Lua 5.5.0 initial fixes

[michaeam]

Trivial test, i.e. by far not complete:

$ pallenec --emit-lua examples/arithmetic/arithmetic.pln
$ $ cat examples/arithmetic/arithmetic.lua
-- Copyright (c) 2020, The Pallene Developers
-- Pallene is licensed under the MIT license.
-- Please refer to the LICENSE and AUTHORS files for details
-- SPDX-License-Identifier: MIT

local m = {}

function m.add(a, b)
    return (a) + (b)
end

function m.subtract(a, b)
    return (a) - (b)
end

return m

[hugomg]

Looks promising!

I'll wait until we sort out the lua-internals PR before we run this through the CI. The CI won't work unless that other PR is merged first.

[hugomg]

Can we declare the variable inside the for loop?

for _line in input:gmatch("([^\n]*)") do
    local line = _line:match("^%s*(.-)%s*$")

[hugomg]

This should be exactly 5.5.

In fact, if Luarocks allowed it, we would specify the minor patch 5.5.0. Pallene is only compatible with one specific minor patch at a time, because we rely on internal APIs that can break even in a minor patch.

[hugomg]

This looks sketchy. luaH_getstr now returns a lu_byte instead of a pointer. It probably makes no sense to cast the return value to TValue* ?

We need to look closer into this, but its possible that this API change is related to the 5.5 changes to the internal representation of arrays, which now stores the TValue tag separately from the payload. https://sol.sbc.org.br/index.php/sblp/article/view/30252