Revert "Use template structs instead of phantoms"

This reverts commit 9ab07e99f527d1fa3adfa02839da477a1528d64b.

8 files changed, 154 insertions, 149 deletions

diff --git a/src/libstore/build.cc b/src/libstore/build.cc
index 56d454b6b..928858203 100644
--- a/src/libstore/build.cc
+++ b/src/libstore/build.cc
@@ -1976,7 +1976,7 @@ HookReply DerivationGoal::tryBuildHook()
 
     /* Tell the hook all the inputs that have to be copied to the
        remote system. */
-    WorkerProto<StorePathSet>::write(worker.store, hook->sink, inputPaths);
+    nix::worker_proto::write(worker.store, hook->sink, inputPaths);
 
     /* Tell the hooks the missing outputs that have to be copied back
        from the remote system. */
@@ -1987,7 +1987,7 @@ HookReply DerivationGoal::tryBuildHook()
             if (buildMode != bmCheck && status.known->isValid()) continue;
             missingPaths.insert(status.known->path);
         }
-        WorkerProto<StorePathSet>::write(worker.store, hook->sink, missingPaths);
+        nix::worker_proto::write(worker.store, hook->sink, missingPaths);
     }
 
     hook->sink = FdSink();
diff --git a/src/libstore/daemon.cc b/src/libstore/daemon.cc
index 98fd2048d..72203d1b2 100644
--- a/src/libstore/daemon.cc
+++ b/src/libstore/daemon.cc
@@ -247,7 +247,7 @@ static void writeValidPathInfo(
 {
     to << (info->deriver ? store->printStorePath(*info->deriver) : "")
        << info->narHash.to_string(Base16, false);
-    WorkerProto<StorePathSet>::write(*store, to, info->references);
+    nix::worker_proto::write(*store, to, info->references);
     to << info->registrationTime << info->narSize;
     if (GET_PROTOCOL_MINOR(clientVersion) >= 16) {
         to << info->ultimate
@@ -272,11 +272,11 @@ static void performOp(TunnelLogger * logger, ref<Store> store,
     }
 
     case wopQueryValidPaths: {
-        auto paths = WorkerProto<StorePathSet>::read(*store, from);
+        auto paths = nix::worker_proto::read(*store, from, Phantom<StorePathSet> {});
         logger->startWork();
         auto res = store->queryValidPaths(paths);
         logger->stopWork();
-        WorkerProto<StorePathSet>::write(*store, to, res);
+        nix::worker_proto::write(*store, to, res);
         break;
     }
 
@@ -292,11 +292,11 @@ static void performOp(TunnelLogger * logger, ref<Store> store,
     }
 
     case wopQuerySubstitutablePaths: {
-        auto paths = WorkerProto<StorePathSet>::read(*store, from);
+        auto paths = nix::worker_proto::read(*store, from, Phantom<StorePathSet> {});
         logger->startWork();
         auto res = store->querySubstitutablePaths(paths);
         logger->stopWork();
-        WorkerProto<StorePathSet>::write(*store, to, res);
+        nix::worker_proto::write(*store, to, res);
         break;
     }
 
@@ -325,7 +325,7 @@ static void performOp(TunnelLogger * logger, ref<Store> store,
             paths = store->queryValidDerivers(path);
         else paths = store->queryDerivationOutputs(path);
         logger->stopWork();
-        WorkerProto<StorePathSet>::write(*store, to, paths);
+        nix::worker_proto::write(*store, to, paths);
         break;
     }
 
@@ -343,7 +343,7 @@ static void performOp(TunnelLogger * logger, ref<Store> store,
         logger->startWork();
         auto outputs = store->queryPartialDerivationOutputMap(path);
         logger->stopWork();
-        WorkerProto<std::map<std::string, std::optional<StorePath>>>::write(*store, to, outputs);
+        nix::worker_proto::write(*store, to, outputs);
         break;
     }
 
