fix corner case in `collapse_vars` & `reduce_vars` (#4748)

fixes #4747

1 files changed, 29 insertions, 0 deletions

diff --git a/test/compress/awaits.js b/test/compress/awaits.js
index 0534d186..937fcb5a 100644
--- a/test/compress/awaits.js
+++ b/test/compress/awaits.js
@@ -1379,3 +1379,32 @@ issue_4738_3: {
     expect_stdout: "PASS"
     node_version: ">=8"
 }
+
+issue_4747: {
+    options = {
+        collapse_vars: true,
+        reduce_vars: true,
+        unused: true,
+    }
+    input: {
+        console.log(function(a) {
+            async function f() {
+                a = "PASS";
+                null.p += "PASS";
+            }
+            f();
+            return a;
+        }("FAIL"));
+    }
+    expect: {
+        console.log(function(a) {
+            (async function() {
+                a = "PASS";
+                null.p += "PASS";
+            })();
+            return a;
+        }("FAIL"));
+    }
+    expect_stdout: "PASS"
+    node_version: ">=8"
+}