src/build-remote/build-remote.cc

@@ -1,11 +1,7 @@
-#include <cstdlib>
-#include <cstring>
 #include <algorithm>
 #include <set>
 #include <memory>
-#include <string_view>
 #include <tuple>
-#include <iomanip>
 #if __APPLE__
 #include <sys/time.h>
 #endif
@@ -18,6 +14,7 @@
 #include "build-result.hh"
 #include "store-api.hh"
 #include "derivations.hh"
+#include "strings.hh"
 #include "local-store.hh"
 #include "legacy.hh"
 #include "experimental-features.hh"

src/libcmd/editor-for.cc

@@ -1,6 +1,7 @@
 #include "editor-for.hh"
 #include "environment-variables.hh"
 #include "source-path.hh"
+#include "strings.hh"
 
 namespace nix {
 

src/libexpr/eval.cc

@@ -19,6 +19,7 @@
 #include "gc-small-vector.hh"
 #include "fetch-to-store.hh"
 #include "flake/flakeref.hh"
+#include "exit.hh"
 
 #include <algorithm>
 #include <iostream>

src/libexpr/eval.hh

@@ -12,6 +12,7 @@
 #include "experimental-features.hh"
 #include "search-path.hh"
 #include "repl-exit-status.hh"
+#include "backed-string-view.hh"
 
 #include <map>
 #include <optional>
@@ -791,4 +792,4 @@ static constexpr std::string_view corepkgsPrefix{"/__corepkgs__/"};
 
 }
 
-#include "eval-inline.hh"
+#include "eval-inline.hh" // IWYU pragma: keep

src/libexpr/nixexpr.hh

@@ -11,6 +11,7 @@
 #include "eval-error.hh"
 #include "pos-idx.hh"
 #include "pos-table.hh"
+#include "strings.hh"
 
 namespace nix {
 

src/libfetchers/fetchers.hh

@@ -7,6 +7,8 @@
 #include "path.hh"
 #include "attrs.hh"
 #include "url.hh"
+#include "ref.hh"
+#include "strings.hh"
 
 #include <memory>
 

src/libmain/progress-bar.cc

@@ -1,8 +1,9 @@
 #include "progress-bar.hh"
+#include "file-system.hh"
 #include "sync.hh"
-#include "store-api.hh"
 #include "names.hh"
 #include "terminal.hh"
+#include "strings.hh"
 
 #include <map>
 #include <thread>

src/libmain/shared.cc

@@ -6,6 +6,8 @@
 #include "loggers.hh"
 #include "current-process.hh"
 #include "terminal.hh"
+#include "strings.hh"
+#include "exit.hh"
 
 #include <algorithm>
 #include <exception>

src/libmain/shared.hh

@@ -7,12 +7,10 @@
 #include "path.hh"
 #include "derived-path.hh"
 #include "processes.hh"
-#include "exit.hh"
+#include "strings.hh"
 
 #include <signal.h>
 
-#include <locale>
-
 
 namespace nix {
 

src/libstore/binary-cache-store.cc

@@ -10,6 +10,7 @@
 #include "nar-accessor.hh"
 #include "thread-pool.hh"
 #include "signals.hh"
+#include "strings.hh"
 
 #include <chrono>
 #include <regex>

src/libstore/build/derivation-goal.cc

@@ -9,6 +9,7 @@
 #include "logging-json.hh"
 #include "substitution-goal.hh"
 #include "drv-output-substitution-goal.hh"
+#include "strings.hh"
 
 #include <fstream>
 #include <sys/types.h>

src/libstore/build/entry-points.cc

@@ -2,6 +2,7 @@
 #include "substitution-goal.hh"
 #include "derivation-goal.hh"
 #include "local-store.hh"
+#include "strings.hh"
 
 namespace nix {
 

src/libstore/build/hook-instance.cc

@@ -2,6 +2,7 @@
 #include "file-system.hh"
 #include "globals.hh"
 #include "hook-instance.hh"
+#include "strings.hh"
 
 namespace nix {
 

src/libstore/build/local-derivation-goal.cc

@@ -1,15 +1,12 @@
 #include "local-derivation-goal.hh"
 #include "indirect-root-store.hh"
-#include "hook-instance.hh"
 #include "machines.hh"
 #include "store-api.hh"
 #include "worker.hh"
 #include "builtins.hh"
 #include "builtins/buildenv.hh"
 #include "path-references.hh"
-#include "finally.hh"
 #include "archive.hh"
-#include "compression.hh"
 #include "daemon.hh"
 #include "topo-sort.hh"
 #include "json-utils.hh"
@@ -19,6 +16,7 @@
 #include "child.hh"
 #include "unix-domain-socket.hh"
 #include "mount.hh"
+#include "strings.hh"
 
