From 139c873b1a8c781c6f686ab06d9008e8fa25a517 Mon Sep 17 00:00:00 2001
From: Kaan <81116098+kaan650@users.noreply.github.com>
Date: Thu, 22 Oct 2026 14:58:01 +0300
Subject: [PATCH] Fix strict mode losing effect errors that are not strings
 (#104)

Co-authored-by: centau <83140718+centau@users.noreply.github.com>
---
 src/graph.luau  | 7 ++++---
 test/tests.luau | 9 +++++++++
 2 files changed, 13 insertions(+), 3 deletions(-)

diff --git a/src/graph.luau b/src/graph.luau
index be76dc1..4cd10ad 100644
--- a/src/graph.luau
+++ b/src/graph.luau
@@ -21,10 +21,11 @@ export type Node<T> =  {
 
 local scopes = { n = 0 } :: { [number]: Node<any>, n: number } -- scopes stack
 
-local function efn(err: string)
-    local trace = debug.traceback(err, 2)
+local function efn(err: unknown)
+    local message = tostring(err)
+    local trace = debug.traceback(message, 2)
 
-    if string.find(err, "^effect error stacktrace") then -- if effect error is nested
+    if string.find(message, "^effect error stacktrace") then -- if effect error is nested
         trace = string.gsub("    " .. trace, "\n", function() -- indent entire error
             return "\n    "
         end)
diff --git a/test/tests.luau b/test/tests.luau
index 8cda87b..a8bf2e0 100644
--- a/test/tests.luau
+++ b/test/tests.luau
@@ -3196,6 +3196,15 @@ TEST("strict", wrap_root(function()
         CHECK(not ok)
     end
 
+    do CASE "error with a non-string value"
+        local ok, err = pcall(effect, function()
+            error({})
+        end)
+
+        CHECK(not ok)
+        CHECK(string.find(err, "table: "))
+    end
+
     do CASE "duplicate properties"
         local ok = pcall(function()
             create "TextLabel" {