Merge bitcoin/bitcoin#25611: univalue: Avoid brittle, narrowing and verbose integral type confusions

fa23c197509f692a815193acc1b50bad2fcbedfe univalue: Avoid narrowing and verbose int constructors (MacroFake)
fa3a9a1e8d9b6dffda772e97c279f3c0af6813f9 rpc: Select int-UniValue constructor for enum value in upgradewallet RPC (MacroFake)

Pull request description:

  As UniValue provides several constructors for integral types, the
  compiler is unable to select one if the passed type does not exactly
  match. This is unintuitive for developers and forces them to write
  verbose and brittle code. (Refer to `-Wnarrowing` compiler warning)

  For example, there are many places where an unsigned int is cast to a
  signed int. While the cast is safe in practice, it is still needlessly
  verbose and confusing as the value can never be negative. In fact it
  might even be unsafe if the unsigned value is large enough to map to a
  negative signed one.

  Fix this issue and other (minor) type issues.

ACKs for top commit:
  aureleoules:
    ACK fa23c197509f692a815193acc1b50bad2fcbedfe.

Tree-SHA512: 7d99b5b90c7d8eed2e3448167255a59e817dd6b8fcfc1b17c69ddefd0db33d1bf4344fbcd8b7f8685b58182c0f572ab9ffa99467afa666ac21843df7ea645033

3 files changed, 24 insertions, 26 deletions

diff --git a/src/rpc/net.cpp b/src/rpc/net.cpp
index 27eea824bc..d88861a0c4 100644
--- a/src/rpc/net.cpp
+++ b/src/rpc/net.cpp
@@ -60,7 +60,7 @@ static RPCHelpMan getconnectioncount()
     NodeContext& node = EnsureAnyNodeContext(request.context);
     const CConnman& connman = EnsureConnman(node);
 
-    return (int)connman.GetNodeCount(ConnectionDirection::Both);
+    return connman.GetNodeCount(ConnectionDirection::Both);
 },
     };
 }
@@ -640,9 +640,9 @@ static RPCHelpMan getnetworkinfo()
     obj.pushKV("timeoffset",    GetTimeOffset());
     if (node.connman) {
         obj.pushKV("networkactive", node.connman->GetNetworkActive());
-        obj.pushKV("connections", (int)node.connman->GetNodeCount(ConnectionDirection::Both));
-        obj.pushKV("connections_in", (int)node.connman->GetNodeCount(ConnectionDirection::In));
-        obj.pushKV("connections_out", (int)node.connman->GetNodeCount(ConnectionDirection::Out));
+        obj.pushKV("connections", node.connman->GetNodeCount(ConnectionDirection::Both));
+        obj.pushKV("connections_in", node.connman->GetNodeCount(ConnectionDirection::In));
+        obj.pushKV("connections_out", node.connman->GetNodeCount(ConnectionDirection::Out));
     }
     obj.pushKV("networks",      GetNetworksInfo());
     obj.pushKV("relayfee",      ValueFromAmount(::minRelayTxFee.GetFeePerK()));
diff --git a/src/univalue/include/univalue.h b/src/univalue/include/univalue.h
index dff544f96f..230a5fd096 100644
--- a/src/univalue/include/univalue.h
+++ b/src/univalue/include/univalue.h
@@ -24,27 +24,25 @@ public:
         typ = initialType;
         val = initialStr;
     }
-    UniValue(uint64_t val_) {
-        setInt(val_);
-    }
-    UniValue(int64_t val_) {
-        setInt(val_);
-    }
-    UniValue(bool val_) {
-        setBool(val_);
-    }
-    UniValue(int val_) {
-        setInt(val_);
-    }
-    UniValue(double val_) {
-        setFloat(val_);
-    }
-    UniValue(const std::string& val_) {
-        setStr(val_);
-    }
-    UniValue(const char *val_) {
-        std::string s(val_);
-        setStr(s);
+    template <typename Ref, typename T = std::remove_cv_t<std::remove_reference_t<Ref>>,
+              std::enable_if_t<std::is_floating_point_v<T> ||                      // setFloat
+                                   std::is_same_v<bool, T> ||                      // setBool
+                                   std::is_signed_v<T> || std::is_unsigned_v<T> || // setInt
+                                   std::is_constructible_v<std::string, T>,        // setStr
+                               bool> = true>
+    UniValue(Ref&& val)
+    {
+        if constexpr (std::is_floating_point_v<T>) {
+            setFloat(val);
+        } else if constexpr (std::is_same_v<bool, T>) {
+            setBool(val);
+        } else if constexpr (std::is_signed_v<T>) {
+            setInt(int64_t{val});
+        } else if constexpr (std::is_unsigned_v<T>) {
+            setInt(uint64_t{val});
+        } else {
+            setStr(std::string{std::forward<Ref>(val)});
+        }
     }
 
     void clear();
diff --git a/src/wallet/rpc/wallet.cpp b/src/wallet/rpc/wallet.cpp
index 4c44c333a6..be1b6de7ac 100644
--- a/src/wallet/rpc/wallet.cpp
+++ b/src/wallet/rpc/wallet.cpp
@@ -532,7 +532,7 @@ static RPCHelpMan upgradewallet()
         "\nUpgrade the wallet. Upgrades to the latest version if no version number is specified.\n"
         "New keys may be generated and a new wallet backup will need to be made.",
         {
-            {"version", RPCArg::Type::NUM, RPCArg::Default{FEATURE_LATEST}, "The version number to upgrade to. Default is the latest wallet version."}
+            {"version", RPCArg::Type::NUM, RPCArg::Default{int{FEATURE_LATEST}}, "The version number to upgrade to. Default is the latest wallet version."}
         },
         RPCResult{
             RPCResult::Type::OBJ, "", "",