refactor(plan): Phase 273 P3+ - Legacy code removal

Phase 273 P3+ 完成: レガシーコード削除 + 未使用 import 整理

Removed Legacy Items:
1. emit_scan_with_init_edgecfg() - Pattern6 固有の emission 関数
   - File deleted: src/mir/builder/emission/loop_scan_with_init.rs (~144 lines)
   - Replaced by: generalized Frag API (Phase 273 P2)

2. CoreCarrierInfo struct - Legacy carrier representation
   - Removed from: src/mir/builder/control_flow/plan/mod.rs (~15 lines)
   - Replaced by: CorePhiInfo (generalized PHI representation)

3. verify_carrier() function - CoreCarrierInfo validator
   - Removed from: src/mir/builder/control_flow/plan/verifier.rs (~15 lines)
   - Replaced by: generalized PHI verification (V7-V9)

Code Cleanup:
- cargo fix applied: unused imports removed (~30 files)
- Verifier invariants updated: V1→V2-V9 (carrier→PHI model)
- Module declaration cleanup in emission/mod.rs

Impact:
- Total lines removed: ~174 lines (net reduction)
- Pattern-agnostic architecture strengthened
- All legacy Pattern6 references eliminated

Tests:
- ✅ VM tests PASS (phase254/256/258)
- ✅ LLVM tests PASS (phase256/258)

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

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

src/mir/builder/control_flow/edgecfg/api/compose.rs

@@ -13,7 +13,6 @@ use std::collections::BTreeMap;
 use crate::mir::basic_block::{BasicBlockId, EdgeArgs};
 use crate::mir::control_form::LoopId;
 use crate::mir::value_id::ValueId;
-use crate::mir::join_ir::lowering::inline_boundary::JumpArgsLayout;
 use super::frag::Frag;
 use super::exit_kind::ExitKind;
 use super::edge_stub::EdgeStub;  // Phase 265 P2: wires/exits 分離で必要

src/mir/builder/control_flow/edgecfg/api/mod.rs

@@ -34,7 +34,7 @@ pub(crate) use compose::{seq, if_, loop_, cleanup};
 
 // 検証関数
 pub use verify::verify_frag_invariants;
-pub use verify::verify_frag_invariants_strict; // Phase 266: strict 版追加
+ // Phase 266: strict 版追加
 
 // Phase 267 P0: wires + branches → MIR terminator 変換
-pub use emit::{emit_wires, emit_frag};
+pub use emit::emit_frag;

src/mir/builder/control_flow/edgecfg/mod.rs

@@ -6,7 +6,5 @@
 pub mod api;
 
 // 公開型（安定）
-pub use api::{ExitKind, EdgeStub, Frag, verify_frag_invariants};
 
 // 合成関数（Phase 264: crate内のみ公開）
-pub(crate) use api::{seq, if_, loop_, cleanup};

src/mir/builder/control_flow/joinir/merge/instruction_rewriter.rs

@@ -18,8 +18,7 @@ use crate::mir::builder::joinir_id_remapper::JoinIrIdRemapper;
 use crate::mir::join_ir::lowering::error_tags;
 use crate::mir::join_ir::lowering::inline_boundary::JoinInlineBoundary;
 // Phase 256 P1.7: Removed join_func_name import - no longer needed
-use crate::mir::types::ConstValue;
-use crate::mir::{BasicBlock, BasicBlockId, MirFunction, MirInstruction, MirModule, MirType, ValueId};
+use crate::mir::{BasicBlock, BasicBlockId, MirInstruction, MirModule, ValueId};
 use std::collections::BTreeMap; // Phase 222.5-E: HashMap → BTreeMap for determinism
 use std::collections::BTreeSet;
 

src/mir/builder/control_flow/joinir/merge/rewriter/mod.rs

@@ -39,5 +39,5 @@ pub(super) mod terminator; // Phase 260 P0.1 Step 5: Terminator remapping extrac
 pub(super) mod type_propagation; // Phase 260 P0.1 Step 4: Type propagation extracted ✅
 