@@ -369,7 +369,7 @@ static void performOp(TunnelLogger * logger, ref<Store> store,
         if (GET_PROTOCOL_MINOR(clientVersion) >= 25) {
             auto name = readString(from);
             auto camStr = readString(from);
-            auto refs = WorkerProto<StorePathSet>::read(*store, from);
+            auto refs = nix::worker_proto::read(*store, from, Phantom<StorePathSet> {});
             bool repairBool;
             from >> repairBool;
             auto repair = RepairFlag{repairBool};
@@ -449,7 +449,7 @@ static void performOp(TunnelLogger * logger, ref<Store> store,
     case wopAddTextToStore: {
         string suffix = readString(from);
         string s = readString(from);
-        auto refs = WorkerProto<StorePathSet>::read(*store, from);
+        auto refs = nix::worker_proto::read(*store, from, Phantom<StorePathSet> {});
         logger->startWork();
         auto path = store->addTextToStore(suffix, s, refs, NoRepair);
         logger->stopWork();
@@ -608,7 +608,7 @@ static void performOp(TunnelLogger * logger, ref<Store> store,
     case wopCollectGarbage: {
         GCOptions options;
         options.action = (GCOptions::GCAction) readInt(from);
-        options.pathsToDelete = WorkerProto<StorePathSet>::read(*store, from);
+        options.pathsToDelete = nix::worker_proto::read(*store, from, Phantom<StorePathSet> {});
         from >> options.ignoreLiveness >> options.maxFreed;
         // obsolete fields
         readInt(from);
@@ -677,7 +677,7 @@ static void performOp(TunnelLogger * logger, ref<Store> store,
         else {
             to << 1
                << (i->second.deriver ? store->printStorePath(*i->second.deriver) : "");
-            WorkerProto<StorePathSet>::write(*store, to, i->second.references);
+            nix::worker_proto::write(*store, to, i->second.references);
             to << i->second.downloadSize
                << i->second.narSize;
         }
@@ -688,11 +688,11 @@ static void performOp(TunnelLogger * logger, ref<Store> store,
         SubstitutablePathInfos infos;
         StorePathCAMap pathsMap = {};
         if (GET_PROTOCOL_MINOR(clientVersion) < 22) {
-            auto paths = WorkerProto<StorePathSet>::read(*store, from);
+            auto paths = nix::worker_proto::read(*store, from, Phantom<StorePathSet> {});
             for (auto & path : paths)
                 pathsMap.emplace(path, std::nullopt);
         } else
-            pathsMap = WorkerProto<StorePathCAMap>::read(*store, from);
+            pathsMap = nix::worker_proto::read(*store, from, Phantom<StorePathCAMap> {});
         logger->startWork();
         store->querySubstitutablePathInfos(pathsMap, infos);
         logger->stopWork();
@@ -700,7 +700,7 @@ static void performOp(TunnelLogger * logger, ref<Store> store,
         for (auto & i : infos) {
             to << store->printStorePath(i.first)
                << (i.second.deriver ? store->printStorePath(*i.second.deriver) : "");
-            WorkerProto<StorePathSet>::write(*store, to, i.second.references);
+            nix::worker_proto::write(*store, to, i.second.references);
             to << i.second.downloadSize << i.second.narSize;
         }
         break;
@@ -710,7 +710,7 @@ static void performOp(TunnelLogger * logger, ref<Store> store,
         logger->startWork();
         auto paths = store->queryAllValidPaths();
         logger->stopWork();
-        WorkerProto<StorePathSet>::write(*store, to, paths);
+        nix::worker_proto::write(*store, to, paths);
         break;
     }
 
@@ -782,7 +782,7 @@ static void performOp(TunnelLogger * logger, ref<Store> store,
         ValidPathInfo info { path, narHash };
         if (deriver != "")
             info.deriver = store->parseStorePath(deriver);
-        info.references = WorkerProto<StorePathSet>::read(*store, from);
+        info.references = nix::worker_proto::read(*store, from, Phantom<StorePathSet> {});
         from >> info.registrationTime >> info.narSize >> info.ultimate;
         info.sigs = readStrings<StringSet>(from);
         info.ca = parseContentAddressOpt(readString(from));
@@ -835,9 +835,9 @@ static void performOp(TunnelLogger * logger, ref<Store> store,
         uint64_t downloadSize, narSize;
         store->queryMissing(targets, willBuild, willSubstitute, unknown, downloadSize, narSize);
         logger->stopWork();
-        WorkerProto<StorePathSet>::write(*store, to, willBuild);
-        WorkerProto<StorePathSet>::write(*store, to, willSubstitute);
-        WorkerProto<StorePathSet>::write(*store, to, unknown);
+        nix::worker_proto::write(*store, to, willBuild);
+        nix::worker_proto::write(*store, to, willSubstitute);
+        nix::worker_proto::write(*store, to, unknown);
         to << downloadSize << narSize;
         break;
     }
diff --git a/src/libstore/derivations.cc b/src/libstore/derivations.cc
index faffe01e7..f8e7d773b 100644
--- a/src/libstore/derivations.cc
+++ b/src/libstore/derivations.cc
@@ -584,7 +584,7 @@ Source & readDerivation(Source & in, const Store & store, BasicDerivation & drv,
         drv.outputs.emplace(std::move(name), std::move(output));
     }
 
