Merge pull request github#7643 from michaelnebel/csharp/struct-improvements

C#: Struct (and to a minor extent anonymous types) improvements

Author: hvitved

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

@@ -1481,6 +1481,8 @@ class FieldOrProperty extends Assignable, Modifiable {
           p.isAutoImplemented()
           or
           p.matchesHandle(any(CIL::TrivialProperty tp))
+          or
+          p.getDeclaringType() instanceof AnonymousClass
         )
       )
   }

csharp/ql/test/library-tests/csharp10/RecordTypes.cs

@@ -9,4 +9,4 @@ public record class MyClassRecord(DateTime stuff) { }
 
 public readonly record struct MyReadonlyRecordStruct(string Stuff) { }
 
-public record struct MyRecordStruct(int Stuff) { }
+public record struct MyRecordStruct1(int Stuff) { }

csharp/ql/test/library-tests/csharp10/StructTypes.cs

@@ -0,0 +1,19 @@
+using System;
+
+// Struct with user declared parameterless constructor.
+public struct MyStructParameterlessConstructor
+{
+    public int X;
+    public readonly int Y;
+    public int Z { get; }
+
+    public MyStructParameterlessConstructor()
+    {
+        X = 1;
+        Y = 2;
+        Z = 3;
+    }
+}
+
+// Struct with compiler generated parameterless constructor.
+public struct MyDefaultStruct { }

csharp/ql/test/library-tests/csharp10/WithExpression.cs

@@ -0,0 +1,30 @@
+using System;
+
+public struct MyStruct
+{
+    public int X;
+    public MyStruct(int x) => X = x;
+}
+
+public record struct MyRecordStruct2(int Y) { }
+
+public class MyWithExamples
+{
+    public void M1()
+    {
+        var s1 = new MyStruct(1);
+        var s2 = s1 with { X = 2 };
+    }
+
+    public void M2()
+    {
+        var r1 = new MyRecordStruct2(4);
+        var r2 = r1 with { Y = 6 };
+    }
+
+    public void M3()
+    {
+        var anon1 = new { A = 3, B = 4 };
+        var anon2 = anon1 with { A = 5 };
+    }
+}

csharp/ql/test/library-tests/csharp10/recordTypes.expected

@@ -2,10 +2,12 @@ recordTypes
 | RecordTypes.cs:3:1:6:2 | MyEntry |
 | RecordTypes.cs:8:1:8:53 | MyClassRecord |
 | RecordTypes.cs:10:1:10:70 | MyReadonlyRecordStruct |
-| RecordTypes.cs:12:1:12:50 | MyRecordStruct |
+| RecordTypes.cs:12:1:12:51 | MyRecordStruct1 |
+| WithExpression.cs:9:1:9:47 | MyRecordStruct2 |
 recordStructs
 | RecordTypes.cs:10:1:10:70 | MyReadonlyRecordStruct |
-| RecordTypes.cs:12:1:12:50 | MyRecordStruct |
+| RecordTypes.cs:12:1:12:51 | MyRecordStruct1 |
+| WithExpression.cs:9:1:9:47 | MyRecordStruct2 |
 recordClass
 | RecordTypes.cs:3:1:6:2 | MyEntry |
 | RecordTypes.cs:8:1:8:53 | MyClassRecord |

csharp/ql/test/library-tests/csharp10/structTypes.expected

@@ -0,0 +1,5 @@
+structAllDefaultConstructors
+| StructTypes.cs:4:15:4:46 | MyStructParameterlessConstructor | StructTypes.cs:10:12:10:43 | MyStructParameterlessConstructor |
+| StructTypes.cs:19:15:19:29 | MyDefaultStruct | StructTypes.cs:19:15:19:29 | MyDefaultStruct |
+structFromSourceDefaultConstructors
+| StructTypes.cs:4:15:4:46 | MyStructParameterlessConstructor | StructTypes.cs:10:12:10:43 | MyStructParameterlessConstructor |

csharp/ql/test/library-tests/csharp10/structTypes.ql

@@ -0,0 +1,15 @@
+import csharp
+
+predicate structDefaultConstructors(Struct struct, Constructor c) {
+  struct.getAConstructor() = c and
+  struct.getFile().getBaseName() = "StructTypes.cs" and
+  c.hasNoParameters()
+}
+
+query predicate structAllDefaultConstructors(Struct struct, Constructor c) {
+  structDefaultConstructors(struct, c)
+}
+
+query predicate structFromSourceDefaultConstructors(Struct struct, Constructor c) {
+  structDefaultConstructors(struct, c) and c.fromSource()
+}

csharp/ql/test/library-tests/csharp10/withExpression.expected

@@ -0,0 +1,3 @@
+| WithExpression.cs:16:18:16:34 | ... with { ... } | MyStruct | WithExpression.cs:16:18:16:19 | access to local variable s1 | WithExpression.cs:16:26:16:34 | { ..., ... } |
+| WithExpression.cs:22:18:22:34 | ... with { ... } | MyRecordStruct2 | WithExpression.cs:22:18:22:19 | access to local variable r1 | WithExpression.cs:22:26:22:34 | { ..., ... } |
+| WithExpression.cs:28:21:28:40 | ... with { ... } | <>__AnonType0<Int32,Int32> | WithExpression.cs:28:21:28:25 | access to local variable anon1 | WithExpression.cs:28:32:28:40 | { ..., ... } |

csharp/ql/test/library-tests/csharp10/withExpression.ql

@@ -0,0 +1,7 @@
+import csharp
+
+query predicate withExpressions(WithExpr with, string type, Expr expr, ObjectInitializer init) {
+  type = with.getType().toStringWithTypes() and
+  expr = with.getExpr() and
+  init = with.getInitializer()
+}

csharp/ql/test/library-tests/dataflow/fields/F.cs

@@ -5,7 +5,7 @@ public class F
 
     static F Create(object o1, object o2) => new F() { Field1 = o1, Field2 = o2 };
 
-    private void M()
+    private void M1()
     {
         var o = Source<object>(1);
         var f = Create(o, null);
@@ -25,6 +25,15 @@ private void M()
         Sink(f.Field2); // $ hasValueFlow=4
     }
 
+    private void M2()
+    {
+        var o = Source<object>(2);
+        object @null = null;
+        var a = new { X = o, Y = @null };
+        Sink(a.X); // $ hasValueFlow=2
+        Sink(a.Y); // no flow
+    }
+
     public static void Sink(object o) { }
 
     static T Source<T>(object source) => throw null;