restore(lang): full lang tree from ff3ef452 (306 files) — compiler, vm, shared, runner, c-abi, etc.\n\n- Restores lang/ directory (files≈306, dirs≈64) as per historical branch with selfhost sources\n- Keeps our recent parser index changes in compiler/* (merged clean by checkout)\n- Unblocks selfhost development and documentation references

lang/src/selfhost/hako_module.toml

@@ -0,0 +1,11 @@
+[module]
+name = "selfhost.mir_builder"
+version = "0.1.0"
+
+[exports]
+README = "mir_builder/README.md"
+LayerGuard = "mir_builder/LAYER_GUARD.hako"
+Builder = "mir_builder/builder.hako"
+Phi = "mir_builder/phi.hako"
+Verify = "mir_builder/verify.hako"
+

lang/src/selfhost/mir_builder/LAYER_GUARD.hako

@@ -0,0 +1,9 @@
+// LAYER_GUARD — selfhost.mir_builder
+// この層の責務: MIR(JSON v0) の生成（将来的に）。VM/LLVM/実行は非対象。
+
+static box LayerGuard {
+  name() { return "selfhost.mir_builder" }
+  allowed_imports() { return ["json", "mir_spec", "fs"] }
+  forbidden_imports() { return ["vm", "llvm", "runtime", "plugins"] }
+}
+

lang/src/selfhost/mir_builder/README.md

@@ -0,0 +1,30 @@
+Self‑Host MIR Builder (Scaffold) — Phase‑20.12b
+
+Purpose
+- Prepare a minimal, opt‑in skeleton to generate MIR(JSON v0) in Hakorune (self‑host) alongside the current Rust generator.
+- Keep default behavior unchanged (Rust MIR remains the source of truth). This module is emit‑only in early phases.
+
+Scope (this scaffold)
+- Files: builder.hako, phi.hako, verify.hako, LAYER_GUARD.hako
+- Behavior: no‑op/identity placeholders with clearly defined interfaces and gates.
+- Docs: specs/mir-json-v0.md describes the minimal JSON v0 shape targeted by this builder.
+
+Non‑Goals (now)
+- Replacing Rust MIR generation by default
+- Emitting full MIR coverage (call/extern/boxcall/complex boxes)
+
+Interfaces (subject to evolution)
+- SelfhostMirBuilder.build(ast_or_src_path) -> json_path (emit‑only; v0 returns input path)
+- SelfhostMirVerify.verify(json_path) -> bool/int (0=ok; v0 always ok)
+- SelfhostPhiBox helpers (shape only; no logic yet)
+
+Gates (opt‑in)
+- NYASH_USE_NY_COMPILER=1 → future: emit‑only builder path
+- NYASH_JSON_ONLY=1 → future: sidecar JSON dump for parity check
+
+Layer Guard
+- See LAYER_GUARD.hako — allowed imports are restricted to shared JSON/MIR helpers. No VM/LLVM interaction here.
+
+Rollback
+- Folder is isolated under lang/src/selfhost/. Removing this directory reverts to current behavior.
+

lang/src/selfhost/mir_builder/builder.hako

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+// builder.hako — Self‑host MIR(JSON v0) Builder (Scaffold)
+// Phase‑20.12b: emit‑only placeholder. Returns input path unchanged.
+
+static box SelfhostMirBuilder {
+  // Build MIR(JSON v0) from AST/source (scaffold)
+  // Returns: json_path (for now, identity)
+  build(input_path) {
+    // TODO(20.12b): parse/load, lower minimal ops (const/binop/compare/branch/ret/phi)
+    return input_path
+  }
+
+  // Future convenience: emit a minimal JSON header for parity checks
+  emit_min_header(json_path) {
+    // TODO(20.12b): write {"version":"0","kind":"Program"} header sidecar
+    return json_path
+  }
+}
+

lang/src/selfhost/mir_builder/phi.hako

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+// phi.hako — PHI helpers (Scaffold)
+// Phase‑20.12b: define shapes; real logic arrives in later steps.
+
+static box SelfhostPhiBox {
+  // Merge two inputs (placeholder)
+  merge2(dst, in1, in2) {
+    // TODO: construct MIR JSON node: {op:"phi", dst, inputs:[[bb1,v1],[bb2,v2]]}
+    return dst
+  }
+
+  // Merge list of (bb,val) pairs (placeholder)
+  mergeN(dst, inputs) {
+    // TODO: validate inputs cover all predecessors
+    return dst
+  }
+}
+

lang/src/selfhost/mir_builder/verify.hako

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+// verify.hako — Selfhost MIR verifier (Scaffold)
+// Phase‑20.12b: minimal contract; always OK for now.
+
+static box SelfhostMirVerify {
+  verify(json_path) {
+    // TODO: parse JSON and check: block start PHIs, pred coverage, no undefined uses
+    return 0 // 0=ok (placeholder)
+  }
+}
+