lua: Unexpected NULL with nested self references

[Aaron Faanes]

(If there's a better list for this, let me know and ignore the rest ;) )

I ran into a problem compiling some old lua code I had lying around. I
managed to isolate the cause of the exception in the following example:

---

local instance = {};

function instance:Constructor()
    function self:Bar() end;
    function self:Bar() end; -- Null PMC access here!
end;

instance:Constructor()

---

I receive the following exception:

lua.pbc: nullpmc.lua:5: Null PMC access in set_pmc_keyed()
stack traceback:
    nullpmc.lua:5: in function 'instance.Constructor_13'
    nullpmc.lua:8: in main chunk
    [PIR]: in function 'docall'
    [PIR]: in function 'handle_script'
    [PIR]: in function 'main'

I've been picking apart the generated code, trying to see what's causing the
issue. The null
access is due to the generated PIR referring to "self" in two different
ways. The following
is, hopefully, a useful snippet:

.annotate 'line', 4
    .const "Sub" fct_17 = "post18"
    newclosure $P19, fct_17
    $P20 = subr."getfenv"()
    $P19."setfenv"($P20)
    set param_self_1[k_Bar], $P19
.annotate 'line', 5
    .const "Sub" fct_23 = "post24"
    newclosure $P25, fct_23
    $P26 = subr."getfenv"()
    $P25."setfenv"($P26)
    find_lex $P27, "self_2"
    set $P27[k_Bar], $P25

As you can see, the first use of self is "param_self_1", which is expected,
but the second use of
self is the non-existent "self_2".

If you look at the PAST generated, "self_2" can be found inside self:Bar()
as the unique name for the
implicit self. I haven't been able to determine how that name managed to
pollute the outer symbol table.

I hope this bug report helps! Let me know if I should file this somewhere
(or if I require a sanity check).

-- 
Aaron Faanes <dafrito at gmail.com>
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