chore(3p/nix): unvendor tvix 0.1 r/4098

Nothing is using this now, and we'll likely never pick this up again,
but we learned a lot in the process.

Every now and then this breaks in some bizarre way on channel bumps
and it's just a waste of time to maintain that.

Change-Id: Idcf2f5acd4ca7070ce18d7149cbfc0d967dc0a44
Reviewed-on: https://cl.tvl.fyi/c/depot/+/5632
Tested-by: BuildkiteCI
Reviewed-by: sterni <sternenseemann@systemli.org>
Reviewed-by: lukegb <lukegb@tvl.fyi>
Autosubmit: tazjin <tazjin@tvl.su>

1 files changed, 0 insertions, 1878 deletions

diff --git a/third_party/nix/src/libexpr/eval.cc b/third_party/nix/src/libexpr/eval.cc
deleted file mode 100644
index 682ea6483213..000000000000
--- a/third_party/nix/src/libexpr/eval.cc
+++ /dev/null
@@ -1,1878 +0,0 @@
-#include "libexpr/eval.hh"
-
-#include <algorithm>
-#include <chrono>
-#include <cstdint>
-#include <cstring>
-#include <fstream>
-#include <iostream>
-#include <memory>
-#include <new>
-#include <optional>
-#include <variant>
-
-#include <absl/base/call_once.h>
-#include <absl/container/flat_hash_set.h>
-#include <absl/strings/match.h>
-#include <glog/logging.h>
-#include <sys/resource.h>
-#include <sys/time.h>
-#include <unistd.h>
-
-#include "libexpr/eval-inline.hh"
-#include "libexpr/function-trace.hh"
-#include "libexpr/value.hh"
-#include "libstore/derivations.hh"
-#include "libstore/download.hh"
-#include "libstore/globals.hh"
-#include "libstore/store-api.hh"
-#include "libutil/hash.hh"
-#include "libutil/json.hh"
-#include "libutil/util.hh"
-#include "libutil/visitor.hh"
-
-namespace nix {
-namespace {
-
-void ConfigureGc() { /* This function intentionally left blank. */
-}
-
-}  // namespace
-
-namespace expr {
-
-absl::once_flag gc_flag;
-
-void InitGC() { absl::call_once(gc_flag, &ConfigureGc); }
-
-}  // namespace expr
-
-static char* dupString(const char* s) {
-  char* t;
-  t = strdup(s);
-  if (t == nullptr) {
-    throw std::bad_alloc();
-  }
-  return t;
-}
-
-std::shared_ptr<Value*> allocRootValue(Value* v) {
-  return std::make_shared<Value*>(v);
-}
-
-static void printValue(std::ostream& str, std::set<const Value*>& active,
-                       const Value& v) {
-  checkInterrupt();
-
-  if (active.find(&v) != active.end()) {
-    str << "<CYCLE>";
-    return;
-  }
-  active.insert(&v);
-
-  switch (v.type) {
-    case tInt:
-      str << v.integer;
-      break;
-    case tBool:
-      str << (v.boolean ? "true" : "false");
-      break;
-    case tString:
-      str << "\"";
-      for (const char* i = v.string.s; *i != 0; i++) {
-        if (*i == '\"' || *i == '\\') {
-          str << "\\" << *i;
-        } else if (*i == '\n') {
-          str << "\\n";
-        } else if (*i == '\r') {
-          str << "\\r";
-        } else if (*i == '\t') {
-          str << "\\t";
-        } else {
-          str << *i;
-        }
-      }
-      str << "\"";
-      break;
-    case tPath:
-      str << v.path;  // !!! escaping?
-      break;
-    case tNull:
-      str << "null";
-      break;
-    case tAttrs: {
-      str << "{ ";
-      for (const auto& [key, value] : *v.attrs) {
-        str << key << " = ";
-        printValue(str, active, *value.value);
-        str << "; ";
-      }
-      str << "}";
-      break;
-    }
-    case tList:
-      str << "[ ";
-      for (unsigned int n = 0; n < v.listSize(); ++n) {
-        printValue(str, active, *(*v.list)[n]);
-        str << " ";
-      }
-      str << "]";
-      break;
-    case tThunk:
-    case tApp:
-      str << "<CODE>";
-      break;
-    case tLambda:
-      str << "<LAMBDA>";
-      break;
-    case tPrimOp:
-      str << "<PRIMOP>";
-      break;
-    case tPrimOpApp:
-      str << "<PRIMOP-APP>";
-      break;
-    case tFloat:
-      str << v.fpoint;
-      break;
-    default:
-      throw Error(
-          absl::StrCat("invalid value of type ", static_cast<int>(v.type)));
-  }
-
-  active.erase(&v);
-}
-
-std::ostream& operator<<(std::ostream& str, const Value& v) {
-  std::set<const Value*> active;
-  printValue(str, active, v);
-  return str;
-}
-
-const Value* getPrimOp(const Value& v) {
-  const Value* primOp = &v;
-  while (primOp->type == tPrimOpApp) {
-    primOp = primOp->primOpApp.left;
-  }
-  assert(primOp->type == tPrimOp);
-  return primOp;
-}
-
-std::string showType(const Value& v) {
-  switch (v.type) {
-    case tInt:
-      return "an integer";
-    case tBool:
-      return "a boolean";
-    case tString:
-      return v.string.context != nullptr ? "a string with context" : "a string";
-    case tPath:
-      return "a path";
-    case tNull:
-      return "null";
-    case tAttrs:
-      return "a set";
-    case tList:
-      return "a list";
-    case tThunk:
-      return "a thunk";
-    case tApp:
-      return "a function application";
-    case tLambda:
-      return "a function";
-    case tBlackhole:
-      return "a black hole";
-    case tPrimOp:
-      return fmt("the built-in function '%s'", std::string(v.primOp->name));
-    case tPrimOpApp:
-      return fmt("the partially applied built-in function '%s'",
-                 std::string(getPrimOp(v)->primOp->name));
-    case _reserved1:
-      LOG(FATAL) << "attempted to show the type string of the deprecated "
-                    "tExternal value";
-      break;
-    case tFloat:
-      return "a float";
-  }
-  LOG(FATAL)
-      << "attempted to determine the type string of an unknown type number ("
-      << static_cast<int>(v.type) << ")";
-  abort();
-}
-
-static Symbol getName(const AttrName& name, EvalState& state, Env& env) {
-  return std::visit(
-      util::overloaded{[&](const Symbol& name) -> Symbol { return name; },
-                       [&](Expr* expr) -> Symbol {
-                         Value nameValue;
-                         expr->eval(state, env, nameValue);
-                         state.forceStringNoCtx(nameValue);
-                         return state.symbols.Create(nameValue.string.s);
-                       }},
-      name);
-}
-
-/* Very hacky way to parse $NIX_PATH, which is colon-separated, but
-   can contain URLs (e.g. "nixpkgs=https://bla...:foo=https://"). */
-static Strings parseNixPath(const std::string& s) {
-  Strings res;
-
-  auto p = s.begin();
-
-  while (p != s.end()) {
-    auto start = p;
-    auto start2 = p;
-
-    while (p != s.end() && *p != ':') {
-      if (*p == '=') {
