refactor(joinir): unify policy decisions and trim routing

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

@@ -5,6 +5,7 @@
 
 use crate::ast::ASTNode;
 use crate::mir::builder::MirBuilder;
+use crate::mir::builder::control_flow::joinir::patterns::policies::PolicyDecision;
 use crate::mir::join_ir::lowering::carrier_info::CarrierInfo;
 use crate::mir::join_ir::lowering::common::body_local_slot::{
     ReadOnlyBodyLocalSlot, ReadOnlyBodyLocalSlotBox,
@@ -19,14 +20,13 @@ use crate::mir::loop_pattern_detection::loop_condition_scope::{CondVarScope, Loo
 ///
 /// This is a "route" decision (not a fallback): we choose exactly one of the supported
 /// strategies and reject otherwise.
-pub enum BodyLocalPolicyDecision {
+pub enum BodyLocalRoute {
-    UsePromotion {
+    Promotion {
         promoted_carrier: CarrierInfo,
         promoted_var: String,
         carrier_name: String,
     },
-    UseReadOnlySlot(ReadOnlyBodyLocalSlot),
+    ReadOnlySlot(ReadOnlyBodyLocalSlot),
-    Reject { reason: String, vars: Vec<String> },
 }
 
 pub fn classify_for_pattern2(
@@ -36,7 +36,7 @@ pub fn classify_for_pattern2(
     break_condition_node: &ASTNode,
     cond_scope: &LoopConditionScope,
     body: &[ASTNode],
-) -> BodyLocalPolicyDecision {
+) -> PolicyDecision<BodyLocalRoute> {
     let vars: Vec<String> = cond_scope
         .vars
         .iter()
@@ -60,19 +60,18 @@ pub fn classify_for_pattern2(
             carrier_info: promoted_carrier,
             promoted_var,
             carrier_name,
-        } => BodyLocalPolicyDecision::UsePromotion {
+        } => PolicyDecision::Use(BodyLocalRoute::Promotion {
             promoted_carrier,
             promoted_var,
             carrier_name,
-        },
+        }),
         ConditionPromotionResult::CannotPromote { reason, .. } => {
             match extract_body_local_inits_for_conditions(&vars, body) {
-                Ok(Some(slot)) => BodyLocalPolicyDecision::UseReadOnlySlot(slot),
+                Ok(Some(slot)) => PolicyDecision::Use(BodyLocalRoute::ReadOnlySlot(slot)),
-                Ok(None) => BodyLocalPolicyDecision::Reject { reason, vars },
+                Ok(None) => PolicyDecision::Reject(reason),
-                Err(slot_err) => BodyLocalPolicyDecision::Reject {
+                Err(slot_err) => PolicyDecision::Reject(format!(
-                    reason: format!("{reason}; read-only-slot rejected: {slot_err}"),
+                    "{reason}; read-only-slot rejected: {slot_err}"
-                    vars,
+                )),
-                },
             }
         }
     }

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

@@ -5,7 +5,7 @@ use crate::ast::ASTNode;
 use crate::mir::builder::MirBuilder;
 use crate::mir::join_ir::lowering::carrier_info::{CarrierInfo, CarrierInit};
 use crate::mir::join_ir::lowering::condition_env::{ConditionBinding, ConditionEnv};
-use super::body_local_policy::{classify_for_pattern2, BodyLocalPolicyDecision};
+use super::body_local_policy::{classify_for_pattern2, BodyLocalRoute};
 use crate::mir::join_ir::lowering::common::body_local_slot::ReadOnlyBodyLocalSlot;
 use crate::mir::join_ir::lowering::common::body_local_derived_emitter::BodyLocalDerivedRecipe;
 use crate::mir::join_ir::lowering::debug_output_box::DebugOutputBox;
@@ -20,6 +20,7 @@ use crate::mir::ValueId;
 use super::policies::p5b_escape_derived_policy::{
     classify_p5b_escape_derived, P5bEscapeDerivedDecision,
 };
+use super::policies::PolicyDecision;
 use std::collections::BTreeMap;
 