 #include <regex>
 #include <queue>

src/libstore/builtins/buildenv.cc

@@ -1,4 +1,5 @@
 #include "buildenv.hh"
+#include "strings.hh"
 
 #include <sys/stat.h>
 #include <sys/types.h>

src/libstore/builtins/fetchurl.cc

@@ -3,6 +3,7 @@
 #include "store-api.hh"
 #include "archive.hh"
 #include "compression.hh"
+#include "strings.hh"
 
 namespace nix {
 

src/libstore/content-address.cc

@@ -1,6 +1,7 @@
 #include "args.hh"
 #include "content-address.hh"
 #include "split.hh"
+#include "strings.hh"
 
 namespace nix {
 

src/libstore/daemon.cc

@@ -2,7 +2,7 @@
 #include "monitor-fd.hh"
 #include "worker-protocol.hh"
 #include "worker-protocol-impl.hh"
-#include "build-result.hh"
+#include "build-result.hh" // IWYU pragma: keep
 #include "store-api.hh"
 #include "store-cast.hh"
 #include "gc-store.hh"
@@ -12,6 +12,7 @@
 #include "finally.hh"
 #include "archive.hh"
 #include "derivations.hh"
+#include "strings.hh"
 #include "args.hh"
 
 #include <sstream>

src/libstore/derivations.cc

@@ -3,11 +3,12 @@
 #include "store-api.hh"
 #include "globals.hh"
 #include "types.hh"
-#include "split.hh"
 #include "common-protocol.hh"
 #include "common-protocol-impl.hh"
-#include "fs-accessor.hh"
 #include "json-utils.hh"
+#include "strings.hh"
+#include "backed-string-view.hh"
+
 #include <boost/container/small_vector.hpp>
 #include <nlohmann/json.hpp>
 

src/libstore/derived-path.hh

@@ -5,6 +5,7 @@
 #include "path.hh"
 #include "outputs-spec.hh"
 #include "comparator.hh"
+#include "ref.hh"
 
 #include <variant>
 

src/libstore/filetransfer.cc

@@ -5,6 +5,7 @@
 #include "s3.hh"
 #include "signals.hh"
 #include "compression.hh"
+#include "strings.hh"
 
 #if ENABLE_S3
 #include <aws/core/client/ClientConfiguration.h>

src/libstore/filetransfer.hh

@@ -2,6 +2,7 @@
 ///@file
 
 #include "box_ptr.hh"
+#include "ref.hh"
 #include "logging.hh"
 #include "serialise.hh"
 #include "types.hh"

src/libstore/gc.cc

@@ -5,6 +5,7 @@
 #include "signals.hh"
 #include "finally.hh"
 #include "unix-domain-socket.hh"
+#include "strings.hh"
 
 #include <queue>
 #include <regex>

src/libstore/legacy-ssh-store.cc

@@ -9,6 +9,7 @@
 #include "path-with-outputs.hh"
 #include "ssh.hh"
 #include "ssh-store.hh"
+#include "strings.hh"
 #include "derivations.hh"
 
 namespace nix {

src/libstore/local-store.cc

@@ -10,6 +10,7 @@
 #include "signals.hh"
 #include "finally.hh"
 #include "compression.hh"
+#include "strings.hh"
 
 #include <algorithm>
 #include <cstring>

src/libstore/lock.hh

@@ -1,11 +1,10 @@
 #pragma once
 ///@file
 
-#include "types.hh"
-
-#include <optional>
+#include <memory>
 
 #include <sys/types.h>
+#include <vector>
 
 namespace nix {
 

src/libstore/machines.hh

@@ -1,7 +1,9 @@
 #pragma once
 ///@file
 
-#include "types.hh"
+#include "ref.hh"
+#include <set>
+#include <vector>
 
 namespace nix {
 

src/libstore/make-content-addressed.cc

@@ -1,5 +1,6 @@
 #include "make-content-addressed.hh"
 #include "references.hh"
+#include "strings.hh"
 
