From 78c8efd851411a3605f667e78efaa342a1c65b53 Mon Sep 17 00:00:00 2001
From: "Alex Lam S.L" <alexlamsl@gmail.com>
Date: Sun, 29 Dec 2019 21:16:53 +0800
Subject: fix corner case in `evaluate` (#3656)

fixes #3655
---
 lib/compress.js | 25 ++++++++++++++++++++++---
 1 file changed, 22 insertions(+), 3 deletions(-)

(limited to 'lib')

diff --git a/lib/compress.js b/lib/compress.js
index 9045a8dd..9c60d0ae 100644
--- a/lib/compress.js
+++ b/lib/compress.js
@@ -5998,6 +5998,7 @@ merge(Compressor.prototype, {
     });
 
     var indexFns = makePredicate("indexOf lastIndexOf");
+    var minus_zero_op = makePredicate("- * / %");
     var commutativeOperators = makePredicate("== === != !== * & | ^");
     function is_object(node) {
         return node instanceof AST_Array
@@ -6459,11 +6460,11 @@ merge(Compressor.prototype, {
               // 0 + n => n
               case "+":
                 if (self.left.value == 0) {
-                    if (self.right.is_number(compressor)) return self.right;
                     if (self.right.is_boolean(compressor)) return make_node(AST_UnaryPrefix, self, {
                         operator: "+",
                         expression: self.right
                     }).optimize(compressor);
+                    if (self.right.is_number(compressor) && !may_be_minus_zero(self.right)) return self.right;
                 }
                 break;
               // 1 * n => n
@@ -6479,8 +6480,12 @@ merge(Compressor.prototype, {
             if (self.right instanceof AST_Number && !self.left.is_constant()) switch (self.operator) {
               // n + 0 => n
               case "+":
-                if (self.right.value == 0 && (self.left.is_boolean(compressor) || self.left.is_number(compressor))) {
-                    return self.left;
+                if (self.right.value == 0) {
+                    if (self.left.is_boolean(compressor)) return make_node(AST_UnaryPrefix, self, {
+                        operator: "+",
+                        expression: self.left
+                    }).optimize(compressor);
+                    if (self.left.is_number(compressor) && !may_be_minus_zero(self.left)) return self.left;
                 }
                 break;
               // n - 0 => n
@@ -6635,6 +6640,20 @@ merge(Compressor.prototype, {
                         && self.left.expression instanceof AST_Number && self.left.expression.value == 1;
             }
         }
+
+        function may_be_minus_zero(node) {
+            var ev = node.evaluate(compressor);
+            if (ev instanceof AST_Node) {
+                var op = ev.operator;
+                if (!op) return true;
+                if (ev instanceof AST_Assign) {
+                    if (op == "=") return may_be_minus_zero(ev.right);
+                    op = op.slice(0, -1);
+                }
+                if (minus_zero_op[op]) return true;
+                if (ev instanceof AST_UnaryPrefix && op == "+") return true;
+            } else if (ev == 0 && 1 / ev < 0) return true;
+        }
     });
 
     function recursive_ref(compressor, def) {
-- 
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