 struct Pattern2DebugLog {
@@ -283,6 +284,12 @@ fn promote_and_prepare_carriers(
 
     let log = Pattern2DebugLog::new(verbose);
     let mut promoted_pairs: Vec<(String, String)> = Vec::new();
+    let cond_body_local_vars: Vec<String> = cond_scope
+        .vars
+        .iter()
+        .filter(|v| matches!(v.scope, crate::mir::loop_pattern_detection::loop_condition_scope::CondVarScope::LoopBodyLocal))
+        .map(|v| v.name.clone())
+        .collect();
 
     if cond_scope.has_loop_body_local() {
         match classify_for_pattern2(
@@ -293,11 +300,11 @@ fn promote_and_prepare_carriers(
             &cond_scope,
             body,
         ) {
-            BodyLocalPolicyDecision::UsePromotion {
+            PolicyDecision::Use(BodyLocalRoute::Promotion {
                 promoted_carrier,
                 promoted_var,
                 carrier_name,
-            } => {
+            }) => {
                 // Phase 133 P1: Check if this is a Trim promotion (A-3 pattern)
                 // Trim promotions are handled by TrimLoopLowerer (apply_trim_and_normalize)
                 // which provides SSOT for env/join_id, so we defer to that path.
@@ -399,7 +406,7 @@ fn promote_and_prepare_carriers(
                     );
                 }
             }
-            BodyLocalPolicyDecision::UseReadOnlySlot(slot) => {
+            PolicyDecision::Use(BodyLocalRoute::ReadOnlySlot(slot)) => {
                 log.log(
                     "body_local_slot",
                     format!(
@@ -410,11 +417,12 @@ fn promote_and_prepare_carriers(
                 inputs.allowed_body_locals_for_conditions = vec![slot.name.clone()];
                 inputs.read_only_body_local_slot = Some(slot);
             }
-            BodyLocalPolicyDecision::Reject { reason, vars } => {
+            PolicyDecision::Reject(reason) => {
                 return Err(error_messages::format_error_pattern2_promotion_failed(
-                    &vars, &reason,
+                    &cond_body_local_vars, &reason,
                 ));
             }
+            PolicyDecision::None => {}
         }
     }
 
@@ -817,7 +825,7 @@ impl MirBuilder {
         // Phase 94: Detect P5b escape-derived (`ch` reassignment + escape counter).
         // Route is explicit; in strict mode, partial matches that require derived support must fail-fast.
         match classify_p5b_escape_derived(analysis_body, &inputs.loop_var_name) {
-            P5bEscapeDerivedDecision::UseDerived(recipe) => {
+            P5bEscapeDerivedDecision::Use(recipe) => {
                 log.log(
                     "phase94",
                     format!(

src/mir/builder/control_flow/joinir/patterns/policies/README.md

@@ -85,8 +85,8 @@
 - Reject理由は`error_tags::freeze()`でタグ付与
 
 ### Decision型の統一
-- `Decision` enum（None / Use(...) / Reject(String)）を統一パターンとして使用
+- `PolicyDecision<T>`（Use / Reject / None）をSSOTにする
-- 例: `P5bEscapeDerivedDecision`, `TrimDecision`（将来）
+- 例: `P5bEscapeDerivedDecision = PolicyDecision<BodyLocalDerivedRecipe>`, `TrimPolicyResult`
 
 ## 使用パターン
 

src/mir/builder/control_flow/joinir/patterns/policies/mod.rs

@@ -8,6 +8,10 @@
 //! - ルーティング決定: 適用可能なLoweringパターンを決定
 //! - Recipe生成: Pattern固有の情報（ConditionOnlyRecipe, BodyLocalDerivedRecipe, etc.）を生成
 //!
+//! ## 決定型のSSOT
+//! - `PolicyDecision<T>` に統一（Use / Reject / None）
+//! - BodyLocal, Trim, P5b escape などすべてここ経由で route することで Pattern2 側の分岐を簡潔に保つ
+//!
 //! ## 設計原則
 //! - **単一判断の原則**: 各policy箱は1つのパターン判断のみ
 //! - **非破壊的判断**: 入力を変更せず、Decision型で結果を返す
@@ -17,11 +21,14 @@
 //! policies/ は「認識とルーティング決定（policy）」を分離する受け皿です。
 //! Phase 94（P5b derived）から段階的に移設を開始しました。
 //!
-//! ### 段階的な移行計画
-//! - Phase 1: ディレクトリ準備 ✅
-//! - Phase 2: 既存policy箱の移動（進行中）
-//! - Phase 3: インターフェース統一（将来）
-//!
 //! 詳細は [README.md](README.md) を参照してください。
 
