A selector that defines the documents this provider is applicable to.
A document symbol provider.
Optionalmetadata: DocumentSymbolProviderMetadataOptional metadata about the provider.
A disposable that unregisters this provider when being disposed.
Register a document symbol provider.
Multiple providers can be registered for a language. In that case providers are asked in parallel and the results are merged. A failing provider (rejected promise or exception) will not cause a failure of the whole operation.