From d49ab9e405a4c925ad284a3dcc697e54ae852904 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?=E7=88=B1=E7=89=B9=E6=AF=8F=E7=BE=8A=E9=98=9F?=
 <t2026104239910027@eduxiji.net>
Date: Sat, 6 Jun 2026 14:45:22 +0800
Subject: [PATCH] =?UTF-8?q?feat:=20=E6=96=B0=E5=A2=9E=20for-var=20?=
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---
 crates/oxide_compiler/src/counter.rs | 16 ++++++++++++++--
 crates/oxide_compiler/src/emitter.rs | 22 +++++++++++++++++-----
 crates/oxide_compiler/src/hash.rs    | 11 ++++++++---
 3 files changed, 39 insertions(+), 10 deletions(-)

diff --git a/crates/oxide_compiler/src/counter.rs b/crates/oxide_compiler/src/counter.rs
index 863229c..13e0533 100644
--- a/crates/oxide_compiler/src/counter.rs
+++ b/crates/oxide_compiler/src/counter.rs
@@ -1,4 +1,4 @@
-use oxide_parser::{Expression, Statement};
+use oxide_parser::{Expression, ForStatementInit, Statement};
 
 use crate::compiler::{is_side_effect_free, CompileCtx, Compiler, Label};
 
@@ -13,8 +13,10 @@ impl Compiler {
                     ctx.alloc_reg();
                     if let Some(init) = &d.init {
                         self.count_expression(init, ctx);
+                        ctx.projected_pc += 1; // STORE_VAR
+                    } else {
+                        ctx.projected_pc += 2; // LOAD_CONST(undefined) + STORE_VAR
                     }
-                    ctx.projected_pc += 1; // STORE_VAR
                 }
             }
             Statement::ReturnStatement(ret) => {
@@ -64,6 +66,16 @@ impl Compiler {
                 if let Some(init) = &fr.init {
                     if let Some(expr) = init.as_expression() {
                         self.count_expression(expr, ctx);
+                    } else if let ForStatementInit::VariableDeclaration(decl) = init {
+                        for d in &decl.declarations {
+                            ctx.alloc_reg();
+                            if let Some(init_expr) = &d.init {
+                                self.count_expression(init_expr, ctx);
+                                ctx.projected_pc += 1; // STORE_VAR
+                            } else {
+                                ctx.projected_pc += 2; // LOAD_CONST(undefined) + STORE_VAR
+                            }
+                        }
                     }
                 }
                 ctx.label_map.insert(start_label, ctx.projected_pc);
diff --git a/crates/oxide_compiler/src/emitter.rs b/crates/oxide_compiler/src/emitter.rs
index 4334595..f27a1f0 100644
--- a/crates/oxide_compiler/src/emitter.rs
+++ b/crates/oxide_compiler/src/emitter.rs
@@ -1,6 +1,6 @@
 use crate::compiler::Label;
 use crate::opcode::{self, OpCode};
-use oxide_parser::{AssignmentOperator, Expression, Statement, UnaryOperator};
+use oxide_parser::{AssignmentOperator, Expression, ForStatementInit, Statement, UnaryOperator};
 
 use crate::compiler::{is_int_literal, is_side_effect_free, BinaryOperator, CompileCtx, Compiler};
 use crate::module::Constant;
@@ -150,10 +150,22 @@ impl Compiler {
                 if let Some(init) = &fr.init {
                     if let Some(expr) = init.as_expression() {
                         self.emit_expression(expr, ctx)?;
-                    } else if init.is_var_declaration() {
-                        return Err(
-                            "for-loop `let` init not yet supported; use expression init".into()
-                        );
+                    } else if let ForStatementInit::VariableDeclaration(decl) = init {
+                        for d in &decl.declarations {
+                            let name = match &d.id {
+                                oxide_parser::BindingPattern::BindingIdentifier(bi) => {
+                                    bi.name.as_str()
+                                }
+                                _ => return Err("destructuring not supported".into()),
+                            };
+                            let var_reg = ctx.alloc_reg();
+                            ctx.declare(name, var_reg)?;
+                            if let Some(init_expr) = &d.init {
+                                let val_reg = self.emit_expression(init_expr, ctx)?;
+                                ctx.emit(opcode::encode(OpCode::STORE_VAR, var_reg, val_reg, 0));
+                                ctx.init_var(name);
+                            }
+                        }
                     }
                 }
 
diff --git a/crates/oxide_compiler/src/hash.rs b/crates/oxide_compiler/src/hash.rs
index 96e7909..1ccd93b 100644
--- a/crates/oxide_compiler/src/hash.rs
+++ b/crates/oxide_compiler/src/hash.rs
@@ -1,4 +1,4 @@
-use oxide_parser::{Expression, Statement};
+use oxide_parser::{Expression, ForStatementInit, Statement};
 
 pub fn structural_hash(program: &oxide_parser::Program) -> u64 {
     use std::hash::Hasher;
@@ -53,8 +53,13 @@ fn hash_statement(stmt: &Statement, h: &mut rustc_hash::FxHasher) {
             if let Some(init) = &fr.init {
                 if let Some(expr) = init.as_expression() {
                     hash_expression(expr, h);
-                } else if init.is_var_declaration() {
-                    0u8.hash(h);
+                } else if let ForStatementInit::VariableDeclaration(decl) = init {
+                    (decl.declarations.len() as u32).hash(h);
+                    for d in &decl.declarations {
+                        if let Some(init_expr) = &d.init {
+                            hash_expression(init_expr, h);
+                        }
+                    }
                 }
             }
             if let Some(test) = &fr.test {