From 6587e7bcff6bfc7718cea96e64823fc2742d3d6e Mon Sep 17 00:00:00 2001
From: Sergei Zimmerman <xokdvium@proton.me>
Date: Thu, 12 Jun 2025 19:42:50 +0000
Subject: [PATCH 1/6] libexpr: Add and use `lambda` getter

---
 src/libcmd/repl.cc                    |  2 +-
 src/libexpr-tests/primops.cc          |  4 ++--
 src/libexpr/eval-profiler.cc          |  2 +-
 src/libexpr/eval.cc                   | 22 +++++++++++-----------
 src/libexpr/include/nix/expr/value.hh |  3 +++
 src/libexpr/primops.cc                |  4 ++--
 src/libexpr/print.cc                  |  8 ++++----
 src/libexpr/value-to-xml.cc           | 12 ++++++------
 src/libflake/flake.cc                 |  4 ++--
 src/nix-build/nix-build.cc            |  4 ++--
 src/nix/flake.cc                      |  4 ++--
 11 files changed, 36 insertions(+), 33 deletions(-)

diff --git a/src/libcmd/repl.cc b/src/libcmd/repl.cc
index f01f12860..8170bd579 100644
--- a/src/libcmd/repl.cc
+++ b/src/libcmd/repl.cc
@@ -484,7 +484,7 @@ ProcessLineResult NixRepl::processLine(std::string line)
                 auto path = state->coerceToPath(noPos, v, context, "while evaluating the filename to edit");
                 return {path, 0};
             } else if (v.isLambda()) {
-                auto pos = state->positions[v.payload.lambda.fun->pos];
+                auto pos = state->positions[v.lambda().fun->pos];
                 if (auto path = std::get_if<SourcePath>(&pos.origin))
                     return {*path, pos.line};
                 else
diff --git a/src/libexpr-tests/primops.cc b/src/libexpr-tests/primops.cc
index 2f864f2c2..6c301f157 100644
--- a/src/libexpr-tests/primops.cc
+++ b/src/libexpr-tests/primops.cc
@@ -667,8 +667,8 @@ namespace nix {
         auto v = eval("derivation");
         ASSERT_EQ(v.type(), nFunction);
         ASSERT_TRUE(v.isLambda());
-        ASSERT_NE(v.payload.lambda.fun, nullptr);
-        ASSERT_TRUE(v.payload.lambda.fun->hasFormals());
+        ASSERT_NE(v.lambda().fun, nullptr);
+        ASSERT_TRUE(v.lambda().fun->hasFormals());
     }
 
     TEST_F(PrimOpTest, currentTime) {
diff --git a/src/libexpr/eval-profiler.cc b/src/libexpr/eval-profiler.cc
index 7053e4ec7..b65bc3a4d 100644
--- a/src/libexpr/eval-profiler.cc
+++ b/src/libexpr/eval-profiler.cc
@@ -204,7 +204,7 @@ FrameInfo SampleStack::getFrameInfoFromValueAndPos(const Value & v, std::span<Va
     /* NOTE: No actual references to garbage collected values are not held in
        the profiler. */
     if (v.isLambda())
-        return LambdaFrameInfo{.expr = v.payload.lambda.fun, .callPos = pos};
+        return LambdaFrameInfo{.expr = v.lambda().fun, .callPos = pos};
     else if (v.isPrimOp()) {
         return getPrimOpFrameInfo(*v.primOp(), args, pos);
     } else if (v.isPrimOpApp())
diff --git a/src/libexpr/eval.cc b/src/libexpr/eval.cc
index 7346a7651..51036a223 100644
--- a/src/libexpr/eval.cc
+++ b/src/libexpr/eval.cc
@@ -147,7 +147,7 @@ PosIdx Value::determinePos(const PosIdx pos) const
     #pragma GCC diagnostic ignored "-Wswitch-enum"
     switch (internalType) {
         case tAttrs: return attrs()->pos;
-        case tLambda: return payload.lambda.fun->pos;
+        case tLambda: return lambda().fun->pos;
         case tApp: return payload.app.left->determinePos(pos);
         default: return pos;
     }
@@ -610,7 +610,7 @@ std::optional<EvalState::Doc> EvalState::getDoc(Value & v)
             };
     }
     if (v.isLambda()) {
-        auto exprLambda = v.payload.lambda.fun;
+        auto exprLambda = v.lambda().fun;
 
         std::ostringstream s;
         std::string name;
@@ -1567,13 +1567,13 @@ void EvalState::callFunction(Value & fun, std::span<Value *> args, Value & vRes,
 
         if (vCur.isLambda()) {
 
-            ExprLambda & lambda(*vCur.payload.lambda.fun);
+            ExprLambda & lambda(*vCur.lambda().fun);
 
             auto size =
                 (!lambda.arg ? 0 : 1) +
                 (lambda.hasFormals() ? lambda.formals->formals.size() : 0);
             Env & env2(allocEnv(size));
-            env2.up = vCur.payload.lambda.env;
+            env2.up = vCur.lambda().env;
 
