rpc: Assert named arguments are unique in RPCHelpMan

src/rpc/util.cpp

@@ -242,6 +242,16 @@ struct Sections {
     }
 };
 
+RPCHelpMan::RPCHelpMan(const std::string& name, const std::string& description, const std::vector<RPCArg>& args)
+    : m_name{name}, m_description{description}, m_args{args}
+{
+    std::set<std::string> named_args;
+    for (const auto& arg : m_args) {
+        // Should have unique named arguments
+        assert(named_args.insert(arg.m_name).second);
+    }
+}
+
 std::string RPCHelpMan::ToString() const
 {
     std::string ret;

src/rpc/util.h

@@ -109,10 +109,7 @@ struct RPCArg {
 class RPCHelpMan
 {
 public:
-    RPCHelpMan(const std::string& name, const std::string& description, const std::vector<RPCArg>& args)
-        : m_name{name}, m_description{description}, m_args{args}
-    {
-    }
+    RPCHelpMan(const std::string& name, const std::string& description, const std::vector<RPCArg>& args);
 
     std::string ToString() const;