-    drv.inputSrcs = WorkerProto<StorePathSet>::read(store, in);
+    drv.inputSrcs = nix::worker_proto::read(store, in, Phantom<StorePathSet> {});
     in >> drv.platform >> drv.builder;
     drv.args = readStrings<Strings>(in);
 
@@ -622,7 +622,7 @@ void writeDerivation(Sink & out, const Store & store, const BasicDerivation & dr
             },
         }, i.second.output);
     }
-    WorkerProto<StorePathSet>::write(store, out, drv.inputSrcs);
+    nix::worker_proto::write(store, out, drv.inputSrcs);
     out << drv.platform << drv.builder << drv.args;
     out << drv.env.size();
     for (auto & i : drv.env)
diff --git a/src/libstore/export-import.cc b/src/libstore/export-import.cc
index b59b34dee..40a6f3c63 100644
--- a/src/libstore/export-import.cc
+++ b/src/libstore/export-import.cc
@@ -45,7 +45,7 @@ void Store::exportPath(const StorePath & path, Sink & sink)
     teeSink
         << exportMagic
         << printStorePath(path);
-    WorkerProto<StorePathSet>::write(*this, teeSink, info->references);
+    nix::worker_proto::write(*this, teeSink, info->references);
     teeSink
         << (info->deriver ? printStorePath(*info->deriver) : "")
         << 0;
@@ -73,7 +73,7 @@ StorePaths Store::importPaths(Source & source, CheckSigsFlag checkSigs)
 
         //Activity act(*logger, lvlInfo, format("importing path '%s'") % info.path);
 
-        auto references = WorkerProto<StorePathSet>::read(*this, source);
+        auto references = nix::worker_proto::read(*this, source, Phantom<StorePathSet> {});
         auto deriver = readString(source);
         auto narHash = hashString(htSHA256, *saved.s);
 
diff --git a/src/libstore/legacy-ssh-store.cc b/src/libstore/legacy-ssh-store.cc
index fdf3f91b9..e056859fd 100644
--- a/src/libstore/legacy-ssh-store.cc
+++ b/src/libstore/legacy-ssh-store.cc
@@ -122,7 +122,7 @@ struct LegacySSHStore : public Store, public virtual LegacySSHStoreConfig
             auto deriver = readString(conn->from);
             if (deriver != "")
                 info->deriver = parseStorePath(deriver);
-            info->references = WorkerProto<StorePathSet>::read(*this, conn->from);
+            info->references = nix::worker_proto::read(*this, conn->from, Phantom<StorePathSet> {});
             readLongLong(conn->from); // download size
             info->narSize = readLongLong(conn->from);
 
@@ -156,7 +156,7 @@ struct LegacySSHStore : public Store, public virtual LegacySSHStoreConfig
                 << printStorePath(info.path)
                 << (info.deriver ? printStorePath(*info.deriver) : "")
                 << info.narHash.to_string(Base16, false);
-            WorkerProto<StorePathSet>::write(*this, conn->to, info.references);
+            nix::worker_proto::write(*this, conn->to, info.references);
             conn->to
                 << info.registrationTime
                 << info.narSize
@@ -185,7 +185,7 @@ struct LegacySSHStore : public Store, public virtual LegacySSHStoreConfig
             conn->to
                 << exportMagic
                 << printStorePath(info.path);
-            WorkerProto<StorePathSet>::write(*this, conn->to, info.references);
+            nix::worker_proto::write(*this, conn->to, info.references);
             conn->to
                 << (info.deriver ? printStorePath(*info.deriver) : "")
                 << 0
@@ -301,10 +301,10 @@ public:
         conn->to
             << cmdQueryClosure
             << includeOutputs;
-        WorkerProto<StorePathSet>::write(*this, conn->to, paths);
+        nix::worker_proto::write(*this, conn->to, paths);
         conn->to.flush();
 
-        for (auto & i : WorkerProto<StorePathSet>::read(*this, conn->from))
+        for (auto & i : nix::worker_proto::read(*this, conn->from, Phantom<StorePathSet> {}))
             out.insert(i);
     }
 
@@ -317,10 +317,10 @@ public:
             << cmdQueryValidPaths
             << false // lock
             << maybeSubstitute;
-        WorkerProto<StorePathSet>::write(*this, conn->to, paths);
+        nix::worker_proto::write(*this, conn->to, paths);
         conn->to.flush();
 
