From 79062f1f2fe04270b6197e401960db69ad2c2c86 Mon Sep 17 00:00:00 2001
From: alexlamsl <alexlamsl@gmail.com>
Date: Thu, 18 Mar 2021 05:41:38 +0800
Subject: [PATCH] fix corner case in `collapse_vars`

---
 lib/compress.js         |  1 +
 test/compress/yields.js | 24 ++++++++++++++++++++++++
 2 files changed, 25 insertions(+)

diff --git a/lib/compress.js b/lib/compress.js
index 0d4f7abc..c6558030 100644
--- a/lib/compress.js
+++ b/lib/compress.js
@@ -2428,6 +2428,7 @@ merge(Compressor.prototype, {
                     if (parent.condition !== node) return node;
                     return find_stop_value(parent, level + 1);
                 }
+                if (parent instanceof AST_Yield) return find_stop_value(parent, level + 1);
                 return null;
             }
 
diff --git a/test/compress/yields.js b/test/compress/yields.js
index 05972e53..d21ebcbf 100644
--- a/test/compress/yields.js
+++ b/test/compress/yields.js
@@ -247,6 +247,30 @@ collapse_vars_4: {
     node_version: ">=4"
 }
 
+collapse_vars_5: {
+    options = {
+        collapse_vars: true,
+    }
+    input: {
+        var a = function* f(b, c) {
+            b = yield c = b;
+            console.log(c);
+        }("PASS");
+        a.next();
+        a.next("FAIL");
+    }
+    expect: {
+        var a = function* f(b, c) {
+            b = yield c = b;
+            console.log(c);
+        }("PASS");
+        a.next();
+        a.next("FAIL");
+    }
+    expect_stdout: "PASS"
+    node_version: ">=4"
+}
+
 collapse_property_lambda: {
     options = {
         collapse_vars: true,