-        start2 = p + 1;
-      }
-      ++p;
-    }
-
-    if (p == s.end()) {
-      if (p != start) {
-        res.push_back(std::string(start, p));
-      }
-      break;
-    }
-
-    if (*p == ':') {
-      if (isUri(std::string(start2, s.end()))) {
-        ++p;
-        while (p != s.end() && *p != ':') {
-          ++p;
-        }
-      }
-      res.push_back(std::string(start, p));
-      if (p == s.end()) {
-        break;
-      }
-    }
-
-    ++p;
-  }
-
-  return res;
-}
-
-EvalState::EvalState(const Strings& _searchPath, const ref<Store>& store)
-    : sWith(symbols.Create("<with>")),
-      sOutPath(symbols.Create("outPath")),
-      sDrvPath(symbols.Create("drvPath")),
-      sType(symbols.Create("type")),
-      sMeta(symbols.Create("meta")),
-      sName(symbols.Create("name")),
-      sValue(symbols.Create("value")),
-      sSystem(symbols.Create("system")),
-      sOutputs(symbols.Create("outputs")),
-      sOutputName(symbols.Create("outputName")),
-      sIgnoreNulls(symbols.Create("__ignoreNulls")),
-      sFile(symbols.Create("file")),
-      sLine(symbols.Create("line")),
-      sColumn(symbols.Create("column")),
-      sFunctor(symbols.Create("__functor")),
-      sToString(symbols.Create("__toString")),
-      sRight(symbols.Create("right")),
-      sWrong(symbols.Create("wrong")),
-      sStructuredAttrs(symbols.Create("__structuredAttrs")),
-      sBuilder(symbols.Create("builder")),
-      sArgs(symbols.Create("args")),
-      sOutputHash(symbols.Create("outputHash")),
-      sOutputHashAlgo(symbols.Create("outputHashAlgo")),
-      sOutputHashMode(symbols.Create("outputHashMode")),
-      sDerivationNix(std::nullopt),
-      repair(NoRepair),
-      store(store),
-      baseEnv(allocEnv(128)),
-      staticBaseEnv(false, nullptr) {
-  expr::InitGC();
-
-  countCalls = getEnv("NIX_COUNT_CALLS").value_or("0") != "0";
-
-  /* Initialise the Nix expression search path. */
-  if (!evalSettings.pureEval) {
-    Strings paths = parseNixPath(getEnv("NIX_PATH").value_or(""));
-    for (auto& i : _searchPath) {
-      addToSearchPath(i);
-    }
-    for (auto& i : paths) {
-      addToSearchPath(i);
-    }
-  }
-  addToSearchPath("nix=" +
-                  canonPath(settings.nixDataDir + "/nix/corepkgs", true));
-
-  if (evalSettings.restrictEval || evalSettings.pureEval) {
-    allowedPaths = PathSet();
-
-    for (auto& i : searchPath) {
-      auto r = resolveSearchPathElem(i);
-      if (!r.first) {
-        continue;
-      }
-
-      auto path = r.second;
-
-      if (store->isInStore(r.second)) {
-        PathSet closure;
-        store->computeFSClosure(store->toStorePath(r.second), closure);
-        for (auto& path : closure) {
-          allowedPaths->insert(path);
-        }
-      } else {
-        allowedPaths->insert(r.second);
-      }
-    }
-  }
-
-  createBaseEnv();
-}
-
-EvalState::~EvalState() = default;
-
-Path EvalState::checkSourcePath(const Path& path_) {
-  TraceFileAccess(path_);
-  if (!allowedPaths) {
-    return path_;
-  }
-
-  auto i = resolvedPaths.find(path_);
-  if (i != resolvedPaths.end()) {
-    return i->second;
-  }
-
-  bool found = false;
-
-  /* First canonicalize the path without symlinks, so we make sure an
-   * attacker can't append ../../... to a path that would be in allowedPaths
-   * and thus leak symlink targets.
-   */
-  Path abspath = canonPath(path_);
-
-  for (auto& i : *allowedPaths) {
-    if (isDirOrInDir(abspath, i)) {
-      found = true;
-      break;
-    }
-  }
-
-  if (!found) {
-    throw RestrictedPathError(
-        "access to path '%1%' is forbidden in restricted mode", abspath);
-  }
-
-  /* Resolve symlinks. */
-  DLOG(INFO) << "checking access to '" << abspath << "'";
-  Path path = canonPath(abspath, true);
-
-  for (auto& i : *allowedPaths) {
-    if (isDirOrInDir(path, i)) {
-      resolvedPaths[path_] = path;
-      return path;
-    }
-  }
-
-  throw RestrictedPathError(
-      "access to path '%1%' is forbidden in restricted mode", path);
-}
-
-void EvalState::checkURI(const std::string& uri) {
-  if (!evalSettings.restrictEval) {
-    return;
-  }
-
-  /* 'uri' should be equal to a prefix, or in a subdirectory of a
-     prefix. Thus, the prefix https://github.co does not permit
-     access to https://github.com. Note: this allows 'http://' and
-     'https://' as prefixes for any http/https URI. */
-  for (auto& prefix : evalSettings.allowedUris.get()) {
-    if (uri == prefix ||
-        (uri.size() > prefix.size() && !prefix.empty() &&
-         absl::StartsWith(uri, prefix) &&
-         (prefix[prefix.size() - 1] == '/' || uri[prefix.size()] == '/'))) {
-      return;
-    }
-  }
-
-  /* If the URI is a path, then check it against allowedPaths as
-     well. */
-  if (absl::StartsWith(uri, "/")) {
-    checkSourcePath(uri);
-    return;
-  }
-
-  if (absl::StartsWith(uri, "file://")) {
-    checkSourcePath(std::string(uri, 7));
-    return;
-  }
-
-  throw RestrictedPathError(
-      "access to URI '%s' is forbidden in restricted mode", uri);
-}
-
-Path EvalState::toRealPath(const Path& path, const PathSet& context) {
-  // FIXME: check whether 'path' is in 'context'.
-  return !context.empty() && store->isInStore(path) ? store->toRealPath(path)
-                                                    : path;
-};
-
-Value* EvalState::addConstant(const std::string& name, Value& v) {
-  Value* v2 = allocValue();
-  *v2 = v;
-  staticBaseEnv.vars[symbols.Create(name)] = baseEnvDispl;
-  baseEnv.values[baseEnvDispl++] = v2;
-  std::string name2 =
-      std::string(name, 0, 2) == "__" ? std::string(name, 2) : name;
-  baseEnv.values[0]->attrs->push_back(Attr(symbols.Create(name2), v2));
-  return v2;
-}
-
-Value* EvalState::addPrimOp(const std::string& name, size_t arity,
-                            PrimOpFun primOp) {
-  if (arity == 0) {
-    Value v;
-    primOp(*this, noPos, nullptr, v);
-    return addConstant(name, v);
-  }
-  std::string name2 =
-      std::string(name, 0, 2) == "__" ? std::string(name, 2) : name;
-  Symbol sym = symbols.Create(name2);
-  Value* v = allocValue();
-  v->type = tPrimOp;
-  v->primOp = std::make_shared<PrimOp>(primOp, arity, sym);
-  staticBaseEnv.vars[symbols.Create(name)] = baseEnvDispl;
-  baseEnv.values[baseEnvDispl++] = v;
-  baseEnv.values[0]->attrs->push_back(Attr(sym, v));
-  return v;
-}
-
-Value& EvalState::getBuiltin(const std::string& name) {