-        return WorkerProto<StorePathSet>::read(*this, conn->from);
+        return nix::worker_proto::read(*this, conn->from, Phantom<StorePathSet> {});
     }
 
     void connect() override
diff --git a/src/libstore/remote-store.cc b/src/libstore/remote-store.cc
index 273466137..43853db4e 100644
--- a/src/libstore/remote-store.cc
+++ b/src/libstore/remote-store.cc
@@ -24,61 +24,65 @@
 
 namespace nix {
 
-std::string WorkerProto<std::string>::read(const Store & store, Source & from)
+namespace worker_proto {
+
+std::string read(const Store & store, Source & from, Phantom<std::string> _)
 {
     return readString(from);
 }
 
-void WorkerProto<std::string>::write(const Store & store, Sink & out, const std::string & str)
+void write(const Store & store, Sink & out, const std::string & str)
 {
     out << str;
 }
 
 
-StorePath WorkerProto<StorePath>::read(const Store & store, Source & from)
+StorePath read(const Store & store, Source & from, Phantom<StorePath> _)
 {
     return store.parseStorePath(readString(from));
 }
 
-void WorkerProto<StorePath>::write(const Store & store, Sink & out, const StorePath & storePath)
+void write(const Store & store, Sink & out, const StorePath & storePath)
 {
     out << store.printStorePath(storePath);
 }
 
 
-ContentAddress WorkerProto<ContentAddress>::read(const Store & store, Source & from)
+ContentAddress read(const Store & store, Source & from, Phantom<ContentAddress> _)
 {
     return parseContentAddress(readString(from));
 }
 
-void WorkerProto<ContentAddress>::write(const Store & store, Sink & out, const ContentAddress & ca)
+void write(const Store & store, Sink & out, const ContentAddress & ca)
 {
     out << renderContentAddress(ca);
 }
 
 
-std::optional<StorePath> WorkerProto<std::optional<StorePath>>::read(const Store & store, Source & from)
+std::optional<StorePath> read(const Store & store, Source & from, Phantom<std::optional<StorePath>> _)
 {
     auto s = readString(from);
     return s == "" ? std::optional<StorePath> {} : store.parseStorePath(s);
 }
 
-void WorkerProto<std::optional<StorePath>>::write(const Store & store, Sink & out, const std::optional<StorePath> & storePathOpt)
+void write(const Store & store, Sink & out, const std::optional<StorePath> & storePathOpt)
 {
     out << (storePathOpt ? store.printStorePath(*storePathOpt) : "");
 }
 
 
-std::optional<ContentAddress> WorkerProto<std::optional<ContentAddress>>::read(const Store & store, Source & from)
+std::optional<ContentAddress> read(const Store & store, Source & from, Phantom<std::optional<ContentAddress>> _)
 {
     return parseContentAddressOpt(readString(from));
 }
 
-void WorkerProto<std::optional<ContentAddress>>::write(const Store & store, Sink & out, const std::optional<ContentAddress> & caOpt)
+void write(const Store & store, Sink & out, const std::optional<ContentAddress> & caOpt)
 {
     out << (caOpt ? renderContentAddress(*caOpt) : "");
 }
 
+}
+
 
 /* TODO: Separate these store impls into different files, give them better names */
 RemoteStore::RemoteStore(const Params & params)
@@ -325,9 +329,9 @@ StorePathSet RemoteStore::queryValidPaths(const StorePathSet & paths, Substitute
         return res;
     } else {
         conn->to << wopQueryValidPaths;
-        WorkerProto<StorePathSet>::write(*this, conn->to, paths);
+        nix::worker_proto::write(*this, conn->to, paths);
         conn.processStderr();
-        return WorkerProto<StorePathSet>::read(*this, conn->from);
+        return worker_proto::read(*this, conn->from, Phantom<StorePathSet> {});
     }
 }
 
@@ -337,7 +341,7 @@ StorePathSet RemoteStore::queryAllValidPaths()
     auto conn(getConnection());
     conn->to << wopQueryAllValidPaths;
     conn.processStderr();
-    return WorkerProto<StorePathSet>::read(*this, conn->from);
+    return nix::worker_proto::read(*this, conn->from, Phantom<StorePathSet> {});
 }
 
