From 30bf06876878495637dfef2f6e31824649abd34b Mon Sep 17 00:00:00 2001
From: "Alex Lam S.L" <alexlamsl@gmail.com>
Date: Mon, 24 Oct 2022 15:16:06 +0100
Subject: [PATCH] fix corner case in `collapse_vars` (#5720)

fixes #5719
---
 lib/compress.js                |  2 +-
 test/compress/collapse_vars.js | 27 +++++++++++++++++++++++++++
 2 files changed, 28 insertions(+), 1 deletion(-)

diff --git a/lib/compress.js b/lib/compress.js
index cde397cf..3bd91656 100644
--- a/lib/compress.js
+++ b/lib/compress.js
@@ -2498,7 +2498,7 @@ Compressor.prototype.compress = function(node) {
                                 hit_index++;
                             }
                             branch.expression = branch.expression.transform(tt);
-                            if (!replace_all) break;
+                            if (!replace_all || verify_ref) break;
                             scan_rhs = false;
                         }
                     }
diff --git a/test/compress/collapse_vars.js b/test/compress/collapse_vars.js
index 2f96bd77..13f01407 100644
--- a/test/compress/collapse_vars.js
+++ b/test/compress/collapse_vars.js
@@ -10121,3 +10121,30 @@ issue_5643: {
     }
     expect_stdout: "42"
 }
+
+issue_5719: {
+    options = {
+        collapse_vars: true,
+        reduce_vars: true,
+        toplevel: true,
+    }
+    input: {
+        var a = 42, b;
+        switch (b = a) {
+          case a:
+          case b:
+          case a++:
+        }
+        console.log(a === b++ ? "PASS" : "FAIL");
+    }
+    expect: {
+        var a = 42, b;
+        switch (b = a) {
+          case a:
+          case b:
+          case a++:
+        }
+        console.log(a === b++ ? "PASS" : "FAIL");
+    }
+    expect_stdout: "PASS"
+}