             Displacement displ = 0;
 
@@ -1603,7 +1603,7 @@ void EvalState::callFunction(Value & fun, std::span<Value *> args, Value & vRes,
                                              symbols[i.name])
                                     .atPos(lambda.pos)
                                     .withTrace(pos, "from call site")
-                                    .withFrame(*fun.payload.lambda.env, lambda)
+                                    .withFrame(*fun.lambda().env, lambda)
                                     .debugThrow();
                         }
                         env2.values[displ++] = i.def->maybeThunk(*this, env2);
@@ -1630,7 +1630,7 @@ void EvalState::callFunction(Value & fun, std::span<Value *> args, Value & vRes,
                                 .atPos(lambda.pos)
                                 .withTrace(pos, "from call site")
                                 .withSuggestions(suggestions)
-                                .withFrame(*fun.payload.lambda.env, lambda)
+                                .withFrame(*fun.lambda().env, lambda)
                                 .debugThrow();
                         }
                     unreachable();
@@ -1825,14 +1825,14 @@ void EvalState::autoCallFunction(const Bindings & args, Value & fun, Value & res
         }
     }
 
-    if (!fun.isLambda() || !fun.payload.lambda.fun->hasFormals()) {
+    if (!fun.isLambda() || !fun.lambda().fun->hasFormals()) {
         res = fun;
         return;
     }
 
-    auto attrs = buildBindings(std::max(static_cast<uint32_t>(fun.payload.lambda.fun->formals->formals.size()), args.size()));
+    auto attrs = buildBindings(std::max(static_cast<uint32_t>(fun.lambda().fun->formals->formals.size()), args.size()));
 
-    if (fun.payload.lambda.fun->formals->ellipsis) {
+    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)
@@ -1840,7 +1840,7 @@ void EvalState::autoCallFunction(const Bindings & args, Value & fun, Value & res
             attrs.insert(v);
     } else {
         // Otherwise, only pass the arguments that the function accepts
-        for (auto & i : fun.payload.lambda.fun->formals->formals) {
+        for (auto & i : fun.lambda().fun->formals->formals) {
             auto j = args.get(i.name);
             if (j) {
                 attrs.insert(*j);
@@ -1850,7 +1850,7 @@ Nix attempted to evaluate a function as a top level expression; in
 this case it must have its arguments supplied either by default
 values, or passed explicitly with '--arg' or '--argstr'. See
 https://nixos.org/manual/nix/stable/language/constructs.html#functions.)", symbols[i.name])
-                    .atPos(i.pos).withFrame(*fun.payload.lambda.env, *fun.payload.lambda.fun).debugThrow();
+                    .atPos(i.pos).withFrame(*fun.lambda().env, *fun.lambda().fun).debugThrow();
             }
         }
     }
diff --git a/src/libexpr/include/nix/expr/value.hh b/src/libexpr/include/nix/expr/value.hh
index febe36f80..26ec5ff38 100644
--- a/src/libexpr/include/nix/expr/value.hh
+++ b/src/libexpr/include/nix/expr/value.hh
@@ -482,6 +482,9 @@ public:
 
     NixFloat fpoint() const
     { return payload.fpoint; }
+
+    Lambda lambda() const
+    { return payload.lambda; }
 };
 
 
diff --git a/src/libexpr/primops.cc b/src/libexpr/primops.cc
index 48bc272f9..a24695bcd 100644
--- a/src/libexpr/primops.cc
+++ b/src/libexpr/primops.cc
@@ -3138,12 +3138,12 @@ static void prim_functionArgs(EvalState & state, const PosIdx pos, Value * * arg
     if (!args[0]->isLambda())
         state.error<TypeError>("'functionArgs' requires a function").atPos(pos).debugThrow();
 
