refactor(builder): 箱理論リファクタリング Phase 1完了

🎯 builder_calls.rs (982行) を箱理論で責務別にモジュール分割

## 成果
✅ builder_calls.rs: 982行 → 766行（-216行、22%削減）
✅ calls/lowering.rs: 354行（新規、箱理論6段階パターン）
✅ calls/utils.rs: 45行（新規、ユーティリティ統一）
✅ ビルド・テスト完全成功（0エラー）

## 箱理論の実装
1. 責務ごとに箱に分離:
   - lowering: 関数lowering専用
   - utils: ユーティリティ統一
   - emit/build: Phase 2で実装予定

2. 境界を明確に:
   - mod.rs で公開インターフェース定義
   - pub(in crate::mir::builder) で適切な可視性制御

3. いつでも戻せる:
   - 段階的移行、各ステップでビルド確認
   - 既存API完全保持（互換性100%）

4. 巨大関数は分割:
   - lower_static_method_as_function: 125行 → 6段階に分解
   - lower_method_as_function: 80行 → 6段階に分解

## 箱理論6段階パターン
1. prepare_lowering_context - Context準備
2. create_function_skeleton - 関数スケルトン作成
3. setup_function_params - パラメータ設定
4. lower_function_body - 本体lowering
5. finalize_function - 関数finalize
6. restore_lowering_context - Context復元

## ファイル構成
src/mir/builder/
├── calls/
│   ├── mod.rs           # 公開インターフェース
│   ├── lowering.rs      # 関数lowering（354行）
│   └── utils.rs         # ユーティリティ（45行）
└── builder_calls.rs     # 削減版（766行）

## 次のステップ
Phase 2: emit.rs 作成（~500行移行）
Phase 3: build.rs 作成（~350行移行）
最終目標: builder_calls.rs を200行以内に

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

Co-Authored-By: Claude <noreply@anthropic.com>
Co-Authored-By: Task先生 <task@anthropic.com>

src/tests/mir_stage1_using_resolver_verify.rs

@@ -2,10 +2,16 @@ use crate::ast::ASTNode;
 use crate::mir::{MirCompiler, MirVerifier};
 use crate::parser::NyashParser;
 
+fn ensure_stage3_env() {
+    std::env::set_var("NYASH_PARSER_STAGE3", "1");
+    std::env::set_var("NYASH_PARSER_ALLOW_SEMICOLON", "1");
+}
+
 /// Minimal Stage‑1 using resolver harness resembling Stage1UsingResolverBox.resolve_for_source.
 /// Focuses on loops over ArrayBox/MapBox and JSON scanning, without FileBox/@ sugar.
 #[test]
 fn mir_stage1_using_resolver_min_fragment_verifies() {
+    ensure_stage3_env();
     let src = r#"
 using lang.compiler.parser.scan.parser_common_utils_box as ParserCommonUtilsBox
 using selfhost.shared.json.utils.json_frag as JsonFragBox
@@ -71,6 +77,7 @@ static box Stage1UsingResolverMini {
 /// Verify MIR/SSA for ParserBox.parse_program2 in isolation by compiling a small wrapper.
 #[test]
 fn mir_parserbox_parse_program2_harness_parses_minimal_source() {
+    ensure_stage3_env();
     // Minimal wrapper that brings ParserBox into scope and calls parse_program2.
     let src = r#"
 using lang.compiler.parser.parser_box as ParserBox

src/tests/mir_stageb_like_args_length.rs

@@ -1,4 +1,10 @@
 use crate::parser::NyashParser;
+use crate::mir::MirPrinter;
+
+fn ensure_stage3_env() {
+    std::env::set_var("NYASH_PARSER_STAGE3", "1");
+    std::env::set_var("NYASH_PARSER_ALLOW_SEMICOLON", "1");
+}
 use crate::ast::ASTNode;
 use crate::mir::{MirCompiler, MirVerifier};
 
@@ -15,6 +21,7 @@ use crate::mir::{MirCompiler, MirVerifier};
 /// を Rust MirBuilder で MIR 化し、SSA/PHI が破綻していないことを検証する。
 #[test]
 fn mir_stageb_like_args_length_verifies() {
+    ensure_stage3_env();
     let src = r#"
 static box StageBArgsBox {
   method resolve_src(args) {
@@ -36,6 +43,10 @@ static box StageBArgsBox {
     // Verify MIR SSA/PHI invariants
     let mut verifier = MirVerifier::new();
     if let Err(errors) = verifier.verify_module(&cr.module) {
+        if std::env::var("NYASH_MIR_TEST_DUMP").ok().as_deref() == Some("1") {
+            let dump = MirPrinter::new().print_module(&cr.module);
+            eprintln!("----- MIR DUMP (StageBArgsBox.resolve_src) -----\n{}", dump);
+        }
         for e in &errors {
             eprintln!("[mir-verify] {}", e);
         }
@@ -61,6 +72,7 @@ static box StageBArgsBox {
 /// を Rust MirBuilder で MIR 化し、SSA/PHI が破綻していないことを検証する。
 #[test]
 fn mir_stageb_like_if_args_length_loop_verifies() {
+    ensure_stage3_env();
     let src = r#"
 static box StageBArgsBox {
   method process(args) {
@@ -84,6 +96,10 @@ static box StageBArgsBox {
 
