Error objects have no file and line in their message #5

Goal

Give Error objects the file and line where they were raised, as string errors have in front of their message.

Why

error( "msg" ) produces file.lua:12: msg, but an Error object's message has no place: it's only in its traceback. A printed or logged error object doesn't say where it came from.

Details

• Listed in docs/api.md, Known Issues (0.4.0).
• The place could be taken with debug.getinfo when the object is created (the traceback already starts there) and stored as a field, or put in front of tostring( err ). Changing the message itself would affect code that compares messages.