C#: Add test case with recursive generics

csharp/ql/integration-tests/all-platforms/diag_recursive_generics/ExtractortMessages.ql

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+import csharp
+import semmle.code.csharp.commons.Diagnostics
+
+query predicate extractorMessages(ExtractorMessage msg, int severity, string elementText) {
+  msg.getSeverity() = severity and msg.getElementText() = elementText
+}

csharp/ql/integration-tests/all-platforms/diag_recursive_generics/Types.ql

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+import csharp
+
+from Class c
+where c.fromSource()
+select c, c.getBaseClass().getQualifiedName()

csharp/ql/integration-tests/all-platforms/diag_recursive_generics/test.cs

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+public class GenA<U> { };
+public class GenB<T> : GenA<GenB<GenB<T>>> { };
+
+class P<T> { }
+class C<U, V> : P<D<V, U>> { }
+class D<W, X> : P<C<W, X>> { }
+
+class A<T> : System.IEquatable<A<T>>
+{
+    public bool Equals(A<T> other) { return true; }
+}
+
+public class Class
+{
+    public static int Main()
+    {
+        GenB<string> a = new GenB<string>();
+        P<D<string, int>> b = new C<int, string>();
+        A<string> c = new A<string>();
+
+        return 0;
+    }
+}

csharp/ql/integration-tests/all-platforms/diag_recursive_generics/test.csproj

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+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <OutputType>Exe</OutputType>
+    <TargetFramework>net7.0</TargetFramework>
+  </PropertyGroup>
+
+ <Target Name="DeleteBinObjFolders" BeforeTargets="Clean">
+   <RemoveDir Directories=".\bin" />
+   <RemoveDir Directories=".\obj" />
+ </Target>
+</Project>

csharp/ql/integration-tests/all-platforms/diag_recursive_generics/test.py

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+from create_database_utils import *
+
+run_codeql_database_create(['dotnet build'], lang="csharp", extra_args=["--extractor-option=cil=false"])