- Condition value lowering: `src/mir/join_ir/lowering/condition_lowerer.rs`
- MIR verification (undefined values): `src/mir/verification/ssa.rs`
- Test fixture: `apps/tests/loop_if_phi.hako`
## Problem
Observed error (VM):
-`use of undefined value ValueId(...)` inside the loop body, originating from the modulo expression in the if-condition.
The symptom appeared in `apps/tests/loop_if_phi.hako`:
```hako
if (i % 2 == 1) { ... } else { ... }
```
## Root Cause
In `lower_if_sum_pattern`, the if-condition was extracted (and its JoinIR value-expression lowered) **before**`i_param` / `sum_param` existed, so `Variable("i")` inside complex expressions resolved through the caller-provided `ConditionEnv`.
That early `ConditionEnv` mapping could not be remapped by the boundary/merger, resulting in JoinIR ValueIds that became undefined host ValueIds in MIR.
## Fix (P0)
- Move `extract_if_condition(...)` so it runs **after**`local_cond_env` is constructed and shadowed:
-`local_cond_env.insert(loop_var, i_param)`
-`local_cond_env.insert(update_var, sum_param)`
- (and any condition bindings remapped to `main_params`)
This ensures complex expressions like `i % 2` resolve `i` to `i_param` (a loop_step param that the merger remaps), preventing undefined ValueIds.
## Fixture Note (Coercion SSOT)
After Phase 275 (C2), implicit `"String" + Integer` is a TypeError. The fixture uses:
-`sum.toString()` instead of `"sum=" + sum` or `str(sum)`.
## Acceptance
-`apps/tests/loop_if_phi.hako` runs on VM without undefined ValueId errors and prints `sum=9`.
