rpc: Run type check against RPCArgs

9 files changed, 72 insertions, 107 deletions

diff --git a/src/rpc/blockchain.cpp b/src/rpc/blockchain.cpp
index 784fb64d36..9db493ea73 100644
--- a/src/rpc/blockchain.cpp
+++ b/src/rpc/blockchain.cpp
@@ -444,11 +444,6 @@ static RPCHelpMan getblockfrompeer()
         },
         [&](const RPCHelpMan& self, const JSONRPCRequest& request) -> UniValue
 {
-    RPCTypeCheck(request.params, {
-        UniValue::VSTR, // blockhash
-        UniValue::VNUM, // peer_id
-    });
-
     const NodeContext& node = EnsureAnyNodeContext(request.context);
     ChainstateManager& chainman = EnsureChainman(node);
     PeerManager& peerman = EnsurePeerman(node);
@@ -654,7 +649,8 @@ static RPCHelpMan getblock()
                 "If verbosity is 3, returns an Object with information about block <hash> and information about each transaction, including prevout information for inputs (only for unpruned blocks in the current best chain).\n",
                 {
                     {"blockhash", RPCArg::Type::STR_HEX, RPCArg::Optional::NO, "The block hash"},
-                    {"verbosity|verbose", RPCArg::Type::NUM, RPCArg::Default{1}, "0 for hex-encoded data, 1 for a JSON object, 2 for JSON object with transaction data, and 3 for JSON object with transaction data including prevout information for inputs"},
+                    {"verbosity|verbose", RPCArg::Type::NUM, RPCArg::Default{1}, "0 for hex-encoded data, 1 for a JSON object, 2 for JSON object with transaction data, and 3 for JSON object with transaction data including prevout information for inputs",
+                     RPCArgOptions{.skip_type_check = true}},
                 },
                 {
                     RPCResult{"for verbosity = 0",
@@ -872,7 +868,11 @@ static RPCHelpMan gettxoutsetinfo()
                 "Note this call may take some time if you are not using coinstatsindex.\n",
                 {
                     {"hash_type", RPCArg::Type::STR, RPCArg::Default{"hash_serialized_2"}, "Which UTXO set hash should be calculated. Options: 'hash_serialized_2' (the legacy algorithm), 'muhash', 'none'."},
-                    {"hash_or_height", RPCArg::Type::NUM, RPCArg::DefaultHint{"the current best block"}, "The block hash or height of the target height (only available with coinstatsindex).", RPCArgOptions{.type_str={"", "string or numeric"}}},
+                    {"hash_or_height", RPCArg::Type::NUM, RPCArg::DefaultHint{"the current best block"}, "The block hash or height of the target height (only available with coinstatsindex).",
+                     RPCArgOptions{
+                         .skip_type_check = true,
+                         .type_str = {"", "string or numeric"},
+                     }},
                     {"use_index", RPCArg::Type::BOOL, RPCArg::Default{true}, "Use coinstatsindex, if available."},
                 },
                 RPCResult{
@@ -1742,7 +1742,11 @@ static RPCHelpMan getblockstats()
                 "\nCompute per block statistics for a given window. All amounts are in satoshis.\n"
                 "It won't work for some heights with pruning.\n",
                 {
-                    {"hash_or_height", RPCArg::Type::NUM, RPCArg::Optional::NO, "The block hash or height of the target block", RPCArgOptions{.type_str={"", "string or numeric"}}},
+                    {"hash_or_height", RPCArg::Type::NUM, RPCArg::Optional::NO, "The block hash or height of the target block",
+                     RPCArgOptions{
+                         .skip_type_check = true,
+                         .type_str = {"", "string or numeric"},
+                     }},
                     {"stats", RPCArg::Type::ARR, RPCArg::DefaultHint{"all values"}, "Values to plot (see result below)",
                         {
                             {"height", RPCArg::Type::STR, RPCArg::Optional::OMITTED, "Selected statistic"},
@@ -2144,8 +2148,6 @@ static RPCHelpMan scantxoutset()
         },
         [&](const RPCHelpMan& self, const JSONRPCRequest& request) -> UniValue
 {
-    RPCTypeCheck(request.params, {UniValue::VSTR, UniValue::VARR});
-
     UniValue result(UniValue::VOBJ);
     if (request.params[0].get_str() == "status") {
         CoinsViewScanReserver reserver;
diff --git a/src/rpc/fees.cpp b/src/rpc/fees.cpp
index cd2f6390e5..62396d4c58 100644
--- a/src/rpc/fees.cpp
+++ b/src/rpc/fees.cpp
@@ -63,8 +63,6 @@ static RPCHelpMan estimatesmartfee()
         },
         [&](const RPCHelpMan& self, const JSONRPCRequest& request) -> UniValue
         {
-            RPCTypeCheck(request.params, {UniValue::VNUM, UniValue::VSTR});
-
             CBlockPolicyEstimator& fee_estimator = EnsureAnyFeeEstimator(request.context);
             const NodeContext& node = EnsureAnyNodeContext(request.context);
             const CTxMemPool& mempool = EnsureMemPool(node);
@@ -155,8 +153,6 @@ static RPCHelpMan estimaterawfee()
         },
         [&](const RPCHelpMan& self, const JSONRPCRequest& request) -> UniValue
         {
-            RPCTypeCheck(request.params, {UniValue::VNUM, UniValue::VNUM}, true);
-
             CBlockPolicyEstimator& fee_estimator = EnsureAnyFeeEstimator(request.context);
 