 // Re-export public API
-pub(super) use helpers::is_skippable_continuation; // Phase 260 P0.1 Step 3: From helpers ✅
+ // Phase 260 P0.1 Step 3: From helpers ✅
 pub(super) use super::instruction_rewriter::merge_and_rewrite; // Still in parent (TODO: extract)

src/mir/builder/control_flow/joinir/patterns/pattern2_lowering_orchestrator.rs

@@ -36,7 +36,6 @@ use super::pattern2_steps::gather_facts_step_box::GatherFactsStepBox;
 use super::pattern2_steps::merge_step_box::MergeStepBox;
 use super::pattern2_steps::normalize_body_step_box::NormalizeBodyStepBox;
 use super::pattern2_steps::post_loop_early_return_step_box::PostLoopEarlyReturnStepBox;
-use super::pattern2_steps::promote_step_box::PromoteStepBox;
 
 pub(crate) struct Pattern2LoweringOrchestrator;
 

src/mir/builder/control_flow/joinir/patterns/pattern2_steps/emit_joinir_step_box.rs

@@ -4,7 +4,6 @@
 
 use crate::ast::ASTNode;
 use crate::mir::builder::MirBuilder;
-use crate::mir::ValueId;
 
 use super::super::pattern2_inputs_facts_box::{Pattern2DebugLog, Pattern2Inputs};
 use crate::mir::join_ir::lowering::inline_boundary::JoinInlineBoundary;

src/mir/builder/control_flow/joinir/patterns/pattern2_steps/promote_step_box.rs

@@ -10,7 +10,7 @@
 use crate::ast::ASTNode;
 use crate::mir::builder::MirBuilder;
 
-use super::super::pattern2::api::{try_promote, PromoteDecision, PromoteStepResult};
+use super::super::pattern2::api::{try_promote, PromoteDecision};
 use super::super::pattern2_inputs_facts_box::Pattern2Inputs;
 
 pub(crate) struct PromoteStepBox;

src/mir/builder/control_flow/joinir/patterns/pattern6_scan_with_init.rs

@@ -33,11 +33,8 @@
 //! - MethodCall allowed_in_condition() = false, but allowed_in_init() = true
 //! - Need to hoist MethodCall to init phase
 
-use super::super::trace;
-use super::common::var; // Phase 255 P2: Use shared var() helper
-use crate::ast::{ASTNode, BinaryOperator, LiteralValue};
-use crate::mir::builder::MirBuilder;
-use crate::mir::ValueId;
+ // Phase 255 P2: Use shared var() helper
+use crate::ast::ASTNode;
 
 // Phase 273 P1: Import DomainPlan types (Plan renamed to DomainPlan)
 use crate::mir::builder::control_flow::plan::{DomainPlan, ScanDirection as PlanScanDirection, ScanWithInitPlan};

src/mir/builder/control_flow/joinir/patterns/pattern8_scan_bool_predicate.rs

@@ -34,7 +34,6 @@
 //! - Pattern 8: Returns boolean (true/false)
 
 use super::super::trace;
-use super::common::var;
 use crate::ast::{ASTNode, BinaryOperator, LiteralValue, UnaryOperator};
 use crate::mir::builder::MirBuilder;
 use crate::mir::ValueId;

src/mir/builder/control_flow/plan/mod.rs

@@ -192,21 +192,7 @@ pub(in crate::mir::builder) struct CoreLoopPlan {
     pub final_values: Vec<(String, ValueId)>,
 }
 
-/// Phase 273 P1: Loop carrier (PHI variable)
-#[derive(Debug, Clone)]
-pub(in crate::mir::builder) struct CoreCarrierInfo {
-    /// Variable name (for variable_map update)
-    pub name: String,
-
-    /// Initial value (from preheader)
-    pub init_value: ValueId,
-
-    /// Step value (from step block, back-edge)
-    pub step_value: ValueId,
-
-    /// PHI destination (loop variable inside loop)
-    pub phi_dst: ValueId,
-}
+// Phase 273 P3: CoreCarrierInfo removed (replaced by CorePhiInfo)
 
 /// Phase 273 P1: Conditional plan
 #[derive(Debug, Clone)]

src/mir/builder/control_flow/plan/normalizer.rs

@@ -12,7 +12,7 @@
 //! Lowerer processes CorePlan without any pattern knowledge.
 