-  return *baseEnv.values[0]->attrs->find(symbols.Create(name))->second.value;
-}
-
-/* Every "format" object (even temporary) takes up a few hundred bytes
-   of stack space, which is a real killer in the recursive
-   evaluator.  So here are some helper functions for throwing
-   exceptions. */
-
-LocalNoInlineNoReturn(void throwEvalError(const char* s,
-                                          const std::string& s2)) {
-  throw EvalError(format(s) % s2);
-}
-
-LocalNoInlineNoReturn(void throwEvalError(const char* s, const std::string& s2,
-                                          const Pos& pos)) {
-  throw EvalError(format(s) % s2 % pos);
-}
-
-LocalNoInlineNoReturn(void throwEvalError(const char* s, const std::string& s2,
-                                          const std::string& s3)) {
-  throw EvalError(format(s) % s2 % s3);
-}
-
-LocalNoInlineNoReturn(void throwEvalError(const char* s, const std::string& s2,
-                                          const std::string& s3,
-                                          const Pos& pos)) {
-  throw EvalError(format(s) % s2 % s3 % pos);
-}
-
-LocalNoInlineNoReturn(void throwEvalError(const char* s, const Symbol& sym,
-                                          const Pos& p1, const Pos& p2)) {
-  throw EvalError(format(s) % sym % p1 % p2);
-}
-
-LocalNoInlineNoReturn(void throwTypeError(const char* s, const Pos& pos)) {
-  throw TypeError(format(s) % pos);
-}
-
-LocalNoInlineNoReturn(void throwTypeError(const char* s,
-                                          const std::string& s1)) {
-  throw TypeError(format(s) % s1);
-}
-
-LocalNoInlineNoReturn(void throwTypeError(const char* s, const ExprLambda& fun,
-                                          const Symbol& s2, const Pos& pos)) {
-  throw TypeError(format(s) % fun.showNamePos() % s2 % pos);
-}
-
-LocalNoInlineNoReturn(void throwAssertionError(const char* s,
-                                               const std::string& s1,
-                                               const Pos& pos)) {
-  throw AssertionError(format(s) % s1 % pos);
-}
-
-LocalNoInlineNoReturn(void throwUndefinedVarError(const char* s,
-                                                  const std::string& s1,
-                                                  const Pos& pos)) {
-  throw UndefinedVarError(format(s) % s1 % pos);
-}
-
-LocalNoInline(void addErrorPrefix(Error& e, const char* s,
-                                  const std::string& s2)) {
-  e.addPrefix(format(s) % s2);
-}
-
-LocalNoInline(void addErrorPrefix(Error& e, const char* s,
-                                  const ExprLambda& fun, const Pos& pos)) {
-  e.addPrefix(format(s) % fun.showNamePos() % pos);
-}
-
-LocalNoInline(void addErrorPrefix(Error& e, const char* s,
-                                  const std::string& s2, const Pos& pos)) {
-  e.addPrefix(format(s) % s2 % pos);
-}
-
-void mkString(Value& v, const char* s) { mkStringNoCopy(v, dupString(s)); }
-
-Value& mkString(Value& v, const std::string& s, const PathSet& context) {
-  mkString(v, s.c_str());
-  if (!context.empty()) {
-    size_t n = 0;
-    v.string.context = static_cast<const char**>(
-        allocBytes((context.size() + 1) * sizeof(char*)));
-    for (auto& i : context) {
-      v.string.context[n++] = dupString(i.c_str());
-    }
-    v.string.context[n] = nullptr;
-  }
-  return v;
-}
-
-void mkPath(Value& v, const char* s) { mkPathNoCopy(v, dupString(s)); }
-
-inline Value* EvalState::lookupVar(Env* env, const ExprVar& var, bool noEval) {
-  for (size_t l = var.level; l != 0u; --l, env = env->up) {
-    ;
-  }
-
-  if (!var.fromWith) {
-    return env->values[var.displ];
-  }
-
-  while (true) {
-    if (env->type == Env::HasWithExpr) {
-      if (noEval) {
-        return nullptr;
-      }
-      if (!env->withAttrsExpr) {
-        CHECK(false) << "HasWithExpr evaluated twice";
-      }
-      Value* v = allocValue();
-      evalAttrs(*env->up, env->withAttrsExpr, *v);
-      env->values[0] = v;
-      env->withAttrsExpr = nullptr;
-      env->type = Env::HasWithAttrs;
-    }
-    Bindings::iterator j = env->values[0]->attrs->find(var.name);
-    if (j != env->values[0]->attrs->end()) {
-      if (countCalls && (j->second.pos != nullptr)) {
-        attrSelects[*j->second.pos]++;
-      }
-      return j->second.value;
-    }
-    if (env->prevWith == 0u) {
-      throwUndefinedVarError("undefined variable '%1%' at %2%", var.name,
-                             var.pos);
-    }
-    for (size_t l = env->prevWith; l != 0u; --l, env = env->up) {
-    }
-  }
-}
-
-Value* EvalState::allocValue() {
-  nrValues++;
-  return new Value;
-}
-
-Env& EvalState::allocEnv(size_t size) {
-  if (size > std::numeric_limits<decltype(Env::size)>::max()) {
-    throw Error("environment size %d is too big", size);
-  }
-
-  nrEnvs++;
-  nrValuesInEnvs += size;
-  Env* env = new Env(size);
-  env->type = Env::Plain;
-
-  return *env;
-}
-
-void EvalState::mkList(Value& v, std::shared_ptr<NixList> list) {
-  nrListElems += list->size();
-  clearValue(v);
-  v.type = tList;
-  v.list = list;
-}
-
-void EvalState::mkList(Value& v, size_t size) {
-  EvalState::mkList(v, std::make_shared<NixList>(size));
-}
-
-unsigned long nrThunks = 0;
-
-static inline void mkThunk(Value& v, Env& env, Expr* expr) {
-  v.type = tThunk;
-  v.thunk.env = &env;
-  v.thunk.expr = expr;
-  nrThunks++;
-}
-
-void EvalState::mkThunk_(Value& v, Expr* expr) { mkThunk(v, baseEnv, expr); }
-
-void EvalState::mkPos(Value& v, Pos* pos) {
-  if ((pos != nullptr) && pos->file.has_value() && pos->file.value().set()) {
-    mkAttrs(v, 3);
-    mkString(*allocAttr(v, sFile), pos->file.value());
-    mkInt(*allocAttr(v, sLine), pos->line);
-    mkInt(*allocAttr(v, sColumn), pos->column);
-  } else {
-    mkNull(v);
-  }
-}
-
-/* Create a thunk for the delayed computation of the given expression
-   in the given environment.  But if the expression is a variable,
-   then look it up right away.  This significantly reduces the number
-   of thunks allocated. */
-Value* Expr::maybeThunk(EvalState& state, Env& env) {
-  Value* v = state.allocValue();
-  mkThunk(*v, env, this);
-  return v;
-}
-
-unsigned long nrAvoided = 0;
-
-Value* ExprVar::maybeThunk(EvalState& state, Env& env) {
-  Value* v = state.lookupVar(&env, *this, true);
-  /* The value might not be initialised in the environment yet.