             unsigned int max_target = fee_estimator.HighestTargetTracked(FeeEstimateHorizon::LONG_HALFLIFE);
diff --git a/src/rpc/mempool.cpp b/src/rpc/mempool.cpp
index 44bff55f96..44f7435a26 100644
--- a/src/rpc/mempool.cpp
+++ b/src/rpc/mempool.cpp
@@ -61,11 +61,6 @@ static RPCHelpMan sendrawtransaction()
                 },
         [&](const RPCHelpMan& self, const JSONRPCRequest& request) -> UniValue
         {
-            RPCTypeCheck(request.params, {
-                UniValue::VSTR,
-                UniValueType(), // VNUM or VSTR, checked inside AmountFromValue()
-            });
-
             CMutableTransaction mtx;
             if (!DecodeHexTx(mtx, request.params[0].get_str())) {
                 throw JSONRPCError(RPC_DESERIALIZATION_ERROR, "TX decode failed. Make sure the tx has at least one input.");
@@ -147,10 +142,6 @@ static RPCHelpMan testmempoolaccept()
                 },
         [&](const RPCHelpMan& self, const JSONRPCRequest& request) -> UniValue
         {
-            RPCTypeCheck(request.params, {
-                UniValue::VARR,
-                UniValueType(), // VNUM or VSTR, checked inside AmountFromValue()
-            });
             const UniValue raw_transactions = request.params[0].get_array();
             if (raw_transactions.size() < 1 || raw_transactions.size() > MAX_PACKAGE_COUNT) {
                 throw JSONRPCError(RPC_INVALID_PARAMETER,
@@ -800,9 +791,6 @@ static RPCHelpMan submitpackage()
             if (!Params().IsMockableChain()) {
                 throw std::runtime_error("submitpackage is for regression testing (-regtest mode) only");
             }
-            RPCTypeCheck(request.params, {
-                UniValue::VARR,
-            });
             const UniValue raw_transactions = request.params[0].get_array();
             if (raw_transactions.size() < 1 || raw_transactions.size() > MAX_PACKAGE_COUNT) {
                 throw JSONRPCError(RPC_INVALID_PARAMETER,
diff --git a/src/rpc/net.cpp b/src/rpc/net.cpp
index d430087358..f1fa11b986 100644
--- a/src/rpc/net.cpp
+++ b/src/rpc/net.cpp
@@ -362,7 +362,6 @@ static RPCHelpMan addconnection()
         throw std::runtime_error("addconnection is for regression testing (-regtest mode) only.");
     }
 
-    RPCTypeCheck(request.params, {UniValue::VSTR, UniValue::VSTR});
     const std::string address = request.params[0].get_str();
     const std::string conn_type_in{TrimString(request.params[1].get_str())};
     ConnectionType conn_type{};
diff --git a/src/rpc/node.cpp b/src/rpc/node.cpp
index d8f2576b6d..8001db1192 100644
--- a/src/rpc/node.cpp
+++ b/src/rpc/node.cpp
@@ -52,7 +52,6 @@ static RPCHelpMan setmocktime()
     // ensure all call sites of GetTime() are accessing this safely.
     LOCK(cs_main);
 
