Disallow implicit conversion for CFeeRate constructor

Author: instagibbs

src/policy/feerate.h

@@ -25,7 +25,7 @@ class CFeeRate
     /** Fee rate of 0 satoshis per kB */
     CFeeRate() : nSatoshisPerK(0) { }
     template<typename I>
-    CFeeRate(const I _nSatoshisPerK): nSatoshisPerK(_nSatoshisPerK) {
+    explicit CFeeRate(const I _nSatoshisPerK): nSatoshisPerK(_nSatoshisPerK) {
         // We've previously had bugs creep in from silent double->int conversion...
         static_assert(std::is_integral<I>::value, "CFeeRate should be used without floats");
     }

src/wallet/rpcwallet.cpp

@@ -2625,7 +2625,7 @@ static UniValue settxfee(const JSONRPCRequest& request)
 
     CAmount nAmount = AmountFromValue(request.params[0]);
     CFeeRate tx_fee_rate(nAmount, 1000);
-    if (tx_fee_rate == 0) {
+    if (tx_fee_rate == CFeeRate(0)) {
         // automatic selection
     } else if (tx_fee_rate < ::minRelayTxFee) {
         throw JSONRPCError(RPC_INVALID_PARAMETER, strprintf("txfee cannot be less than min relay tx fee (%s)", ::minRelayTxFee.ToString()));