-     In that case, ignore it. */
-  if (v != nullptr) {
-    nrAvoided++;
-    return v;
-  }
-  return Expr::maybeThunk(state, env);
-}
-
-Value* ExprString::maybeThunk(EvalState& state, Env& env) {
-  nrAvoided++;
-  return &v;
-}
-
-Value* ExprInt::maybeThunk(EvalState& state, Env& env) {
-  nrAvoided++;
-  return &v;
-}
-
-Value* ExprFloat::maybeThunk(EvalState& state, Env& env) {
-  nrAvoided++;
-  return &v;
-}
-
-Value* ExprPath::maybeThunk(EvalState& state, Env& env) {
-  nrAvoided++;
-  return &v;
-}
-
-void EvalState::evalFile(const Path& path_, Value& v) {
-  auto path = checkSourcePath(path_);
-
-  FileEvalCache::iterator i;
-  if ((i = fileEvalCache.find(path)) != fileEvalCache.end()) {
-    v = i->second;
-    return;
-  }
-
-  Path path2 = resolveExprPath(path);
-  if ((i = fileEvalCache.find(path2)) != fileEvalCache.end()) {
-    v = i->second;
-    return;
-  }
-
-  VLOG(2) << "evaluating file '" << path2 << "'";
-  Expr* e = nullptr;
-
-  auto j = fileParseCache.find(path2);
-  if (j != fileParseCache.end()) {
-    e = j->second;
-  }
-
-  if (e == nullptr) {
-    e = parseExprFromFile(checkSourcePath(path2));
-  }
-
-  fileParseCache[path2] = e;
-
-  try {
-    eval(e, v);
-  } catch (Error& e) {
-    addErrorPrefix(e, "while evaluating the file '%1%':\n", path2);
-    throw;
-  }
-
-  fileEvalCache[path2] = v;
-  if (path != path2) {
-    fileEvalCache[path] = v;
-  }
-}
-
-void EvalState::resetFileCache() {
-  fileEvalCache.clear();
-  fileParseCache.clear();
-}
-
-void EvalState::eval(Expr* e, Value& v) { e->eval(*this, baseEnv, v); }
-
-inline bool EvalState::evalBool(Env& env, Expr* e) {
-  Value v;
-  e->eval(*this, env, v);
-  if (v.type != tBool) {
-    throwTypeError("value is %1% while a Boolean was expected", v);
-  }
-  return v.boolean;
-}
-
-inline bool EvalState::evalBool(Env& env, Expr* e, const Pos& pos) {
-  Value v;
-  e->eval(*this, env, v);
-  if (v.type != tBool) {
-    throwTypeError("value is %1% while a Boolean was expected, at %2%", v, pos);
-  }
-  return v.boolean;
-}
-
-inline void EvalState::evalAttrs(Env& env, Expr* e, Value& v) {
-  e->eval(*this, env, v);
-  if (v.type != tAttrs) {
-    throwTypeError("value is %1% while a set was expected", v);
-  }
-}
-
-void Expr::eval(EvalState& state, Env& env, Value& v) { abort(); }
-
-void ExprInt::eval(EvalState& state, Env& env, Value& v) { v = this->v; }
-
-void ExprFloat::eval(EvalState& state, Env& env, Value& v) { v = this->v; }
-
-void ExprString::eval(EvalState& state, Env& env, Value& v) { v = this->v; }
-
-void ExprPath::eval(EvalState& state, Env& env, Value& v) { v = this->v; }
-
-void ExprAttrs::eval(EvalState& state, Env& env, Value& value) {
-  state.mkAttrs(value, attrs.size() + dynamicAttrs.size());
-  Env* dynamicEnv = &env;
-
-  if (recursive) {
-    /* Create a new environment that contains the attributes in
-       this `rec'. */
-    Env& env2(state.allocEnv(attrs.size()));
-    env2.up = &env;
-    dynamicEnv = &env2;
-
-    /* The recursive attributes are evaluated in the new
-       environment, while the inherited attributes are evaluated
-       in the original environment. */
-    size_t displ = 0;
-    for (auto& attr : attrs) {
-      Value* vAttr;
-      vAttr =
-          attr.second.e->maybeThunk(state, attr.second.inherited ? env : env2);
-      env2.values[displ++] = vAttr;
-      value.attrs->push_back(Attr(attr.first, vAttr, &attr.second.pos));
-    }
-  } else {
-    // TODO(tazjin): insert range
-    for (auto& i : attrs) {
-      value.attrs->push_back(
-          Attr(i.first, i.second.e->maybeThunk(state, env), &i.second.pos));
-    }
-  }
-
-  /* Dynamic attrs apply *after* rec. */
-  for (auto& i : dynamicAttrs) {
-    Value nameVal;
-    i.nameExpr->eval(state, *dynamicEnv, nameVal);
-    state.forceValue(nameVal, i.pos);
-    if (nameVal.type == tNull) {
-      continue;
-    }
-    state.forceStringNoCtx(nameVal);
-    Symbol nameSym = state.symbols.Create(nameVal.string.s);
-    Bindings::iterator j = value.attrs->find(nameSym);
-    if (j != value.attrs->end()) {
-      throwEvalError("dynamic attribute '%1%' at %2% already defined at %3%",
-                     nameSym, i.pos, *j->second.pos);
-    }
-
-    value.attrs->push_back(
-        Attr(nameSym, i.valueExpr->maybeThunk(state, *dynamicEnv), &i.pos));
-  }
-}
-
-void ExprLet::eval(EvalState& state, Env& env, Value& v) {
-  /* Create a new environment that contains the attributes in this
-     `let'. */
-  Env& env2(state.allocEnv(attrs->attrs.size()));
-  env2.up = &env;
-
-  /* The recursive attributes are evaluated in the new environment,
-     while the inherited attributes are evaluated in the original
-     environment. */
-  size_t displ = 0;
-  for (auto& i : attrs->attrs) {
-    env2.values[displ++] =
-        i.second.e->maybeThunk(state, i.second.inherited ? env : env2);
-  }
-
-  body->eval(state, env2, v);
-}
-
-void ExprList::eval(EvalState& state, Env& env, Value& v) {
-  state.mkList(v, elems.size());
-  for (size_t n = 0; n < elems.size(); ++n) {
-    (*v.list)[n] = elems[n]->maybeThunk(state, env);
-  }
-}
-
-void ExprVar::eval(EvalState& state, Env& env, Value& v) {
-  Value* v2 = state.lookupVar(&env, *this, false);
-  state.forceValue(*v2, pos);
-  v = *v2;
-}
-
-static std::string showAttrPath(EvalState& state, Env& env,
-                                const AttrPath& attrPath) {
-  std::ostringstream out;
-  bool first = true;
-  for (auto& i : attrPath) {
-    if (!first) {
-      out << '.';
-    } else {
-      first = false;
-    }
-    out << getName(i, state, env);
-  }
-  return out.str();
-}
-
-uint64_t nrLookups = 0;
-
-void ExprSelect::eval(EvalState& state, Env& env, Value& v) {
-  Value vTmp;
-  Pos* pos2 = nullptr;
-  Value* vAttrs = &vTmp;
-
-  e->eval(state, env, vTmp);
-
-  try {
-    for (auto& i : attrPath) {
-      nrLookups++;
-      Bindings::iterator j;
-      Symbol name = getName(i, state, env);
-      if (def != nullptr) {
-        state.forceValue(*vAttrs, pos);
-        if (vAttrs->type != tAttrs ||
-            (j = vAttrs->attrs->find(name)) == vAttrs->attrs->end()) {
-          def->eval(state, env, v);
-          return;
-        }
-      } else {
-        state.forceAttrs(*vAttrs, pos);
-        if ((j = vAttrs->attrs->find(name)) == vAttrs->attrs->end()) {
-          throwEvalError("attribute '%1%' missing, at %2%", name, pos);
-        }
-      }
-      vAttrs = j->second.value;
-      pos2 = j->second.pos;
-      if (state.countCalls && (pos2 != nullptr)) {
-        state.attrSelects[*pos2]++;
-      }
-    }
-
-    state.forceValue(*vAttrs, (pos2 != nullptr ? *pos2 : this->pos));
-
-  } catch (Error& e) {
-    // This code relies on 'sDerivationNix' being correcty mutated at
-    // some prior point (it would previously otherwise have been a
-    // nullptr).
-    //
-    // We haven't seen this fail, so for now the contained value is
-    // just accessed at the risk of potentially crashing.
