From 12a6728c4ea72d9caebafc73ff552552ba6f1b54 Mon Sep 17 00:00:00 2001
From: "Alex Lam S.L" <alexlamsl@gmail.com>
Date: Sun, 6 Mar 2022 09:56:00 +0000
Subject: [PATCH] fix corner case in `hoist_vars` (#5379)

fixes #5378
---
 lib/compress.js             | 47 +++++++++++++++++++------------------
 test/compress/hoist_vars.js | 31 ++++++++++++++++++++++++
 2 files changed, 55 insertions(+), 23 deletions(-)

diff --git a/lib/compress.js b/lib/compress.js
index 1889db0c..80ace965 100644
--- a/lib/compress.js
+++ b/lib/compress.js
@@ -7844,15 +7844,15 @@ Compressor.prototype.compress = function(node) {
                         && !consts.has(sym.name)
                         && self.find_variable(sym.name) === sym.definition();
                 })) return node;
-                node.definitions.forEach(function(def) {
-                    vars.set(def.name.name, def);
+                node.definitions.forEach(function(defn) {
+                    vars.set(defn.name.name, defn);
                     ++vars_found;
                 });
                 var seq = node.to_assignments();
                 if (p instanceof AST_ForEnumeration && p.init === node) {
                     if (seq) return seq;
-                    var def = node.definitions[0].name;
-                    return make_node(AST_SymbolRef, def, def);
+                    var sym = node.definitions[0].name;
+                    return make_node(AST_SymbolRef, sym, sym);
                 }
                 if (p instanceof AST_For && p.init === node) return seq;
                 if (!seq) return in_list ? List.skip : make_node(AST_EmptyStatement, node);
@@ -7867,21 +7867,22 @@ Compressor.prototype.compress = function(node) {
         self.transform(tt);
         if (vars_found > 0) {
             // collect only vars which don't show up in self's arguments list
-            var defs = [];
+            var defns = [];
             if (self instanceof AST_Lambda) self.each_argname(function(argname) {
                 vars.del(argname.name);
             });
-            vars.each(function(def, name) {
-                def = def.clone();
-                def.value = null;
-                defs.push(def);
-                vars.set(name, def);
+            vars.each(function(defn, name) {
+                defn = defn.clone();
+                defn.name = defn.name.clone();
+                defn.value = null;
+                defns.push(defn);
+                vars.set(name, defn);
+                defn.name.definition().orig.unshift(defn.name);
             });
-            if (defs.length > 0) {
+            if (defns.length > 0) {
                 // try to merge in assignments
                 insert_vars(self.body);
-                defs = make_node(AST_Var, self, { definitions: defs });
-                hoisted.push(defs);
+                hoisted.push(make_node(AST_Var, self, { definitions: defns }));
             }
         }
         self.body = dirs.concat(hoisted, self.body);
@@ -7895,13 +7896,13 @@ Compressor.prototype.compress = function(node) {
                         && expr.operator == "="
                         && (sym = expr.left) instanceof AST_Symbol
                         && vars.has(sym.name)) {
-                        var def = vars.get(sym.name);
-                        if (def.value) break;
+                        var defn = vars.get(sym.name);
+                        if (defn.value) break;
                         var value = expr.right;
                         if (value instanceof AST_Sequence) value = value.clone();
-                        def.value = value;
-                        remove(defs, def);
-                        defs.push(def);
+                        defn.value = value;
+                        remove(defns, defn);
+                        defns.push(defn);
                         body.shift();
                         continue;
                     }
@@ -7910,11 +7911,11 @@ Compressor.prototype.compress = function(node) {
                         && assign.operator == "="
                         && (sym = assign.left) instanceof AST_Symbol
                         && vars.has(sym.name)) {
-                        var def = vars.get(sym.name);
-                        if (def.value) break;
-                        def.value = assign.right;
-                        remove(defs, def);
-                        defs.push(def);
+                        var defn = vars.get(sym.name);
+                        if (defn.value) break;
+                        defn.value = assign.right;
+                        remove(defns, defn);
+                        defns.push(defn);
                         stat.body = make_sequence(expr, expr.expressions.slice(1));
                         continue;
                     }
diff --git a/test/compress/hoist_vars.js b/test/compress/hoist_vars.js
index 626300e3..30fb4837 100644
--- a/test/compress/hoist_vars.js
+++ b/test/compress/hoist_vars.js
@@ -499,3 +499,34 @@ issue_5195: {
     }
     expect_stdout: "[object Object]"
 }
+
+issue_5378: {
+    options = {
+        hoist_vars: true,
+        inline: true,
+        toplevel: true,
+    }
+    input: {
+        var a = 2;
+        while (a--)
+            (function() {
+                var b;
+                var c;
+                while (console.log(b));
+                --b;
+            })();
+    }
+    expect: {
+        var a = 2;
+        while (a--) {
+            b = void 0;
+            var b, c;
+            while (console.log(b));
+            --b;
+        }
+    }
+    expect_stdout: [
+        "undefined",
+        "undefined",
+    ]
+}