verbose_errors improvement

* Use std::format instead of sprintf for verbose errors when decoding table keys
* Add a unit test for the different table key types

1 files changed, 1 insertions, 1 deletions

diff --git a/tests/lanes_as_upvalue.lua b/tests/lanes_as_upvalue.lua
index beef22e..1c316e4 100644
--- a/tests/lanes_as_upvalue.lua
+++ b/tests/lanes_as_upvalue.lua
@@ -8,4 +8,4 @@ local g = lanes.gen( "*", { name = 'auto', error_trace_level = "extended"}, foo)
 
 -- this should raise an error as lanes.timer_lane is a Lane (a non-deep full userdata)
 local res, err = pcall( g)
-print( "Generating lane yielded: ", tostring( res), tostring( err))
+assert(res == false and type(err) == "string", "got " .. tostring(res) .. " " .. tostring(err))