fix(compiler): expand multi-values in obj:method(...) calls#248
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The method-call codegen hardcoded `arg_count = length(args) + 1`, so
`obj:m(unpack(vals))` compiled as a call with a fixed argument count and
discarded every unpacked value after the first. Reference Lua treats
`t:m(unpack(vals))` as sugar for `t.m(t, vals[1], vals[2], ...)`.
Extend `gen_expr(%Expr.MethodCall{...})` to use the same last-argument
classification (`:vararg` / `:multi_call` / `:normal`) that `Expr.Call`
already has, offset by one register for the implicit `self` slot:
- vararg tail → `call(base, -(arg_count + 2), ...)`
- inner call → patch inner result_count to -2; outer
`call(base, {:multi, 1 + fixed_count}, ...)`
- normal → unchanged
No executor change needed: `:call` dispatch operates purely on register
layout regardless of whether the function reached `R[base]` via `:self`
or `:move`.
Fixes #247.
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Summary
obj:method(unpack(args))drops all but first unpacked value #247:obj:m(unpack(vals))was dropping every value after the first because the method-call codegen hardcoded a fixedarg_count.gen_expr(%Expr.MethodCall{...})now mirrors the last-argument classification (:vararg/:multi_call/:normal) thatExpr.Callalready had, offset by one register for the implicitselfslot.:calldispatch operates purely on register layout regardless of whether the function reachedR[base]via:selfor:move.The user-visible knock-on from #247 —
("%s,%s,%s"):format(table.unpack(args))raising aMatchErrorinstring.format— is a symptom of the same bug and is resolved by this change. It surfaced in real code throughsay/init.lua(str:format(unpack(strings))), which is whatluassertuses.Test plan
mix test test/language/function_test.exs— 5 new regressions coveringtable.unpack, vararg, inner-call expansion, leading fixed args before an unpack, and thestring:formatknock-onmix test— full suite passes (1889 tests, 0 failures, 30 skipped)obj:method(unpack(args))drops all but first unpacked value #247 produce the documented expected output (n=3,[a,b,c])