refactor(3p/nix/libexpr): Remove the nix::Symbol default constructor r/1280

Having a default constructor for this causes a variety of annoying
situations across the codebase in which this is initialised to an
unexpected value, leading to constant guarding against those
conditions.

It turns out there's actually no intrinsic reason that this default
constructor needs to exist. The biggest one was addressed in CL/1138
and this commit cleans up the remaining bits.

Change-Id: I4a847f50bc90e72f028598196592a7d8730a4e01
Reviewed-on: https://cl.tvl.fyi/c/depot/+/1139
Reviewed-by: isomer <isomer@tvl.fyi>
Tested-by: BuildkiteCI

1 files changed, 5 insertions, 10 deletions

diff --git a/third_party/nix/src/libexpr/nixexpr.cc b/third_party/nix/src/libexpr/nixexpr.cc
index 2de37f50e9b9..94e7d335cff0 100644
--- a/third_party/nix/src/libexpr/nixexpr.cc
+++ b/third_party/nix/src/libexpr/nixexpr.cc
@@ -187,11 +187,11 @@ void ExprConcatStrings::show(std::ostream& str) const {
 void ExprPos::show(std::ostream& str) const { str << "__curPos"; }
 
 std::ostream& operator<<(std::ostream& str, const Pos& pos) {
-  if (!pos) {
+  if (!pos || !pos.file.has_value()) {
     str << "undefined position";
   } else {
     str << (format(ANSI_BOLD "%1%" ANSI_NORMAL ":%2%:%3%") %
-            (std::string)pos.file % pos.line % pos.column)
+            (std::string)pos.file.value() % pos.line % pos.column)
                .str();
   }
   return str;
@@ -401,17 +401,12 @@ void ExprConcatStrings::bindVars(const StaticEnv& env) {
 void ExprPos::bindVars(const StaticEnv& env) {}
 
 /* Storing function names. */
-
-void Expr::setName(Symbol& name) {}
-
-void ExprLambda::setName(Symbol& name) {
-  this->name = name;
-  body->setName(name);
-}
+void ExprLambda::setName(Symbol& name) { this->name = name; }
 
 std::string ExprLambda::showNamePos() const {
   return (format("%1% at %2%") %
-          (name.set() ? "'" + (std::string)name + "'" : "anonymous function") %
+          (name.has_value() ? "'" + (std::string)name.value() + "'"
+                            : "anonymous function") %
           pos)
       .str();
 }