restore(lang/compiler): bring back lang/src/compiler from e917d400; add Hako index canaries and docs; implement Rust-side index operator (Array/Map get/set) with Fail‑Fast diagnostics

- restore: lang/src/compiler/** (parser/emit/builder/pipeline_v2) from e917d400
- docs: docs/development/selfhosting/index-operator-hako.md
- smokes(hako): tools/smokes/v2/profiles/quick/core/index_operator_hako.sh (opt-in)
- smokes(vm): adjust index_operator_vm.sh for semicolon gate + stable error text
- rust/parser: allow IndexExpr and assignment LHS=Index; postfix parse LBRACK chain
- rust/builder: lower arr/map index to BoxCall get/set; annotate array/map literals; Fail‑Fast for unsupported types
- CURRENT_TASK: mark Rust side done; add Hako tasks checklist

Note: files disappeared likely due to branch FF to a lineage without lang/src/compiler; no explicit delete commit found. Added anchor checks and suggested CI guard in follow-up.

crates/nyash_kernel/src/lib.rs

@@ -234,7 +234,7 @@ pub extern "C" fn nyash_box_from_i64(val: i64) -> i64 {
 pub extern "C" fn nyash_env_box_new(type_name: *const i8) -> i64 {
     use nyash_rust::{
         box_trait::NyashBox,
-        runtime::{host_handles as handles, box_registry::get_global_registry},
+        runtime::{box_registry::get_global_registry, host_handles as handles},
     };
     use std::ffi::CStr;
     if type_name.is_null() {
@@ -283,7 +283,7 @@ pub extern "C" fn nyash_env_box_new_i64x(
 ) -> i64 {
     use nyash_rust::{
         box_trait::{IntegerBox, NyashBox},
-        runtime::{host_handles as handles, box_registry::get_global_registry},
+        runtime::{box_registry::get_global_registry, host_handles as handles},
     };
     use std::ffi::CStr;
     if type_name.is_null() {
@@ -353,7 +353,7 @@ pub extern "C" fn nyash_any_length_h_export(handle: i64) -> i64 {
     use nyash_rust::runtime::host_handles as handles;
     if std::env::var("NYASH_JIT_TRACE_LEN").ok().as_deref() == Some("1") {
         let present = if handle > 0 {
-                handles::get(handle as u64).is_some()
+            handles::get(handle as u64).is_some()
         } else {
             false
         };

crates/nyash_kernel/src/plugin/future.rs

@@ -112,8 +112,9 @@ pub extern "C" fn nyash_future_spawn_method_h(
     }
     // Prepare FutureBox and register handle
     let fut_box = std::sync::Arc::new(nyash_rust::boxes::future::FutureBox::new());
-    let handle =
-    nyash_rust::runtime::host_handles::to_handle_arc(fut_box.clone() as std::sync::Arc<dyn NyashBox>);
+    let handle = nyash_rust::runtime::host_handles::to_handle_arc(
+        fut_box.clone() as std::sync::Arc<dyn NyashBox>
+    );
     // Copy data for async task
     let cap: usize = 512;
     let tlv = buf.clone();
@@ -245,7 +246,7 @@ pub extern "C" fn nyash_future_spawn_instance3_i64(a0: i64, a1: i64, a2: i64, ar
     }
     // Resolve receiver invoke and type id/name
     let (instance_id, real_type_id, invoke) =
-    if let Some(obj) = nyash_rust::runtime::host_handles::get(a0 as u64) {
+        if let Some(obj) = nyash_rust::runtime::host_handles::get(a0 as u64) {
             if let Some(p) = obj.as_any().downcast_ref::<PluginBoxV2>() {
                 (p.instance_id(), p.inner.type_id, Some(p.inner.invoke_fn))
             } else {
@@ -265,7 +266,7 @@ pub extern "C" fn nyash_future_spawn_instance3_i64(a0: i64, a1: i64, a2: i64, ar
     // Determine method name string (from a1 handle→StringBox, or a1 as C string pointer, or legacy VM args)
     let mut method_name: Option<String> = None;
     if a1 > 0 {
-    if let Some(obj) = nyash_rust::runtime::host_handles::get(a1 as u64) {
+        if let Some(obj) = nyash_rust::runtime::host_handles::get(a1 as u64) {
             if let Some(p) = obj.as_any().downcast_ref::<PluginBoxV2>() {
                 if p.box_type == "StringBox" {
                     // Limit the lifetime of the read guard to this inner block by avoiding an outer binding
@@ -388,8 +389,9 @@ pub extern "C" fn nyash_future_spawn_instance3_i64(a0: i64, a1: i64, a2: i64, ar
     }
     // Create Future and schedule async invoke
     let fut_box = std::sync::Arc::new(nyash_rust::boxes::future::FutureBox::new());
-    let handle =
-    nyash_rust::runtime::host_handles::to_handle_arc(fut_box.clone() as std::sync::Arc<dyn NyashBox>);
+    let handle = nyash_rust::runtime::host_handles::to_handle_arc(
+        fut_box.clone() as std::sync::Arc<dyn NyashBox>
+    );
     let tlv = buf.clone();
     nyash_rust::runtime::global_hooks::spawn_task(
         "nyash.future.spawn_instance3_i64",

