codeql/csharp/extractor/Semmle.Extraction.CSharp/Entities/Expressions/ElementAccess.cs

using Microsoft.CodeAnalysis.CSharp.Syntax;
using Semmle.Extraction.CSharp.Populators;
using Semmle.Extraction.Kinds;
using Microsoft.CodeAnalysis.CSharp;
using Microsoft.CodeAnalysis;
using Semmle.Extraction.Entities;

namespace Semmle.Extraction.CSharp.Entities.Expressions
{
    abstract class ElementAccess : Expression<ExpressionSyntax>
    {
        protected ElementAccess(ExpressionNodeInfo info, ExpressionSyntax qualifier, BracketedArgumentListSyntax argumentList)
            : base(info.SetKind(GetKind(info.Context, qualifier)))
        {
            Qualifier = qualifier;
            ArgumentList = argumentList;
        }

        readonly ExpressionSyntax Qualifier;
        readonly BracketedArgumentListSyntax ArgumentList;

        protected override void Populate()
        {
            if (Kind == ExprKind.POINTER_INDIRECTION)
            {
                var qualifierInfo = new ExpressionNodeInfo(cx, Qualifier, this, 0);
                var add = new Expression(new ExpressionInfo(cx, qualifierInfo.Type, Location, ExprKind.ADD, this, 0, false, null));
                qualifierInfo.SetParent(add, 0);
                CreateFromNode(qualifierInfo);
                PopulateArguments(cx, ArgumentList, 1);
            }
            else
            {
                var child = -1;
                Create(cx, Qualifier, this, child++);
                foreach (var a in ArgumentList.Arguments)
                {
                    cx.Extract(a, this, child++);
                }

                var symbolInfo = cx.GetSymbolInfo(base.Syntax);

                var indexer = symbolInfo.Symbol as IPropertySymbol;
                if (indexer != null)
                {
                    cx.Emit(Tuples.expr_access(this, Indexer.Create(cx, indexer)));
                }
            }
        }

        public sealed override Microsoft.CodeAnalysis.Location ReportingLocation => base.ReportingLocation;

        static ExprKind GetKind(Context cx, ExpressionSyntax qualifier)
        {
            var qualifierType = cx.GetType(qualifier);

            // This is a compilation error, so make a guess and continue.
            if (qualifierType == null) return ExprKind.ARRAY_ACCESS;

            if (qualifierType.TypeKind == Microsoft.CodeAnalysis.TypeKind.Pointer)
            {
                // Convert expressions of the form a[b] into *(a+b)
                return ExprKind.POINTER_INDIRECTION;
            }

            return IsDynamic(cx, qualifier) ?
                ExprKind.DYNAMIC_ELEMENT_ACCESS :
                qualifierType.TypeKind == Microsoft.CodeAnalysis.TypeKind.Array ?
                    ExprKind.ARRAY_ACCESS :
                    ExprKind.INDEXER_ACCESS;
        }
    }

    class NormalElementAccess : ElementAccess
    {
        NormalElementAccess(ExpressionNodeInfo info)
            : base(info, ((ElementAccessExpressionSyntax)info.Node).Expression, ((ElementAccessExpressionSyntax)info.Node).ArgumentList) { }

        public static Expression Create(ExpressionNodeInfo info) => new NormalElementAccess(info).TryPopulate();
    }

    class BindingElementAccess : ElementAccess
    {
        BindingElementAccess(ExpressionNodeInfo info)
            : base(info, FindConditionalQualifier(info.Node), ((ElementBindingExpressionSyntax)info.Node).ArgumentList) { }

        public static Expression Create(ExpressionNodeInfo info) => new BindingElementAccess(info).TryPopulate();

        protected override void Populate()
        {
            base.Populate();
            MakeConditional();
        }
    }
}