src/vs/editor/contrib/parameterHints/parameterHintsWidget.ts/ParameterHintsWidget/getParameterLabel
class ParameterHintsWidget:	private getParameterLabel(signature: modes.SignatureInformation, paramIdx: number): string {
		const param = signature.parameters[paramIdx];
		if (Array.isArray(param.label)) {
			return signature.label.substring(param.label[0], param.label[1]);
		} else {
			return param.label;
		}
	}