From 00a32802328b58daa7af48ccac60f6154ef05639 Mon Sep 17 00:00:00 2001
From: pennae <github@quasiparticle.net>
Date: Sat, 5 Mar 2022 17:31:50 +0100
Subject: [PATCH] don't use Symbol in Pos to represent a path

PosTable deduplicates origin information, so using symbols for paths is no
longer necessary. moving away from path Symbols also reduces the usage of
symbols for things that are not keys in attribute sets, which will become
important in the future when we turn symbols into indices as well.
---
 src/libexpr/eval.cc    | 4 ++--
 src/libexpr/eval.hh    | 2 ++
 src/libexpr/nixexpr.hh | 6 +++---
 src/libexpr/parser.y   | 6 +++---
 src/libexpr/primops.cc | 2 +-
 src/libutil/error.hh   | 6 +-----
 6 files changed, 12 insertions(+), 14 deletions(-)

diff --git a/src/libexpr/eval.cc b/src/libexpr/eval.cc
index e6314f63e..39f1a625f 100644
--- a/src/libexpr/eval.cc
+++ b/src/libexpr/eval.cc
@@ -934,7 +934,7 @@ void EvalState::mkThunk_(Value & v, Expr * expr)
 void EvalState::mkPos(Value & v, PosIdx p)
 {
     auto pos = positions[p];
-    if (pos.file.set()) {
+    if (!pos.file.empty()) {
         auto attrs = buildBindings(3);
         attrs.alloc(sFile).mkString(pos.file);
         attrs.alloc(sLine).mkInt(pos.line);
@@ -1296,7 +1296,7 @@ void ExprSelect::eval(EvalState & state, Env & env, Value & v)
 
     } catch (Error & e) {
         auto pos2r = state.positions[pos2];
-        if (pos2 && pos2r.file != state.sDerivationNix)
+        if (pos2 && pos2r.file != state.derivationNixPath)
             state.addErrorTrace(e, pos2, "while evaluating the attribute '%1%'",
                 showAttrPath(state, env, attrPath));
         throw;
diff --git a/src/libexpr/eval.hh b/src/libexpr/eval.hh
index b05e8d5d0..71d6e7e7f 100644
--- a/src/libexpr/eval.hh
+++ b/src/libexpr/eval.hh
@@ -75,6 +75,8 @@ public:
     SymbolTable symbols;
     PosTable positions;
 
+    static inline std::string derivationNixPath = "//builtin/derivation.nix";
+
     const Symbol sWith, sOutPath, sDrvPath, sType, sMeta, sName, sValue,
         sSystem, sOverrides, sOutputs, sOutputName, sIgnoreNulls,
         sFile, sLine, sColumn, sFunctor, sToString,
diff --git a/src/libexpr/nixexpr.hh b/src/libexpr/nixexpr.hh
index d9392cff5..2e12f0b4f 100644
--- a/src/libexpr/nixexpr.hh
+++ b/src/libexpr/nixexpr.hh
@@ -26,7 +26,7 @@ MakeError(RestrictedPathError, Error);
 
 struct Pos
 {
-    Symbol file;
+    std::string file;
     FileOrigin origin;
     uint32_t line;
     uint32_t column;
@@ -64,10 +64,10 @@ public:
         explicit Origin(uint32_t idx): idx(idx), file{}, origin{} {}
 
     public:
-        const Symbol file;
+        const std::string file;
         const FileOrigin origin;
 
-        Origin(Symbol file, FileOrigin origin): file(file), origin(origin) {}
+        Origin(std::string file, FileOrigin origin): file(std::move(file)), origin(origin) {}
     };
 
     struct Offset {
diff --git a/src/libexpr/parser.y b/src/libexpr/parser.y
index 0052a8070..1f950a057 100644
--- a/src/libexpr/parser.y
+++ b/src/libexpr/parser.y
@@ -648,14 +648,14 @@ Expr * EvalState::parse(char * text, size_t length, FileOrigin origin,
     const PathView path, const PathView basePath, StaticEnv & staticEnv)
 {
     yyscan_t scanner;
-    Symbol file;
+    std::string file;
     switch (origin) {
         case foFile:
-            file = symbols.create(path);
+            file = path;
             break;
         case foStdin:
         case foString:
-            file = symbols.create(text);
+            file = text;
             break;
         default:
             assert(false);
diff --git a/src/libexpr/primops.cc b/src/libexpr/primops.cc
index 9cdcfd0b9..81fb5acfb 100644
--- a/src/libexpr/primops.cc
+++ b/src/libexpr/primops.cc
@@ -3915,7 +3915,7 @@ void EvalState::createBaseEnv()
 
     /* Add a wrapper around the derivation primop that computes the
        `drvPath' and `outPath' attributes lazily. */
-    sDerivationNix = symbols.create("//builtin/derivation.nix");
+    sDerivationNix = symbols.create(derivationNixPath);
     auto vDerivation = allocValue();
     addConstant("derivation", vDerivation);
 
diff --git a/src/libutil/error.hh b/src/libutil/error.hh
index 348018f57..f4706e3ed 100644
--- a/src/libutil/error.hh
+++ b/src/libutil/error.hh
@@ -87,11 +87,7 @@ struct ErrPos {
         origin = pos.origin;
         line = pos.line;
         column = pos.column;
-        // is file symbol null?
-        if (pos.file.set())
-            file = pos.file;
-        else
-            file = "";
+        file = pos.file;
         return *this;
     }