src/vs/workbench/common/editor/editorGroupModel.ts/EditorGroupModel/findEditor
class EditorGroupModel:	private findEditor(candidate: EditorInput | null, options?: IMatchEditorOptions): [EditorInput, number /* index */] | undefined {
		const index = this.indexOf(candidate, this.editors, options);
		if (index === -1) {
			return undefined;
		}

		return [this.editors[index], index];
	}