxRefunds)
-	}
+	// Compute refund counter, capped to a refund quotient.
+	gasRefund := st.calcRefund()
 	st.gasRemaining += gasRefund
 	if rules.IsPrague {
 		// After EIP-7623: Data-heavy transactions pay the floor gas.
@@ -625,17 +615,28 @@ func (st *stateTransition) applyAuthorization(msg *Message, auth *types.SetCodeA
 	return nil
 }
 
-func (st *stateTransition) refundAmount(refundQuotient uint64) uint64 {
-	// Apply refund counter, capped to a refund quotient
-	refund := st.gasUsed() / refundQuotient
+// calcRefund computes refund counter, capped to a refund quotient.
+func (st *stateTransition) calcRefund() uint64 {
+	var refund uint64
+	if !st.evm.ChainConfig().IsLondon(st.evm.Context.BlockNumber) {
+		// Before EIP-3529: refunds were capped to gasUsed / 2
+		refund = st.gasUsed() / params.RefundQuotient
+	} else {
+		// After EIP-3529: refunds are capped to gasUsed / 5
+		refund = st.gasUsed() / params.RefundQuotientEIP3529
+	}
 	if refund > st.state.GetRefund() {
 		refund = st.state.GetRefund()
 	}
+	if st.evm.Config.Tracer != nil && st.evm.Config.Tracer.OnGasChange != nil && refund > 0 {
+		st.evm.Config.Tracer.OnGasChange(st.gasRemaining, st.gasRemaining+refund, tracing.GasChangeTxRefunds)
+	}
 	return refund
 }
 
+// returnGas returns ETH for remaining gas,
+// exchanged at the original rate.
 func (st *stateTransition) returnGas() {
-	// Return ETH for remaining gas, exchanged at the original rate.
 	remaining := uint256.NewInt(st.gasRemaining)
 	remaining.Mul(remaining, uint256.MustFromBig(st.msg.GasPrice))
 	st.state.AddBalance(st.msg.From, remaining, tracing.BalanceIncreaseGasReturn)