 use super::{
-    CoreCarrierInfo, CoreEffectPlan, CoreLoopPlan, CorePhiInfo, CorePlan, DomainPlan,
+    CoreEffectPlan, CoreLoopPlan, CorePhiInfo, CorePlan, DomainPlan,
     ScanWithInitPlan, SplitScanPlan,
 };
 use crate::mir::builder::control_flow::joinir::patterns::router::LoopPatternContext;

src/mir/builder/control_flow/plan/verifier.rs

@@ -1,4 +1,4 @@
-//! Phase 273 P1: PlanVerifier - CorePlan 不変条件検証 (fail-fast)
+//! Phase 273 P3: PlanVerifier - CorePlan 不変条件検証 (fail-fast)
 //!
 //! # Responsibilities
 //!
@@ -6,16 +6,20 @@
 //! - Fail fast on close-but-unsupported patterns
 //! - Prevent silent miscompilation
 //!
-//! # Invariants (V1-V6)
+//! # Invariants (V2-V9)
 //!
-//! - V1: Carrier completeness (name/init_value/step_value present)
 //! - V2: Condition validity (valid ValueId)
 //! - V3: Exit validity (Return in function, Break/Continue in loop)
 //! - V4: Seq non-empty
 //! - V5: If completeness (then_plans non-empty)
 //! - V6: ValueId validity (all ValueIds pre-generated)
+//! - V7: PHI non-empty (loops require at least one carrier)
+//! - V8: Frag entry matches header_bb
+//! - V9: block_effects contains header_bb
+//!
+//! Phase 273 P3: V1 (Carrier completeness) removed with CoreCarrierInfo
 
-use super::{CoreCarrierInfo, CoreEffectPlan, CoreExitPlan, CoreIfPlan, CoreLoopPlan, CorePlan};
+use super::{CoreEffectPlan, CoreExitPlan, CoreIfPlan, CoreLoopPlan, CorePlan};
 use crate::mir::ValueId;
 
 /// Phase 273 P1: PlanVerifier - CorePlan 不変条件検証 (fail-fast)
@@ -132,21 +136,7 @@ impl PlanVerifier {
         Ok(())
     }
 
-    /// V1: Carrier completeness
-    fn verify_carrier(carrier: &CoreCarrierInfo, depth: usize, index: usize) -> Result<(), String> {
-        if carrier.name.is_empty() {
-            return Err(format!(
-                "[V1] Carrier[{}] at depth {} has empty name",
-                index, depth
-            ));
-        }
-
-        Self::verify_value_id_basic(carrier.init_value, depth, &format!("carrier[{}].init_value", index))?;
-        Self::verify_value_id_basic(carrier.step_value, depth, &format!("carrier[{}].step_value", index))?;
-        Self::verify_value_id_basic(carrier.phi_dst, depth, &format!("carrier[{}].phi_dst", index))?;
-
-        Ok(())
-    }
+    // Phase 273 P3: verify_carrier() removed (CoreCarrierInfo replaced by CorePhiInfo)
 
     /// V5: If completeness
     fn verify_if(if_plan: &CoreIfPlan, depth: usize, in_loop: bool) -> Result<(), String> {