-    if (!args[0]->payload.lambda.fun->hasFormals()) {
+    if (!args[0]->lambda().fun->hasFormals()) {
         v.mkAttrs(&state.emptyBindings);
         return;
     }
 
-    const auto &formals = args[0]->payload.lambda.fun->formals->formals;
+    const auto &formals = args[0]->lambda().fun->formals->formals;
     auto attrs = state.buildBindings(formals.size());
     for (auto & i : formals)
         attrs.insert(i.name, state.getBool(i.def), i.pos);
diff --git a/src/libexpr/print.cc b/src/libexpr/print.cc
index 06bae9c5c..f0e0eed2d 100644
--- a/src/libexpr/print.cc
+++ b/src/libexpr/print.cc
@@ -453,13 +453,13 @@ private:
 
         if (v.isLambda()) {
             output << "lambda";
-            if (v.payload.lambda.fun) {
-                if (v.payload.lambda.fun->name) {
-                    output << " " << state.symbols[v.payload.lambda.fun->name];
+            if (v.lambda().fun) {
+                if (v.lambda().fun->name) {
+                    output << " " << state.symbols[v.lambda().fun->name];
                 }
 
                 std::ostringstream s;
-                s << state.positions[v.payload.lambda.fun->pos];
+                s << state.positions[v.lambda().fun->pos];
                 output << " @ " << filterANSIEscapes(toView(s));
             }
         } else if (v.isPrimOp()) {
diff --git a/src/libexpr/value-to-xml.cc b/src/libexpr/value-to-xml.cc
index e26fff71b..54ff06f9e 100644
--- a/src/libexpr/value-to-xml.cc
+++ b/src/libexpr/value-to-xml.cc
@@ -126,18 +126,18 @@ static void printValueAsXML(EvalState & state, bool strict, bool location,
                 break;
             }
             XMLAttrs xmlAttrs;
-            if (location) posToXML(state, xmlAttrs, state.positions[v.payload.lambda.fun->pos]);
+            if (location) posToXML(state, xmlAttrs, state.positions[v.lambda().fun->pos]);
             XMLOpenElement _(doc, "function", xmlAttrs);
 
-            if (v.payload.lambda.fun->hasFormals()) {
+            if (v.lambda().fun->hasFormals()) {
                 XMLAttrs attrs;
-                if (v.payload.lambda.fun->arg) attrs["name"] = state.symbols[v.payload.lambda.fun->arg];
-                if (v.payload.lambda.fun->formals->ellipsis) attrs["ellipsis"] = "1";
+                if (v.lambda().fun->arg) attrs["name"] = state.symbols[v.lambda().fun->arg];
+                if (v.lambda().fun->formals->ellipsis) attrs["ellipsis"] = "1";
                 XMLOpenElement _(doc, "attrspat", attrs);
-                for (auto & i : v.payload.lambda.fun->formals->lexicographicOrder(state.symbols))
+                for (auto & i : v.lambda().fun->formals->lexicographicOrder(state.symbols))
                     doc.writeEmptyElement("attr", singletonAttrs("name", state.symbols[i.name]));
             } else
-                doc.writeEmptyElement("varpat", singletonAttrs("name", state.symbols[v.payload.lambda.fun->arg]));
+                doc.writeEmptyElement("varpat", singletonAttrs("name", state.symbols[v.lambda().fun->arg]));
 
             break;
         }
diff --git a/src/libflake/flake.cc b/src/libflake/flake.cc
index 24252d710..41141d41d 100644
--- a/src/libflake/flake.cc
+++ b/src/libflake/flake.cc
@@ -252,8 +252,8 @@ static Flake readFlake(
     if (auto outputs = vInfo.attrs()->get(sOutputs)) {
         expectType(state, nFunction, *outputs->value, outputs->pos);
 