-    if ((pos2 != nullptr) && pos2->file != state.sDerivationNix.value()) {
-      addErrorPrefix(e, "while evaluating the attribute '%1%' at %2%:\n",
-                     showAttrPath(state, env, attrPath), *pos2);
-    }
-    throw;
-  }
-
-  v = *vAttrs;
-}
-
-void ExprOpHasAttr::eval(EvalState& state, Env& env, Value& v) {
-  Value vTmp;
-  Value* vAttrs = &vTmp;
-
-  e->eval(state, env, vTmp);
-
-  for (auto& i : attrPath) {
-    state.forceValue(*vAttrs);
-    Bindings::iterator j;
-    Symbol name = getName(i, state, env);
-    if (vAttrs->type != tAttrs ||
-        (j = vAttrs->attrs->find(name)) == vAttrs->attrs->end()) {
-      mkBool(v, false);
-      return;
-    }
-    vAttrs = j->second.value;
-  }
-
-  mkBool(v, true);
-}
-
-void ExprLambda::eval(EvalState& state, Env& env, Value& v) {
-  v.type = tLambda;
-  v.lambda.env = &env;
-  v.lambda.fun = this;
-}
-
-void ExprApp::eval(EvalState& state, Env& env, Value& v) {
-  /* FIXME: vFun prevents GCC from doing tail call optimisation. */
-  Value vFun;
-  e1->eval(state, env, vFun);
-  state.callFunction(vFun, *(e2->maybeThunk(state, env)), v, pos);
-}
-
-void EvalState::callPrimOp(Value& fun, Value& arg, Value& v, const Pos& pos) {
-  /* Figure out the number of arguments still needed. */
-  size_t argsDone = 0;
-  Value* primOp = &fun;
-  while (primOp->type == tPrimOpApp) {
-    argsDone++;
-    primOp = primOp->primOpApp.left;
-  }
-  assert(primOp->type == tPrimOp);
-  auto arity = primOp->primOp->arity;
-  auto argsLeft = arity - argsDone;
-
-  if (argsLeft == 1) {
-    /* We have all the arguments, so call the primop. */
-
-    /* Put all the arguments in an array. */
-    Value* vArgs[arity];
-    auto n = arity - 1;
-    vArgs[n--] = &arg;
-    for (Value* arg = &fun; arg->type == tPrimOpApp;
-         arg = arg->primOpApp.left) {
-      vArgs[n--] = arg->primOpApp.right;
-    }
-
-    /* And call the primop. */
-    nrPrimOpCalls++;
-    if (countCalls) {
-      primOpCalls[primOp->primOp->name]++;
-    }
-    primOp->primOp->fun(*this, pos, vArgs, v);
-  } else {
-    Value* fun2 = allocValue();
-    *fun2 = fun;
-    v.type = tPrimOpApp;
-    v.primOpApp.left = fun2;
-    v.primOpApp.right = &arg;
-  }
-}
-
-void EvalState::callFunction(Value& fun, Value& arg, Value& v, const Pos& pos) {
-  auto trace = evalSettings.traceFunctionCalls
-                   ? std::make_unique<FunctionCallTrace>(pos)
-                   : nullptr;
-
-  forceValue(fun, pos);
-
-  if (fun.type == tPrimOp || fun.type == tPrimOpApp) {
-    callPrimOp(fun, arg, v, pos);
-    return;
-  }
-
-  // If the value to be called is an attribute set, check whether it
-  // contains an appropriate function in the '__functor' element and
-  // use that.
-  if (fun.type == tAttrs) {
-    auto found = fun.attrs->find(sFunctor);
-    if (found != fun.attrs->end()) {
-      // fun may be allocated on the stack of the calling function,
-      // but for functors we may keep a reference, so heap-allocate a
-      // copy and use that instead
-      auto& fun2 = *allocValue();
-      fun2 = fun;
-      /* !!! Should we use the attr pos here? */
-      Value v2;
-      // functors are called with the element itself as the first
-      // parameter, which is partially applied here
-      callFunction(*found->second.value, fun2, v2, pos);
-      return callFunction(v2, arg, v, pos);
-    }
-  }
-
-  if (fun.type != tLambda) {
-    throwTypeError(
-        "attempt to call something which is not a function but %1%, at %2%",
-        fun, pos);
-  }
-
-  ExprLambda& lambda(*fun.lambda.fun);
-
-  auto size = (lambda.arg.empty() ? 0 : 1) +
-              (lambda.matchAttrs ? lambda.formals->formals.size() : 0);
-  Env& env2(allocEnv(size));
-  env2.up = fun.lambda.env;
-
-  size_t displ = 0;
-
-  if (!lambda.matchAttrs) {
-    env2.values[displ++] = &arg;
-
-  } else {
-    forceAttrs(arg, pos);
-
-    if (!lambda.arg.empty()) {
-      env2.values[displ++] = &arg;
-    }
-
-    /* For each formal argument, get the actual argument.  If
-       there is no matching actual argument but the formal
-       argument has a default, use the default. */
-    size_t attrsUsed = 0;
-    for (auto& i : lambda.formals->formals) {
-      Bindings::iterator j = arg.attrs->find(i.name);
-      if (j == arg.attrs->end()) {
-        if (i.def == nullptr) {
-          throwTypeError("%1% called without required argument '%2%', at %3%",
-                         lambda, i.name, pos);
-        }
-        env2.values[displ++] = i.def->maybeThunk(*this, env2);
-      } else {
-        attrsUsed++;
-        env2.values[displ++] = j->second.value;
-      }
-    }
-
-    /* Check that each actual argument is listed as a formal
-       argument (unless the attribute match specifies a `...'). */
-    if (!lambda.formals->ellipsis && attrsUsed != arg.attrs->size()) {
-      /* Nope, so show the first unexpected argument to the
-         user. */
-      for (auto& i : *arg.attrs) {
-        if (lambda.formals->argNames.find(i.second.name) ==
-            lambda.formals->argNames.end()) {
-          throwTypeError("%1% called with unexpected argument '%2%', at %3%",
-                         lambda, i.second.name, pos);
-        }
-      }
-      abort();  // shouldn't happen
-    }
-  }
-
-  nrFunctionCalls++;
-  if (countCalls) {
-    incrFunctionCall(&lambda);
-  }
-
-  /* Evaluate the body.  This is conditional on showTrace, because
-     catching exceptions makes this function not tail-recursive. */
-  if (settings.showTrace) {
-    try {
-      lambda.body->eval(*this, env2, v);
-    } catch (Error& e) {
-      addErrorPrefix(e, "while evaluating %1%, called from %2%:\n", lambda,
-                     pos);
-      throw;
-    }
-  } else {
-    fun.lambda.fun->body->eval(*this, env2, v);
-  }
-}
-
-// Lifted out of callFunction() because it creates a temporary that
-// prevents tail-call optimisation.