src/mir/builder/emission/loop_scan_with_init.rs

@@ -1,143 +0,0 @@
-//! Phase 272 P0.1: Pattern6 Scan with Init - Emission Entrypoint
-//!
-//! ## Purpose
-//! Thin entrypoint for Pattern6 Frag construction and MIR terminator emission.
-//! This module only handles terminator wiring via EdgeCFG Frag API.
-//! Block allocation and value computation (len, substring, match check) are done by Pattern6.
-//!
-//! ## Pattern Structure
-//! ```nyash
-//! index_of(s, ch) {
-//!     local i = 0
-//!     loop(i < s.length()) {
-//!         if s.substring(i, i + 1) == ch {
-//!             return i
-//!         }
-//!         i = i + 1
-//!     }
-//!     return -1
-//! }
-//! ```
-//!
-//! ## P0 Scope
-//! - Forward scan only (step = 1)
-//! - Fixed needle (ch)
-//! - No ret_not_found_bb (after_bb handles AST return -1)
-//!
-//! ## Critical SSOT
-//! 1. Return in wires (not exits) - emit_frag() generates terminators from wires/branches only
-//! 2. after_bb has no terminator - let subsequent AST lowering handle "return -1"
-//! 3. Frag assembly is direct field access (no with_* API)
-//! 4. BranchStub/EdgeStub field names match current implementation
-//! 5. Return Void (loop as statement, not expression)
-
-use crate::mir::builder::MirBuilder;
-use crate::mir::builder::control_flow::edgecfg::api::{
-    BranchStub, EdgeStub, ExitKind, Frag, emit_frag,
-};
-use crate::mir::basic_block::{BasicBlockId, EdgeArgs};
-use crate::mir::join_ir::lowering::inline_boundary::JumpArgsLayout;
-use crate::mir::ValueId;
-
-/// Emit Scan with Init EdgeCFG Fragment
-///
-/// ## Arguments
-/// - `b`: MirBuilder (for emit_frag access to current_function)
-/// - `header_bb`: Loop condition check block (i < s.length())
-/// - `body_bb`: Substring + match check + early return branch
-/// - `step_bb`: Increment i and jump back to header
-/// - `after_bb`: Normal loop exit (no terminator - subsequent AST lowering handles "return -1")
-/// - `ret_found_bb`: Early exit Return(i) block
-/// - `cond_loop`: ValueId for (i < s.length())
-/// - `cond_match`: ValueId for (ch == needle)
-/// - `i_found`: ValueId for loop variable i (return value for found case)
-///
-/// ## Frag Structure
-/// - **branches**:
-///   1. header: cond_loop true→body, false→after
-///   2. body: cond_match true→ret_found, false→step
-/// - **wires**:
-///   - step → header (Normal Jump)
-///   - ret_found_bb → Return(i) - **IN WIRES, NOT EXITS**
-/// - **exits**: empty (no upward propagation in P0)
-///
-/// ## Returns
-/// `Ok(())` - Frag emitted successfully
-/// `Err` - emit_frag failed or current_function is None
-pub(in crate::mir::builder) fn emit_scan_with_init_edgecfg(
-    b: &mut MirBuilder,
-    header_bb: BasicBlockId,
-    body_bb: BasicBlockId,
-    step_bb: BasicBlockId,
-    after_bb: BasicBlockId,
-    ret_found_bb: BasicBlockId,
-    cond_loop: ValueId,
-    cond_match: ValueId,
-    i_found: ValueId,
-) -> Result<(), String> {
-    // EdgeArgs::empty() helper
-    let empty_args = EdgeArgs {
-        layout: JumpArgsLayout::CarriersOnly,
-        values: vec![],
-    };
-
-    // Return(i) arguments (contains found index)
-    let ret_found_args = EdgeArgs {
-        layout: JumpArgsLayout::CarriersOnly,
-        values: vec![i_found],
-    };
-
-    // branches (BranchStub) - current field names
-    let branches = vec![
-        BranchStub {
-            from: header_bb,
-            cond: cond_loop,
-            then_target: body_bb,
-            then_args: empty_args.clone(),
-            else_target: after_bb,
-            else_args: empty_args.clone(),
-        },
-        BranchStub {
-            from: body_bb,
-            cond: cond_match,
-            then_target: ret_found_bb,
-            then_args: empty_args.clone(),
-            else_target: step_bb,
-            else_args: empty_args.clone(),
-        },
-    ];
-
-    // wires (EdgeStub) - current field names
-    let wires = vec![
-        // step_bb → header_bb Jump (Normal)
-        EdgeStub {
-            from: step_bb,
-            kind: ExitKind::Normal,
-            target: Some(header_bb),
-            args: empty_args,
-        },
-        // ret_found_bb Return(i) - THIS GOES IN WIRES!
-        EdgeStub {
-            from: ret_found_bb,
-            kind: ExitKind::Return,
-            target: None,
-            args: ret_found_args,
-        },
-        // P0: No ret_not_found wire - after_bb handles AST return -1
-    ];
-
-    // Frag assembly (direct field access - no with_* API exists)
-    let mut frag = Frag::new(header_bb);
-    frag.branches = branches;
-    frag.wires = wires;
-    // exits is empty (no upward propagation in P0)
-
-    // emit_frag generates MIR terminators
-    if let Some(ref mut func) = b.scope_ctx.current_function {
-        emit_frag(func, &frag)?;
-    } else {
-        return Err("[emit_scan_with_init_edgecfg] current_function is None".to_string());
-    }
-
-    Ok(())
-}

