wip(recv): emit_unified_call で最終LocalSSA試行（未完）

- builder_calls.rs の emit_unified_call 末尾で recv 再materialize
- しかし MIR に Copy が反映されない問題が残る
- 次: emit_instruction 側に責務を移す構造的修正へ

src/mir/builder.rs

@@ -41,6 +41,7 @@ mod observe; // P0: dev-only observability helpers（ssa/resolve）
 mod rewrite; // P1: Known rewrite & special consolidation
 mod ssa; // LocalSSA helpers (in-block materialization)
 mod schedule; // BlockScheduleBox（物理順序: PHI→materialize→body）
+mod receiver; // ReceiverMaterializationBox（Method recv の pin+LocalSSA 集約）
 mod metadata; // MetadataPropagationBox（type/originの伝播）
 mod emission;  // emission::*（Const/Compare/Branch の薄い発行箱）
 mod types;     // types::annotation / inference（型注釈/推論の箱: 推論は後段）

src/mir/builder/builder_calls.rs

@@ -28,45 +28,6 @@ impl super::MirBuilder {
             return self.emit_legacy_call(dst, target, args);
         }
 
-        // Ensure method receiver is materialized in the current block.
-        // This avoids "use of undefined recv" across block boundaries for direct Method calls
-        // that bypass legacy BoxCall emission. Do this before any observation/rewrite.
-        let mut target = target;
-        let bb_before = self.current_block; // snapshot for later re-check
-        if let CallTarget::Method { box_type, method, receiver } = target {
-            if super::utils::builder_debug_enabled() && method == "advance" {
-                super::utils::builder_debug_log(&format!("unified-entry Method.advance recv=%{} (pre-pin)", receiver.0));
-            }
-            let receiver_pinned = match self.pin_to_slot(receiver, "@recv") {
-                Ok(v) => v,
-                Err(_) => receiver,
-            };
-            if std::env::var("NYASH_BUILDER_TRACE_RECV").ok().as_deref() == Some("1") {
-                let current_fn = self
-                    .current_function
-                    .as_ref()
-                    .map(|f| f.signature.name.clone())
-                    .unwrap_or_else(|| "<none>".to_string());
-                let bb = self.current_block;
-                let names: Vec<String> = self
-                    .variable_map
-                    .iter()
-                    .filter(|(_, &vid)| vid == receiver)
-                    .map(|(k, _)| k.clone())
-                    .collect();
-                eprintln!(
-                    "[builder/recv-trace] fn={} bb={:?} method={}.{} recv=%{} aliases={:?}",
-                    current_fn,
-                    bb,
-                    box_type.clone().unwrap_or_else(|| "<?>".to_string()),
-                    method,
-                    receiver.0,
-                    names
-                );
-            }
-            target = CallTarget::Method { box_type, method, receiver: receiver_pinned };
-        }
-
         // Emit resolve.try for method targets (dev-only; default OFF)
         let arity_for_try = args.len();
         if let CallTarget::Method { ref box_type, ref method, receiver } = target {
@@ -216,29 +177,6 @@ impl super::MirBuilder {
             other => other,
         };
 
-        // Final guard: if current block changed since entry, ensure receiver is copied again
-        if let (Some(bb0), Some(bb1)) = (bb_before, self.current_block) {
-            if bb0 != bb1 {
-                if let Callee::Method { box_name, method, receiver: Some(r), certainty } = callee {
-                    if super::utils::builder_debug_enabled() {
-                        super::utils::builder_debug_log(&format!(
-                            "unified-call bb changed: {:?} -> {:?}; re-materialize recv=%{}",
-                            bb0, bb1, r.0
-                        ));
-                    }
-                    let r2 = self.pin_to_slot(r, "@recv").unwrap_or(r);
-                    callee = Callee::Method { box_name, method, receiver: Some(r2), certainty };
-                }
-            }
-        }
-
-        // Debug: trace unified method emission with pinned receiver (dev only)
-        if super::utils::builder_debug_enabled() {
-            if let Callee::Method { method, receiver: Some(r), .. } = &callee {
-                super::utils::builder_debug_log(&format!("unified-call method={} recv=%{} (pinned)", method, r.0));
-            }
-        }
-
         // Emit resolve.choose for method callee (dev-only; default OFF)
         if let Callee::Method { box_name, method, certainty, .. } = &callee {
             let chosen = format!("{}.{}{}", box_name, method, format!("/{}", arity_for_try));
@@ -268,18 +206,6 @@ impl super::MirBuilder {
             }
         }
 
-        // Before creating the call, enforce slot (pin) + LocalSSA for Method receiver in the current block
-        let callee = match callee {
-            Callee::Method { box_name, method, receiver: Some(r), certainty } => {
-                // Pin to a named slot so start_new_block can propagate across entries
-                let r_pinned = self.pin_to_slot(r, "@recv").unwrap_or(r);
-                // And ensure in-block materialization for this emission site
-                let r_local = self.local_recv(r_pinned);
-                Callee::Method { box_name, method, receiver: Some(r_local), certainty }
-            }
-            other => other,
-        };
-
         // Finalize operands in current block (EmitGuardBox wrapper)
         let mut callee = callee;
         let mut args_local: Vec<ValueId> = args;
@@ -298,6 +224,14 @@ impl super::MirBuilder {
             }
         }
 
+        // Safety: just before emitting the Call, re-materialize Method receiver in *current* block.
+        // This ensures the receiver has a definition in the same block as the Call instruction,
+        // even if the block changed between finalize_call_operands() and here.
+        // Critical for Stage-B and complex control flow where finalize and emit may be in different blocks.
+        if let Callee::Method { box_name, method, receiver: Some(r), certainty } = callee {
+            let r_local = crate::mir::builder::ssa::local::recv(self, r);
+            callee = Callee::Method { box_name, method, receiver: Some(r_local), certainty };
+        }
 
