From 383163afa67c5726e18da145d6eb012ee1b064e3 Mon Sep 17 00:00:00 2001
From: "Alex Lam S.L" <alexlamsl@gmail.com>
Date: Tue, 17 Nov 2020 10:03:31 +0000
Subject: [PATCH] fix corner case in `collapse_vars` (#4287)

fixes #4286
---
 lib/compress.js               | 21 ++++++--------------
 test/compress/destructured.js | 37 +++++++++++++++++++++++++++++++++++
 2 files changed, 43 insertions(+), 15 deletions(-)

diff --git a/lib/compress.js b/lib/compress.js
index e4426fa3..fe2e6242 100644
--- a/lib/compress.js
+++ b/lib/compress.js
@@ -1972,15 +1972,9 @@ merge(Compressor.prototype, {
             function find_stop_value(node, level) {
                 var parent = scanner.parent(level);
                 if (parent instanceof AST_Array) return find_stop_value(parent, level + 1);
-                if (parent instanceof AST_Assign) {
-                    if (may_throw(parent)) return node;
-                    if (parent.left instanceof AST_SymbolRef) {
-                        var name = parent.left.name;
-                        if (lhs.name == name) return node;
-                        if (value_def.name == name) return node;
-                    }
-                    return find_stop_value(parent, level + 1);
-                }
+                if (parent instanceof AST_Assign) return may_throw(parent) || parent.left.match_symbol(function(ref) {
+                    return ref instanceof AST_SymbolRef && (lhs.name == ref.name || value_def.name == ref.name);
+                }) ? node : find_stop_value(parent, level + 1);
                 if (parent instanceof AST_Binary) {
                     if (lazy_op[parent.operator] && parent.left !== node) {
                         do {
@@ -2034,12 +2028,9 @@ merge(Compressor.prototype, {
                     if (parent.operator == "delete") return node;
                     return find_stop_value(parent, level + 1);
                 }
-                if (parent instanceof AST_VarDef) {
-                    var name = parent.name.name;
-                    if (lhs.name == name) return node;
-                    if (value_def.name == name) return node;
-                    return find_stop_value(parent, level + 1);
-                }
+                if (parent instanceof AST_VarDef) return parent.name.match_symbol(function(sym) {
+                    return sym instanceof AST_SymbolDeclaration && (lhs.name == sym.name || value_def.name == sym.name);
+                }) ? node : find_stop_value(parent, level + 1);
                 if (parent instanceof AST_While) {
                     if (parent.condition !== node) return node;
                     return find_stop_value(parent, level + 1);
diff --git a/test/compress/destructured.js b/test/compress/destructured.js
index 1555e3e3..6feb5bd6 100644
--- a/test/compress/destructured.js
+++ b/test/compress/destructured.js
@@ -1403,3 +1403,40 @@ issue_4284_3: {
     expect_stdout: "PASS"
     node_version: ">=6"
 }
+
+issue_4286_1: {
+    options = {
+        collapse_vars: true,
+        toplevel: true,
+    }
+    input: {
+        var a = "PASS", b;
+        (0 && a)[{ a } = b = a];
+        console.log(b);
+    }
+    expect: {
+        var a = "PASS", b;
+        (0 && a)[{ a } = b = a];
+        console.log(b);
+    }
+    expect_stdout: "PASS"
+    node_version: ">=6"
+}
+
+issue_4286_2: {
+    options = {
+        collapse_vars: true,
+        toplevel: true,
+    }
+    input: {
+        a = [ "PASS" ];
+        var b, { a } = b = a;
+        console.log(b[0]);
+    }
+    expect: {
+        var b, { a } = b = a = [ "PASS" ];
+        console.log(b[0]);
+    }
+    expect_stdout: "PASS"
+    node_version: ">=6"
+}
-- 
2.34.1