-        if (outputs->value->isLambda() && outputs->value->payload.lambda.fun->hasFormals()) {
-            for (auto & formal : outputs->value->payload.lambda.fun->formals->formals) {
+        if (outputs->value->isLambda() && outputs->value->lambda().fun->hasFormals()) {
+            for (auto & formal : outputs->value->lambda().fun->formals->formals) {
                 if (formal.name != state.sSelf)
                     flake.inputs.emplace(state.symbols[formal.name], FlakeInput {
                         .ref = parseFlakeRef(state.fetchSettings, std::string(state.symbols[formal.name]))
diff --git a/src/nix-build/nix-build.cc b/src/nix-build/nix-build.cc
index 80ebf6bfa..e302aca67 100644
--- a/src/nix-build/nix-build.cc
+++ b/src/nix-build/nix-build.cc
@@ -387,8 +387,8 @@ static void main_nix_build(int argc, char * * argv)
                 return false;
             }
             bool add = false;
-            if (v.type() == nFunction && v.payload.lambda.fun->hasFormals()) {
-                for (auto & i : v.payload.lambda.fun->formals->formals) {
+            if (v.type() == nFunction && v.lambda().fun->hasFormals()) {
+                for (auto & i : v.lambda().fun->formals->formals) {
                     if (state->symbols[i.name] == "inNixShell") {
                         add = true;
                         break;
diff --git a/src/nix/flake.cc b/src/nix/flake.cc
index 95cf85663..13f7363fc 100644
--- a/src/nix/flake.cc
+++ b/src/nix/flake.cc
@@ -492,8 +492,8 @@ struct CmdFlakeCheck : FlakeCommand
                 if (!v.isLambda()) {
                     throw Error("overlay is not a function, but %s instead", showType(v));
                 }
-                if (v.payload.lambda.fun->hasFormals()
-                    || !argHasName(v.payload.lambda.fun->arg, "final"))
+                if (v.lambda().fun->hasFormals()
+                    || !argHasName(v.lambda().fun->arg, "final"))
                     throw Error("overlay does not take an argument named 'final'");
                 // FIXME: if we have a 'nixpkgs' input, use it to
                 // evaluate the overlay.

From 441fa86e82da65a71e01a5c45e3459287ab4d01e Mon Sep 17 00:00:00 2001
From: Sergei Zimmerman <xokdvium@proton.me>
Date: Thu, 12 Jun 2025 19:48:42 +0000
Subject: [PATCH 2/6] libexpr: Add and use `thunk` getter

---
 src/libexpr/eval.cc                         | 10 +++++-----
 src/libexpr/include/nix/expr/eval-inline.hh |  4 ++--
 src/libexpr/include/nix/expr/value.hh       |  5 ++++-
 3 files changed, 11 insertions(+), 8 deletions(-)

diff --git a/src/libexpr/eval.cc b/src/libexpr/eval.cc
index 51036a223..badb271f2 100644
--- a/src/libexpr/eval.cc
+++ b/src/libexpr/eval.cc
@@ -160,10 +160,10 @@ bool Value::isTrivial() const
         internalType != tApp
         && internalType != tPrimOpApp
         && (internalType != tThunk
-            || (dynamic_cast<ExprAttrs *>(payload.thunk.expr)
-                && ((ExprAttrs *) payload.thunk.expr)->dynamicAttrs.empty())
-            || dynamic_cast<ExprLambda *>(payload.thunk.expr)
-            || dynamic_cast<ExprList *>(payload.thunk.expr));
+            || (dynamic_cast<ExprAttrs *>(thunk().expr)
+                && ((ExprAttrs *) thunk().expr)->dynamicAttrs.empty())
+            || dynamic_cast<ExprLambda *>(thunk().expr)
+            || dynamic_cast<ExprList *>(thunk().expr));
 }
 
 
@@ -2163,7 +2163,7 @@ void EvalState::forceValueDeep(Value & v)
                 try {
                     // If the value is a thunk, we're evaling. Otherwise no trace necessary.
                     auto dts = debugRepl && i.value->isThunk()
-                        ? makeDebugTraceStacker(*this, *i.value->payload.thunk.expr, *i.value->payload.thunk.env, i.pos,
+                        ? makeDebugTraceStacker(*this, *i.value->thunk().expr, *i.value->thunk().env, i.pos,
                             "while evaluating the attribute '%1%'", symbols[i.name])
                         : nullptr;
 
diff --git a/src/libexpr/include/nix/expr/eval-inline.hh b/src/libexpr/include/nix/expr/eval-inline.hh
index 6e5759c0b..97bf71a6b 100644
--- a/src/libexpr/include/nix/expr/eval-inline.hh
+++ b/src/libexpr/include/nix/expr/eval-inline.hh
@@ -89,9 +89,9 @@ Env & EvalState::allocEnv(size_t size)
 void EvalState::forceValue(Value & v, const PosIdx pos)
 {
     if (v.isThunk()) {
-        Env * env = v.payload.thunk.env;
+        Env * env = v.thunk().env;
         assert(env || v.isBlackhole());
-        Expr * expr = v.payload.thunk.expr;
+        Expr * expr = v.thunk().expr;
         try {
             v.mkBlackhole();
             //checkInterrupt();
diff --git a/src/libexpr/include/nix/expr/value.hh b/src/libexpr/include/nix/expr/value.hh
index 26ec5ff38..29f8ac379 100644
--- a/src/libexpr/include/nix/expr/value.hh
+++ b/src/libexpr/include/nix/expr/value.hh
@@ -485,6 +485,9 @@ public:
 
