doc: Pick better named args for MutableTransactionSignatureCreator

Argument names of "nInIn" are not helpful.

Author: MarcoFalke

src/psbt.cpp

@@ -223,7 +223,7 @@ void UpdatePSBTOutput(const SigningProvider& provider, PartiallySignedTransactio
     // Construct a would-be spend of this output, to update sigdata with.
     // Note that ProduceSignature is used to fill in metadata (not actual signatures),
     // so provider does not need to provide any private keys (it can be a HidingSigningProvider).
-    MutableTransactionSignatureCreator creator(&tx, /* index */ 0, out.nValue, SIGHASH_ALL);
+    MutableTransactionSignatureCreator creator(&tx, /*input_idx=*/0, out.nValue, SIGHASH_ALL);
     ProduceSignature(provider, creator, out.scriptPubKey, sigdata);
 
     // Put redeem_script, witness_script, key paths, into PSBTOutput.

src/script/sign.cpp

@@ -17,16 +17,16 @@
 
 typedef std::vector<unsigned char> valtype;
 
-MutableTransactionSignatureCreator::MutableTransactionSignatureCreator(const CMutableTransaction* txToIn, unsigned int nInIn, const CAmount& amountIn, int nHashTypeIn)
-    : txTo(txToIn), nIn(nInIn), nHashType(nHashTypeIn), amount(amountIn), checker(txTo, nIn, amountIn, MissingDataBehavior::FAIL),
+MutableTransactionSignatureCreator::MutableTransactionSignatureCreator(const CMutableTransaction* tx, unsigned int input_idx, const CAmount& amount, int hash_type)
+    : txTo{tx}, nIn{input_idx}, nHashType{hash_type}, amount{amount}, checker{txTo, nIn, amount, MissingDataBehavior::FAIL},
       m_txdata(nullptr)
 {
 }
 
-MutableTransactionSignatureCreator::MutableTransactionSignatureCreator(const CMutableTransaction* txToIn, unsigned int nInIn, const CAmount& amountIn, const PrecomputedTransactionData* txdata, int nHashTypeIn)
-    : txTo(txToIn), nIn(nInIn), nHashType(nHashTypeIn), amount(amountIn),
-      checker(txdata ? MutableTransactionSignatureChecker(txTo, nIn, amount, *txdata, MissingDataBehavior::FAIL) :
-          MutableTransactionSignatureChecker(txTo, nIn, amount, MissingDataBehavior::FAIL)),
+MutableTransactionSignatureCreator::MutableTransactionSignatureCreator(const CMutableTransaction* tx, unsigned int input_idx, const CAmount& amount, const PrecomputedTransactionData* txdata, int hash_type)
+    : txTo{tx}, nIn{input_idx}, nHashType{hash_type}, amount{amount},
+      checker{txdata ? MutableTransactionSignatureChecker{txTo, nIn, amount, *txdata, MissingDataBehavior::FAIL} :
+                       MutableTransactionSignatureChecker{txTo, nIn, amount, MissingDataBehavior::FAIL}},
       m_txdata(txdata)
 {
 }

src/script/sign.h

@@ -45,8 +45,8 @@ class MutableTransactionSignatureCreator : public BaseSignatureCreator {
     const PrecomputedTransactionData* m_txdata;
 
 public:
-    MutableTransactionSignatureCreator(const CMutableTransaction* txToIn, unsigned int nInIn, const CAmount& amountIn, int nHashTypeIn);
-    MutableTransactionSignatureCreator(const CMutableTransaction* txToIn, unsigned int nInIn, const CAmount& amountIn, const PrecomputedTransactionData* txdata, int nHashTypeIn);
+    MutableTransactionSignatureCreator(const CMutableTransaction* tx, unsigned int input_idx, const CAmount& amount, int hash_type);
+    MutableTransactionSignatureCreator(const CMutableTransaction* tx, unsigned int input_idx, const CAmount& amount, const PrecomputedTransactionData* txdata, int hash_type);
     const BaseSignatureChecker& Checker() const override { return checker; }
     bool CreateSig(const SigningProvider& provider, std::vector<unsigned char>& vchSig, const CKeyID& keyid, const CScript& scriptCode, SigVersion sigversion) const override;
     bool CreateSchnorrSig(const SigningProvider& provider, std::vector<unsigned char>& sig, const XOnlyPubKey& pubkey, const uint256* leaf_hash, const uint256* merkle_root, SigVersion sigversion) const override;