-    RPCTypeCheck(request.params, {UniValue::VNUM});
     const int64_t time{request.params[0].getInt<int64_t>()};
     if (time < 0) {
         throw JSONRPCError(RPC_INVALID_PARAMETER, strprintf("Mocktime cannot be negative: %s.", time));
@@ -106,8 +105,6 @@ static RPCHelpMan mockscheduler()
         throw std::runtime_error("mockscheduler is for regression testing (-regtest mode) only");
     }
 
-    // check params are valid values
-    RPCTypeCheck(request.params, {UniValue::VNUM});
     int64_t delta_seconds = request.params[0].getInt<int64_t>();
     if (delta_seconds <= 0 || delta_seconds > 3600) {
         throw std::runtime_error("delta_time must be between 1 and 3600 seconds (1 hr)");
@@ -295,18 +292,18 @@ static RPCHelpMan echo(const std::string& name)
                 "\nIt will return an internal bug report when arg9='trigger_internal_bug' is passed.\n"
                 "\nThe difference between echo and echojson is that echojson has argument conversion enabled in the client-side table in "
                 "bitcoin-cli and the GUI. There is no server-side difference.",
-                {
-                    {"arg0", RPCArg::Type::STR, RPCArg::Optional::OMITTED_NAMED_ARG, ""},
-                    {"arg1", RPCArg::Type::STR, RPCArg::Optional::OMITTED_NAMED_ARG, ""},
-                    {"arg2", RPCArg::Type::STR, RPCArg::Optional::OMITTED_NAMED_ARG, ""},
-                    {"arg3", RPCArg::Type::STR, RPCArg::Optional::OMITTED_NAMED_ARG, ""},
-                    {"arg4", RPCArg::Type::STR, RPCArg::Optional::OMITTED_NAMED_ARG, ""},
-                    {"arg5", RPCArg::Type::STR, RPCArg::Optional::OMITTED_NAMED_ARG, ""},
-                    {"arg6", RPCArg::Type::STR, RPCArg::Optional::OMITTED_NAMED_ARG, ""},
-                    {"arg7", RPCArg::Type::STR, RPCArg::Optional::OMITTED_NAMED_ARG, ""},
-                    {"arg8", RPCArg::Type::STR, RPCArg::Optional::OMITTED_NAMED_ARG, ""},
-                    {"arg9", RPCArg::Type::STR, RPCArg::Optional::OMITTED_NAMED_ARG, ""},
-                },
+        {
+            {"arg0", RPCArg::Type::STR, RPCArg::Optional::OMITTED_NAMED_ARG, "", RPCArgOptions{.skip_type_check = true}},
+            {"arg1", RPCArg::Type::STR, RPCArg::Optional::OMITTED_NAMED_ARG, "", RPCArgOptions{.skip_type_check = true}},
+            {"arg2", RPCArg::Type::STR, RPCArg::Optional::OMITTED_NAMED_ARG, "", RPCArgOptions{.skip_type_check = true}},
+            {"arg3", RPCArg::Type::STR, RPCArg::Optional::OMITTED_NAMED_ARG, "", RPCArgOptions{.skip_type_check = true}},
+            {"arg4", RPCArg::Type::STR, RPCArg::Optional::OMITTED_NAMED_ARG, "", RPCArgOptions{.skip_type_check = true}},
+            {"arg5", RPCArg::Type::STR, RPCArg::Optional::OMITTED_NAMED_ARG, "", RPCArgOptions{.skip_type_check = true}},
+            {"arg6", RPCArg::Type::STR, RPCArg::Optional::OMITTED_NAMED_ARG, "", RPCArgOptions{.skip_type_check = true}},
+            {"arg7", RPCArg::Type::STR, RPCArg::Optional::OMITTED_NAMED_ARG, "", RPCArgOptions{.skip_type_check = true}},
+            {"arg8", RPCArg::Type::STR, RPCArg::Optional::OMITTED_NAMED_ARG, "", RPCArgOptions{.skip_type_check = true}},
+            {"arg9", RPCArg::Type::STR, RPCArg::Optional::OMITTED_NAMED_ARG, "", RPCArgOptions{.skip_type_check = true}},
+        },
                 RPCResult{RPCResult::Type::ANY, "", "Returns whatever was passed in"},
                 RPCExamples{""},
         [&](const RPCHelpMan& self, const JSONRPCRequest& request) -> UniValue
diff --git a/src/rpc/output_script.cpp b/src/rpc/output_script.cpp
index 2ac6d6d76f..911c769e61 100644
--- a/src/rpc/output_script.cpp
+++ b/src/rpc/output_script.cpp
@@ -195,8 +195,6 @@ static RPCHelpMan getdescriptorinfo()
         },
         [&](const RPCHelpMan& self, const JSONRPCRequest& request) -> UniValue
         {
-            RPCTypeCheck(request.params, {UniValue::VSTR});
-
             FlatSigningProvider provider;
             std::string error;
             auto desc = Parse(request.params[0].get_str(), provider, error);
@@ -247,7 +245,6 @@ static RPCHelpMan deriveaddresses()
         },
         [&](const RPCHelpMan& self, const JSONRPCRequest& request) -> UniValue
         {
-            RPCTypeCheck(request.params, {UniValue::VSTR, UniValueType()}); // Range argument is checked later
             const std::string desc_str = request.params[0].get_str();
 
