From a06e20304b042ab5cd2ad051fb60cf50a7934bb7 Mon Sep 17 00:00:00 2001
From: "Alex Lam S.L" <alexlamsl@gmail.com>
Date: Tue, 27 Apr 2021 15:52:37 +0100
Subject: [PATCH] fix corner case in `pure_getters` (#4877)

fixes #4876
---
 lib/compress.js              |  7 +++++--
 test/compress/assignments.js | 29 +++++++++++++++++++++++++++++
 2 files changed, 34 insertions(+), 2 deletions(-)

diff --git a/lib/compress.js b/lib/compress.js
index 150b554ee5..3847015dbe 100644
--- a/lib/compress.js
+++ b/lib/compress.js
@@ -3683,10 +3683,13 @@ merge(Compressor.prototype, {
         def(AST_Node, is_strict);
         def(AST_Array, return_false);
         def(AST_Assign, function(compressor) {
-            if (this.operator != "=") return false;
+            var op = this.operator;
+            var sym = this.left;
             var rhs = this.right;
+            if (op != "=") {
+                return lazy_op[op.slice(0, -1)] && (sym._dot_throw(compressor) || rhs._dot_throw(compressor));
+            }
             if (!rhs._dot_throw(compressor)) return false;
-            var sym = this.left;
             if (!(sym instanceof AST_SymbolRef)) return true;
             if (rhs instanceof AST_Binary && rhs.operator == "||" && sym.name == rhs.left.name) {
                 return rhs.right._dot_throw(compressor);
diff --git a/test/compress/assignments.js b/test/compress/assignments.js
index 3973e2f57a..fba763d35a 100644
--- a/test/compress/assignments.js
+++ b/test/compress/assignments.js
@@ -672,3 +672,32 @@ issue_4827_3: {
     expect_stdout: "undefined"
     node_version: ">=15"
 }
+
+issue_4876: {
+    options = {
+        pure_getters: "strict",
+        reduce_vars: true,
+        side_effects: true,
+        toplevel: true,
+    }
+    input: {
+        try {
+            var a = null;
+            var b = a &&= 42;
+            b.p;
+        } catch (e) {
+            console.log("PASS");
+        }
+    }
+    expect: {
+        try {
+            var a = null;
+            var b = a &&= 42;
+            b.p;
+        } catch (e) {
+            console.log("PASS");
+        }
+    }
+    expect_stdout: "PASS"
+    node_version: ">=15"
+}