 namespace nix {
 

src/libstore/misc.cc

@@ -1,12 +1,12 @@
 #include "derivations.hh"
 #include "parsed-derivations.hh"
 #include "globals.hh"
-#include "local-store.hh"
 #include "store-api.hh"
 #include "thread-pool.hh"
 #include "topo-sort.hh"
 #include "closure.hh"
 #include "filetransfer.hh"
+#include "strings.hh"
 
 namespace nix {
 

src/libstore/nar-accessor.hh

@@ -1,10 +1,12 @@
 #pragma once
 ///@file
 
+#include "fs-accessor.hh"
+#include "ref.hh"
+
 #include <functional>
 
 #include <nlohmann/json_fwd.hpp>
-#include "fs-accessor.hh"
 
 namespace nix {
 

src/libstore/nar-info-disk-cache.cc

@@ -4,6 +4,7 @@
 #include "sqlite.hh"
 #include "globals.hh"
 #include "users.hh"
+#include "strings.hh"
 
 #include <sqlite3.h>
 #include <nlohmann/json.hpp>

src/libstore/nar-info.cc

@@ -1,4 +1,4 @@
-#include "globals.hh"
+#include "strings.hh"
 #include "nar-info.hh"
 #include "store-api.hh"
 

src/libstore/optimise-store.cc

@@ -1,6 +1,7 @@
 #include "local-store.hh"
 #include "globals.hh"
 #include "signals.hh"
+#include "strings.hh"
 
 #include <cstring>
 #include <sys/types.h>

src/libstore/parsed-derivations.cc

@@ -1,4 +1,5 @@
 #include "parsed-derivations.hh"
+#include "strings.hh"
 
 #include <nlohmann/json.hpp>
 #include <regex>

src/libstore/path-info.cc

@@ -1,5 +1,6 @@
 #include "path-info.hh"
 #include "store-api.hh"
+#include "strings.hh"
 
 namespace nix {
 

src/libstore/path-with-outputs.cc

@@ -1,7 +1,6 @@
 #include "path-with-outputs.hh"
 #include "store-api.hh"
-
-#include <regex>
+#include "strings.hh"
 
 namespace nix {
 

src/libstore/platform/darwin.cc

@@ -2,6 +2,7 @@
 #include "signals.hh"
 #include "platform/darwin.hh"
 #include "regex.hh"
+#include "strings.hh"
 
 #include <sys/proc_info.h>
 #include <sys/sysctl.h>

src/libstore/platform/linux.cc

@@ -5,6 +5,7 @@
 #include "signals.hh"
 #include "platform/linux.hh"
 #include "regex.hh"
+#include "strings.hh"
 
 #include <grp.h>
 #include <regex>

src/libstore/profiles.cc

@@ -1,12 +1,11 @@
 #include "profiles.hh"
-#include "store-api.hh"
 #include "local-fs-store.hh"
 #include "users.hh"
+#include "strings.hh"
 
 #include <sys/types.h>
 #include <sys/stat.h>
 #include <unistd.h>
-#include <errno.h>
 #include <stdio.h>
 
 

src/libstore/remote-store.cc

@@ -15,6 +15,8 @@
 #include "finally.hh"
 #include "logging.hh"
 #include "filetransfer.hh"
+#include "strings.hh"
+
 #include <nlohmann/json.hpp>
 
 namespace nix {
@@ -64,7 +66,7 @@ void RemoteStore::initConnection(Connection & conn)
 {
     /* Send the magic greeting, check for the reply. */
     try {
-        conn.from.endOfFileError = "Nix daemon disconnected unexpectedly (maybe it crashed?)";
+        conn.from.specialEndOfFileError = "Nix daemon disconnected unexpectedly (maybe it crashed?)";
         conn.to << WORKER_MAGIC_1;
         conn.to.flush();
 

src/libstore/s3-binary-cache-store.cc

@@ -7,6 +7,7 @@
 #include "globals.hh"
 #include "compression.hh"
 #include "filetransfer.hh"
+#include "strings.hh"
 
