**Problem**:
When if-statement has no explicit else-branch:
- Else-branch entry creates single-pred PHIs (e.g., %9 → %22)
- But else_var_map_end_opt was returned as None
- merge_modified_vars fell back to pre_if values
- Continuation block used old ValueIds → SSA violation
**Root Cause**:
if_form.rs L126 returned (void_val, None, None) instead of
passing the PHI-renamed variable_map to merge_modified_vars.
**Fix**:
Return Some(self.variable_map.clone()) for empty else-branch
to propagate PHI-renamed ValueIds to merge block.
**Test**:
✅ mir_stage1_using_resolver_full_collect_entries_verifies now passes
✅ MIR verifier confirms no undefined value errors
🤖 Generated with [Claude Code](https://claude.com/claude-code)
Co-Authored-By: Claude <noreply@anthropic.com>
Root Cause:
- Else blocks were not propagating variable assignments to outer scope
- Bug 1 (if_form.rs): PHI materialization happened before variable_map reset,
causing PHI nodes to be lost
- Bug 2 (phi.rs): Variable merge didn't check if else branch modified variables
Changes:
- src/mir/builder/if_form.rs:93-127
- Reordered: reset variable_map BEFORE materializing PHI nodes
- Now matches then-branch pattern (reset → materialize → execute)
- Applied to both "else" and "no else" branches for consistency
- src/mir/builder/phi.rs:137-154
- Added else_modified_var check to detect variable modifications
- Use modified value from else_var_map_end_opt when available
- Fall back to pre-if value only when truly not modified
Test Results:
✅ Simple block: { x=42 } → 42
✅ If block: if 1 { x=42 } → 42
✅ Else block: if 0 { x=99 } else { x=42 } → 42 (FIXED!)
✅ Stage-B body extraction: "return 42" correctly extracted (was null)
Impact:
- Else block variable assignments now work correctly
- Stage-B compiler body extraction restored
- Selfhost builder path can now function
- Foundation for Phase 21.x progress
🤖 Generated with [Claude Code](https://claude.com/claude-code)
Co-Authored-By: Claude <noreply@anthropic.com>
- Unify standard method calls to emit_unified_call; route via RouterPolicy and apply rewrite::{special,known} at a single entry.\n- Stabilize emit-time invariants: LocalSSA finalize + BlockSchedule PHI→Copy→Call ordering; metadata propagation on copies.\n- Known rewrite default ON (userbox only, strict guards) with opt-out flag NYASH_REWRITE_KNOWN_DEFAULT=0.\n- Expand TypeAnnotation whitelist (is_digit_char/is_hex_digit_char/is_alpha_char/Map.has).\n- Docs: unified-method-resolution design note; Quick Reference normalization note; selfhosting/quickstart.\n- Tools: add tools/selfhost_smoke.sh (dev-only).\n- Keep behavior unchanged for Unknown/core/user-instance via BoxCall fallback; all tests green (quick/integration).
- SSOT using profiles (aliases/packages via nyash.toml), AST prelude merge
- Parser/member guards; Builder pin/PHI and instance→function rewrite (dev on)
- VM refactors (handlers split) and JSON roundtrip/nested stabilization
- CURRENT_TASK.md updated with scope and acceptance criteria
Notes: dev-only guards remain togglable via env; no default behavior changes for prod.
