fix(es/compat): Insert the variable declaration nearest to the availa…

…ble statements (#7067)

**Related issue:**

 - Closes #7064.

crates/swc/tests/fixture/issues-7xxx/7064/case1/input/.swcrc

@@ -0,0 +1,12 @@
+{
+    "jsc": {
+        "parser": {
+            "syntax": "typescript",
+            "decorators": true
+        },
+        "target": "es2020"
+    },
+    "module": {
+        "type": "commonjs"
+    }
+}

crates/swc/tests/fixture/issues-7xxx/7064/case1/input/index.js

@@ -0,0 +1,7 @@
+function method() {
+    const obj = {};
+    obj.prop ??= "x".repeat(10000000);
+  }
+
+  method();
+  // the large string should be eventually GCed along with the large string, but it will never happen in SWC+es2020

crates/swc/tests/fixture/issues-7xxx/7064/case1/output/index.js

@@ -0,0 +1,7 @@
+"use strict";
+function method() {
+    var _obj;
+    const obj = {};
+    (_obj = obj).prop ?? (_obj.prop = "x".repeat(10000000));
+}
+method(); // the large string should be eventually GCed along with the large string, but it will never happen in SWC+es2020

crates/swc_ecma_transforms_compat/src/es2021/logical_assignments.rs

@@ -174,12 +174,12 @@ impl VisitMut for Operators {
         }
     }
 
-    fn visit_mut_module(&mut self, n: &mut Module) {
+    fn visit_mut_module_items(&mut self, n: &mut Vec<ModuleItem>) {
         n.visit_mut_children_with(self);
 
         if !self.vars.is_empty() {
             prepend_stmt(
-                &mut n.body,
+                n,
                 VarDecl {
                     span: DUMMY_SP,
                     kind: VarDeclKind::Var,
@@ -191,12 +191,12 @@ impl VisitMut for Operators {
         }
     }
 
-    fn visit_mut_script(&mut self, n: &mut Script) {
+    fn visit_mut_stmts(&mut self, n: &mut Vec<Stmt>) {
         n.visit_mut_children_with(self);
 
         if !self.vars.is_empty() {
             prepend_stmt(
-                &mut n.body,
+                n,
                 VarDecl {
                     span: DUMMY_SP,
                     kind: VarDeclKind::Var,