fix corner case in reduce_vars (#3975)

fixes #3974
2020-06-09 03:33:47 +01:00
parent 08c4729eb4
commit d764b6cc3b
2 changed files with 28 additions and 1 deletions
--- a/lib/compress.js
+++ b/lib/compress.js
@@ -4032,7 +4032,9 @@ merge(Compressor.prototype, {
            return all(this.elements);
        });
        def(AST_Binary, function() {
-            return this.left.is_constant_expression() && this.right.is_constant_expression();
+            return this.left.is_constant_expression()
+                && this.right.is_constant_expression()
+                && (this.operator != "in" || is_object(this.right.tail_node()));
        });
        def(AST_Constant, return_true);
        def(AST_Lambda, function(scope) {