Default "tostring" for a table is an error-reporting function?

[Dirk Laurie <dirk.laurie@...>]

We all know that Lua 5.3.4 is the brightest, shiniest Lua ever.
Here's just one reason why:

$ lua
Lua 5.3.4  Copyright (C) 1994-2017 Lua.org, PUC-Rio
> a=setmetatable({},{__name="Jedi Knight"})
> a
Jedi Knight: 0x2089510

However, the documentation of this feature in the Manual is scanty, even coy.

* In §2.4, it says:

"Some functions in the standard library (e.g., `tostring`) use other fields
in metatables for their own purposes."

* In the entry for luaL_newmetatable in §5.1, it says:

"(The entry __name is used by some error-reporting functions.)"

Now one _could_ make out a case that anything containing an actual
memory address is an error-reporting function ...

But for a feature as popular as this one is sure to be, maybe just a tiny
bit extra in §2.4?

"Some functions in the standard library use other fields in metatables for
their own purposes. E.g., `tostring` replaces `table`, `userdata` etc. by the
value of `__name`."