src/vs/workbench/api/common/extHostFileSystem.ts/ExtHostFileSystem/_getFsProvider
class ExtHostFileSystem:	private _getFsProvider(handle: number): vscode.FileSystemProvider {
		const provider = this._fsProvider.get(handle);
		if (!provider) {
			const err = new Error();
			err.name = 'ENOPRO';
			err.message = `no provider`;
			throw err;
		}
		return provider;
	}