+#[derive(Debug, Clone)]
+pub enum PolicyDecision<T> {
+    Use(T),
+    Reject(String),
+    None,
+}
+
 pub(in crate::mir::builder) mod p5b_escape_derived_policy;
+pub(in crate::mir::builder) mod trim_policy;

src/mir/builder/control_flow/joinir/patterns/policies/p5b_escape_derived_policy.rs

@@ -13,13 +13,9 @@ use crate::config::env::joinir_dev;
 use crate::mir::builder::control_flow::joinir::patterns::escape_pattern_recognizer::EscapeSkipPatternInfo;
 use crate::mir::join_ir::lowering::common::body_local_derived_emitter::BodyLocalDerivedRecipe;
 use crate::mir::join_ir::lowering::error_tags;
+use super::PolicyDecision;
 
-#[derive(Debug)]
+pub type P5bEscapeDerivedDecision = PolicyDecision<BodyLocalDerivedRecipe>;
-pub enum P5bEscapeDerivedDecision {
-    None,
-    UseDerived(BodyLocalDerivedRecipe),
-    Reject(String),
-}
 
 /// Detect a P5b derived body-local (`ch`) recipe from a Pattern2 loop body.
 ///
@@ -43,7 +39,7 @@ pub fn classify_p5b_escape_derived(
     }
 
     match build_recipe_from_info(body, &info) {
-        Ok(Some(recipe)) => P5bEscapeDerivedDecision::UseDerived(recipe),
+        Ok(Some(recipe)) => P5bEscapeDerivedDecision::Use(recipe),
         Ok(None) => {
             // Escape pattern exists but there is no body-local reassignment to cover.
             P5bEscapeDerivedDecision::None
@@ -257,7 +253,7 @@ mod tests {
         ];
 
         match classify_p5b_escape_derived(&body, "i") {
-            P5bEscapeDerivedDecision::UseDerived(recipe) => {
+            P5bEscapeDerivedDecision::Use(recipe) => {
                 assert_eq!(recipe.name, "ch");
                 assert_eq!(recipe.loop_counter_name, "i");
                 assert_eq!(recipe.pre_delta, 1);

src/mir/builder/control_flow/joinir/patterns/policies/trim_policy.rs

@@ -0,0 +1,51 @@
+//! Trim pattern policy box (判定専用)
+//!
+//! 目的: Trim 形状かどうかを判定し、ConditionScope を返すだけに責務を絞る。
+//! 生成（lowering）は従来通り TrimLoopLowerer 側が担当する。
+
+use crate::ast::ASTNode;
+use crate::mir::builder::control_flow::joinir::patterns::trim_loop_lowering::TrimLoopLowerer;
+use crate::mir::join_ir::lowering::loop_scope_shape::LoopScopeShape;
+use crate::mir::loop_pattern_detection::loop_condition_scope::{
+    CondVarInfo, CondVarScope, LoopConditionScope, LoopConditionScopeBox,
+};
+
+use super::PolicyDecision;
+
+/// 判定結果（生成に必要な最小情報だけ運ぶ）
+#[derive(Debug, Clone)]
+pub struct TrimPolicyResult {
+    pub cond_scope: LoopConditionScope,
+    pub condition_body_locals: Vec<CondVarInfo>,
+}
+
+pub fn classify_trim_like_loop(
+    scope: &LoopScopeShape,
+    loop_cond: &ASTNode,
+    break_cond: &ASTNode,
+    loop_var_name: &str,
+) -> PolicyDecision<TrimPolicyResult> {
+    let cond_scope =
+        LoopConditionScopeBox::analyze(loop_var_name, &[loop_cond, break_cond], Some(scope));
+
+    if !cond_scope.has_loop_body_local() {
+        return PolicyDecision::None;
+    }
+
+    let condition_body_locals: Vec<_> = cond_scope
+        .vars
+        .iter()
+        .filter(|v| v.scope == CondVarScope::LoopBodyLocal)
+        .filter(|v| TrimLoopLowerer::is_var_used_in_condition(&v.name, break_cond))
+        .cloned()
+        .collect();
+
+    if condition_body_locals.is_empty() {
+        return PolicyDecision::None;
+    }
+
+    PolicyDecision::Use(TrimPolicyResult {
+        cond_scope,
+        condition_body_locals,
+    })
+}

