public static void ReportAmbiguousBinaryOperator(this ICollection <Diagnostic> diagnostics, TextSpan span, BinaryOperatorKind operatorKind, Type leftType, Type rightType)
        {
            var operatorName  = operatorKind.ToDisplayName();
            var leftTypeName  = leftType.ToDisplayName();
            var rightTypeName = rightType.ToDisplayName();

            diagnostics.Report(span, DiagnosticId.AmbiguousBinaryOperator, operatorName, leftTypeName, rightTypeName);
        }