C#: Introduce extractor support for collection expressions.

Author: michaelnebel

csharp/extractor/Semmle.Extraction.CSharp/Entities/Expressions/Collections/Collection.cs

@@ -0,0 +1,38 @@
+using System.IO;
+using Microsoft.CodeAnalysis.CSharp;
+using Microsoft.CodeAnalysis.CSharp.Syntax;
+using Semmle.Util;
+using Semmle.Extraction.Kinds;
+
+namespace Semmle.Extraction.CSharp.Entities.Expressions
+{
+    internal class Collection : Expression<CollectionExpressionSyntax>
+    {
+        private Collection(ExpressionNodeInfo info) : base(info.SetKind(ExprKind.COLLECTION)) { }
+
+        protected override void PopulateExpression(TextWriter trapFile) =>
+            Syntax.Elements.ForEach((element, i) =>
+            {
+                switch (element.Kind())
+                {
+                    case SyntaxKind.ExpressionElement:
+                        {
+                            Create(Context, ((ExpressionElementSyntax)element).Expression, this, i);
+                            return;
+                        }
+                    case SyntaxKind.SpreadElement:
+                        {
+                            Spread.Create(Context, (SpreadElementSyntax)element, this, i);
+                            return;
+                        }
+                    default:
+                        {
+                            Context.ModelError(element, $"Unhandled collection element type {element.Kind()}");
+                            return;
+                        }
+                }
+            });
+
+        public static Expression Create(ExpressionNodeInfo info) => new Collection(info).TryPopulate();
+    }
+}

csharp/extractor/Semmle.Extraction.CSharp/Entities/Expressions/Collections/Spread.cs

@@ -0,0 +1,17 @@
+using Microsoft.CodeAnalysis.CSharp.Syntax;
+using Semmle.Extraction.Kinds;
+
+namespace Semmle.Extraction.CSharp.Entities.Expressions
+{
+    internal class Spread : Expression
+    {
+        public Spread(Context cx, SpreadElementSyntax syntax, IExpressionParentEntity parent, int child) :
+            base(new ExpressionInfo(cx, null, cx.CreateLocation(syntax.GetLocation()), ExprKind.SPREAD_ELEMENT, parent, child, false, null))
+        {
+            Create(cx, syntax.Expression, this, 0);
+        }
+
+        public static Expression Create(Context cx, SpreadElementSyntax syntax, IExpressionParentEntity parent, int child) =>
+            new Spread(cx, syntax, parent, child);
+    }
+}

csharp/extractor/Semmle.Extraction.CSharp/Entities/Expressions/Factory.cs

@@ -256,6 +256,9 @@ internal static Expression Create(ExpressionNodeInfo info)
                     case SyntaxKind.WithExpression:
                         return WithExpression.Create(info);
 
+                    case SyntaxKind.CollectionExpression:
+                        return Collection.Create(info);
+
                     default:
                         info.Context.ModelError(info.Node, $"Unhandled expression '{info.Node}' of kind '{info.Node.Kind()}'");
                         return new Unknown(info);