From 87e67ec29958a4167d5c202ae3a0fe4be1e10faf Mon Sep 17 00:00:00 2001
From: "Alex Lam S.L" <alexlamsl@gmail.com>
Date: Thu, 7 Nov 2019 20:38:03 +0800
Subject: [PATCH] fix corner case in `collapse_vars` (#3574)

fixes #3573
---
 lib/compress.js                |  1 +
 test/compress/collapse_vars.js | 33 +++++++++++++++++++++++++++++++++
 2 files changed, 34 insertions(+)

diff --git a/lib/compress.js b/lib/compress.js
index ba789816..0d19640d 100644
--- a/lib/compress.js
+++ b/lib/compress.js
@@ -1283,6 +1283,7 @@ merge(Compressor.prototype, {
                             }
                             branch.expression = branch.expression.transform(scanner);
                             if (!replace_all) break;
+                            scan_rhs = false;
                         }
                     }
                     abort = true;
diff --git a/test/compress/collapse_vars.js b/test/compress/collapse_vars.js
index cf4e45a5..86e8d632 100644
--- a/test/compress/collapse_vars.js
+++ b/test/compress/collapse_vars.js
@@ -6435,3 +6435,36 @@ call_assign_order: {
     }
     expect_stdout: "PASS PASS"
 }
+
+issue_3573: {
+    options = {
+        collapse_vars: true,
+    }
+    input: {
+        var c = 0;
+        (function(b) {
+            while (--b) {
+                b = NaN;
+                switch (0 / this < 0) {
+                  case c++, false:
+                  case c++, NaN:
+                }
+            }
+        })(3);
+        console.log(c);
+    }
+    expect: {
+        var c = 0;
+        (function(b) {
+            while (--b) {
+                b = NaN;
+                switch (0 / this < 0) {
+                  case c++, false:
+                  case c++, NaN:
+                }
+            }
+        })(3);
+        console.log(c);
+    }
+    expect_stdout: "1"
+}
-- 
2.34.1