fix: 脚本顶层 var/function 声明落 globalThis（DEFINE_GLOBAL_PROP 非可配置数据属性）

crates/oxide_vm/src/vm.rs

@@ -1318,6 +1318,10 @@ impl Vm {
                     self.dispatch_define_prop(rd, a, b)?;
                 }
 
+                OpCode::DEFINE_GLOBAL_PROP => {
+                    self.dispatch_define_global_prop(rd, a, b)?;
+                }
+
                 OpCode::RETURN => match self.dispatch_return(rd) {
                     Ok(Some(result)) => return Ok(result),
                     Ok(None) => {}

crates/oxide_vm/src/vm_dispatch_ctrl.rs

@@ -178,6 +178,26 @@ impl Vm {
         }
     }
 
+    /// 定义全局 var 绑定数据属性：rd=全局对象，a=值，b=键。
+    /// 属性可写/可枚举/不可配置（CreateGlobalVarBinding 的属性描述符）。
+    ///
+    /// # 边界与前提
+    /// - 已有同名不可写属性（NaN/undefined/Infinity 等内置）时静默跳过：规范中
+    ///   var 绑定仍建立（寄存器侧），全局对象属性保持原样，不抛错。
+    /// - 已有同名可写数据属性（重复 var 声明）时按定义更新值。
+    pub(crate) fn dispatch_define_global_prop(&mut self, rd: usize, a: usize, b: usize) -> Result<(), String> {
+        vm_trace!("DEFINE_GLOBAL_PROP rd={} value={} key={}", rd, a, b);
+        let obj_val = self.regs[rd];
+        if !obj_val.is_object() {
+            return Ok(());
+        }
+        let prop_name_si = self.property_key_si(self.regs[b]);
+        let value = self.regs[a];
+        let obj = unsafe { &mut *obj_val.as_js_object_ptr() };
+        let _ = self.define_data_property(obj, prop_name_si, value, PropAttributes::new(true, true, false));
+        Ok(())
+    }
+
     /// break 完成：`crossed`（rd 槽）为 emit 词法算出的逃出 finally 域数。
     /// 逐个穿越 finally 后跳转到目标；crossed 为 0 时直接跳转。
     pub(crate) fn dispatch_break(&mut self, instr: u32) {

crates/oxide_vm/tests/global_var_binding_tests.rs

@@ -0,0 +1,100 @@
+//! 脚本顶层 var/function 声明落 globalThis 的运行时行为测试。
+
+use oxide_compiler::compiler::Compiler;
+use oxide_parser::Allocator;
+use oxide_vm::vm::Vm;
+
+fn eval_truthy(source: &str) {
+    let allocator = Allocator::default();
+    let program = oxide_parser::parse(&allocator, source).expect("parse");
+    let module = Compiler::new().compile(&program).expect("compile");
+    let mut vm = Vm::new();
+    let result = vm.run(&module).expect("run");
+    assert!(result.is_bool() && result.as_bool(), "expected true, got: {result:?}\nsource: {source}");
+}
+
+fn eval_string(source: &str) -> String {
+    let allocator = Allocator::default();
+    let program = oxide_parser::parse(&allocator, source).expect("parse");
+    let module = Compiler::new().compile(&program).expect("compile");
+    let mut vm = Vm::new();
+    let result = vm.run(&module).expect("run");
+    vm.lookup_str(result).unwrap_or_default()
+}
+
+#[test]
+fn top_level_var_lands_on_global_this() {
+    eval_truthy("var x = 5; globalThis.x === 5");
+    eval_truthy("var y = 10; typeof globalThis.y === 'number'");
+}
+
+#[test]
+fn top_level_function_lands_on_global_this() {
+    eval_truthy("function foo(){ return 1; } globalThis.foo() === 1");
+    eval_truthy("function foo(){ return 1; } typeof globalThis.foo === 'function'");
+}
+
+#[test]
+fn let_const_class_do_not_land_on_global_this() {
+    eval_truthy("let z = 5; typeof globalThis.z === 'undefined'");
+    eval_truthy("const c = 1; typeof globalThis.c === 'undefined'");
+    eval_truthy("class C {} typeof globalThis.C === 'undefined'");
+}
+
+#[test]
+fn function_local_var_does_not_land_on_global_this() {
+    eval_truthy("function f(){ var v = 1; } f(); typeof globalThis.v === 'undefined'");
+}
+
+#[test]
+fn block_level_var_lands_on_global_this() {
+    eval_truthy("{ var b = 2; } globalThis.b === 2");
+}
+
+#[test]
+fn redeclaration_updates_global_property() {
+    eval_truthy("var x = 1; var x = 2; globalThis.x === 2");
+}
+
+#[test]
+fn var_global_property_is_non_configurable() {
+    eval_truthy("var x = 1; Object.getOwnPropertyDescriptor(globalThis, 'x').configurable === false");
+    eval_truthy("var x = 1; Object.getOwnPropertyDescriptor(globalThis, 'x').enumerable === true");
+    eval_truthy("var x = 1; delete globalThis.x === false");
+    eval_truthy("var x = 1; delete globalThis.x; typeof globalThis.x === 'number'");
+}
+
+#[test]
+fn var_name_shows_in_get_own_property_names() {
+    eval_truthy("var x = 1; Object.getOwnPropertyNames(globalThis).indexOf('x') >= 0");
+    eval_truthy("function foo(){} Object.getOwnPropertyNames(globalThis).indexOf('foo') >= 0");
+}
+
+#[test]
+fn function_declared_var_lands_after_user_assignment() {
+    eval_truthy("globalThis.x = 99; var x = 5; globalThis.x === 5");
+}
+
+#[test]
+fn async_harness_done_pattern() {
+    // asyncHelpers.js 依赖顶层 function $DONE 落 globalThis。
+    eval_truthy("function $DONE(){} Object.prototype.hasOwnProperty.call(globalThis, '$DONE')");
+    eval_truthy("function $DONE(){} typeof globalThis.$DONE === 'function'");
+}
+
+#[test]
+fn var_without_initializer_creates_undefined_property() {
+    eval_truthy("var x; typeof globalThis.x === 'undefined'");
+    eval_truthy("var x; Object.prototype.hasOwnProperty.call(globalThis, 'x')");
+}
+
+#[test]
+fn function_internal_reference_still_works() {
+    eval_truthy("function foo(){ return 1; } var r = foo(); r === 1");
+}
+
+#[test]
+fn descriptor_attributes_match_spec() {
+    let d = eval_string("var x = 1; JSON.stringify(Object.getOwnPropertyDescriptor(globalThis, 'x'))");
+    assert_eq!(d, r#"{"value":1,"writable":true,"enumerable":true,"configurable":false}"#);
+}