     Lambda lambda() const
     { return payload.lambda; }
+
+    ClosureThunk thunk() const
+    { return payload.thunk; }
 };
 
 
@@ -492,7 +495,7 @@ extern ExprBlackHole eBlackHole;
 
 bool Value::isBlackhole() const
 {
-    return internalType == tThunk && payload.thunk.expr == (Expr*) &eBlackHole;
+    return internalType == tThunk && thunk().expr == (Expr*) &eBlackHole;
 }
 
 void Value::mkBlackhole()

From f07a9f863e16bb71ec330abf6c2ec5d5bff68788 Mon Sep 17 00:00:00 2001
From: Sergei Zimmerman <xokdvium@proton.me>
Date: Thu, 12 Jun 2025 19:51:44 +0000
Subject: [PATCH 3/6] libexpr: Add and use `primOpApp` getter

---
 src/libexpr/eval.cc                   | 10 +++++-----
 src/libexpr/include/nix/expr/value.hh |  3 +++
 2 files changed, 8 insertions(+), 5 deletions(-)

diff --git a/src/libexpr/eval.cc b/src/libexpr/eval.cc
index badb271f2..f9bff7b98 100644
--- a/src/libexpr/eval.cc
+++ b/src/libexpr/eval.cc
@@ -525,9 +525,9 @@ std::ostream & operator<<(std::ostream & output, const PrimOp & primOp)
 
 const PrimOp * Value::primOpAppPrimOp() const
 {
-    Value * left = payload.primOpApp.left;
+    Value * left = primOpApp().left;
     while (left && !left->isPrimOp()) {
-        left = left->payload.primOpApp.left;
+        left = left->primOpApp().left;
     }
 
     if (!left)
@@ -1702,7 +1702,7 @@ void EvalState::callFunction(Value & fun, std::span<Value *> args, Value & vRes,
             Value * primOp = &vCur;
             while (primOp->isPrimOpApp()) {
                 argsDone++;
-                primOp = primOp->payload.primOpApp.left;
+                primOp = primOp->primOpApp().left;
             }
             assert(primOp->isPrimOp());
             auto arity = primOp->primOp()->arity;
@@ -1718,8 +1718,8 @@ void EvalState::callFunction(Value & fun, std::span<Value *> args, Value & vRes,
 
                 Value * vArgs[maxPrimOpArity];
                 auto n = argsDone;
-                for (Value * arg = &vCur; arg->isPrimOpApp(); arg = arg->payload.primOpApp.left)
-                    vArgs[--n] = arg->payload.primOpApp.right;
+                for (Value * arg = &vCur; arg->isPrimOpApp(); arg = arg->primOpApp().left)
+                    vArgs[--n] = arg->primOpApp().right;
 
                 for (size_t i = 0; i < argsLeft; ++i)
                     vArgs[argsDone + i] = args[i];
diff --git a/src/libexpr/include/nix/expr/value.hh b/src/libexpr/include/nix/expr/value.hh
index 29f8ac379..797e31191 100644
--- a/src/libexpr/include/nix/expr/value.hh
+++ b/src/libexpr/include/nix/expr/value.hh
@@ -488,6 +488,9 @@ public:
 
     ClosureThunk thunk() const
     { return payload.thunk; }
+
+    FunctionApplicationThunk primOpApp() const
+    { return payload.primOpApp; }
 };
 
 

From c041d71406f706d971ee0ad53d555450de7ad03d Mon Sep 17 00:00:00 2001
From: Sergei Zimmerman <xokdvium@proton.me>
Date: Thu, 12 Jun 2025 19:53:44 +0000
Subject: [PATCH 4/6] libexpr: Add and use `app` getter

