From f639a30bd2410d1d40f63f5ca0080eb2ba5fe84d Mon Sep 17 00:00:00 2001
From: "Alex Lam S.L" <alexlamsl@gmail.com>
Date: Tue, 11 Jan 2022 05:13:46 +0000
Subject: [PATCH] fix corner cases in `typeofs` (#5286)

---
 lib/compress.js         |  36 ++++++++--
 test/compress/typeof.js | 143 ++++++++++++++++++++++++++++++++++++++++
 2 files changed, 174 insertions(+), 5 deletions(-)

diff --git a/lib/compress.js b/lib/compress.js
index 8c9e3f76..b1838a1c 100644
--- a/lib/compress.js
+++ b/lib/compress.js
@@ -8764,14 +8764,40 @@ Compressor.prototype.compress = function(node) {
             return;
         }
         if (!body) return;
+        var abort = false;
         var def = sym.definition();
-        var tw = new TreeWalker(function(node) {
-            if (node instanceof AST_Scope) {
-                var parent = tw.parent();
-                if (parent instanceof AST_Call && parent.expression === node) return;
+        var fn;
+        var tw = new TreeWalker(function(node, descend) {
+            if (abort) return true;
+            if (node instanceof AST_Assign) {
+                var ref = node.left;
+                if (!(ref instanceof AST_SymbolRef && ref.definition() === def)) return;
+                node.right.walk(tw);
+                switch (node.operator) {
+                  case "=":
+                  case "&&=":
+                    abort = true;
+                }
+                return true;
+            }
+            if (node instanceof AST_Call) {
+                descend();
+                fn = node.expression.tail_node();
+                if (fn instanceof AST_Lambda) {
+                    fn.walk(tw);
+                } else {
+                    abort = true;
+                }
+                return true;
+            }
+            if (node instanceof AST_Scope) {
+                if (node === fn) return;
+                return true;
+            }
+            if (node instanceof AST_SymbolRef) {
+                if (node.definition() === def) node.defined = true;
                 return true;
             }
-            if (node instanceof AST_SymbolRef && node.definition() === def) node.defined = true;
         });
         body.walk(tw);
 
diff --git a/test/compress/typeof.js b/test/compress/typeof.js
index 320817ee..6b4b8d25 100644
--- a/test/compress/typeof.js
+++ b/test/compress/typeof.js
@@ -436,6 +436,149 @@ emberjs_global: {
     expect_stdout: Error("PASS")
 }
 
+reassign: {
+    options = {
+        comparisons: true,
+        conditionals: true,
+        passes: 2,
+        typeofs: true,
+    }
+    input: {
+        A = console;
+        if ("undefined" == typeof A)
+            console.log("FAIL 1");
+        else {
+            A = void 0;
+            while (console.log(void 0 === A ? "PASS" : "FAIL 2"));
+        }
+    }
+    expect: {
+        A = console;
+        if ("undefined" == typeof A)
+            console.log("FAIL 1");
+        else {
+            A = void 0;
+            while (console.log(void 0 === A ? "PASS" : "FAIL 2"));
+        }
+    }
+    expect_stdout: "PASS"
+}
+
+reassign_call: {
+    options = {
+        comparisons: true,
+        conditionals: true,
+        passes: 2,
+        typeofs: true,
+    }
+    input: {
+        A = console;
+        function f() {
+            A = void 0;
+        }
+        if ("undefined" == typeof A)
+            console.log("FAIL 1");
+        else {
+            f();
+            while (console.log(void 0 === A ? "PASS" : "FAIL 2"));
+        }
+    }
+    expect: {
+        A = console;
+        function f() {
+            A = void 0;
+        }
+        if ("undefined" == typeof A)
+            console.log("FAIL 1");
+        else {
+            f();
+            while (console.log(void 0 === A ? "PASS" : "FAIL 2"));
+        }
+    }
+    expect_stdout: "PASS"
+}
+
+reassign_conditional: {
+    options = {
+        comparisons: true,
+        conditionals: true,
+        passes: 2,
+        typeofs: true,
+    }
+    input: {
+        A = console;
+        if ("undefined" == typeof A)
+            console.log("FAIL 1");
+        else {
+            A &&= void 0;
+            while (console.log(void 0 === A ? "PASS" : "FAIL 2"));
+        }
+    }
+    expect: {
+        A = console;
+        if ("undefined" == typeof A)
+            console.log("FAIL 1");
+        else {
+            A &&= void 0;
+            while (console.log(void 0 === A ? "PASS" : "FAIL 2"));
+        }
+    }
+    expect_stdout: "PASS"
+    node_version: ">=15"
+}
+
+reassign_iife: {
+    options = {
+        comparisons: true,
+        conditionals: true,
+        passes: 2,
+        typeofs: true,
+    }
+    input: {
+        A = console;
+        if ("undefined" == typeof A)
+            console.log("FAIL 1");
+        else (function() {
+            A = void 0;
+        })(console.log(void 0 === A ? "FAIL 2" : "PASS"));
+    }
+    expect: {
+        A = console;
+        "undefined" == typeof A ? console.log("FAIL 1") : function() {
+            A = void 0;
+        }(console.log((A, false) ? "FAIL 2" : "PASS"));
+    }
+    expect_stdout: "PASS"
+}
+
+reassign_property: {
+    options = {
+        comparisons: true,
+        conditionals: true,
+        passes: 2,
+        typeofs: true,
+    }
+    input: {
+        A = console;
+        if ("undefined" == typeof A)
+            console.log("FAIL 1");
+        else {
+            A.p = void 0;
+            while (console.log(void 0 === A ? "FAIL 2" : "PASS"));
+        }
+    }
+    expect: {
+        A = console;
+        if ("undefined" == typeof A)
+            console.log("FAIL 1");
+        else {
+            A.p = void 0;
+            while (console.log((A, false) ? "FAIL 2" : "PASS"));
+        }
+    }
+    expect_stdout: "PASS"
+}
+
 issue_3817: {
     options = {
         comparisons: true,