From 155bbc2f731d37e944be041f3dc3e51bb71fdb83 Mon Sep 17 00:00:00 2001
From: Aayush Sabharwal <aayush.sabharwal@gmail.com>
Date: Fri, 9 May 2025 15:02:08 +0530
Subject: [PATCH] refactor: add error message for wrapped variable in
 `collect_var!`

---
 src/utils.jl | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/src/utils.jl b/src/utils.jl
index d0fd3d40f9..90431a7749 100644
--- a/src/utils.jl
+++ b/src/utils.jl
@@ -606,6 +606,17 @@ end
 
 function collect_var!(unknowns, parameters, var, iv; depth = 0)
     isequal(var, iv) && return nothing
+    if Symbolics.iswrapped(var)
+        error("""
+        Internal Error. Please open an issue with an MWE.
+
+        Encountered a wrapped value in `collect_var!`. This function should only ever \
+        receive unwrapped symbolic variables. This is likely a bug in the code generating \
+        an expression passed to `collect_vars!` or `collect_scoped_vars!`. A common cause \
+        is using `substitute` or `fast_substitute` with rules where the values are \
+        wrapped symbolic variables.
+        """)
+    end
     check_scope_depth(getmetadata(var, SymScope, LocalScope()), depth) || return nothing
     var = setmetadata(var, SymScope, LocalScope())
     if iscalledparameter(var)