ShaderTools.Hlsl.Parser.DirectiveParser.ParseDirectiveTerm C# (CSharp) Method

        private ExpressionSyntax ParseDirectiveTerm()
        {
            ExpressionSyntax expr;

            var tk = Current.Kind;
            switch (tk)
            {
                case SyntaxKind.IdentifierToken:
                    expr = ParseIdentifier();
                    break;
                case SyntaxKind.FalseKeyword:
                case SyntaxKind.TrueKeyword:
                case SyntaxKind.IntegerLiteralToken:
                case SyntaxKind.FloatLiteralToken:
                    expr = new LiteralExpressionSyntax(SyntaxFacts.GetLiteralExpression(Current.Kind), NextToken());
                    break;
                case SyntaxKind.OpenParenToken:
                    expr = ParseDirectiveParenthesizedExpression();
                    break;
                default:
                    expr = CreateMissingIdentifierName();

                    if (tk == SyntaxKind.EndOfFileToken)
                        expr = WithDiagnostic(expr, DiagnosticId.ExpressionExpected);
                    else
                        expr = WithDiagnostic(expr, DiagnosticId.InvalidExprTerm, tk.GetText());

                    break;
            }

            // Might be function invocation. We only have one function in the preprocessor - "defined".
            if (Current.Kind == SyntaxKind.OpenParenToken && expr.Kind == SyntaxKind.IdentifierName
                && ((IdentifierNameSyntax) expr).Name.ContextualKind == SyntaxKind.DefinedKeyword)
            {
                _lexer.ExpandMacros = false;

                var openParen = Match(SyntaxKind.OpenParenToken);
                var name = new IdentifierNameSyntax(NextToken());

                _lexer.ExpandMacros = true;

                var closeParen = Match(SyntaxKind.CloseParenToken);
                expr = new FunctionInvocationExpressionSyntax((IdentifierNameSyntax) expr, new ArgumentListSyntax(
                    openParen,
                    new SeparatedSyntaxList<ExpressionSyntax>(new List<SyntaxNode> { name }),
                    closeParen));
            }

            return expr;
        }