 
@@ -354,9 +358,9 @@ StorePathSet RemoteStore::querySubstitutablePaths(const StorePathSet & paths)
         return res;
     } else {
         conn->to << wopQuerySubstitutablePaths;
-        WorkerProto<StorePathSet>::write(*this, conn->to, paths);
+        nix::worker_proto::write(*this, conn->to, paths);
         conn.processStderr();
-        return WorkerProto<StorePathSet>::read(*this, conn->from);
+        return worker_proto::read(*this, conn->from, Phantom<StorePathSet> {});
     }
 }
 
@@ -378,7 +382,7 @@ void RemoteStore::querySubstitutablePathInfos(const StorePathCAMap & pathsMap, S
             auto deriver = readString(conn->from);
             if (deriver != "")
                 info.deriver = parseStorePath(deriver);
-            info.references = WorkerProto<StorePathSet>::read(*this, conn->from);
+            info.references = worker_proto::read(*this, conn->from, Phantom<StorePathSet> {});
             info.downloadSize = readLongLong(conn->from);
             info.narSize = readLongLong(conn->from);
             infos.insert_or_assign(i.first, std::move(info));
@@ -391,9 +395,9 @@ void RemoteStore::querySubstitutablePathInfos(const StorePathCAMap & pathsMap, S
             StorePathSet paths;
             for (auto & path : pathsMap)
                 paths.insert(path.first);
-            WorkerProto<StorePathSet>::write(*this, conn->to, paths);
+            worker_proto::write(*this, conn->to, paths);
         } else
-            WorkerProto<StorePathCAMap>::write(*this, conn->to, pathsMap);
+            worker_proto::write(*this, conn->to, pathsMap);
         conn.processStderr();
         size_t count = readNum<size_t>(conn->from);
         for (size_t n = 0; n < count; n++) {
@@ -401,7 +405,7 @@ void RemoteStore::querySubstitutablePathInfos(const StorePathCAMap & pathsMap, S
             auto deriver = readString(conn->from);
             if (deriver != "")
                 info.deriver = parseStorePath(deriver);
-            info.references = WorkerProto<StorePathSet>::read(*this, conn->from);
+            info.references = worker_proto::read(*this, conn->from, Phantom<StorePathSet> {});
             info.downloadSize = readLongLong(conn->from);
             info.narSize = readLongLong(conn->from);
         }
@@ -416,7 +420,7 @@ ref<const ValidPathInfo> RemoteStore::readValidPathInfo(ConnectionHandle & conn,
     auto narHash = Hash::parseAny(readString(conn->from), htSHA256);
     auto info = make_ref<ValidPathInfo>(path, narHash);
     if (deriver != "") info->deriver = parseStorePath(deriver);
-    info->references = WorkerProto<StorePathSet>::read(*this, conn->from);
+    info->references = worker_proto::read(*this, conn->from, Phantom<StorePathSet> {});
     conn->from >> info->registrationTime >> info->narSize;
     if (GET_PROTOCOL_MINOR(conn->daemonVersion) >= 16) {
         conn->from >> info->ultimate;
@@ -460,7 +464,7 @@ void RemoteStore::queryReferrers(const StorePath & path,
     auto conn(getConnection());
     conn->to << wopQueryReferrers << printStorePath(path);
     conn.processStderr();
-    for (auto & i : WorkerProto<StorePathSet>::read(*this, conn->from))
+    for (auto & i : worker_proto::read(*this, conn->from, Phantom<StorePathSet> {}))
         referrers.insert(i);
 }
 
@@ -470,7 +474,7 @@ StorePathSet RemoteStore::queryValidDerivers(const StorePath & path)
     auto conn(getConnection());
     conn->to << wopQueryValidDerivers << printStorePath(path);
     conn.processStderr();
-    return WorkerProto<StorePathSet>::read(*this, conn->from);
+    return worker_proto::read(*this, conn->from, Phantom<StorePathSet> {});
 }
 
 
@@ -482,7 +486,7 @@ StorePathSet RemoteStore::queryDerivationOutputs(const StorePath & path)
     }
     conn->to << wopQueryDerivationOutputs << printStorePath(path);
     conn.processStderr();
-    return WorkerProto<StorePathSet>::read(*this, conn->from);
+    return worker_proto::read(*this, conn->from, Phantom<StorePathSet> {});
 }
 
