Remove conditional logic and consolidate NODE_IF implementation to use
variable-sized nodes exclusively. This eliminates dual code paths and
completes the NODE_IF migration started in previous commits.
Changes:
- inline new_if_var into new_if, remove p->var_nodes_enabled condition
- remove new_unless function, replace calls with new_if (swap then/else)
- remove codegen_if function, merge nil? optimization into gen_if_var
- remove NODE_IF case from main codegen switch (always wrapped in NODE_VARIABLE)
- fix nil? optimization to handle both traditional and variable-sized nodes
- update gen_if_var to use direct struct field access instead of macros
The nil? optimization now works with both node representations:
- Traditional: NODE_TYPE(condition) == NODE_CALL (preserved)
- Variable-sized: NODE_VARIABLE wrapper containing NODE_CALL struct
This ensures obj.nil? patterns generate optimized OP_JMPNIL bytecode
regardless of AST node representation.
Co-authored-by: Claude <noreply@anthropic.com>
Yukihiro "Matz" Matsumoto
01b2a7bd22