-void EvalState::incrFunctionCall(ExprLambda* fun) { functionCalls[fun]++; }
-
-void EvalState::autoCallFunction(Bindings* args, Value& fun, Value& res) {
-  forceValue(fun);
-
-  if (fun.type == tAttrs) {
-    auto found = fun.attrs->find(sFunctor);
-    if (found != fun.attrs->end()) {
-      Value* v = allocValue();
-      callFunction(*found->second.value, fun, *v, noPos);
-      forceValue(*v);
-      return autoCallFunction(args, *v, res);
-    }
-  }
-
-  if (fun.type != tLambda || !fun.lambda.fun->matchAttrs) {
-    res = fun;
-    return;
-  }
-
-  Value* actualArgs = allocValue();
-  mkAttrs(*actualArgs, fun.lambda.fun->formals->formals.size());
-
-  if (fun.lambda.fun->formals->ellipsis) {
-    // If the formals have an ellipsis (eg the function accepts extra args) pass
-    // all available automatic arguments (which includes arguments specified on
-    // the command line via --arg/--argstr)
-    for (auto& [_, v] : *args) {
-      actualArgs->attrs->push_back(v);
-    }
-  } else {
-    // Otherwise, only pass the arguments that the function accepts
-    for (auto& i : fun.lambda.fun->formals->formals) {
-      Bindings::iterator j = args->find(i.name);
-      if (j != args->end()) {
-        actualArgs->attrs->push_back(j->second);
-      } else if (i.def == nullptr) {
-        throwTypeError(
-            "cannot auto-call a function that has an argument without a "
-            "default "
-            "value ('%1%')",
-            i.name);
-      }
-    }
-  }
-
-  callFunction(fun, *actualArgs, res, noPos);
-}
-
-void ExprWith::eval(EvalState& state, Env& env, Value& v) {
-  Env& env2(state.allocEnv(1));
-  env2.up = &env;
-  env2.prevWith = prevWith;
-  env2.type = Env::HasWithExpr;
-  /* placeholder for result of attrs */
-  env2.values[0] = nullptr;
-  env2.withAttrsExpr = this->attrs;
-
-  body->eval(state, env2, v);
-}
-
-void ExprIf::eval(EvalState& state, Env& env, Value& v) {
-  (state.evalBool(env, cond) ? then : else_)->eval(state, env, v);
-}
-
-void ExprAssert::eval(EvalState& state, Env& env, Value& v) {
-  if (!state.evalBool(env, cond, pos)) {
-    std::ostringstream out;
-    cond->show(out);
-    throwAssertionError("assertion %1% failed at %2%", out.str(), pos);
-  }
-  body->eval(state, env, v);
-}
-
-void ExprOpNot::eval(EvalState& state, Env& env, Value& v) {
-  mkBool(v, !state.evalBool(env, e));
-}
-
-void ExprOpEq::eval(EvalState& state, Env& env, Value& v) {
-  Value v1;
-  e1->eval(state, env, v1);
-  Value v2;
-  e2->eval(state, env, v2);
-  mkBool(v, state.eqValues(v1, v2));
-}
-
-void ExprOpNEq::eval(EvalState& state, Env& env, Value& v) {
-  Value v1;
-  e1->eval(state, env, v1);
-  Value v2;
-  e2->eval(state, env, v2);
-  mkBool(v, !state.eqValues(v1, v2));
-}
-
-void ExprOpAnd::eval(EvalState& state, Env& env, Value& v) {
-  mkBool(v, state.evalBool(env, e1, pos) && state.evalBool(env, e2, pos));
-}
-
-void ExprOpOr::eval(EvalState& state, Env& env, Value& v) {
-  mkBool(v, state.evalBool(env, e1, pos) || state.evalBool(env, e2, pos));
-}
-
-void ExprOpImpl::eval(EvalState& state, Env& env, Value& v) {
-  mkBool(v, !state.evalBool(env, e1, pos) || state.evalBool(env, e2, pos));
-}
-
-void ExprOpUpdate::eval(EvalState& state, Env& env, Value& dest) {
-  Value v1;
-  Value v2;
-  state.evalAttrs(env, e1, v1);
-  state.evalAttrs(env, e2, v2);
-
-  state.nrOpUpdates++;
-
-  clearValue(dest);
-  dest.type = tAttrs;
-  dest.attrs = Bindings::Merge(*v1.attrs, *v2.attrs);
-}
-
-void ExprOpConcatLists::eval(EvalState& state, Env& env, Value& v) {
-  Value v1;
-  e1->eval(state, env, v1);
-  Value v2;
-  e2->eval(state, env, v2);
-  state.concatLists(v, {&v1, &v2}, pos);
-}
-
-void EvalState::concatLists(Value& v, const NixList& lists, const Pos& pos) {
-  nrListConcats++;
-
-  auto outlist = std::make_shared<NixList>();
-
-  for (Value* list : lists) {
-    forceList(*list, pos);
-    outlist->insert(outlist->end(), list->list->begin(), list->list->end());
-  }
-
-  mkList(v, outlist);
-}
-
-void ExprConcatStrings::eval(EvalState& state, Env& env, Value& v) {
-  PathSet context;
-  std::ostringstream s;
-  NixInt n = 0;
-  NixFloat nf = 0;
-
-  bool first = !forceString;
-  ValueType firstType = tString;
-
-  for (auto& i : *es) {
-    Value vTmp;
-    i->eval(state, env, vTmp);
-
-    /* If the first element is a path, then the result will also
-       be a path, we don't copy anything (yet - that's done later,
-       since paths are copied when they are used in a derivation),
-       and none of the strings are allowed to have contexts. */
-    if (first) {
-      firstType = vTmp.type;
-      first = false;
-    }
-
-    if (firstType == tInt) {
-      if (vTmp.type == tInt) {
-        n += vTmp.integer;
-      } else if (vTmp.type == tFloat) {
-        // Upgrade the type from int to float;
-        firstType = tFloat;
-        nf = n;
-        nf += vTmp.fpoint;
-      } else {
-        throwEvalError("cannot add %1% to an integer, at %2%", showType(vTmp),
-                       pos);
-      }
-    } else if (firstType == tFloat) {
-      if (vTmp.type == tInt) {
-        nf += vTmp.integer;
-      } else if (vTmp.type == tFloat) {
-        nf += vTmp.fpoint;
-      } else {
-        throwEvalError("cannot add %1% to a float, at %2%", showType(vTmp),
-                       pos);
-      }
-    } else {
-      s << state.coerceToString(pos, vTmp, context, false,
-                                firstType == tString);
-    }
-  }
-
-  if (firstType == tInt) {
-    mkInt(v, n);
-  } else if (firstType == tFloat) {
-    mkFloat(v, nf);
-  } else if (firstType == tPath) {
-    if (!context.empty()) {
-      throwEvalError(
-          "a string that refers to a store path cannot be appended to a path, "
-          "at %1%",
-          pos);
-    }
-    auto path = canonPath(s.str());
-    mkPath(v, path.c_str());
-  } else {
-    mkString(v, s.str(), context);
-  }
-}
-
-void ExprPos::eval(EvalState& state, Env& env, Value& v) {
-  state.mkPos(v, &pos);
-}
-
-template <typename T>
-using traceable_flat_hash_set = absl::flat_hash_set<T>;
-
-void EvalState::forceValueDeep(Value& v) {
-  traceable_flat_hash_set<const Value*> seen;
-
-  std::function<void(Value & v)> recurse;
-
-  recurse = [&](Value& v) {
-    if (seen.find(&v) != seen.end()) {
-      return;
-    }
-    seen.insert(&v);
-
-    forceValue(v);
-
-    if (v.type == tAttrs) {
-      for (auto& i : *v.attrs) {
-        try {
-          recurse(*i.second.value);
-        } catch (Error& e) {
-          addErrorPrefix(e, "while evaluating the attribute '%1%' at %2%:\n",
-                         i.second.name, *i.second.pos);
-          throw;
-        }
-      }
-    } else if (v.isList()) {
-      for (size_t n = 0; n < v.listSize(); ++n) {
-        recurse(*(*v.list)[n]);
-      }
-    }
-  };
-
-  recurse(v);
-}
-
-NixInt EvalState::forceInt(Value& v, const Pos& pos) {
-  forceValue(v, pos);
-  if (v.type != tInt) {
-    throwTypeError("value is %1% while an integer was expected, at %2%", v,
-                   pos);
-  }
-  return v.integer;
-}
-
-NixFloat EvalState::forceFloat(Value& v, const Pos& pos) {
-  forceValue(v, pos);
-  if (v.type == tInt) {
-    return static_cast<NixFloat>(v.integer);
-  }
-  if (v.type != tFloat) {
-    throwTypeError("value is %1% while a float was expected, at %2%", v, pos);
-  }
