This is a feature request for the TypeScript team to ship an xclangspec file with the TypeScript sources in order to provide support for syntax highlighting of the language in the Xcode IDE.
Google has done the same for their Go language; see here for an example of the xclangspec file format: https://code.google.com/p/go/source/browse/misc/xcode/go.xclangspec?r=30b0c392132645259e053a2ba8904383a55bab03