fix(es/minifier): Abort seq inliner on ** (#8947)

**Related issue:**

 - Closes #8942

crates/swc_ecma_minifier/src/compress/optimize/dead_code.rs

@@ -68,6 +68,10 @@ impl Optimizer<'_> {
         if let Expr::Assign(assign) = e {
             // x += 1 => x + 1
             if let Some(op) = assign.op.to_update() {
+                if op == op!("**") {
+                    return false;
+                }
+
                 if let Some(lhs) = assign.left.as_ident() {
                     //
                     if self

crates/swc_ecma_minifier/src/compress/optimize/sequences.rs

@@ -1562,6 +1562,7 @@ impl Optimizer<'_> {
             | Expr::Tpl(..)
             | Expr::TaggedTpl(..) => return Ok(false),
 
+            // See https://github.com/swc-project/swc/issues/8924 and https://github.com/swc-project/swc/issues/8942
             Expr::Assign(AssignExpr {
                 op: op!("**="),
                 right,
@@ -1572,7 +1573,7 @@ impl Optimizer<'_> {
                 right,
                 ..
             }) => {
-                if is_pure_undefined(&self.expr_ctx, right) {
+                if !right.is_lit() {
                     return Ok(false);
                 }
             }

crates/swc_ecma_minifier/tests/exec.rs

@@ -11224,6 +11224,21 @@ console.log(eval(foo));",
     );
 }
 
+#[test]
+fn issue_8942() {
+    run_default_exec_test(
+        "
+        'use strict';
+        const k = (() => {
+            let x = 1;
+            x **= undefined / x;
+            return x;
+        })();
+        console.log(k);
+        ",
+    );
+}
+
 #[test]
 fn issue_8937() {
     run_default_exec_test(

crates/swc_ecma_minifier/tests/fixture/issues/8924/output.js

@@ -1,2 +1,5 @@
 "use strict";
-const k = NaN;
+const k = (()=>{
+    let x = 1;
+    return x **= void 0;
+})();