crates/nyash_kernel/src/plugin/invoke.rs

@@ -77,7 +77,7 @@ pub extern "C" fn nyash_plugin_invoke3_f64(
         unsafe extern "C" fn(u32, u32, u32, *const u8, usize, *mut u8, *mut usize) -> i32,
     > = None;
     if a0 > 0 {
-    if let Some(obj) = nyash_rust::runtime::host_handles::get(a0 as u64) {
+        if let Some(obj) = nyash_rust::runtime::host_handles::get(a0 as u64) {
             if let Some(p) = obj.as_any().downcast_ref::<PluginBoxV2>() {
                 instance_id = p.instance_id();
                 invoke = Some(p.inner.invoke_fn);
@@ -160,7 +160,7 @@ fn nyash_plugin_invoke_name_common_i64(method: &str, argc: i64, a0: i64, a1: i64
         unsafe extern "C" fn(u32, u32, u32, *const u8, usize, *mut u8, *mut usize) -> i32,
     > = None;
     if a0 > 0 {
-    if let Some(obj) = nyash_rust::runtime::host_handles::get(a0 as u64) {
+        if let Some(obj) = nyash_rust::runtime::host_handles::get(a0 as u64) {
             if let Some(p) = obj.as_any().downcast_ref::<PluginBoxV2>() {
                 instance_id = p.instance_id();
                 type_id = p.inner.type_id;
@@ -263,7 +263,7 @@ pub extern "C" fn nyash_plugin_invoke_by_name_i64(
         unsafe extern "C" fn(u32, u32, u32, *const u8, usize, *mut u8, *mut usize) -> i32,
     > = None;
     if recv_handle > 0 {
-    if let Some(obj) = nyash_rust::runtime::host_handles::get(recv_handle as u64) {
+        if let Some(obj) = nyash_rust::runtime::host_handles::get(recv_handle as u64) {
             if let Some(p) = obj.as_any().downcast_ref::<PluginBoxV2>() {
                 instance_id = p.instance_id();
                 type_id = p.inner.type_id;
@@ -401,7 +401,7 @@ pub extern "C" fn nyash_plugin_invoke3_tagged_i64(
         unsafe extern "C" fn(u32, u32, u32, *const u8, usize, *mut u8, *mut usize) -> i32,
     > = None;
     if a0 > 0 {
-    if let Some(obj) = nyash_rust::runtime::host_handles::get(a0 as u64) {
+        if let Some(obj) = nyash_rust::runtime::host_handles::get(a0 as u64) {
             if let Some(p) = obj.as_any().downcast_ref::<PluginBoxV2>() {
                 instance_id = p.instance_id();
                 real_type_id = p.inner.type_id;

crates/nyash_kernel/src/plugin/invoke_core.rs

@@ -15,7 +15,7 @@ pub struct Receiver {
 pub fn resolve_receiver_for_a0(a0: i64) -> Option<Receiver> {
     // 1) Handle registry (preferred)
     if a0 > 0 {
-    if let Some(obj) = nyash_rust::runtime::host_handles::get(a0 as u64) {
+        if let Some(obj) = nyash_rust::runtime::host_handles::get(a0 as u64) {
             if let Some(p) = obj.as_any().downcast_ref::<PluginBoxV2>() {
                 return Some(Receiver {
                     instance_id: p.instance_id(),