             int64_t range_begin = 0;
diff --git a/src/rpc/rawtransaction.cpp b/src/rpc/rawtransaction.cpp
index c712536b91..981dead3b8 100644
--- a/src/rpc/rawtransaction.cpp
+++ b/src/rpc/rawtransaction.cpp
@@ -162,7 +162,7 @@ static std::vector<RPCArg> CreateTxDoc()
                     },
                 },
             },
-        },
+         RPCArgOptions{.skip_type_check = true}},
         {"locktime", RPCArg::Type::NUM, RPCArg::Default{0}, "Raw locktime. Non-0 value also locktime-activates inputs"},
         {"replaceable", RPCArg::Type::BOOL, RPCArg::Default{true}, "Marks this transaction as BIP125-replaceable.\n"
                 "Allows this transaction to be replaced by a transaction with higher fees. If provided, it is an error if explicit sequence numbers are incompatible."},
@@ -185,7 +185,8 @@ static RPCHelpMan getrawtransaction()
                 "If verbosity is 2, returns a JSON Object with information about the transaction, including fee and prevout information.",
                 {
                     {"txid", RPCArg::Type::STR_HEX, RPCArg::Optional::NO, "The transaction id"},
-                    {"verbosity|verbose", RPCArg::Type::NUM, RPCArg::Default{0}, "0 for hex-encoded data, 1 for a JSON object, and 2 for JSON object with fee and prevout"},
+                    {"verbosity|verbose", RPCArg::Type::NUM, RPCArg::Default{0}, "0 for hex-encoded data, 1 for a JSON object, and 2 for JSON object with fee and prevout",
+                     RPCArgOptions{.skip_type_check = true}},
                     {"blockhash", RPCArg::Type::STR_HEX, RPCArg::Optional::OMITTED_NAMED_ARG, "The block in which to look for the transaction"},
                 },
                 {
@@ -354,14 +355,6 @@ static RPCHelpMan createrawtransaction()
                 },
         [&](const RPCHelpMan& self, const JSONRPCRequest& request) -> UniValue
 {
-    RPCTypeCheck(request.params, {
-        UniValue::VARR,
-        UniValueType(), // ARR or OBJ, checked later
-        UniValue::VNUM,
-        UniValue::VBOOL
-        }, true
-    );
-
     std::optional<bool> rbf;
     if (!request.params[3].isNull()) {
         rbf = request.params[3].get_bool();
@@ -397,8 +390,6 @@ static RPCHelpMan decoderawtransaction()
                 },
         [&](const RPCHelpMan& self, const JSONRPCRequest& request) -> UniValue
 {
-    RPCTypeCheck(request.params, {UniValue::VSTR, UniValue::VBOOL});
-
     CMutableTransaction mtx;
 
