fix corner case in `collapse_vars` (#3898)

fixes #3897

1 files changed, 34 insertions, 0 deletions

diff --git a/test/compress/collapse_vars.js b/test/compress/collapse_vars.js
index 0dd8754d..97975b1c 100644
--- a/test/compress/collapse_vars.js
+++ b/test/compress/collapse_vars.js
@@ -8050,3 +8050,37 @@ issue_3894: {
         "PASS",
     ]
 }
+
+issue_3897: {
+    options = {
+        collapse_vars: true,
+    }
+    input: {
+        var a = 0;
+        (function() {
+            function f(b) {
+                b = a = 1 + a;
+                a = 1 + a;
+                console.log(b);
+            }
+            f();
+        })();
+        console.log(a);
+    }
+    expect: {
+        var a = 0;
+        (function() {
+            function f(b) {
+                b = a = 1 + a;
+                a = 1 + a;
+                console.log(b);
+            }
+            f();
+        })();
+        console.log(a);
+    }
+    expect_stdout: [
+        "1",
+        "2",
+    ]
+}