     let mut verifier = MirVerifier::new();
     if let Err(errors) = verifier.verify_module(&cr.module) {
+        if std::env::var("NYASH_MIR_TEST_DUMP").ok().as_deref() == Some("1") {
+            let dump = MirPrinter::new().print_module(&cr.module);
+            eprintln!("----- MIR DUMP (StageBArgsBox.process if+loop) -----\n{}", dump);
+        }
         for e in &errors {
             eprintln!("[mir-verify] {}", e);
         }
@@ -107,6 +123,7 @@ static box StageBArgsBox {
 /// }
 #[test]
 fn mir_stageb_like_nested_if_loop_verifies() {
+    ensure_stage3_env();
     let src = r#"
 static box TestNested {
   method complex(data) {
@@ -135,6 +152,10 @@ static box TestNested {
 
     let mut verifier = MirVerifier::new();
     if let Err(errors) = verifier.verify_module(&cr.module) {
+        if std::env::var("NYASH_MIR_TEST_DUMP").ok().as_deref() == Some("1") {
+            let dump = MirPrinter::new().print_module(&cr.module);
+            eprintln!("----- MIR DUMP (TestNested.complex nested if+loop) -----\n{}", dump);
+        }
         for e in &errors {
             eprintln!("[mir-verify] {}", e);
         }
@@ -151,6 +172,7 @@ static box TestNested {
 /// }
 #[test]
 fn mir_stageb_like_loop_cond_uses_length_verifies() {
+    ensure_stage3_env();
     let src = r#"
 static box StageBArgsBox {
   method process(args) {
@@ -172,6 +194,10 @@ static box StageBArgsBox {
 
     let mut verifier = MirVerifier::new();
     if let Err(errors) = verifier.verify_module(&cr.module) {
+        if std::env::var("NYASH_MIR_TEST_DUMP").ok().as_deref() == Some("1") {
+            let dump = MirPrinter::new().print_module(&cr.module);
+            eprintln!("----- MIR DUMP (StageBArgsBox.process loop cond uses length) -----\n{}", dump);
+        }
         for e in &errors {
             eprintln!("[mir-verify] {}", e);
         }
@@ -188,6 +214,7 @@ static box StageBArgsBox {
 /// }
 #[test]
 fn mir_stageb_like_conditional_and_loop_length_verifies() {
+    ensure_stage3_env();
     let src = r#"
 static box TestNested2 {
   method walk(data) {
@@ -209,6 +236,10 @@ static box TestNested2 {
 
     let mut verifier = MirVerifier::new();
     if let Err(errors) = verifier.verify_module(&cr.module) {
+        if std::env::var("NYASH_MIR_TEST_DUMP").ok().as_deref() == Some("1") {
+            let dump = MirPrinter::new().print_module(&cr.module);
+            eprintln!("----- MIR DUMP (TestNested2.walk conditional+loop length) -----\n{}", dump);
+        }
         for e in &errors {
             eprintln!("[mir-verify] {}", e);
         }
@@ -221,6 +252,7 @@ static box TestNested2 {
 /// - 文字列内/エスケープなどの分岐を含むが、ここでは最小限の骨格のみを再現。
 #[test]
 fn mir_jsonscanbox_like_seek_array_end_verifies() {
+    ensure_stage3_env();
     let src = r#"
 using selfhost.shared.json.core.string_scan as StringScanBox
 
@@ -252,6 +284,10 @@ static box JsonScanBoxMini {
 
     let mut verifier = MirVerifier::new();
     if let Err(errors) = verifier.verify_module(&cr.module) {
+        if std::env::var("NYASH_MIR_TEST_DUMP").ok().as_deref() == Some("1") {
+            let dump = MirPrinter::new().print_module(&cr.module);
+            eprintln!("----- MIR DUMP (JsonScanBoxMini.seek_array_end) -----\n{}", dump);
+        }
         for e in &errors {
             eprintln!("[mir-verify] {}", e);
         }

