Some documentation updates for Lua 5.5

[bjornbm]

Mainly update to parts of the documentation to reflect that Lua 5.5 is a compiler target. Rather low hanging fruit I will admit.

Someone should confirm that “The options 5.4 and 5.5 are equivalent to 5.3, but also allow using the <close>
variable annotation.” (i.e., 5.5 does not introduce other changes that deserve mention. I admit I did not dig deep.)

[hishamhm]

Thanks! This is much appreciated!

Perhaps a "non-difference" that might be worth mentioning in the documentation is that Teal does allow modifiying the for index variables (like Lua 5.4 and below) even when the target is Lua 5.5.

[bjornbm]

Perhaps a "non-difference" that might be worth mentioning in the documentation is that Teal does allow modifiying the for index variables (like Lua 5.4 and below) even when the target is Lua 5.5.

Where would be a suitable place for this? https://github.com/teal-language/tl/blob/main/docs/src/teal_standard_library_and_lua_compatibility.md?

Also, if this is the desired behavior in Teal code, I think that when the target is 5.5 (or any target that should be compatible with 5.5) the following transformation should be used to avoid a crash (attempt to assign to const variable 'i') on 5.5:

for i = 1, 5 do
   i = i + 1
   print(i)
end

Should become:

for i = 1, 5 do local i = i
   i = i + 1
   print(i)
end

(Deserves a new issue if you agree)

[hishamhm]

@bjornbm the compiler already does this :)

[bjornbm]

@hishamhm I believe I am seeing the numeric for exception reported as a one of the incidental observations in #1158:

Not addressed here

Two things I ran into while testing, both out of scope:

Numeric for has the same problem, and it is worse. Lua 5.5 also makes the
control variable of a numeric for a constant, and lua_compat.adjust_code
has no fornum case at all. So ordinary, non-macro Teal code that writes to a
numeric for variable type checks cleanly and then produces invalid Lua on 5.5:

$ lua5.5 ./tl run fornum.tl
Internal Compiler Error: Teal generator produced invalid Lua. Please report a
bug at https://github.com/teal-language/tl

fornum.tl:3: attempt to assign to const variable 'i'

This reproduces on master without any of the changes here and affects code that
has nothing to do with macros. It needs lua_compat and visitors changes, so
I left it alone — happy to open a separate issue for it.

I tried with an “pairs”-for and then the a local copy of the key is indeed assigned if the target is 5.4 or 5.5. So it seems the numeric for case was forgotten.

[hishamhm]

Let's not document this line here. Instead, let's open an issue to get this fixed.

[bjornbm]

Note removed. We have #1160 for this since yesterday.

[hishamhm]

Ahh sure, sorry!