[JuliaLowering] Avoid creating global binding for keyword slurp argument (#60600)
When `use_ssa_kw_temps=false` (i.e., when a keyword default depends on
another keyword name), `kw_val_vars` was set to `kw_names` which
included the slurp argument. Since the slurp argument is passed via
`remaining_kws`, including it in `kw_val_vars` caused:
1. The slurp name to be referenced as an unbound `Identifier` in kwcall
2. Scope analysis resolving it as a global binding
3. The call to body method having an extra argument
This fix excludes the slurp argument from `kw_val_vars` when
`has_kw_slurp=true`, since it's always the last element of `kw_names`.
IR change in kwcall method for `f(; a=1, b=a, kws...) = (a, b, kws)`:
Before:
22 TestMod.#f#0
23 slot₅/a
24 slot₆/b
25 Main.kws # unwanted global
26 (call %₂₂ %₂₃ %₂₄ %₂₅ %₂₁ slot₃/#self#) # extra argument
After:
22 TestMod.#f#0
23 slot₅/a
24 slot₆/b
25 (call %₂₂ %₂₃ %₂₄ %₂₁ slot₃/#self#) # correct
This fix is important not only for the correctness of the IR generated
by JuliaLowering, but also it eliminates false positive undefined global
variable reports that JETLS would report for cases like the following:
```julia
function f_kw_slurp_dep(; a=1, b=a, kws...)
(a, b, kws)
end
```
Co-authored-by: Claude Opus 4.5 <noreply@anthropic.com>
julia
64d45186 - [JuliaLowering] Avoid creating global binding for keyword slurp argument (#60600)
