src/vs/workbench/api/common/extHostLanguageFeatures.ts/SignatureHelpAdapter/reviveContext
class SignatureHelpAdapter:	private reviveContext(context: extHostProtocol.ISignatureHelpContextDto): vscode.SignatureHelpContext {
		let activeSignatureHelp: vscode.SignatureHelp | undefined = undefined;
		if (context.activeSignatureHelp) {
			const revivedSignatureHelp = typeConvert.SignatureHelp.to(context.activeSignatureHelp);
			const saved = this._cache.get(context.activeSignatureHelp.id, 0);
			if (saved) {
				activeSignatureHelp = saved;
				activeSignatureHelp.activeSignature = revivedSignatureHelp.activeSignature;
				activeSignatureHelp.activeParameter = revivedSignatureHelp.activeParameter;
			} else {
				activeSignatureHelp = revivedSignatureHelp;
			}
		}
		return { ...context, activeSignatureHelp };
	}