 #include <aws/core/Aws.h>
 #include <aws/core/VersionConfig.h>

src/libstore/ssh-store.cc

@@ -1,13 +1,11 @@
 #include "ssh-store.hh"
 #include "store-api.hh"
-#include "local-fs-store.hh"
 #include "remote-store.hh"
 #include "remote-store-connection.hh"
-#include "remote-fs-accessor.hh"
-#include "archive.hh"
 #include "worker-protocol.hh"
 #include "pool.hh"
 #include "ssh.hh"
+#include "strings.hh"
 
 namespace nix {
 

src/libstore/store-api.cc

@@ -5,10 +5,10 @@
 #include "nar-info-disk-cache.hh"
 #include "thread-pool.hh"
 #include "url.hh"
-#include "references.hh"
 #include "archive.hh"
-#include "remote-store.hh"
+#include "uds-remote-store.hh"
 #include "signals.hh"
+#include "strings.hh"
 // FIXME this should not be here, see TODO below on
 // `addMultipleToStore`.
 #include "worker-protocol.hh"

src/libutil/args.cc

@@ -1,10 +1,11 @@
 #include "args.hh"
 #include "args/root.hh"
 #include "hash.hh"
-#include "json-utils.hh"
+#include "strings.hh"
+#include "json-utils.hh" // IWYU pragma: keep (instances)
 #include "environment-variables.hh"
 
-#include "experimental-features-json.hh"
+#include "experimental-features-json.hh" // IWYU pragma: keep (instances)
 #include "logging.hh"
 
 #include <glob.h>

src/libutil/args.hh

@@ -3,6 +3,8 @@
 
 #include "experimental-features.hh"
 #include "types.hh"
+#include "ref.hh"
+
 #include <functional>
 #include <map>
 #include <memory>

src/libutil/backed-string-view.hh

@@ -0,0 +1,69 @@
+#pragma once
+/// @file String view that can be either owned or borrowed.
+#include <variant>
+#include <string>
+#include <string_view>
+
+/**
+ * This wants to be a little bit like rust's Cow type.
+ * Some parts of the evaluator benefit greatly from being able to reuse
+ * existing allocations for strings, but have to be able to also use
+ * newly allocated storage for values.
+ *
+ * We do not define implicit conversions, even with ref qualifiers,
+ * since those can easily become ambiguous to the reader and can degrade
+ * into copying behaviour we want to avoid.
+ */
+class BackedStringView {
+private:
+    std::variant<std::string, std::string_view> data;
+
+    /**
+     * Needed to introduce a temporary since operator-> must return
+     * a pointer. Without this we'd need to store the view object
+     * even when we already own a string.
+     */
+    class Ptr {
+    private:
+        std::string_view view;
+    public:
+        Ptr(std::string_view view): view(view) {}
+        const std::string_view * operator->() const { return &view; }
+    };
+
+public:
+    BackedStringView(std::string && s): data(std::move(s)) {}
+    BackedStringView(std::string_view sv): data(sv) {}
+    template<size_t N>
+    BackedStringView(const char (& lit)[N]): data(std::string_view(lit)) {}
+
+    BackedStringView(const BackedStringView &) = delete;
+    BackedStringView & operator=(const BackedStringView &) = delete;
+
+    /**
+     * We only want move operations defined since the sole purpose of
+     * this type is to avoid copies.
+     */
+    BackedStringView(BackedStringView && other) = default;
+    BackedStringView & operator=(BackedStringView && other) = default;
+
+    bool isOwned() const
+    {
+        return std::holds_alternative<std::string>(data);
+    }
+
+    std::string toOwned() &&
+    {
+        return isOwned()
+            ? std::move(std::get<std::string>(data))
+            : std::string(std::get<std::string_view>(data));
+    }
+
+    std::string_view operator*() const
+    {
+        return isOwned()
+            ? std::get<std::string>(data)
+            : std::get<std::string_view>(data);
+    }
+    Ptr operator->() const { return Ptr(**this); }
+};

src/libutil/error.cc

@@ -3,6 +3,7 @@
 #include "logging.hh"
 #include "position.hh"
 #include "terminal.hh"
+#include "strings.hh"
 
 #include <iostream>
 #include <optional>

src/libutil/file-system.cc

@@ -10,6 +10,7 @@
 #include "logging.hh"
 #include "serialise.hh"
 #include "signals.hh"
+#include "strings.hh"
 #include "types.hh"
 #include "users.hh"
 

src/libutil/hash.cc

@@ -10,6 +10,7 @@
 #include "charptr-cast.hh"
 #include "logging.hh"
 #include "split.hh"
+#include "strings.hh"
 
