export as namespace doesn't support nesting namespaces

<!-- BUGS: Please use this template. --> <!-- QUESTIONS: This is not a general support forum! Ask Qs at http://stackoverflow.com/questions/tagged/typescript --> <!-- SUGGESTIONS: See https://github.com/Microsoft/TypeScript-wiki/blob/master/Writing-Good-Design-Proposals.md --> <!-- Please try to reproduce the issue with `typescript@next`. It may have already been fixed. --> I'm using rollup to generate a UMD module from my TypeScript source. It's part of a bigger product, so one component exports to a root namespace (e.g. `mylib`) and another exports to a namespace nested under that (e.g. `mylib.plugins.myplugin`). Rollup is generating the necessary UMD logic to walk down from the global scope creating namespaces as needed, but I can't model that in my TypeScript `d.ts` file. The `export as namespace` syntax is working great in the first case, but not the second. It looks like TypeScript doesn't support nested namespaces for this purpose. Is this by design or just an omission? **TypeScript Version:** 2.7.0-dev.20180103 **Code**: Two files, a `d.ts` containing an `export as namespace foo.bar` declaration and a script that references it. *declaration.d.ts* ```ts export var baz; export as namespace foo.bar; ``` *app.ts* ```ts console.log(foo.bar.baz); ``` Compile with: `tsc .\test.d.ts .\main.ts` **Expected behavior:** The file compiles correctly to the following JS: ```js console.log(foo.bar.baz); ``` **Actual behavior:** Error ``` declaration.d.ts(3,24): error TS1005: ';' expected. ``` If I change `declaration.d.ts` to use `export as namespace foo` (and update `app.ts` as needed), the compilation succeeds.