test(mir): Phase 25.1 StaticCompiler receiver回帰防止テスト追加

## テスト内容
1. MIR compile & verify（SSA検証）
2. VM実行でRC=0（receiver捏造バグ検出）
3. StringBox正規化確認（ParserBox→StringBox）

## 検証項目
- ✅ StringHelpers.skip_ws/2 呼び出し成功
- ✅ receiver型推論正常動作
- ✅ 文字列メソッド正規化動作確認

Co-Authored-By: ChatGPT5 <chatgpt@openai.com>

src/tests/mir_stage1_staticcompiler_receiver.rs

@@ -0,0 +1,136 @@
+/*!
+ * Phase 25.1 StaticCompiler receiver型推論バグ回帰防止テスト
+ *
+ * ## 問題再現
+ * - StringHelpers.skip_ws/2 呼び出しで receiver 型情報なし
+ * - ParserBox.length が Global("ParserBox.length") に変換されてVM落ち
+ *
+ * ## 修正内容
+ * - Phase 1: guard.rs でreceiver型なし→Global変換
+ * - Phase 2: unified_emitter.rs で guard→materialization 順序反転
+ * - Phase 3-A: emit_string型注釈追加
+ * - Phase 3-B: BinOp(Add)型注釈強化
+ * - Phase 3-C: StaticCompiler文字列メソッド→StringBox正規化
+ *
+ * ## 検証項目
+ * 1. MIR compile + verify が通る
+ * 2. VM実行でRC=0（エラー落ちしない）
+ * 3. StringBox.length に正規化されている
+ */
+
+use crate::ast::ASTNode;
+use crate::backend::VM;
+use crate::mir::{instruction::MirInstruction, MirCompiler, MirVerifier};
+use crate::parser::NyashParser;
+
+fn ensure_stage3_env() {
+    std::env::set_var("NYASH_PARSER_STAGE3", "1");
+    std::env::set_var("HAKO_PARSER_STAGE3", "1");
+    std::env::set_var("NYASH_ENABLE_USING", "1");
+    std::env::set_var("HAKO_ENABLE_USING", "1");
+}
+
+/// Stage1Cli + StringHelpers.skip_ws テスト用フィクスチャ
+fn stage1_staticcompiler_fixture_src() -> String {
+    let stage1_cli_src = include_str!("../../lang/src/runner/stage1_cli.hako");
+    let test_main_src = r#"
+using lang.src.runner.stage1_cli as Stage1Cli
+
+static box Main {
+  main(args) {
+    env.set("STAGE1_SOURCE_TEXT", "static box Main { main() { return StringHelpers.skip_ws(\"  a\", 0) } }")
+    local prog = Stage1Cli.emit_program_json_from_text()
+    print("[stage1_staticcompiler_receiver] prog=" + ("" + prog))
+    return 0
+  }
+}
+"#;
+    format!("{stage1_cli_src}\n\n{test_main_src}")
+}
+
+/// Test 1: MIR compile & verify が通ることを確認
+#[test]
+fn mir_stage1_staticcompiler_receiver_compiles_and_verifies() {
+    ensure_stage3_env();
+    let src = stage1_staticcompiler_fixture_src();
+
+    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) {
+        for e in &errors {
+            eprintln!("[rust-mir-verify] {}", e);
+        }
+        panic!("MIR verification failed for stage1_staticcompiler_receiver");
+    }
+}
+
+/// Test 2: VM実行でRC=0（receiver捏造バグがないことを確認）
+#[test]
+fn mir_stage1_staticcompiler_receiver_exec_succeeds() {
+    ensure_stage3_env();
+    std::env::set_var("NYASH_DISABLE_PLUGINS", "1"); // Plugin依存を排除
+
+    let src = stage1_staticcompiler_fixture_src();
+
+    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();
+    verifier.verify_module(&cr.module).expect("verify");
+
+    // VM実行
+    let mut vm = VM::new();
+    let result = vm.execute_module(&cr.module);
+
+    // RC=0 を期待（receiver捏造バグがあると "Unknown: ParserBox.length" で落ちる）
+    assert!(
+        result.is_ok(),
+        "VM should execute successfully without receiver fabrication error"
+    );
+}
+
+/// Test 3: StringBox正規化が行われていることを確認（MIR検証）
+#[test]
+fn mir_stage1_staticcompiler_receiver_normalizes_to_stringbox() {
+    ensure_stage3_env();
+    let src = stage1_staticcompiler_fixture_src();
+
+    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");
+
+    // StringHelpers.skip_ws 内の .length() 呼び出しを探す
+    let mut found_stringbox_length = false;
+
+    for (fname, func) in cr.module.functions.iter() {
+        if fname.contains("StringHelpers") {
+            for (bb_id, block) in &func.blocks {
+                for inst in &block.instructions {
+                    if let MirInstruction::Call { callee, .. } = inst {
+                        if let Some(crate::mir::Callee::Method {
+                            box_name, method, ..
+                        }) = callee
+                        {
+                            if box_name == "StringBox" && method == "length" {
+                                found_stringbox_length = true;
+                                eprintln!(
+                                    "[test] Found StringBox.length in {} bb={:?}",
+                                    fname, bb_id
+                                );
+                            }
+                        }
+                    }
+                }
+            }
+        }
+    }
+
+    assert!(
+        found_stringbox_length,
+        "Expected StaticCompiler string methods to be normalized to StringBox"
+    );
+}

src/tests/mod.rs

@@ -15,6 +15,7 @@ pub mod mir_loopform_exit_phi;
 pub mod mir_loopform_complex;
 pub mod mir_static_box_naming;
 pub mod mir_stage1_cli_emit_program_min;
+pub mod mir_stage1_staticcompiler_receiver; // Phase 25.1: StaticCompiler receiver型推論バグ回帰防止
 pub mod mir_stage1_using_resolver_verify;
 pub mod stage1_cli_entry_ssa_smoke;
 pub mod mir_stageb_like_args_length;