 #include <sys/types.h>
 #include <sys/stat.h>

src/libutil/meson.build

@@ -53,6 +53,7 @@ libutil_headers = files(
   'archive.hh',
   'args/root.hh',
   'args.hh',
+  'backed-string-view.hh',
   'box_ptr.hh',
   'canon-path.hh',
   'cgroup.hh',

src/libutil/processes.cc

@@ -3,6 +3,7 @@
 #include "finally.hh"
 #include "logging.hh"
 #include "processes.hh"
+#include "strings.hh"
 #include "serialise.hh"
 #include "signals.hh"
 

src/libutil/regex.cc

@@ -1,6 +1,9 @@
 #include <string>
 #include <regex>
 
+// Declared as extern in precompiled-headers.hh
+template class std::basic_regex<char>;
+
 namespace nix::regex {
 std::string quoteRegexChars(const std::string & raw)
 {

src/libutil/serialise.cc

@@ -9,6 +9,21 @@
 
 namespace nix {
 
+namespace {
+/**
+ * Convert a little-endian integer to host order.
+ */
+template<typename T>
+T readLittleEndian(unsigned char * p)
+{
+    T x = 0;
+    for (size_t i = 0; i < sizeof(x); ++i, ++p) {
+        x |= ((T) *p) << (i * 8);
+    }
+    return x;
+}
+}
+
 template<typename T>
 T readNum(Source & source)
 {
@@ -152,7 +167,7 @@ size_t FdSource::readUnbuffered(char * data, size_t len)
         n = ::read(fd, data, len);
     } while (n == -1 && errno == EINTR);
     if (n == -1) { _good = false; throw SysError("reading from file"); }
-    if (n == 0) { _good = false; throw EndOfFile(std::string(*endOfFileError)); }
+    if (n == 0) { _good = false; throw EndOfFile(endOfFileError()); }
     read += n;
     return n;
 }
@@ -163,6 +178,11 @@ bool FdSource::good()
     return _good;
 }
 
+std::string FdSource::endOfFileError() const
+{
+    return specialEndOfFileError.has_value() ? *specialEndOfFileError : "unexpected end-of-file";
+}
+
 
 size_t StringSource::read(char * data, size_t len)
 {

src/libutil/serialise.hh

@@ -1,12 +1,10 @@
 #pragma once
 ///@file
 
-#include <concepts>
 #include <memory>
 
 #include "charptr-cast.hh"
 #include "generator.hh"
-#include "strings.hh"
 #include "types.hh"
 #include "file-descriptor.hh"
 
@@ -153,7 +151,10 @@ struct FdSource : BufferedSource
 {
     int fd;
     size_t read = 0;
-    BackedStringView endOfFileError{"unexpected end-of-file"};
+    /** Defaults to "unexpected end-of-file" */
+    std::optional<std::string> specialEndOfFileError;
+
+    std::string endOfFileError() const;
 
     FdSource() : fd(-1) { }
     FdSource(int fd) : fd(fd) { }

src/libutil/source-path.cc

@@ -1,4 +1,5 @@
 #include "source-path.hh"
+#include "strings.hh"
 
 namespace nix {
 

src/libutil/strings.hh

@@ -164,19 +164,6 @@ template<class N>
 std::optional<N> string2Float(const std::string_view s);
 
 
-/**
- * Convert a little-endian integer to host order.
- */
-template<typename T>
-T readLittleEndian(unsigned char * p)
-{
-    T x = 0;
-    for (size_t i = 0; i < sizeof(x); ++i, ++p) {
-        x |= ((T) *p) << (i * 8);
-    }
-    return x;
-}
-
 /**
  * Convert a string to lower case.
  */

src/libutil/types.hh

@@ -1,17 +1,15 @@
 #pragma once
 ///@file
 
-#include "ref.hh"
-
 #include <list>
 #include <optional>
 #include <set>
 #include <string>
-#include <limits>
+#include <string_view>
 #include <map>
-#include <variant>
 #include <vector>
 #include <span>
+#include <stdint.h> // IWYU pragma: keep (this is used literally everywhere)
 
 namespace nix {
 
@@ -166,70 +164,4 @@ constexpr auto enumerate(T && iterable)
 template<class... Ts> struct overloaded : Ts... { using Ts::operator()...; };
 template<class... Ts> overloaded(Ts...) -> overloaded<Ts...>;
 