---
 src/libexpr/eval.cc                         | 2 +-
 src/libexpr/include/nix/expr/eval-inline.hh | 2 +-
 src/libexpr/include/nix/expr/value.hh       | 3 +++
 3 files changed, 5 insertions(+), 2 deletions(-)

diff --git a/src/libexpr/eval.cc b/src/libexpr/eval.cc
index f9bff7b98..37018007f 100644
--- a/src/libexpr/eval.cc
+++ b/src/libexpr/eval.cc
@@ -148,7 +148,7 @@ PosIdx Value::determinePos(const PosIdx pos) const
     switch (internalType) {
         case tAttrs: return attrs()->pos;
         case tLambda: return lambda().fun->pos;
-        case tApp: return payload.app.left->determinePos(pos);
+        case tApp: return app().left->determinePos(pos);
         default: return pos;
     }
     #pragma GCC diagnostic pop
diff --git a/src/libexpr/include/nix/expr/eval-inline.hh b/src/libexpr/include/nix/expr/eval-inline.hh
index 97bf71a6b..7d13d7cc7 100644
--- a/src/libexpr/include/nix/expr/eval-inline.hh
+++ b/src/libexpr/include/nix/expr/eval-inline.hh
@@ -106,7 +106,7 @@ void EvalState::forceValue(Value & v, const PosIdx pos)
         }
     }
     else if (v.isApp())
-        callFunction(*v.payload.app.left, *v.payload.app.right, v, pos);
+        callFunction(*v.app().left, *v.app().right, v, pos);
 }
 
 
diff --git a/src/libexpr/include/nix/expr/value.hh b/src/libexpr/include/nix/expr/value.hh
index 797e31191..d25511c45 100644
--- a/src/libexpr/include/nix/expr/value.hh
+++ b/src/libexpr/include/nix/expr/value.hh
@@ -491,6 +491,9 @@ public:
 
     FunctionApplicationThunk primOpApp() const
     { return payload.primOpApp; }
+
+    FunctionApplicationThunk app() const
+    { return payload.app; }
 };
 
 

From e4df1891237b58050e7b10380f7f62551ade2783 Mon Sep 17 00:00:00 2001
From: Sergei Zimmerman <xokdvium@proton.me>
Date: Thu, 12 Jun 2025 19:57:46 +0000
Subject: [PATCH 5/6] libexpr: Add and use `pathStr` getter

---
 src/libexpr-c/nix_api_value.cc        | 2 +-
 src/libexpr/eval.cc                   | 6 +++---
 src/libexpr/include/nix/expr/value.hh | 5 ++++-
 src/libexpr/primops.cc                | 2 +-
 4 files changed, 9 insertions(+), 6 deletions(-)

diff --git a/src/libexpr-c/nix_api_value.cc b/src/libexpr-c/nix_api_value.cc
index 298d94845..8afe35a4b 100644
--- a/src/libexpr-c/nix_api_value.cc
+++ b/src/libexpr-c/nix_api_value.cc
@@ -252,7 +252,7 @@ const char * nix_get_path_string(nix_c_context * context, const nix_value * valu
         // We could use v.path().to_string().c_str(), but I'm concerned this
         // crashes. Looks like .path() allocates a CanonPath with a copy of the
         // string, then it gets the underlying data from that.
-        return v.payload.path.path;
+        return v.pathStr();
     }
     NIXC_CATCH_ERRS_NULL
 }
diff --git a/src/libexpr/eval.cc b/src/libexpr/eval.cc
index 37018007f..66ac2e9fd 100644
--- a/src/libexpr/eval.cc
+++ b/src/libexpr/eval.cc
@@ -2368,7 +2368,7 @@ BackedStringView EvalState::coerceToString(
             !canonicalizePath && !copyToStore
             ? // FIXME: hack to preserve path literals that end in a
               // slash, as in /foo/${x}.
-              v.payload.path.path
+              v.pathStr()
             : copyToStore
             ? store->printStorePath(copyPathToStore(context, v.path()))
             : std::string(v.path().path.abs());
@@ -2643,7 +2643,7 @@ void EvalState::assertEqValues(Value & v1, Value & v2, const PosIdx pos, std::st
                 ValuePrinter(*this, v2, errorPrintOptions))
                 .debugThrow();
         }
-        if (strcmp(v1.payload.path.path, v2.payload.path.path) != 0) {
+        if (strcmp(v1.pathStr(), v2.pathStr()) != 0) {
             error<AssertionError>(
                 "path '%s' is not equal to path '%s'",
                 ValuePrinter(*this, v1, errorPrintOptions),
@@ -2811,7 +2811,7 @@ bool EvalState::eqValues(Value & v1, Value & v2, const PosIdx pos, std::string_v
             return
                 // FIXME: compare accessors by their fingerprint.
                 v1.payload.path.accessor == v2.payload.path.accessor
-                && strcmp(v1.payload.path.path, v2.payload.path.path) == 0;
+                && strcmp(v1.pathStr(), v2.pathStr()) == 0;
 
