feat(joinir): Phase 224-D - ConditionAlias for promoted variable resolution

- Add ConditionAlias type to CarrierInfo (old_name → carrier_name)
- Record aliases in DigitPosPromoter and TrimPatternInfo
- Resolve aliases in Pattern2 ConditionEnv building
- digit_pos now correctly resolves to is_digit_pos carrier

Fixes "Variable 'digit_pos' not bound in ConditionEnv" error.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

src/mir/builder/control_flow/joinir/patterns/pattern2_with_break.rs

@@ -210,16 +210,6 @@ impl MirBuilder {
             }
         }
 
-        // Phase 201: Allocate carrier ValueIds from Param region and SET join_id
-        // This ensures carriers are also in the safe Param region
-        // CRITICAL: We must set join_id so the lowerer can access it
-        for carrier in &mut carrier_info.carriers {
-            let carrier_join_id = join_value_space.alloc_param();
-            carrier.join_id = Some(carrier_join_id);
-            eprintln!("[pattern2/phase201] Allocated carrier '{}' param ID: {:?}",
-                carrier.name, carrier_join_id);
-        }
-
         // Phase 191: Create empty body-local environment
         // LoopBodyLocalInitLowerer will populate it during init lowering
         use crate::mir::join_ir::lowering::loop_body_local_env::LoopBodyLocalEnv;
@@ -228,10 +218,6 @@ impl MirBuilder {
         eprintln!("[pattern2/body-local] Phase 201: Created empty body-local environment (param_count={})",
             join_value_space.param_count());
 
-        // Phase 201: Create alloc_join_value closure using JoinValueSpace
-        // This ensures all param allocations go through the unified space
-        let mut alloc_join_value = || join_value_space.alloc_param();
-
         // Debug: Log condition bindings
         eprintln!("[cf_loop/pattern2] Phase 201: ConditionEnv contains {} variables:", env.len());
         eprintln!("  Loop param '{}' → JoinIR {:?}", loop_var_name, env.get(&loop_var_name));
@@ -352,6 +338,62 @@ impl MirBuilder {
             }
         }
 
+        // Phase 224-D: Allocate join_ids for ALL carriers (including newly merged ones)
+        // This must happen AFTER promotion/merge to include promoted carriers
+        eprintln!("[pattern2/phase224d] Allocating join_ids for {} carriers", carrier_info.carriers.len());
+        for carrier in &mut carrier_info.carriers {
+            let carrier_join_id = join_value_space.alloc_param();
+            carrier.join_id = Some(carrier_join_id);
+            eprintln!("[pattern2/phase224d] Allocated carrier '{}' param ID: {:?}",
+                carrier.name, carrier_join_id);
+        }
+
+        // Phase 224-D: Save carriers with join_ids BEFORE filtering
+        let carriers_with_join_ids = carrier_info.carriers.clone();
+
+        // Phase 224-D: Add condition aliases to ConditionEnv
+        // This allows promoted variables to be referenced by their original names in conditions
+        for alias in &carrier_info.condition_aliases {
+            // Check if the carrier_name matches the loop_var_name (promoted as main carrier)
+            if alias.carrier_name == carrier_info.loop_var_name {
+                // Use loop variable's join_id from env
+                if let Some(join_id) = env.get(&carrier_info.loop_var_name) {
+                    env.insert(alias.old_name.clone(), join_id);
+                    eprintln!(
+                        "[pattern2/phase224d] Added condition alias '{}' → loop_var '{}' (join_id={:?})",
+                        alias.old_name, carrier_info.loop_var_name, join_id
+                    );
+                }
+            } else {
+                // Find the carrier's join_id in the carriers list (BEFORE filtering, with join_ids)
+                if let Some(carrier) = carriers_with_join_ids.iter().find(|c| c.name == alias.carrier_name) {
+                    if let Some(join_id) = carrier.join_id {
+                        // Add alias mapping: old_name → carrier's join_id
+                        env.insert(alias.old_name.clone(), join_id);
+                        eprintln!(
+                            "[pattern2/phase224d] Added condition alias '{}' → carrier '{}' (join_id={:?})",
+                            alias.old_name, alias.carrier_name, join_id
+                        );
+                    } else {
+                        eprintln!(
+                            "[pattern2/phase224d] WARNING: Carrier '{}' has no join_id yet!",
+                            alias.carrier_name
+                        );
+                    }
+                } else {
+                    eprintln!(
+                        "[pattern2/phase224d] WARNING: Carrier '{}' not found in carriers list!",
+                        alias.carrier_name
+                    );
+                }
+            }
+        }
+
+        // Phase 201: Create alloc_join_value closure using JoinValueSpace
+        // This ensures all param allocations go through the unified space
+        // NOTE: Must be created AFTER all direct join_value_space.alloc_param() calls
+        let mut alloc_join_value = || join_value_space.alloc_param();
+
         // Phase 180-3: Delegate Trim/P5 processing to TrimLoopLowerer
         let effective_break_condition = if let Some(trim_result) = super::trim_loop_lowering::TrimLoopLowerer::try_lower_trim_like_loop(
             self,

src/mir/builder/control_flow/joinir/patterns/pattern4_carrier_analyzer.rs

@@ -73,6 +73,7 @@ impl Pattern4CarrierAnalyzer {
             carriers: updated_carriers,
             trim_helper: all_carriers.trim_helper.clone(),
             promoted_loopbodylocals: all_carriers.promoted_loopbodylocals.clone(), // Phase 224
+            condition_aliases: all_carriers.condition_aliases.clone(), // Phase 224-D
         })
     }