upgrade AST<->ESTree translation (#4870)

fixes #968

lib/compress.js

@@ -6562,6 +6562,10 @@ merge(Compressor.prototype, {
                 }
                 return insert_statements(body, node, in_list);
             }
+            if (node instanceof AST_Import) {
+                if (node.properties && node.properties == 0) node.properties = null;
+                return node;
+            }
             if (node instanceof AST_Sequence) {
                 if (node.expressions.length > 1) return;
                 return maintain_this_binding(compressor, tt.parent(), node, node.expressions[0]);

lib/parse.js

@@ -2526,7 +2526,7 @@ function parse($TEXT, options) {
         while (!is("eof"))
             body.push(statement());
         S.input.pop_directives_stack();
-        var end = prev();
+        var end = prev() || start;
         var toplevel = options.toplevel;
         if (toplevel) {
             toplevel.body = toplevel.body.concat(body);