fix corner case in `reduce_vars` (#4281)

fixes #4280

1 files changed, 9 insertions, 1 deletions

diff --git a/lib/compress.js b/lib/compress.js
index 7297938a..a16c9a69 100644
--- a/lib/compress.js
+++ b/lib/compress.js
@@ -619,7 +619,15 @@ merge(Compressor.prototype, {
                         if (node.key instanceof AST_Node) node.key.walk(tw);
                         fixed = function() {
                             var key = node.key;
-                            return make_node(typeof key == "string" ? AST_Dot : AST_Sub, node, {
+                            var type = AST_Sub;
+                            if (typeof key == "string") {
+                                if (is_identifier_string(key)) {
+                                    type = AST_Dot;
+                                } else {
+                                    key = make_node_from_constant(key, node);
+                                }
+                            }
+                            return make_node(type, node, {
                                 expression: save(),
                                 property: key
                             });