src/vs/platform/files/common/inMemoryFilesystemProvider.ts/InMemoryFileSystemProvider/_lookup
class InMemoryFileSystemProvider:	private _lookup(uri: URI, silent: boolean): Entry | undefined {
		const parts = uri.path.split('/');
		let entry: Entry = this.root;
		for (const part of parts) {
			if (!part) {
				continue;
			}
			let child: Entry | undefined;
			if (entry instanceof Directory) {
				child = entry.entries.get(part);
			}
			if (!child) {
				if (!silent) {
					throw new FileSystemProviderError('file not found', FileSystemProviderErrorCode.FileNotFound);
				} else {
					return undefined;
				}
			}
			entry = child;
		}
		return entry;
	}