fix various for-of bugs (#2800)

- disable `rename` pass on harmony due to problem with for-of loops

fixes #2794

lib/minify.js

@@ -151,7 +151,9 @@ function minify(files, options) {
             toplevel = toplevel.wrap_commonjs(options.wrap);
         }
         if (timings) timings.rename = Date.now();
-        if (options.rename) {
+        // disable rename on harmony due to expand_names bug in for-of loops
+        // https://github.com/mishoo/UglifyJS2/issues/2794
+        if (0 && options.rename) {
             toplevel.figure_out_scope(options.mangle);
             toplevel.expand_names(options.mangle);
         }

lib/output.js

@@ -766,6 +766,7 @@ function OutputStream(options) {
             || p instanceof AST_Arrow                         // x => (x, x)
             || p instanceof AST_DefaultAssign                 // x => (x = (0, function(){}))
             || p instanceof AST_Expansion                     // [...(a, b)]
+            || p instanceof AST_ForOf && this === p.object    // for (e of (foo, bar)) {}
         ;
     });
 
@@ -1046,11 +1047,7 @@ function OutputStream(options) {
         output.with_parens(function(){
             self.init.print(output);
             output.space();
-            if (self instanceof AST_ForOf) {
-                output.print("of");
-            } else {
-                output.print("in");
-            }
+            output.print(self instanceof AST_ForOf ? "of" : "in");
             output.space();
             self.object.print(output);
         });