feat: for-await-of + Symbol.asyncIterator + AsyncFromSyncIterator

crates/oxide_emit/src/stmt/iteration/for_of.rs

@@ -1,16 +1,28 @@
-//! for-of 语句 emit：`emit_for_of_statement` 迭代器协议遍历。
+//! for-of 与 for-await-of 语句 emit。
+//!
+//! 同步 for-of 用 FOR_OF_* 指令；`for await` 用 FOR_AWAIT_OF_*：初始化取异步
+//! 迭代器（缺失 `@@asyncIterator` 时回退 AsyncFromSyncIterator），每步
+//! `next()` 结果经 `AWAIT` 挂起后检查 done。体内 await 语义由 `AWAIT` 指令
+//! 原生提供（每次迭代都 await）。
 
 use crate::{CompileCtx, Emitter};
 use oxide_bytecode::opcode::OpCode;
 use oxide_ir::inst::Inst;
 use oxide_ir::operand::Operand;
-use oxide_parser::{ForStatementLeft, Statement};
+use oxide_parser::{ForOfStatement, ForStatementLeft, Statement};
 
 impl Emitter {
     pub(crate) fn emit_for_of_statement(&self, stmt: &Statement, ctx: &mut CompileCtx) -> Result<Option<u32>, String> {
         let Statement::ForOfStatement(fo) = stmt else {
             return Ok(None);
         };
+        if fo.r#await {
+            return self.emit_for_await_of_statement(fo, ctx);
+        }
+        self.emit_sync_for_of_statement(fo, ctx)
+    }
+
+    fn emit_sync_for_of_statement(&self, fo: &ForOfStatement, ctx: &mut CompileCtx) -> Result<Option<u32>, String> {
         let start_label = ctx.next_label_id();
         let end_label = ctx.next_label_id();
         let iter_src_reg = self.emit_expression(&fo.right, ctx)?;
@@ -23,7 +35,59 @@ impl Emitter {
         ctx.inst(Inst::jmp_if_false(has_reg, end_label));
         let val_reg = ctx.alloc_reg();
         ctx.inst(Inst::new(OpCode::FOR_OF_NEXT, Operand::Reg(val_reg), Operand::None, Operand::None));
-        match &fo.left {
+        self.emit_for_of_left_assignment(&fo.left, val_reg, ctx)?;
+        self.emit_statement(&fo.body, ctx)?;
+        ctx.inst(Inst::jmp(start_label));
+        ctx.labels.set_label_pos(end_label, ctx.insts.len());
+        ctx.inst(Inst::new(OpCode::FOR_OF_CLOSE, Operand::None, Operand::None, Operand::None));
+        ctx.pop_label_scopes(n_labeled);
+        ctx.pop_loop();
+        Ok(None)
+    }
+
+    /// for-await-of：异步迭代器协议遍历，每步经 `AWAIT` 挂起等待 next() 结果。
+    ///
+    /// 指令序列：INIT 取异步迭代器 → 循环顶 NEXT 调 next() 写 promise → `AWAIT`
+    /// 挂起（恢复值经 reg 0 交付）→ LOAD_VAR 拷贝为结果对象 → DONE 检查 done →
+    /// FOR_OF_NEXT 读 value → 绑定左侧 → 循环体 → CLOSE 异步收尾。
+    fn emit_for_await_of_statement(&self, fo: &ForOfStatement, ctx: &mut CompileCtx) -> Result<Option<u32>, String> {
+        let start_label = ctx.next_label_id();
+        let end_label = ctx.next_label_id();
+        let iter_src_reg = self.emit_expression(&fo.right, ctx)?;
+        ctx.inst(Inst::new(OpCode::FOR_AWAIT_OF_INIT, Operand::None, Operand::Reg(iter_src_reg), Operand::None));
+        ctx.labels.set_label_pos(start_label, ctx.insts.len());
+        ctx.push_loop(end_label, start_label);
+        let n_labeled = ctx.take_pending_loop_labels(end_label, start_label);
+        let next_reg = ctx.alloc_reg();
+        ctx.inst(Inst::new(OpCode::FOR_AWAIT_OF_NEXT, Operand::Reg(next_reg), Operand::None, Operand::None));
+        ctx.inst(Inst::await_expr(Operand::Reg(next_reg)));
+        let result_reg = ctx.alloc_reg();
+        ctx.inst(Inst::new(OpCode::LOAD_VAR, Operand::Reg(result_reg), Operand::None, Operand::None));
+        let has_reg = ctx.alloc_reg();
+        ctx.inst(Inst::new(
+            OpCode::FOR_AWAIT_OF_DONE,
+            Operand::Reg(has_reg),
+            Operand::Reg(result_reg),
+            Operand::None,
+        ));
+        ctx.inst(Inst::jmp_if_false(has_reg, end_label));
+        let val_reg = ctx.alloc_reg();
+        ctx.inst(Inst::new(OpCode::FOR_OF_NEXT, Operand::Reg(val_reg), Operand::None, Operand::None));
+        self.emit_for_of_left_assignment(&fo.left, val_reg, ctx)?;
+        self.emit_statement(&fo.body, ctx)?;
+        ctx.inst(Inst::jmp(start_label));
+        ctx.labels.set_label_pos(end_label, ctx.insts.len());
+        ctx.inst(Inst::new(OpCode::FOR_AWAIT_OF_CLOSE, Operand::None, Operand::None, Operand::None));
+        ctx.pop_label_scopes(n_labeled);
+        ctx.pop_loop();
+        Ok(None)
+    }
+
+    /// for-of/for-await-of 左侧绑定：把当前迭代值 `val_reg` 写入声明/赋值目标。
+    fn emit_for_of_left_assignment(
+        &self, left: &ForStatementLeft, val_reg: u32, ctx: &mut CompileCtx,
+    ) -> Result<(), String> {
+        match left {
             ForStatementLeft::VariableDeclaration(decl) => {
                 for d in &decl.declarations {
                     self.emit_binding_pattern(&d.id, val_reg, decl.kind, false, ctx)?;
@@ -42,12 +106,6 @@ impl Emitter {
             }
             _ => return Err("unsupported for-of left-hand side".into()),
         }
-        self.emit_statement(&fo.body, ctx)?;
-        ctx.inst(Inst::jmp(start_label));
-        ctx.labels.set_label_pos(end_label, ctx.insts.len());
-        ctx.inst(Inst::new(OpCode::FOR_OF_CLOSE, Operand::None, Operand::None, Operand::None));
-        ctx.pop_label_scopes(n_labeled);
-        ctx.pop_loop();
-        Ok(None)
+        Ok(())
     }
 }