-
-
-/**
- * This wants to be a little bit like rust's Cow type.
- * Some parts of the evaluator benefit greatly from being able to reuse
- * existing allocations for strings, but have to be able to also use
- * newly allocated storage for values.
- *
- * We do not define implicit conversions, even with ref qualifiers,
- * since those can easily become ambiguous to the reader and can degrade
- * into copying behaviour we want to avoid.
- */
-class BackedStringView {
-private:
-    std::variant<std::string, std::string_view> data;
-
-    /**
-     * Needed to introduce a temporary since operator-> must return
-     * a pointer. Without this we'd need to store the view object
-     * even when we already own a string.
-     */
-    class Ptr {
-    private:
-        std::string_view view;
-    public:
-        Ptr(std::string_view view): view(view) {}
-        const std::string_view * operator->() const { return &view; }
-    };
-
-public:
-    BackedStringView(std::string && s): data(std::move(s)) {}
-    BackedStringView(std::string_view sv): data(sv) {}
-    template<size_t N>
-    BackedStringView(const char (& lit)[N]): data(std::string_view(lit)) {}
-
-    BackedStringView(const BackedStringView &) = delete;
-    BackedStringView & operator=(const BackedStringView &) = delete;
-
-    /**
-     * We only want move operations defined since the sole purpose of
-     * this type is to avoid copies.
-     */
-    BackedStringView(BackedStringView && other) = default;
-    BackedStringView & operator=(BackedStringView && other) = default;
-
-    bool isOwned() const
-    {
-        return std::holds_alternative<std::string>(data);
-    }
-
-    std::string toOwned() &&
-    {
-        return isOwned()
-            ? std::move(std::get<std::string>(data))
-            : std::string(std::get<std::string_view>(data));
-    }
-
-    std::string_view operator*() const
-    {
-        return isOwned()
-            ? std::get<std::string>(data)
-            : std::get<std::string_view>(data);
-    }
-    Ptr operator->() const { return Ptr(**this); }
-};
-
 }

src/nix-store/nix-store.cc

@@ -1,6 +1,7 @@
 #include "archive.hh"
 #include "derivations.hh"
 #include "dotgraph.hh"
+#include "exit.hh"
 #include "globals.hh"
 #include "build-result.hh"
 #include "store-cast.hh"
@@ -17,7 +18,6 @@
 
 #include <iostream>
 #include <algorithm>
-#include <cstdio>
 
 #include <sys/types.h>
 #include <sys/stat.h>

src/nix/doctor.cc

@@ -7,6 +7,7 @@
 #include "store-api.hh"
 #include "local-fs-store.hh"
 #include "worker-protocol.hh"
+#include "exit.hh"
 
 using namespace nix;
 

src/nix/verify.cc

@@ -1,10 +1,9 @@
 #include "command.hh"
 #include "shared.hh"
 #include "store-api.hh"
-#include "sync.hh"
 #include "thread-pool.hh"
 #include "signals.hh"
-#include "references.hh"
+#include "exit.hh"
 
 #include <atomic>
 

src/pch/precompiled-headers.hh

@@ -58,3 +58,19 @@
 #include <unistd.h>
 
 #include <nlohmann/json.hpp>
+
+// This stuff is here to force the compiler to actually apply the extern
+// template directives in all compilation units. To borrow a term, under
+// complex microarchitectural conditions, clang ignores the extern template
+// declaration, as revealed in the profile.
+//
+// In most cases, extern template works fine in the header itself. We don't
+// have any idea why this happens.
+
+// Here because of all the regexes everywhere (it is infeasible to block instantiation everywhere)
+// For some reason this does not actually prevent the instantiation of
+// regex::_M_compile, and the regex compiler (my interpretation of what this is
+// supposed to do is make the template bits out-of-line), but it *does* prevent
+// a bunch of codegen of regex stuff, which seems to save about 30s on-cpu.
+// Instantiated in libutil/regex.cc.
+extern template class std::basic_regex<char>;

tests/unit/libstore/derivation.cc

@@ -1,8 +1,8 @@
 #include <nlohmann/json.hpp>
 #include <gtest/gtest.h>
 
-#include "experimental-features.hh"
 #include "derivations.hh"
+#include "strings.hh"
 
 #include "tests/libstore.hh"
 #include "tests/characterization.hh"

tests/unit/libstore/protocol.hh

@@ -1,6 +1,7 @@
 #include <nlohmann/json.hpp>
 #include <gtest/gtest.h>
 
+#include "strings.hh"
 #include "tests/libstore.hh"
 #include "tests/characterization.hh"
 

tests/unit/libutil/references.cc

@@ -1,4 +1,5 @@
 #include "references.hh"
+#include "strings.hh"
 #include <gtest/gtest.h>
 
 namespace nix {