enhance `side_effects` (#3383)

1 files changed, 12 insertions, 4 deletions

diff --git a/lib/compress.js b/lib/compress.js
index 0a195940..13fc953d 100644
--- a/lib/compress.js
+++ b/lib/compress.js
@@ -4172,10 +4172,18 @@ merge(Compressor.prototype, {
             var right = this.right.drop_side_effect_free(compressor, first_in_statement);
             if (!right) return this.left.drop_side_effect_free(compressor, first_in_statement);
             if (lazy_op[this.operator]) {
-                if (right === this.right) return this;
-                var node = this.clone();
-                node.right = right.drop_side_effect_free(compressor);
-                return node;
+                var node;
+                if (right === this.right) {
+                    node = this;
+                } else {
+                    node = this.clone();
+                    node.right = right.drop_side_effect_free(compressor);
+                }
+                return (first_in_statement ? best_of_statement : best_of_expression)(node, make_node(AST_Binary, this, {
+                    operator: node.operator == "&&" ? "||" : "&&",
+                    left: node.left.negate(compressor, first_in_statement),
+                    right: node.right
+                }));
             } else {
                 var left = this.left.drop_side_effect_free(compressor, first_in_statement);
                 if (!left) return right;