src/vs/workbench/api/common/extHostLanguageFeatures.ts/ExtHostLanguageFeatures/registerCompletionItemProvider
class ExtHostLanguageFeatures:	registerCompletionItemProvider(extension: IExtensionDescription, selector: vscode.DocumentSelector, provider: vscode.CompletionItemProvider, triggerCharacters: string[]): vscode.Disposable {
		const handle = this._addNewAdapter(new CompletionsAdapter(this._documents, this._commands.converter, provider, this._apiDeprecation, extension), extension);
		this._proxy.$registerCompletionsProvider(handle, this._transformDocumentSelector(selector), triggerCharacters, CompletionsAdapter.supportsResolving(provider), `${extension.identifier.value}(${triggerCharacters.join('')})`);
		return this._createDisposable(handle);
	}