Please document compiler APIs

Would it be possible to get some documentation on the compiler APIs?

I am working on some TypeScript tooling, and I am using ts.createSourceFile() to get the AST for a TypeScript source file. However, the tree in SourceFile.statements is missing some information. For example, I need to know the type of an Expression when a PropertyDeclaration only has an initializer but no declared type. I have tried TypeChecker.getContextualType() but it always returns undefined; also the implementation doesn't look right. There are internal methods like TypeChecker.getTypeOfExpression() that look promising, but they are not visible. Also I read some mention of 'bindings', but I haven't found a way to get them.

Another example is type resolution: When I encounter a TypeNode or something similar within the AST, I usually need to know about its declaration: Where does it come from? Is it local? Where is it imported from? Of course I can write that myself with some effort, but surely such logic already exists within the compiler, I just don't know where.

Start by reviewing the compiler API areas named in the issue: ts.createSourceFile(), SourceFile.statements, TypeChecker.getContextualType(), getTypeOfExpression(), bindings, and type resolution. Document the supported public APIs for retrieving expression types and declarations, including how imports and local declarations are identified; done means these workflows are clearly explained for TypeScript tooling authors.