C#: Synthesize an empty body for primary constructors.

Author: michaelnebel

csharp/extractor/Semmle.Extraction.CSharp/Entities/Constructor.cs

@@ -32,6 +32,12 @@ public override void Populate(TextWriter trapFile)
             trapFile.constructors(this, Symbol.ContainingType.Name, ContainingType, (Constructor)OriginalDefinition);
             trapFile.constructor_location(this, Location);
 
+            if (IsPrimary)
+            {
+                // Create a synthetic empty body for primary constructors.
+                Statements.SyntheticEmptyBlock.Create(Context, this, 0, Location);
+            }
+
             if (Symbol.IsImplicitlyDeclared)
             {
                 var lineCounts = new LineCounts() { Total = 2, Code = 1, Comment = 0 };

csharp/extractor/Semmle.Extraction.CSharp/Entities/Statements/SyntheticEmptyBlock.cs

@@ -0,0 +1,24 @@
+using System.IO;
+using Microsoft.CodeAnalysis.CSharp;
+using Microsoft.CodeAnalysis.CSharp.Syntax;
+using Semmle.Extraction.Entities;
+using Semmle.Extraction.Kinds;
+
+namespace Semmle.Extraction.CSharp.Entities.Statements
+{
+    internal class SyntheticEmptyBlock : Statement<BlockSyntax>
+    {
+        private SyntheticEmptyBlock(Context cx, BlockSyntax block, IStatementParentEntity parent, int child, Location location)
+            : base(cx, block, StmtKind.BLOCK, parent, child, location) { }
+
+        public static SyntheticEmptyBlock Create(Context cx, IStatementParentEntity parent, int child, Location location)
+        {
+            var block = SyntaxFactory.Block();
+            var ret = new SyntheticEmptyBlock(cx, block, parent, child, location);
+            ret.TryPopulate();
+            return ret;
+        }
+
+        protected override void PopulateStatement(TextWriter trapFile) { }
+    }
+}

csharp/ql/lib/semmle/code/csharp/Callable.qll

@@ -416,7 +416,9 @@ class InstanceConstructor extends Constructor {
  */
 class PrimaryConstructor extends Constructor {
   PrimaryConstructor() {
-    not this.hasBody() and
+    // In the extractor we use the constructor location as the location for the
+    // synthesized empty body of the constructor.
+    this.getLocation() = this.getBody().getLocation() and
     this.getDeclaringType().fromSource() and
     this.fromSource()
   }