fix corner case in `merge_vars` (#4407)

fixes #4406

2 files changed, 31 insertions, 1 deletions

diff --git a/lib/compress.js b/lib/compress.js
index 1249e620..ab68c45d 100644
--- a/lib/compress.js
+++ b/lib/compress.js
@@ -4801,7 +4801,7 @@ merge(Compressor.prototype, {
             if (node instanceof AST_Call) {
                 var exp = node.expression;
                 var tail = exp.tail_node();
-                if (!(tail instanceof AST_Function)) return;
+                if (!is_function(tail)) return;
                 if (exp !== tail) exp.expressions.slice(0, -1).forEach(function(node) {
                     node.walk(tw);
                 });
diff --git a/test/compress/async.js b/test/compress/async.js
index 79189c7d..4fd16efd 100644
--- a/test/compress/async.js
+++ b/test/compress/async.js
@@ -567,3 +567,33 @@ issue_4377: {
     expect_stdout: "function"
     node_version: ">=8"
 }
+
+issue_4406: {
+    options = {
+        merge_vars: true,
+    }
+    input: {
+        A = "PASS";
+        B = "FAIL";
+        (function() {
+            var a, b;
+            a = A;
+            (async function({
+                [console.log(a)]: {},
+            }) {})((b = B) && { undefined: b });
+        })();
+    }
+    expect: {
+        A = "PASS";
+        B = "FAIL";
+        (function() {
+            var a, b;
+            a = A;
+            (async function({
+                [console.log(a)]: {},
+            }) {})((b = B) && { undefined: b });
+        })();
+    }
+    expect_stdout: "PASS"
+    node_version: ">=8"
+}