 
@@ -492,7 +496,7 @@ std::map<std::string, std::optional<StorePath>> RemoteStore::queryPartialDerivat
         auto conn(getConnection());
         conn->to << wopQueryDerivationOutputMap << printStorePath(path);
         conn.processStderr();
-        return WorkerProto<std::map<std::string, std::optional<StorePath>>>::read(*this, conn->from);
+        return worker_proto::read(*this, conn->from, Phantom<std::map<std::string, std::optional<StorePath>>> {});
     } else {
         // Fallback for old daemon versions.
         // For floating-CA derivations (and their co-dependencies) this is an
@@ -537,7 +541,7 @@ ref<const ValidPathInfo> RemoteStore::addCAToStore(
             << wopAddToStore
             << name
             << renderContentAddressMethod(caMethod);
-        WorkerProto<StorePathSet>::write(*this, conn->to, references);
+        worker_proto::write(*this, conn->to, references);
         conn->to << repair;
 
         conn.withFramedSink([&](Sink & sink) {
@@ -554,7 +558,7 @@ ref<const ValidPathInfo> RemoteStore::addCAToStore(
             [&](TextHashMethod thm) -> void {
                 std::string s = dump.drain();
                 conn->to << wopAddTextToStore << name << s;
-                WorkerProto<StorePathSet>::write(*this, conn->to, references);
+                worker_proto::write(*this, conn->to, references);
                 conn.processStderr();
             },
             [&](FixedOutputHashMethod fohm) -> void {
@@ -623,7 +627,7 @@ void RemoteStore::addToStore(const ValidPathInfo & info, Source & source,
             sink
                 << exportMagic
                 << printStorePath(info.path);
-            WorkerProto<StorePathSet>::write(*this, sink, info.references);
+            worker_proto::write(*this, sink, info.references);
             sink
                 << (info.deriver ? printStorePath(*info.deriver) : "")
                 << 0 // == no legacy signature
@@ -633,7 +637,7 @@ void RemoteStore::addToStore(const ValidPathInfo & info, Source & source,
 
         conn.processStderr(0, source2.get());
 
-        auto importedPaths = WorkerProto<StorePathSet>::read(*this, conn->from);
+        auto importedPaths = worker_proto::read(*this, conn->from, Phantom<StorePathSet> {});
         assert(importedPaths.size() <= 1);
     }
 
@@ -642,7 +646,7 @@ void RemoteStore::addToStore(const ValidPathInfo & info, Source & source,
                  << printStorePath(info.path)
                  << (info.deriver ? printStorePath(*info.deriver) : "")
                  << info.narHash.to_string(Base16, false);
-        WorkerProto<StorePathSet>::write(*this, conn->to, info.references);
+        worker_proto::write(*this, conn->to, info.references);
         conn->to << info.registrationTime << info.narSize
                  << info.ultimate << info.sigs << renderContentAddress(info.ca)
                  << repair << !checkSigs;
@@ -764,7 +768,7 @@ void RemoteStore::collectGarbage(const GCOptions & options, GCResults & results)
 
     conn->to
         << wopCollectGarbage << options.action;
-    WorkerProto<StorePathSet>::write(*this, conn->to, options.pathsToDelete);
+    worker_proto::write(*this, conn->to, options.pathsToDelete);
     conn->to << options.ignoreLiveness
         << options.maxFreed
         /* removed options */
@@ -826,9 +830,9 @@ void RemoteStore::queryMissing(const std::vector<StorePathWithOutputs> & targets
             ss.push_back(p.to_string(*this));
         conn->to << ss;
         conn.processStderr();
-        willBuild = WorkerProto<StorePathSet>::read(*this, conn->from);
-        willSubstitute = WorkerProto<StorePathSet>::read(*this, conn->from);
-        unknown = WorkerProto<StorePathSet>::read(*this, conn->from);
+        willBuild = worker_proto::read(*this, conn->from, Phantom<StorePathSet> {});
+        willSubstitute = worker_proto::read(*this, conn->from, Phantom<StorePathSet> {});
+        unknown = worker_proto::read(*this, conn->from, Phantom<StorePathSet> {});
         conn->from >> downloadSize >> narSize;
         return;
     }
diff --git a/src/libstore/worker-protocol.hh b/src/libstore/worker-protocol.hh
index bb87cf3ec..fd6c2b2cf 100644
--- a/src/libstore/worker-protocol.hh
+++ b/src/libstore/worker-protocol.hh
@@ -66,96 +66,95 @@ typedef enum {
 class Store;
 struct Source;
 