src/mir/builder/emission/mod.rs

@@ -4,13 +4,13 @@
 //! - branch.rs: Branch/Jump 発行の薄い関数
 //! - phi.rs: PHI挿入の薄いラッパー（builder context extraction）
 //! - loop_predicate_scan.rs: Pattern8 bool predicate scan EdgeCFG Frag (Phase 269 P1)
-//! - loop_scan_with_init.rs: Pattern6 scan with init EdgeCFG Frag (Phase 272 P0.1)
 //! - loop_split_scan.rs: Pattern7 split scan EdgeCFG Frag (Phase 272 P0.2)
+//!
+//! Phase 273 P3: loop_scan_with_init.rs removed (replaced by generalized Frag API)
 
 pub mod branch;
 pub mod compare;
 pub mod constant;
 pub(in crate::mir::builder) mod phi;  // Phase 272 P0.2 Refactoring
 pub(in crate::mir::builder) mod loop_predicate_scan;  // Phase 269 P1
-pub(in crate::mir::builder) mod loop_scan_with_init;  // Phase 272 P0.1
 pub(in crate::mir::builder) mod loop_split_scan;  // Phase 272 P0.2

src/mir/builder/lifecycle.rs

@@ -44,7 +44,6 @@ use crate::mir::join_ir::lowering::generic_type_resolver::GenericTypeResolver;
 // Phase 83: P3-D 既知メソッド戻り値型推論箱
 use crate::mir::join_ir::lowering::method_return_hint::MethodReturnHintBox;
 // Phase 84-2: Copy命令型伝播箱（ChatGPT Pro設計）
-use crate::mir::phi_core::copy_type_propagator::CopyTypePropagator;
 // Phase 84-3: PHI + Copy グラフ型推論箱（ChatGPT Pro設計）
 use crate::mir::phi_core::phi_type_resolver::PhiTypeResolver;
 

src/mir/join_ir/lowering/carrier_info.rs

@@ -28,7 +28,6 @@ use std::collections::BTreeSet;
 #[cfg(feature = "normalized_dev")]
 use crate::mir::BindingId; // Phase 76+78: BindingId for promoted carriers
 
-use crate::mir::join_ir::JoinFuncId;
 
 /// Phase 227: CarrierRole - Distinguishes loop state carriers from condition-only carriers
 ///

src/mir/join_ir/lowering/inline_boundary.rs

@@ -44,7 +44,6 @@
 //! ```
 
 use super::carrier_info::{CarrierRole, ExitReconnectMode};
-use crate::mir::join_ir::JoinFuncId;
 use crate::mir::ValueId;
 use std::collections::BTreeSet;
 

src/mir/join_ir_vm_bridge/handlers/jump.rs

@@ -89,10 +89,9 @@
 //!   jump_args_layout = CarriersOnly
 //! ```
 
-use crate::ast::Span;
 use crate::mir::join_ir::{JoinContId, JoinFuncId};
 use crate::mir::join_ir::lowering::inline_boundary::JumpArgsLayout;
-use crate::mir::{BasicBlock, BasicBlockId, EffectMask, MirFunction, MirInstruction, ValueId};
+use crate::mir::{BasicBlock, BasicBlockId, MirFunction, MirInstruction, ValueId};
 use std::collections::BTreeMap;
 
 use super::super::{join_func_name, JoinIrVmBridgeError};

src/mir/join_ir_vm_bridge/joinir_function_converter.rs

@@ -6,9 +6,7 @@
 //! - 関数署名の管理
 
 use crate::mir::join_ir::{JoinFuncId, JoinFunction, JoinModule};
-use crate::mir::phi_core::copy_type_propagator::CopyTypePropagator;
-use crate::mir::phi_core::phi_type_resolver::PhiTypeResolver;
-use crate::mir::{BasicBlockId, EffectMask, FunctionSignature, MirFunction, MirInstruction, MirModule, MirType};
+use crate::mir::{BasicBlockId, EffectMask, FunctionSignature, MirFunction, MirModule, MirType};
 use std::collections::BTreeMap;
 
 use super::join_func_name;

src/mir/verification/cfg.rs

@@ -1,7 +1,7 @@
 use crate::mir::function::MirFunction;
 use crate::mir::verification::utils;
 use crate::mir::verification_types::VerificationError;
-use crate::mir::{BasicBlockId, MirInstruction, ValueId};
+use crate::mir::{BasicBlockId, ValueId};
 use std::collections::{HashMap, HashSet};
 
 /// Verify CFG references and reachability