compress `undefined` property names (#2811)

- enforce property names as string
- handle `void 0` as `undefined` in `hoist_props` & `reduce_vars`

1 files changed, 16 insertions, 5 deletions

diff --git a/lib/compress.js b/lib/compress.js
index 89056796..bda5d7a6 100644
--- a/lib/compress.js
+++ b/lib/compress.js
@@ -404,14 +404,15 @@ merge(Compressor.prototype, {
         }
 
         function read_property(obj, key) {
-            if (key instanceof AST_Constant) key = key.getValue();
-            if (key instanceof AST_Node) return null;
+            key = get_value(key);
+            if (key instanceof AST_Node) return;
             var value;
             if (obj instanceof AST_Array) {
                 var elements = obj.elements;
                 if (key == "length") return make_node_from_constant(elements.length, obj);
                 if (typeof key == "number" && key in elements) value = elements[key];
             } else if (obj instanceof AST_Object) {
+                key = "" + key;
                 var props = obj.properties;
                 for (var i = props.length; --i >= 0;) {
                     var prop = props[i];
@@ -1855,6 +1856,18 @@ merge(Compressor.prototype, {
         }));
     };
 
+    function get_value(key) {
+        if (key instanceof AST_Constant) {
+            return key.getValue();
+        }
+        if (key instanceof AST_UnaryPrefix
+            && key.operator == "void"
+            && key.expression instanceof AST_Constant) {
+            return;
+        }
+        return key;
+    }
+
     function is_undefined(node, compressor) {
         return node.is_undefined
             || node instanceof AST_Undefined
@@ -3295,9 +3308,7 @@ merge(Compressor.prototype, {
             if (node instanceof AST_PropAccess && node.expression instanceof AST_SymbolRef) {
                 var defs = defs_by_id[node.expression.definition().id];
                 if (defs) {
-                    var key = node.property;
-                    if (key instanceof AST_Node) key = key.getValue();
-                    var def = defs.get(key);
+                    var def = defs.get(get_value(node.property));
                     var sym = make_node(AST_SymbolRef, node, {
                         name: def.name,
                         scope: node.expression.scope,