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

@@ -44,8 +44,9 @@ use crate::mir::join_ir::lowering::loop_scope_shape::LoopScopeShape;
 use crate::mir::loop_pattern_detection::loop_body_carrier_promoter::{
     LoopBodyCarrierPromoter, PromotionRequest, PromotionResult,
 };
-use crate::mir::loop_pattern_detection::loop_condition_scope::LoopConditionScopeBox;
 use crate::mir::ValueId;
+use super::policies::trim_policy::{classify_trim_like_loop, TrimPolicyResult};
+use super::policies::PolicyDecision;
 
 /// Trim pattern lowering orchestrator
 ///
@@ -96,7 +97,10 @@ impl TrimLoopLowerer {
     /// # Returns
     ///
     /// `true` if `var_name` appears anywhere in `cond_node`, `false` otherwise
-    fn is_var_used_in_condition(var_name: &str, cond_node: &ASTNode) -> bool {
+    pub(in crate::mir::builder::control_flow::joinir::patterns) fn is_var_used_in_condition(
+        var_name: &str,
+        cond_node: &ASTNode,
+    ) -> bool {
         match cond_node {
             ASTNode::Variable { name, .. } => name == var_name,
             ASTNode::BinaryOp { left, right, .. } => {
@@ -179,63 +183,14 @@ impl TrimLoopLowerer {
         let trace = crate::mir::builder::control_flow::joinir::trace::trace();
         let verbose = crate::config::env::joinir_dev_enabled() || trace.is_joinir_enabled();
 
-        // Phase 180-2: Skeleton implementation
+        let TrimPolicyResult {
-        // TODO: Phase 180-3 will implement full logic from Pattern2
+            cond_scope,
-
+            condition_body_locals,
-        // Step 1: Check if condition references LoopBodyLocal variables
+        } = match classify_trim_like_loop(scope, loop_cond, break_cond, loop_var_name) {
-        let cond_scope =
+            PolicyDecision::Use(res) => res,
-            LoopConditionScopeBox::analyze(loop_var_name, &[loop_cond, break_cond], Some(scope));
+            PolicyDecision::None => return Ok(None),
-
+            PolicyDecision::Reject(reason) => return Err(reason),
-        trace.emit_if(
+        };
-            "trim",
-            "scope",
-            &format!(
-                "Analyzing condition scope: {} variables",
-                cond_scope.vars.len()
-            ),
-            verbose,
-        );
-
-        if !cond_scope.has_loop_body_local() {
-            // Not a Trim pattern - normal loop
-            trace.emit_if(
-                "trim",
-                "scope",
-                "No LoopBodyLocal detected, skipping Trim lowering",
-                verbose,
-            );
-            return Ok(None);
-        }
-
-        trace.emit_if(
-            "trim",
-            "scope",
-            "LoopBodyLocal detected in condition scope",
-            verbose,
-        );
-
-        // Phase 183-2: Filter to only condition LoopBodyLocal (skip body-only)
-        use crate::mir::loop_pattern_detection::loop_condition_scope::CondVarScope;
-        let condition_body_locals: Vec<_> = cond_scope
-            .vars
-            .iter()
-            .filter(|v| v.scope == CondVarScope::LoopBodyLocal)
-            .filter(|v| {
-                // Check if variable is actually used in break condition
-                Self::is_var_used_in_condition(&v.name, break_cond)
-            })
-            .collect();
-
-        if condition_body_locals.is_empty() {
-            // All LoopBodyLocal are body-only (not in conditions) → Not a Trim pattern
-            trace.emit_if(
-                "trim",
-                "phase183",
-                "All LoopBodyLocal are body-only (not in conditions), skipping Trim lowering",
-                verbose,
-            );
-            return Ok(None);
-        }
 
         trace.emit_if(
             "trim",