+/* To guide overloading */
 template<typename T>
-struct WorkerProto {
-    static T read(const Store & store, Source & from);
-    static void write(const Store & store, Sink & out, const T & t);
-};
-
-#define MAKE_WORKER_PROTO(T) \
-    template<> \
-    struct WorkerProto< T > { \
-        static T read(const Store & store, Source & from); \
-        static void write(const Store & store, Sink & out, const T & t); \
-    }
+struct Phantom {};
+
+
+namespace worker_proto {
+/* FIXME maybe move more stuff inside here */
+
+#define MAKE_WORKER_PROTO(TEMPLATE, T) \
+    TEMPLATE T read(const Store & store, Source & from, Phantom< T > _); \
+    TEMPLATE void write(const Store & store, Sink & out, const T & str)
+
+MAKE_WORKER_PROTO(, std::string);
+MAKE_WORKER_PROTO(, StorePath);
+MAKE_WORKER_PROTO(, ContentAddress);
+
+MAKE_WORKER_PROTO(template<typename T>, std::set<T>);
+MAKE_WORKER_PROTO(template<typename T>, std::optional<T>);
 
-MAKE_WORKER_PROTO(std::string);
-MAKE_WORKER_PROTO(StorePath);
-MAKE_WORKER_PROTO(ContentAddress);
+#define X_ template<typename K, typename V>
+#define Y_ std::map<K, V>
+MAKE_WORKER_PROTO(X_, Y_);
+#undef X_
+#undef Y_
 
 template<typename T>
-struct WorkerProto<std::set<T>> {
-
-    static std::set<T> read(const Store & store, Source & from)
-    {
-        std::set<T> resSet;
-        auto size = readNum<size_t>(from);
-        while (size--) {
-            resSet.insert(WorkerProto<T>::read(store, from));
-        }
-        return resSet;
+std::set<T> read(const Store & store, Source & from, Phantom<std::set<T>> _)
+{
+    std::set<T> resSet;
+    auto size = readNum<size_t>(from);
+    while (size--) {
+        resSet.insert(read(store, from, Phantom<T> {}));
     }
+    return resSet;
+}
 
-    static void write(const Store & store, Sink & out, const std::set<T> & resSet)
-    {
-        out << resSet.size();
-        for (auto & key : resSet) {
-            WorkerProto<T>::write(store, out, key);
-        }
+template<typename T>
+void write(const Store & store, Sink & out, const std::set<T> & resSet)
+{
+    out << resSet.size();
+    for (auto & key : resSet) {
+        write(store, out, key);
     }
-
-};
+}
 
 template<typename K, typename V>
-struct WorkerProto<std::map<K, V>> {
-
-    static std::map<K, V> read(const Store & store, Source & from)
-    {
-        std::map<K, V> resMap;
-        auto size = readNum<size_t>(from);
-        while (size--) {
-            auto k = WorkerProto<K>::read(store, from);
-            auto v = WorkerProto<V>::read(store, from);
-            resMap.insert_or_assign(std::move(k), std::move(v));
-        }
-        return resMap;
+std::map<K, V> read(const Store & store, Source & from, Phantom<std::map<K, V>> _)
+{
+    std::map<K, V> resMap;
+    auto size = readNum<size_t>(from);
+    while (size--) {
+        auto k = read(store, from, Phantom<K> {});
+        auto v = read(store, from, Phantom<V> {});
+        resMap.insert_or_assign(std::move(k), std::move(v));
     }
+    return resMap;
+}
 
-    static void write(const Store & store, Sink & out, const std::map<K, V> & resMap)
-    {
-        out << resMap.size();
-        for (auto & i : resMap) {
-            WorkerProto<K>::write(store, out, i.first);
-            WorkerProto<V>::write(store, out, i.second);
-        }
+template<typename K, typename V>
+void write(const Store & store, Sink & out, const std::map<K, V> & resMap)
+{
+    out << resMap.size();
+    for (auto & i : resMap) {
+        write(store, out, i.first);
+        write(store, out, i.second);
     }
-
-};
+}
 
 template<typename T>
-struct WorkerProto<std::optional<T>> {
-
-    static std::optional<T> read(const Store & store, Source & from)
-    {
-        auto tag = readNum<uint8_t>(from);
-        switch (tag) {
-        case 0:
-            return std::nullopt;
-        case 1:
-            return WorkerProto<T>::read(store, from);
-        default:
-            throw Error("got an invalid tag bit for std::optional: %#04x", (size_t)tag);
-        }
-    }
-
-    static void write(const Store & store, Sink & out, const std::optional<T> & optVal)
-    {
-        out << (uint64_t) (optVal ? 1 : 0);
-        if (optVal)
-            WorkerProto<T>::write(store, out, *optVal);
+std::optional<T> read(const Store & store, Source & from, Phantom<std::optional<T>> _)
+{
+    auto tag = readNum<uint8_t>(from);
+    switch (tag) {
+    case 0:
+        return std::nullopt;
+    case 1:
+        return read(store, from, Phantom<T> {});
+    default:
+        throw Error("got an invalid tag bit for std::optional: %#04x", (size_t)tag);
     }
+}
 