-  return v.fpoint;
-}
-
-bool EvalState::forceBool(Value& v, const Pos& pos) {
-  forceValue(v);
-  if (v.type != tBool) {
-    throwTypeError("value is %1% while a Boolean was expected, at %2%", v, pos);
-  }
-  return v.boolean;
-}
-
-bool EvalState::isFunctor(Value& fun) {
-  return fun.type == tAttrs && fun.attrs->find(sFunctor) != fun.attrs->end();
-}
-
-void EvalState::forceFunction(Value& v, const Pos& pos) {
-  forceValue(v);
-  if (v.type != tLambda && v.type != tPrimOp && v.type != tPrimOpApp &&
-      !isFunctor(v)) {
-    throwTypeError("value is %1% while a function was expected, at %2%", v,
-                   pos);
-  }
-}
-
-std::string EvalState::forceString(Value& v, const Pos& pos) {
-  forceValue(v, pos);
-  if (v.type != tString) {
-    if (pos) {
-      throwTypeError("value is %1% while a string was expected, at %2%", v,
-                     pos);
-    } else {
-      throwTypeError("value is %1% while a string was expected", v);
-    }
-  }
-  return std::string(v.string.s);
-}
-
-void copyContext(const Value& v, PathSet& context) {
-  if (v.string.context != nullptr) {
-    for (const char** p = v.string.context; *p != nullptr; ++p) {
-      context.insert(*p);
-    }
-  }
-}
-
-std::string EvalState::forceString(Value& v, PathSet& context, const Pos& pos) {
-  std::string s = forceString(v, pos);
-  copyContext(v, context);
-  return s;
-}
-
-std::string EvalState::forceStringNoCtx(Value& v, const Pos& pos) {
-  std::string s = forceString(v, pos);
-  if (v.string.context != nullptr) {
-    if (pos) {
-      throwEvalError(
-          "the string '%1%' is not allowed to refer to a store path (such as "
-          "'%2%'), at %3%",
-          v.string.s, v.string.context[0], pos);
-    } else {
-      throwEvalError(
-          "the string '%1%' is not allowed to refer to a store path (such as "
-          "'%2%')",
-          v.string.s, v.string.context[0]);
-    }
-  }
-  return s;
-}
-
-bool EvalState::isDerivation(Value& v) {
-  if (v.type != tAttrs) {
-    return false;
-  }
-  Bindings::iterator i = v.attrs->find(sType);
-  if (i == v.attrs->end()) {
-    return false;
-  }
-  forceValue(*i->second.value);
-  if (i->second.value->type != tString) {
-    return false;
-  }
-  return strcmp(i->second.value->string.s, "derivation") == 0;
-}
-
-std::optional<std::string> EvalState::tryAttrsToString(const Pos& pos, Value& v,
-                                                       PathSet& context,
-                                                       bool coerceMore,
-                                                       bool copyToStore) {
-  auto i = v.attrs->find(sToString);
-  if (i != v.attrs->end()) {
-    Value v1;
-    callFunction(*i->second.value, v, v1, pos);
-    return coerceToString(pos, v1, context, coerceMore, copyToStore);
-  }
-
-  return {};
-}
-
-std::string EvalState::coerceToString(const Pos& pos, Value& v,
-                                      PathSet& context, bool coerceMore,
-                                      bool copyToStore) {
-  forceValue(v);
-
-  std::string s;
-
-  if (v.type == tString) {
-    copyContext(v, context);
-    return v.string.s;
-  }
-
-  if (v.type == tPath) {
-    Path path(canonPath(v.path));
-    return copyToStore ? copyPathToStore(context, path) : path;
-  }
-
-  if (v.type == tAttrs) {
-    auto maybeString =
-        tryAttrsToString(pos, v, context, coerceMore, copyToStore);
-    if (maybeString) {
-      return *maybeString;
-    }
-    auto i = v.attrs->find(sOutPath);
-    if (i == v.attrs->end()) {
-      throwTypeError("cannot coerce a set to a string, at %1%", pos);
-    }
-    return coerceToString(pos, *i->second.value, context, coerceMore,
-                          copyToStore);
-  }
-
-  if (coerceMore) {
-    /* Note that `false' is represented as an empty string for
-       shell scripting convenience, just like `null'. */
-    if (v.type == tBool && v.boolean) {
-      return "1";
-    }
-    if (v.type == tBool && !v.boolean) {
-      return "";
-    }
-    if (v.type == tInt) {
-      return std::to_string(v.integer);
-    }
-    if (v.type == tFloat) {
-      return std::to_string(v.fpoint);
-    }
-    if (v.type == tNull) {
-      return "";
-    }
-
-    if (v.isList()) {
-      std::string result;
-      for (size_t n = 0; n < v.listSize(); ++n) {
-        result += coerceToString(pos, *(*v.list)[n], context, coerceMore,
-                                 copyToStore);
-        if (n < v.listSize() - 1
-            /* !!! not quite correct */
-            && (!(*v.list)[n]->isList() || (*v.list)[n]->listSize() != 0)) {
-          result += " ";
-        }
-      }
-      return result;
-    }
-  }
-
-  throwTypeError("cannot coerce %1% to a string, at %2%", v, pos);
-}
-
-std::string EvalState::copyPathToStore(PathSet& context, const Path& path) {
-  if (nix::isDerivation(path)) {
-    throwEvalError("file names are not allowed to end in '%1%'", drvExtension);
-  }
-
-  Path dstPath;
-  if (!srcToStore[path].empty()) {
-    dstPath = srcToStore[path];
-  } else {
-    dstPath =
-        settings.readOnlyMode
-            ? store
-                  ->computeStorePathForPath(baseNameOf(path),
-                                            checkSourcePath(path))
-                  .first
-            : store->addToStore(baseNameOf(path), checkSourcePath(path), true,
-                                htSHA256, defaultPathFilter, repair);
-    srcToStore[path] = dstPath;
-    VLOG(2) << "copied source '" << path << "' -> '" << dstPath << "'";
-  }
-
-  context.insert(dstPath);
-  return dstPath;
-}
-
-Path EvalState::coerceToPath(const Pos& pos, Value& v, PathSet& context) {
-  std::string path = coerceToString(pos, v, context, false, false);
-  if (path.empty() || path[0] != '/') {
-    throwEvalError("string '%1%' doesn't represent an absolute path, at %2%",
-                   path, pos);
-  }
-  return path;
-}
-
-bool EvalState::eqValues(Value& v1, Value& v2) {
-  forceValue(v1);
-  forceValue(v2);
-
-  /* !!! Hack to support some old broken code that relies on pointer
-     equality tests between sets.  (Specifically, builderDefs calls
-     uniqList on a list of sets.)  Will remove this eventually. */
-  if (&v1 == &v2) {
-    return true;
-  }
-
-  // Special case type-compatibility between float and int
-  if (v1.type == tInt && v2.type == tFloat) {
-    return v1.integer == v2.fpoint;
-  }
-  if (v1.type == tFloat && v2.type == tInt) {
-    return v1.fpoint == v2.integer;
-  }
-
-  // All other types are not compatible with each other.
-  if (v1.type != v2.type) {
-    return false;
-  }
-
-  switch (v1.type) {
-    case tInt:
-      return v1.integer == v2.integer;
-
-    case tBool:
-      return v1.boolean == v2.boolean;
-
-    case tString:
-      return strcmp(v1.string.s, v2.string.s) == 0;
-
-    case tPath:
-      return strcmp(v1.path, v2.path) == 0;
-
-    case tNull:
-      return true;
-
-    case tList:
-      if (v1.listSize() != v2.listSize()) {
-        return false;
-      }
-      for (size_t n = 0; n < v1.listSize(); ++n) {
-        if (!eqValues(*(*v1.list)[n], *(*v2.list)[n])) {
-          return false;
-        }
-      }
-      return true;
-
-    case tAttrs: {
-      // As an optimisation if both values are pointing towards the
-      // same attribute set, we can skip all this extra work.
