If it walks like a duck and quacks like a duck, it is a duck. For TypeScript if it has all the members structurally then it is okay for other things (irrespecitive of name) that accept that structure.

Operating Environment. I'd like to use the term Operating System, but that is not necessarily what I mean here. Think Browser,Node.js,WScriptHost etc.

Re-Parsing as the user edits the code.