         case nNull:
             return true;
diff --git a/src/libexpr/include/nix/expr/value.hh b/src/libexpr/include/nix/expr/value.hh
index d25511c45..fc9ce1b39 100644
--- a/src/libexpr/include/nix/expr/value.hh
+++ b/src/libexpr/include/nix/expr/value.hh
@@ -445,7 +445,7 @@ public:
         assert(internalType == tPath);
         return SourcePath(
             ref(payload.path.accessor->shared_from_this()),
-            CanonPath(CanonPath::unchecked_t(), payload.path.path));
+            CanonPath(CanonPath::unchecked_t(), pathStr()));
     }
 
     std::string_view string_view() const
@@ -494,6 +494,9 @@ public:
 
     FunctionApplicationThunk app() const
     { return payload.app; }
+
+    const char * pathStr() const
+    { return payload.path.path; }
 };
 
 
diff --git a/src/libexpr/primops.cc b/src/libexpr/primops.cc
index a24695bcd..60f44ca62 100644
--- a/src/libexpr/primops.cc
+++ b/src/libexpr/primops.cc
@@ -651,7 +651,7 @@ struct CompareValues
                     // Note: we don't take the accessor into account
                     // since it's not obvious how to compare them in a
                     // reproducible way.
-                    return strcmp(v1->payload.path.path, v2->payload.path.path) < 0;
+                    return strcmp(v1->pathStr(), v2->pathStr()) < 0;
                 case nList:
                     // Lexicographic comparison
                     for (size_t i = 0;; i++) {

From bc6b52aff012592a9794df979c0617c85f46c2c3 Mon Sep 17 00:00:00 2001
From: Sergei Zimmerman <xokdvium@proton.me>
Date: Thu, 12 Jun 2025 20:01:38 +0000
Subject: [PATCH 6/6] libexpr: Add and use `pathAccessor` getter

---
 src/libexpr/eval.cc                   | 4 ++--
 src/libexpr/include/nix/expr/value.hh | 5 ++++-
 2 files changed, 6 insertions(+), 3 deletions(-)

diff --git a/src/libexpr/eval.cc b/src/libexpr/eval.cc
index 66ac2e9fd..ae422a3d4 100644
--- a/src/libexpr/eval.cc
+++ b/src/libexpr/eval.cc
@@ -2636,7 +2636,7 @@ void EvalState::assertEqValues(Value & v1, Value & v2, const PosIdx pos, std::st
         return;
 
     case nPath:
-        if (v1.payload.path.accessor != v2.payload.path.accessor) {
+        if (v1.pathAccessor() != v2.pathAccessor()) {
             error<AssertionError>(
                 "path '%s' is not equal to path '%s' because their accessors are different",
                 ValuePrinter(*this, v1, errorPrintOptions),
@@ -2810,7 +2810,7 @@ bool EvalState::eqValues(Value & v1, Value & v2, const PosIdx pos, std::string_v
         case nPath:
             return
                 // FIXME: compare accessors by their fingerprint.
-                v1.payload.path.accessor == v2.payload.path.accessor
+                v1.pathAccessor() == v2.pathAccessor()
                 && strcmp(v1.pathStr(), v2.pathStr()) == 0;
 
         case nNull:
diff --git a/src/libexpr/include/nix/expr/value.hh b/src/libexpr/include/nix/expr/value.hh
index fc9ce1b39..80bee59e9 100644
--- a/src/libexpr/include/nix/expr/value.hh
+++ b/src/libexpr/include/nix/expr/value.hh
@@ -444,7 +444,7 @@ public:
     {
         assert(internalType == tPath);
         return SourcePath(
-            ref(payload.path.accessor->shared_from_this()),
+            ref(pathAccessor()->shared_from_this()),
             CanonPath(CanonPath::unchecked_t(), pathStr()));
     }
 
@@ -497,6 +497,9 @@ public:
 
     const char * pathStr() const
     { return payload.path.path; }
+
+    SourceAccessor * pathAccessor() const
+    { return payload.path.accessor; }
 };