-      if (v1.attrs == v2.attrs) {
-        return true;
-      }
-
-      /* If both sets denote a derivation (type = "derivation"),
-         then compare their outPaths. */
-      if (isDerivation(v1) && isDerivation(v2)) {
-        Bindings::iterator i = v1.attrs->find(sOutPath);
-        Bindings::iterator j = v2.attrs->find(sOutPath);
-        if (i != v1.attrs->end() && j != v2.attrs->end()) {
-          return eqValues(*i->second.value, *j->second.value);
-        }
-      }
-
-      return v1.attrs->Equal(v2.attrs.get(), *this);
-    }
-
-    /* Functions are incomparable. */
-    case tLambda:
-    case tPrimOp:
-    case tPrimOpApp:
-      return false;
-
-    case tFloat:
-      return v1.fpoint == v2.fpoint;
-
-    default:
-      throwEvalError("cannot compare %1% with %2%", showType(v1), showType(v2));
-  }
-}
-
-void EvalState::printStats() {
-  bool showStats = getEnv("NIX_SHOW_STATS").value_or("0") != "0";
-
-  struct rusage buf;
-  getrusage(RUSAGE_SELF, &buf);
-  float cpuTime = buf.ru_utime.tv_sec +
-                  (static_cast<float>(buf.ru_utime.tv_usec) / 1000000);
-
-  uint64_t bEnvs = nrEnvs * sizeof(Env) + nrValuesInEnvs * sizeof(Value*);
-  uint64_t bLists = nrListElems * sizeof(Value*);
-  uint64_t bValues = nrValues * sizeof(Value);
-  uint64_t bAttrsets =
-      nrAttrsets * sizeof(Bindings) + nrAttrsInAttrsets * sizeof(Attr);
-
-  if (showStats) {
-    auto outPath = getEnv("NIX_SHOW_STATS_PATH").value_or("-");
-    std::fstream fs;
-    if (outPath != "-") {
-      fs.open(outPath, std::fstream::out);
-    }
-    JSONObject topObj(outPath == "-" ? std::cerr : fs, true);
-    topObj.attr("cpuTime", cpuTime);
-    {
-      auto envs = topObj.object("envs");
-      envs.attr("number", nrEnvs);
-      envs.attr("elements", nrValuesInEnvs);
-      envs.attr("bytes", bEnvs);
-    }
-    {
-      auto lists = topObj.object("list");
-      lists.attr("elements", nrListElems);
-      lists.attr("bytes", bLists);
-      lists.attr("concats", nrListConcats);
-    }
-    {
-      auto values = topObj.object("values");
-      values.attr("number", nrValues);
-      values.attr("bytes", bValues);
-    }
-    {
-      auto syms = topObj.object("symbols");
-      syms.attr("number", symbols.Size());
-      syms.attr("bytes", symbols.TotalSize());
-    }
-    {
-      auto sets = topObj.object("sets");
-      sets.attr("number", nrAttrsets);
-      sets.attr("bytes", bAttrsets);
-      sets.attr("elements", nrAttrsInAttrsets);
-    }
-    {
-      auto sizes = topObj.object("sizes");
-      sizes.attr("Env", sizeof(Env));
-      sizes.attr("Value", sizeof(Value));
-      sizes.attr("Bindings", sizeof(Bindings));
-      sizes.attr("Attr", sizeof(Attr));
-    }
-    topObj.attr("nrOpUpdates", nrOpUpdates);
-    topObj.attr("nrOpUpdateValuesCopied", nrOpUpdateValuesCopied);
-    topObj.attr("nrThunks", nrThunks);
-    topObj.attr("nrAvoided", nrAvoided);
-    topObj.attr("nrLookups", nrLookups);
-    topObj.attr("nrPrimOpCalls", nrPrimOpCalls);
-    topObj.attr("nrFunctionCalls", nrFunctionCalls);
-
-    if (countCalls) {
-      {
-        auto obj = topObj.object("primops");
-        for (auto& i : primOpCalls) {
-          obj.attr(i.first, i.second);
-        }
-      }
-      {
-        auto list = topObj.list("functions");
-        for (auto& i : functionCalls) {
-          auto obj = list.object();
-          if (i.first->name.has_value()) {
-            obj.attr("name", (const std::string&)i.first->name.value());
-          } else {
-            obj.attr("name", nullptr);
-          }
-          if (i.first->pos) {
-            obj.attr("file", (const std::string&)i.first->pos.file);
-            obj.attr("line", i.first->pos.line);
-            obj.attr("column", i.first->pos.column);
-          }
-          obj.attr("count", i.second);
-        }
-      }
-      {
-        auto list = topObj.list("attributes");
-        for (auto& i : attrSelects) {
-          auto obj = list.object();
-          if (i.first) {
-            obj.attr("file", (const std::string&)i.first.file);
-            obj.attr("line", i.first.line);
-            obj.attr("column", i.first.column);
-          }
-          obj.attr("count", i.second);
-        }
-      }
-    }
-
-    // TODO(tazjin): what is this? commented out because .dump() is gone.
-    // if (getEnv("NIX_SHOW_SYMBOLS", "0") != "0") {
-    //   auto list = topObj.list("symbols");
-    //   symbols.dump([&](const std::string& s) { list.elem(s); });
-    // }
-  }
-}
-
-void EvalState::TraceFileAccess(const Path& realPath) {
-  if (file_access_trace_fn) {
-    if (last_traced_file != realPath) {
-      file_access_trace_fn(realPath);
-      // Basic deduplication.
-      last_traced_file = std::string(realPath);
-    }
-  }
-}
-
-void EvalState::EnableFileAccessTracing(std::function<void(const Path&)> fn) {
-  file_access_trace_fn = fn;
-}
-
-size_t valueSize(const Value& v) {
-  traceable_flat_hash_set<const Bindings*> seenBindings;
-  traceable_flat_hash_set<const Env*> seenEnvs;
-  traceable_flat_hash_set<const NixList*> seenLists;
-  traceable_flat_hash_set<const char*> seenStrings;
-  traceable_flat_hash_set<const Value*> seenValues;
-
-  auto doString = [&](const char* s) -> size_t {
-    if (seenStrings.find(s) != seenStrings.end()) {
-      return 0;
-    }
-    seenStrings.insert(s);
-    return strlen(s) + 1;
-  };
-
-  std::function<size_t(const Value& v)> doValue;
-  std::function<size_t(const Env& v)> doEnv;
-
-  doValue = [&](const Value& v) -> size_t {
-    if (seenValues.find(&v) != seenValues.end()) {
-      return 0;
-    }
-    seenValues.insert(&v);
-
-    size_t sz = sizeof(Value);
-
-    switch (v.type) {
-      case tString:
-        sz += doString(v.string.s);
-        if (v.string.context != nullptr) {
-          for (const char** p = v.string.context; *p != nullptr; ++p) {
-            sz += doString(*p);
-          }
-        }
-        break;
-      case tPath:
-        sz += doString(v.path);
-        break;
-      case tAttrs:
-        if (seenBindings.find(v.attrs.get()) == seenBindings.end()) {
-          seenBindings.insert(v.attrs.get());
-          sz += sizeof(Bindings);
-          for (const auto& i : *v.attrs) {
-            sz += doValue(*i.second.value);
-          }
-        }
-        break;
-      case tList:
-        if (seenLists.find(v.list.get()) == seenLists.end()) {
-          seenLists.insert(v.list.get());
-          sz += v.listSize() * sizeof(Value*);
-          for (const Value* v : *v.list) {
-            sz += doValue(*v);
-          }
-        }
-        break;
-      case tThunk:
-        sz += doEnv(*v.thunk.env);
-        break;
-      case tApp:
-        sz += doValue(*v.app.left);
-        sz += doValue(*v.app.right);
-        break;
-      case tLambda:
-        sz += doEnv(*v.lambda.env);
-        break;
-      case tPrimOpApp:
-        sz += doValue(*v.primOpApp.left);
-        sz += doValue(*v.primOpApp.right);
-        break;
-      default:;
-    }
-
-    return sz;
-  };
-
-  doEnv = [&](const Env& env) -> size_t {
-    if (seenEnvs.find(&env) != seenEnvs.end()) {
-      return 0;
-    }
-    seenEnvs.insert(&env);
-
-    size_t sz = sizeof(Env) + sizeof(Value*) * env.size;
-
-    if (env.type != Env::HasWithExpr) {
-      for (const Value* v : env.values) {
-        if (v != nullptr) {
-          sz += doValue(*v);
-        }
-      }
-    } else {
-      // TODO(kanepyork): trace ExprWith? how important is this accounting?
-    }
-
-    if (env.up != nullptr) {
-      sz += doEnv(*env.up);
-    }
-
-    return sz;
-  };
-
-  return doValue(v);
-}
-
-EvalSettings evalSettings;
-
-static GlobalConfig::Register r1(&evalSettings);
-
-}  // namespace nix