-};
+template<typename T>
+void write(const Store & store, Sink & out, const std::optional<T> & optVal)
+{
+    out << (uint64_t) (optVal ? 1 : 0);
+    if (optVal)
+        nix::worker_proto::write(store, out, *optVal);
+}
 
 /* Specialization which uses and empty string for the empty case, taking
    advantage of the fact these types always serialize to non-empty strings.
@@ -163,7 +162,9 @@ struct WorkerProto<std::optional<T>> {
    std::optional<T>, where <= is the compatability partial order, T is one of
    the types below.
  */
-MAKE_WORKER_PROTO(std::optional<StorePath>);
-MAKE_WORKER_PROTO(std::optional<ContentAddress>);
+MAKE_WORKER_PROTO(, std::optional<StorePath>);
+MAKE_WORKER_PROTO(, std::optional<ContentAddress>);
+
+}
 
 }
diff --git a/src/nix-store/nix-store.cc b/src/nix-store/nix-store.cc
index 141dab478..4dcdebe2f 100644
--- a/src/nix-store/nix-store.cc
+++ b/src/nix-store/nix-store.cc
@@ -822,7 +822,7 @@ static void opServe(Strings opFlags, Strings opArgs)
             case cmdQueryValidPaths: {
                 bool lock = readInt(in);
                 bool substitute = readInt(in);
-                auto paths = WorkerProto<StorePathSet>::read(*store, in);
+                auto paths = nix::worker_proto::read(*store, in, Phantom<StorePathSet> {});
                 if (lock && writeAllowed)
                     for (auto & path : paths)
                         store->addTempRoot(path);
@@ -852,19 +852,19 @@ static void opServe(Strings opFlags, Strings opArgs)
                         }
                 }
 
-                WorkerProto<StorePathSet>::write(*store, out, store->queryValidPaths(paths));
+                nix::worker_proto::write(*store, out, store->queryValidPaths(paths));
                 break;
             }
 
             case cmdQueryPathInfos: {
-                auto paths = WorkerProto<StorePathSet>::read(*store, in);
+                auto paths = nix::worker_proto::read(*store, in, Phantom<StorePathSet> {});
                 // !!! Maybe we want a queryPathInfos?
                 for (auto & i : paths) {
                     try {
                         auto info = store->queryPathInfo(i);
                         out << store->printStorePath(info->path)
                             << (info->deriver ? store->printStorePath(*info->deriver) : "");
-                        WorkerProto<StorePathSet>::write(*store, out, info->references);
+                        nix::worker_proto::write(*store, out, info->references);
                         // !!! Maybe we want compression?
                         out << info->narSize // downloadSize
                             << info->narSize;
@@ -892,7 +892,7 @@ static void opServe(Strings opFlags, Strings opArgs)
 
             case cmdExportPaths: {
                 readInt(in); // obsolete
-                store->exportPaths(WorkerProto<StorePathSet>::read(*store, in), out);
+                store->exportPaths(nix::worker_proto::read(*store, in, Phantom<StorePathSet> {}), out);
                 break;
             }
 
@@ -941,9 +941,9 @@ static void opServe(Strings opFlags, Strings opArgs)
             case cmdQueryClosure: {
                 bool includeOutputs = readInt(in);
                 StorePathSet closure;
-                store->computeFSClosure(WorkerProto<StorePathSet>::read(*store, in),
+                store->computeFSClosure(nix::worker_proto::read(*store, in, Phantom<StorePathSet> {}),
                     closure, false, includeOutputs);
-                WorkerProto<StorePathSet>::write(*store, out, closure);
+                nix::worker_proto::write(*store, out, closure);
                 break;
             }
 
@@ -958,7 +958,7 @@ static void opServe(Strings opFlags, Strings opArgs)
                 };
                 if (deriver != "")
                     info.deriver = store->parseStorePath(deriver);
-                info.references = WorkerProto<StorePathSet>::read(*store, in);
+                info.references = nix::worker_proto::read(*store, in, Phantom<StorePathSet> {});
                 in >> info.registrationTime >> info.narSize >> info.ultimate;
                 info.sigs = readStrings<StringSet>(in);
                 info.ca = parseContentAddressOpt(readString(in));