extensions/typescript-language-features/src/languageFeatures/semanticTokens.ts/DocumentSemanticTokensProvider/provideDocumentRangeSemanticTokens
class DocumentSemanticTokensProvider:	public async provideDocumentRangeSemanticTokens(document: vscode.TextDocument, range: vscode.Range, token: vscode.CancellationToken): Promise<vscode.SemanticTokens | null> {
		const file = this.client.toOpenedFilePath(document);
		if (!file || (document.offsetAt(range.end) - document.offsetAt(range.start) > CONTENT_LENGTH_LIMIT)) {
			return null;
		}

		const start = document.offsetAt(range.start);
		const length = document.offsetAt(range.end) - start;
		return this.provideSemanticTokens(document, { file, start, length }, token);
	}