src/tests/mir_stageb_loop_break_continue.rs

@@ -0,0 +1,141 @@
+use crate::ast::ASTNode;
+use crate::mir::{MirCompiler, MirPrinter, MirVerifier};
+use crate::parser::NyashParser;
+
+fn ensure_stage3_env() {
+    std::env::set_var("NYASH_PARSER_STAGE3", "1");
+    std::env::set_var("NYASH_PARSER_ALLOW_SEMICOLON", "1");
+}
+
+/// Stage‑B 風: loop + break/continue + ArrayBox.length/get
+///
+/// static box LoopBreakContinueBox {
+///   method sum_positive_until_null(arr) {
+///     if arr == null { return 0 }
+///     local i = 0
+///     local acc = 0
+///     loop (i < arr.length()) {
+///       local v = arr.get(i)
+///       if v == null { break }
+///       if v < 0 {
+///         i = i + 1
+///         continue
+///       }
+///       acc = acc + v
+///       i = i + 1
+///     }
+///     return acc
+///   }
+/// }
+#[test]
+fn mir_stageb_loop_break_continue_verifies() {
+    ensure_stage3_env();
+    let src = r#"
+static box LoopBreakContinueBox {
+  method sum_positive_until_null(arr) {
+    if arr == null { return 0 }
+    local i = 0
+    local acc = 0
+    loop (i < arr.length()) {
+      local v = arr.get(i)
+      if v == null { break }
+      if v < 0 {
+        i = i + 1
+        continue
+      }
+      acc = acc + v
+      i = i + 1
+    }
+    return acc
+  }
+}
+"#;
+
+    let ast: ASTNode = NyashParser::parse_from_string(src).expect("parse ok");
+    let mut mc = MirCompiler::with_options(false);
+    let cr = mc.compile(ast).expect("compile");
+
+    let mut verifier = MirVerifier::new();
+    if let Err(errors) = verifier.verify_module(&cr.module) {
+        if std::env::var("NYASH_MIR_TEST_DUMP").ok().as_deref() == Some("1") {
+            let dump = MirPrinter::new().print_module(&cr.module);
+            eprintln!("----- MIR DUMP (LoopBreakContinueBox.sum_positive_until_null) -----\n{}", dump);
+        }
+        for e in &errors {
+            eprintln!("[mir-verify] {}", e);
+        }
+        panic!("MIR verification failed for StageB-like loop+break/continue pattern");
+    }
+}
+
+/// Stage‑B 風: 入れ子ループ + break/continue + length/get
+///
+/// static box LoopNestedBreakBox {
+///   method nested_walk(arr) {
+///     if arr == null { return 0 }
+///     local i = 0
+///     local total = 0
+///     loop (i < arr.length()) {
+///       local inner = arr.get(i)
+///       if inner == null {
+///         i = i + 1
+///         continue
+///       }
+///       local j = 0
+///       loop (j < inner.length()) {
+///         local v = inner.get(j)
+///         if v == null { break }
+///         total = total + v
+///         j = j + 1
+///       }
+///       i = i + 1
+///     }
+///     return total
+///   }
+/// }
+#[test]
+fn mir_stageb_nested_loop_break_continue_verifies() {
+    ensure_stage3_env();
+    let src = r#"
+static box LoopNestedBreakBox {
+  method nested_walk(arr) {
+    if arr == null { return 0 }
+    local i = 0
+    local total = 0
+    loop (i < arr.length()) {
+      local inner = arr.get(i)
+      if inner == null {
+        i = i + 1
+        continue
+      }
+      local j = 0
+      loop (j < inner.length()) {
+        local v = inner.get(j)
+        if v == null { break }
+        total = total + v
+        j = j + 1
+      }
+      i = i + 1
+    }
+    return total
+  }
+}
+"#;
+
+    let ast: ASTNode = NyashParser::parse_from_string(src).expect("parse ok");
+    let mut mc = MirCompiler::with_options(false);
+    let cr = mc.compile(ast).expect("compile");
+
+    let mut verifier = MirVerifier::new();
+    if let Err(errors) = verifier.verify_module(&cr.module) {
+        if std::env::var("NYASH_MIR_TEST_DUMP").ok().as_deref() == Some("1") {
+            let dump = MirPrinter::new().print_module(&cr.module);
+            eprintln!("----- MIR DUMP (LoopNestedBreakBox.nested_walk) -----\n{}", dump);
+        }
+        for e in &errors {
+            eprintln!("[mir-verify] {}", e);
+        }
+        panic!("MIR verification failed for StageB-like nested loop+break/continue pattern");
+    }
+}
+

src/tests/mod.rs

@@ -7,6 +7,7 @@ pub mod identical_exec_collections;
 pub mod identical_exec_instance;
 pub mod identical_exec_string;
 pub mod mir_stageb_like_args_length;
+pub mod mir_stageb_loop_break_continue;
 pub mod mir_stage1_using_resolver_verify;
 pub mod mir_vm_poc;
 pub mod nyash_abi_basic;