A set of one or more available refactoring actions, grouped under a parent refactoring.

Builder to manage the program state changes

A list of comma-separated expressions. This node is only created by transformations.

Reports config file diagnostics

A linked list of formatted diagnostic messages to be used as part of a multiline message.
It is built from the bottom up, leaving the head to be the "main" diagnostic.
While it seems that DiagnosticMessageChain is structurally similar to DiagnosticMessage,
the difference is that messages are all preformatted in DMC.

The document registry represents a store of SourceFile objects that can be shared between
multiple LanguageService instances. A LanguageService instance holds on the SourceFile (AST)
of files in the context.
SourceFile objects account for most of the memory usage by the language service. Sharing
the same DocumentRegistry instance between different instances of LanguageService allow
for more efficient memory utilization since all projects will share at least the library
file (lib.d.ts).

A more advanced use of the document registry is to serialize sourceFile objects to disk
and re-hydrate them when needed.

To create a default DocumentRegistry, use createDocumentRegistry to create one, and pass it
to all subsequent createLanguageService calls.

The builder that can handle the changes in program and iterate through changed file to emit the files
The semantic diagnostics are cached per file and managed by clearing for the changed/affected files

Return code used by getEmitOutput function to indicate status of the function

This is either an `export =` or an `export default` declaration.
Unless `isExportEquals` is set, this node was parsed as an `export default`.