From 4f6a3d7e9efafdcddedef0245475fdd4314fc54d Mon Sep 17 00:00:00 2001
From: Qyriad <qyriad@qyriad.me>
Date: Sun, 7 Jul 2024 18:45:06 -0600
Subject: [PATCH] libexpr: include the type of the non-derivation value in the
 type error

Change-Id: Id4717b5b0df7c09b0dbf17e642d8713a0a3efbae
---
 src/libexpr/get-drvs.cc | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/src/libexpr/get-drvs.cc b/src/libexpr/get-drvs.cc
index fe4d3a7d5..d7869d09b 100644
--- a/src/libexpr/get-drvs.cc
+++ b/src/libexpr/get-drvs.cc
@@ -447,7 +447,8 @@ static void getDerivations(EvalState & state, Value & vIn,
         return;
     } else if (v.type() != nAttrs) {
         state.error<TypeError>(
-            "expression does not evaluate to a derivation (or a list or set of those)"
+            "expression was expected to be a derivation or collection of derivations, but instead was %s",
+            showType(v.type(), true)
         ).debugThrow();
     }