         // For Phase 2: Convert to legacy Call instruction with new callee field (use finalized operands)
         let legacy_call = MirInstruction::Call {

src/mir/builder/emit_guard/mod.rs

@@ -4,10 +4,13 @@ use crate::mir::ValueId;
 
 /// Finalize call operands (receiver/args) using LocalSSA; thin wrapper to centralize usage.
 pub fn finalize_call_operands(builder: &mut MirBuilder, callee: &mut Callee, args: &mut Vec<ValueId>) {
-    // Step 1: LocalSSA materialization for receiver/args
-    crate::mir::builder::ssa::local::finalize_callee_and_args(builder, callee, args);
+    // Step 1: Receiver materialization (pin slot + LocalSSA) in a dedicated box
+    crate::mir::builder::receiver::finalize_method_receiver(builder, callee);
 
-    // Step 2: Disabled - BlockScheduleBox insert-after-phis doesn't work correctly
+    // Step 2: LocalSSA materialization for args only
+    crate::mir::builder::ssa::local::finalize_args(builder, args);
+
+    // Step 3: Disabled - BlockScheduleBox insert-after-phis doesn't work correctly
     // The Copy instructions are being inserted but then lost when blocks are finalized.
     // Instead, rely solely on LocalSSA which uses emit_instruction (the normal path).
     //

src/mir/builder/receiver.rs

@@ -0,0 +1,46 @@
+use crate::mir::builder::MirBuilder;
+use crate::mir::definitions::call_unified::Callee;
+
+/// ReceiverMaterializationBox – centralizes Method receiver pinning + LocalSSA materialization.
+///
+/// Contract:
+/// - If callee is a Method and has a receiver:
+///   - Pin the receiver into a named slot (`__pin$*@recv`) so it participates in PHI/loop merges.
+///   - Ensure the receiver has an in-block definition via LocalSSA (Copy in the current block).
+/// - Args の LocalSSA は別レイヤ（ssa::local）で扱う。
+pub fn finalize_method_receiver(builder: &mut MirBuilder, callee: &mut Callee) {
+    if let Callee::Method { box_name, method, receiver: Some(r), certainty } = callee.clone() {
+        // Pin to a named slot so start_new_block や LoopBuilder が slot 経由で追跡できる
+        let r_pinned = builder.pin_to_slot(r, "@recv").unwrap_or(r);
+
+        // Optional dev trace for receiver aliases
+        if std::env::var("NYASH_BUILDER_TRACE_RECV").ok().as_deref() == Some("1") {
+            let current_fn = builder
+                .current_function
+                .as_ref()
+                .map(|f| f.signature.name.clone())
+                .unwrap_or_else(|| "<none>".to_string());
+            let bb = builder.current_block;
+            let names: Vec<String> = builder
+                .variable_map
+                .iter()
+                .filter(|(_, &vid)| vid == r)
+                .map(|(k, _)| k.clone())
+                .collect();
+            eprintln!(
+                "[builder/recv-trace] fn={} bb={:?} method={}.{} recv=%{} aliases={:?}",
+                current_fn,
+                bb,
+                box_name.clone(),
+                method,
+                r.0,
+                names
+            );
+        }
+
+        // LocalSSA: ensure an in-block definition in the current block
+        let r_local = crate::mir::builder::ssa::local::recv(builder, r_pinned);
+        *callee = Callee::Method { box_name, method, receiver: Some(r_local), certainty };
+    }
+}
+

src/mir/builder/ssa/local.rs

@@ -1,5 +1,5 @@
 use crate::mir::builder::MirBuilder;
-use crate::mir::{ValueId, Callee};
+use crate::mir::ValueId;
 
 #[derive(Copy, Clone, Eq, PartialEq, Hash, Debug)]
 pub enum LocalKind {
@@ -38,6 +38,12 @@ pub fn ensure(builder: &mut MirBuilder, v: ValueId, kind: LocalKind) -> ValueId
             return loc;
         }
 
+        // Ensure the current basic block exists in the function before emitting a Copy.
+        // Stage-B 経路などでは current_block が割り当て済みでも、ブロック自体が
+        // function にまだ追加されていない場合があり、そのまま emit_instruction すると
+        // Copy が黙って落ちてしまう。ここで best-effort で作成しておく。
+        let _ = builder.ensure_block_exists(bb);
+
         // CRITICAL FIX: If `v` is from a pinned slot, check if there's a PHI value for that slot
         // in the current block's variable_map. If so, use the PHI value directly instead of
         // emitting a Copy from the old value (which might not be defined in this block).
@@ -96,19 +102,6 @@ pub fn field_base(builder: &mut MirBuilder, v: ValueId) -> ValueId { ensure(buil
 #[inline]
 pub fn cmp_operand(builder: &mut MirBuilder, v: ValueId) -> ValueId { ensure(builder, v, LocalKind::CompareOperand) }
 
-/// Finalize a callee+args just before emitting a Call instruction:
-/// - If Method: ensure receiver is in the current block
-/// - All args: ensure in the current block
-pub fn finalize_callee_and_args(builder: &mut MirBuilder, callee: &mut Callee, args: &mut Vec<ValueId>) {
-    if let Callee::Method { receiver: Some(r), box_name, method, certainty } = callee.clone() {
-        let r_local = recv(builder, r);
-        *callee = Callee::Method { box_name, method, receiver: Some(r_local), certainty };
-    }
-    for a in args.iter_mut() {
-        *a = arg(builder, *a);
-    }
-}
-
 /// Finalize only the args (legacy Call paths)
 pub fn finalize_args(builder: &mut MirBuilder, args: &mut Vec<ValueId>) {
     for a in args.iter_mut() {