     bool try_witness = request.params[1].isNull() ? true : request.params[1].get_bool();
@@ -451,8 +442,6 @@ static RPCHelpMan decodescript()
         },
         [&](const RPCHelpMan& self, const JSONRPCRequest& request) -> UniValue
 {
-    RPCTypeCheck(request.params, {UniValue::VSTR});
-
     UniValue r(UniValue::VOBJ);
     CScript script;
     if (request.params[0].get_str().size() > 0){
@@ -702,8 +691,6 @@ static RPCHelpMan signrawtransactionwithkey()
                 },
         [&](const RPCHelpMan& self, const JSONRPCRequest& request) -> UniValue
 {
-    RPCTypeCheck(request.params, {UniValue::VSTR, UniValue::VARR, UniValue::VARR, UniValue::VSTR}, true);
-
     CMutableTransaction mtx;
     if (!DecodeHexTx(mtx, request.params[0].get_str())) {
         throw JSONRPCError(RPC_DESERIALIZATION_ERROR, "TX decode failed. Make sure the tx has at least one input.");
@@ -981,8 +968,6 @@ static RPCHelpMan decodepsbt()
                 },
         [&](const RPCHelpMan& self, const JSONRPCRequest& request) -> UniValue
 {
-    RPCTypeCheck(request.params, {UniValue::VSTR});
-
     // Unserialize the transactions
     PartiallySignedTransaction psbtx;
     std::string error;
@@ -1395,8 +1380,6 @@ static RPCHelpMan combinepsbt()
                 },
         [&](const RPCHelpMan& self, const JSONRPCRequest& request) -> UniValue
 {
-    RPCTypeCheck(request.params, {UniValue::VARR}, true);
-
     // Unserialize the transactions
     std::vector<PartiallySignedTransaction> psbtxs;
     UniValue txs = request.params[0].get_array();
@@ -1450,8 +1433,6 @@ static RPCHelpMan finalizepsbt()
                 },
         [&](const RPCHelpMan& self, const JSONRPCRequest& request) -> UniValue
 {
-    RPCTypeCheck(request.params, {UniValue::VSTR, UniValue::VBOOL}, true);
-
     // Unserialize the transactions
     PartiallySignedTransaction psbtx;
     std::string error;
@@ -1499,14 +1480,6 @@ static RPCHelpMan createpsbt()
         [&](const RPCHelpMan& self, const JSONRPCRequest& request) -> UniValue
 {
 
-    RPCTypeCheck(request.params, {
-        UniValue::VARR,
-        UniValueType(), // ARR or OBJ, checked later
-        UniValue::VNUM,
-        UniValue::VBOOL,
-        }, true
-    );
-
     std::optional<bool> rbf;
     if (!request.params[3].isNull()) {
         rbf = request.params[3].get_bool();
@@ -1560,8 +1533,6 @@ static RPCHelpMan converttopsbt()
                 },
         [&](const RPCHelpMan& self, const JSONRPCRequest& request) -> UniValue
 {
-    RPCTypeCheck(request.params, {UniValue::VSTR, UniValue::VBOOL, UniValue::VBOOL}, true);
-
     // parse hex string from parameter
     CMutableTransaction tx;
     bool permitsigdata = request.params[1].isNull() ? false : request.params[1].get_bool();
@@ -1623,8 +1594,6 @@ static RPCHelpMan utxoupdatepsbt()
             },
         [&](const RPCHelpMan& self, const JSONRPCRequest& request) -> UniValue
 {
-    RPCTypeCheck(request.params, {UniValue::VSTR, UniValue::VARR}, true);
-
     // Unserialize the transactions
     PartiallySignedTransaction psbtx;
     std::string error;
@@ -1714,8 +1683,6 @@ static RPCHelpMan joinpsbts()
             },
         [&](const RPCHelpMan& self, const JSONRPCRequest& request) -> UniValue
 {
-    RPCTypeCheck(request.params, {UniValue::VARR}, true);
-
     // Unserialize the transactions
     std::vector<PartiallySignedTransaction> psbtxs;
     UniValue txs = request.params[0].get_array();
@@ -1842,8 +1809,6 @@ static RPCHelpMan analyzepsbt()
             },
         [&](const RPCHelpMan& self, const JSONRPCRequest& request) -> UniValue
 {
-    RPCTypeCheck(request.params, {UniValue::VSTR});
-
     // Unserialize the transaction
     PartiallySignedTransaction psbtx;
     std::string error;
diff --git a/src/rpc/util.cpp b/src/rpc/util.cpp
index 53785b1941..bb850a9171 100644
--- a/src/rpc/util.cpp
+++ b/src/rpc/util.cpp
@@ -30,23 +30,6 @@ std::string GetAllOutputTypes()
     return Join(ret, ", ");
 }
 
