Merge pull request github#15667 from michaelnebel/csharp/syntheticconstructorbody

C#: Add synthetic bodies and inititializers for default constuctors.

Author: michaelnebel

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

@@ -32,9 +32,9 @@ public override void Populate(TextWriter trapFile)
             trapFile.constructors(this, Symbol.ContainingType.Name, ContainingType, (Constructor)OriginalDefinition);
             trapFile.constructor_location(this, Location);
 
-            if (IsPrimary)
+            if (MakeSynthetic)
             {
-                // Create a synthetic empty body for primary constructors.
+                // Create a synthetic empty body for primary and default constructors.
                 Statements.SyntheticEmptyBlock.Create(Context, this, 0, Location);
             }
 
@@ -49,9 +49,9 @@ public override void Populate(TextWriter trapFile)
         protected override void ExtractInitializers(TextWriter trapFile)
         {
             // Do not extract initializers for constructed types.
-            // Only extract initializers for constructors with a body and primary constructors.
-            if (Block is null && ExpressionBody is null && !IsPrimary ||
-                !IsSourceDeclaration)
+            // Extract initializers for constructors with a body, primary constructors
+            // and default constructors for classes and structs declared in source code.
+            if (Block is null && ExpressionBody is null && !MakeSynthetic)
             {
                 return;
             }
@@ -161,6 +161,16 @@ private void ExtractSourceInitializer(TextWriter trapFile, ITypeSymbol? type, IM
 
         private bool IsPrimary => PrimaryConstructorSyntax is not null;
 
+        // This is a default constructor in a class or struct declared in source.
+        private bool IsDefault =>
+            Symbol.IsImplicitlyDeclared &&
+            Symbol.ContainingType.FromSource() &&
+            Symbol.ContainingType.TypeKind is TypeKind.Class or TypeKind.Struct &&
+            Symbol.ContainingType.IsSourceDeclaration() &&
+            !Symbol.ContainingType.IsAnonymousType;
+
+        private bool MakeSynthetic => IsPrimary || IsDefault;
+
         [return: NotNullIfNotNull(nameof(constructor))]
         public static new Constructor? Create(Context cx, IMethodSymbol? constructor)
         {

csharp/extractor/Semmle.Extraction.CSharp/Entities/Statement`1.cs

@@ -10,12 +10,15 @@ internal abstract class Statement<TSyntax> : Statement where TSyntax : CSharpSyn
         protected readonly TSyntax Stmt;
         private readonly Location location;
 
-        protected Statement(Context cx, TSyntax stmt, Kinds.StmtKind kind, IStatementParentEntity parent, int child, Location location)
+        protected Statement(Context cx, TSyntax stmt, Kinds.StmtKind kind, IStatementParentEntity parent, int child, Location location, bool isCompilerGenerated = false)
             : base(cx, kind, parent, child)
         {
             Stmt = stmt;
             this.location = location;
-            cx.BindComments(this, location.Symbol);
+            if (!isCompilerGenerated)
+            {
+                cx.BindComments(this, location.Symbol);
+            }
         }
 
         protected Statement(Context cx, TSyntax stmt, Kinds.StmtKind kind, IStatementParentEntity parent, int child)

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

@@ -9,7 +9,7 @@ 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) { }
+            : base(cx, block, StmtKind.BLOCK, parent, child, location, isCompilerGenerated: true) { }
 
         public static SyntheticEmptyBlock Create(Context cx, IStatementParentEntity parent, int child, Location location)
         {

csharp/ql/lib/semmle/code/csharp/dataflow/internal/DataFlowDispatch.qll

@@ -20,13 +20,7 @@ private import semmle.code.csharp.frameworks.system.collections.Generic
  */
 DotNet::Callable getCallableForDataFlow(DotNet::Callable c) {
   exists(DotNet::Callable unboundDecl | unboundDecl = c.getUnboundDeclaration() |
-    (
-      result.hasBody()
-      or
-      // take synthesized bodies into account, e.g. implicit constructors
-      // with field initializer assignments
-      result = any(ControlFlow::Nodes::ElementNode n).getEnclosingCallable()
-    ) and
+    result.hasBody() and
     if unboundDecl.getFile().fromSource()
     then
       // C# callable with C# implementation in the database