fix(minifier): preserve iife with directives (#27060)

do not fold iife when body contains directives.

ref #24331

crates/oxc_minifier/src/peephole/substitute_alternate_syntax.rs

@@ -1919,7 +1919,7 @@ impl<'a> PeepholeOptimizations {
                 return;
             }
             let Some(body) = f.get_function_body_mut() else { return };
-            if body.statements.len() != 1 {
+            if body.statements.len() != 1 || !body.directives.is_empty() {
                 return;
             }
             match &mut body.statements[0] {

crates/oxc_minifier/tests/peephole/remove_unused_expression.rs

@@ -489,6 +489,20 @@ fn test_fold_iife() {
     test("a((() => true)());", "a(!0)");
     test("a((() => { return true })());", "a(!0)");
 
+    test("(() => { 'use strict'; return a() })()", "a()");
+    test_same_options_source_type(
+        "(() => { 'use strict'; return a() })()",
+        SourceType::cjs(),
+        &CompressOptions::smallest(),
+    );
+    test("(() => { 'use strict'; a() })()", "a()");
+    test_same_options_source_type(
+        "(() => { 'use strict'; a() })()",
+        SourceType::cjs(),
+        &CompressOptions::smallest(),
+    );
+    test_same("(() => { 'use cache'; return a() })()");
+
     test_same("var a = (function () { b() })()");
     test_same("var a = (function () { return b() })()");
     test_same("var a = (function () { return this })()");