-void RPCTypeCheck(const UniValue& params,
-                  const std::list<UniValueType>& typesExpected,
-                  bool fAllowNull)
-{
-    unsigned int i = 0;
-    for (const UniValueType& t : typesExpected) {
-        if (params.size() <= i)
-            break;
-
-        const UniValue& v = params[i];
-        if (!(fAllowNull && v.isNull())) {
-            RPCTypeCheckArgument(v, t);
-        }
-        i++;
-    }
-}
-
 void RPCTypeCheckArgument(const UniValue& value, const UniValueType& typeExpected)
 {
     if (!typeExpected.typeAny && value.type() != typeExpected.type) {
@@ -579,6 +562,9 @@ UniValue RPCHelpMan::HandleRequest(const JSONRPCRequest& request) const
     if (request.mode == JSONRPCRequest::GET_HELP || !IsValidNumArgs(request.params.size())) {
         throw std::runtime_error(ToString());
     }
+    for (size_t i{0}; i < m_args.size(); ++i) {
+        m_args.at(i).MatchesType(request.params[i]);
+    }
     UniValue ret = m_fun(*this, request);
     if (gArgs.GetBoolArg("-rpcdoccheck", DEFAULT_RPC_DOC_CHECK)) {
         CHECK_NONFATAL(std::any_of(m_results.m_results.begin(), m_results.m_results.end(), [&ret](const RPCResult& res) { return res.MatchesType(ret); }));
@@ -677,6 +663,44 @@ UniValue RPCHelpMan::GetArgMap() const
     return arr;
 }
 
+void RPCArg::MatchesType(const UniValue& request) const
+{
+    if (m_opts.skip_type_check) return;
+    if (IsOptional() && request.isNull()) return;
+    switch (m_type) {
+    case Type::STR_HEX:
+    case Type::STR: {
+        RPCTypeCheckArgument(request, UniValue::VSTR);
+        return;
+    }
+    case Type::NUM: {
+        RPCTypeCheckArgument(request, UniValue::VNUM);
+        return;
+    }
+    case Type::AMOUNT: {
+        // VNUM or VSTR, checked inside AmountFromValue()
+        return;
+    }
+    case Type::RANGE: {
+        // VNUM or VARR, checked inside ParseRange()
+        return;
+    }
+    case Type::BOOL: {
+        RPCTypeCheckArgument(request, UniValue::VBOOL);
+        return;
+    }
+    case Type::OBJ:
+    case Type::OBJ_USER_KEYS: {
+        RPCTypeCheckArgument(request, UniValue::VOBJ);
+        return;
+    }
+    case Type::ARR: {
+        RPCTypeCheckArgument(request, UniValue::VARR);
+        return;
+    }
+    } // no default case, so the compiler can warn about missing cases
+}
+
 std::string RPCArg::GetFirstName() const
 {
     return m_names.substr(0, m_names.find("|"));
diff --git a/src/rpc/util.h b/src/rpc/util.h
index 387fee34d3..a86300d8b4 100644
--- a/src/rpc/util.h
+++ b/src/rpc/util.h
@@ -63,13 +63,6 @@ struct UniValueType {
 };
 
 /**
- * Type-check arguments; throws JSONRPCError if wrong type given. Does not check that
- * the right number of arguments are passed, just that any passed are the correct type.
- */
-void RPCTypeCheck(const UniValue& params,
-                  const std::list<UniValueType>& typesExpected, bool fAllowNull=false);
-
-/**
  * Type-check one argument; throws JSONRPCError if wrong type given.
  */
 void RPCTypeCheckArgument(const UniValue& value, const UniValueType& typeExpected);
@@ -138,6 +131,7 @@ enum class OuterType {
 };
 
 struct RPCArgOptions {
+    bool skip_type_check{false};
     std::string oneline_description{};   //!< Should be empty unless it is supposed to override the auto-generated summary line
     std::vector<std::string> type_str{}; //!< Should be empty unless it is supposed to override the auto-generated type strings. Vector length is either 0 or 2, m_opts.type_str.at(0) will override the type of the value in a key-value pair, m_opts.type_str.at(1) will override the type in the argument description.
     bool hidden{false};                  //!< For testing only
@@ -217,6 +211,9 @@ struct RPCArg {
 
     bool IsOptional() const;
 
+    /** Check whether the request JSON type matches. */
+    void MatchesType(const UniValue& request) const;
+
     /** Return the first of all aliases */
     std::string GetFirstName() const;