What's even more cursed is this:

nix::EvalState::eqValues (this=0x555555e8b770, v1=..., v2=..., pos=..., errorCtx="while testing two values for equality") at lix/libexpr/eval.cc:2613
2613        forceValue(v2, pos);
(gdb)
2616        if (v1.type() == nInt && v2.type() == nFloat) {
(gdb)
2619        if (v1.type() == nFloat && v2.type() == nInt) {
(gdb)
2624        if (v1.type() != v2.type()) return false;
(gdb)
2629        auto pointerEq = [&] { return v1.pointerEqProxy() == v2.pointerEqProxy(); };
(gdb)
2631        switch (v1.type()) {
(gdb)
2658                if (pointerEq()) return true;
(gdb)
2661                if (isDerivation(v1) && isDerivation(v2)) {
(gdb)
2669                if (v1.attrs()->size() != v2.attrs()->size()) return false;
(gdb) p v1.attrs()->size()
$1 = 2
(gdb) p v2.attrs()->size()
$2 = 3

It's not equal because the attrset size is incorrect? How???

In reply to @raitobezarius:matrix.org
i want to go and say that zomg the fact that we broke eval based on this behavior :')

In reply to @xokdvium:matrix.org
Updates never replace anything - they copy to a new attribute set though. It's puzzling

Yeah so doing this does help:

diff --git a/lix/libexpr/eval.cc b/lix/libexpr/eval.cc
index f1ba9e01c..5a5acd6aa 100644
--- a/lix/libexpr/eval.cc
+++ b/lix/libexpr/eval.cc
@@ -2682,6 +2682,7 @@ bool EvalState::eqValues(Value & v1, Value & v2, const PosIdx pos, std::string_v
 
         /* Functions are incomparable. */
         case nFunction:
+           if (pointerEq()) return true;
             return false;
 
         case nExternal:

But I'm not sure about all the consequences :)

Yeah so doing this does help:

diff --git a/lix/libexpr/eval.cc b/lix/libexpr/eval.cc
index f1ba9e01c..5a5acd6aa 100644
--- a/lix/libexpr/eval.cc
+++ b/lix/libexpr/eval.cc
@@ -2682,6 +2682,7 @@ bool EvalState::eqValues(Value & v1, Value & v2, const PosIdx pos, std::string_v
 
         /* Functions are incomparable. */
         case nFunction:
+            if (pointerEq()) return true;
             return false;
 
         case nExternal:

But I'm not sure about all the consequences :)

~~What's even more cursed is this~~:

• xokdvium got confused, don't mind the noise *

In reply to @aloisw:julia0815.de
I think https://git.lix.systems/lix-project/lix/commit/80654b84b610f4c0622dd10f0af78a8a2ce97048 is the offending change btw. Currently building that and its parent to confirm.