The Symbol interface of the compiler is undocumented

**TypeScript Version:** master <!-- Search terms you tried before logging this (so others can find this issue more easily) --> **Search Terms:** Symbol interface compiler **Code** https://github.com/microsoft/TypeScript/blob/15daf42b2c0bc4f06970c9e4688f1a93bff0f7a0/src/services/types.ts#L31 The ["Using the Compiler API" docs](https://github.com/Microsoft/TypeScript/wiki/Using-the-Compiler-API) have examples which use Symbols, but they don't say what they are and neither do the API docs in the source. It'd be incredibly helpful if the core compiler types were at least minimally documented, along with a few of the TypeChecker methods. Context: I'm trying to use the compiler API for linting and want to verify that an identifier references a particular declaration.