C#: Add a locations example.

Author: michaelnebel

csharp/ql/test/library-tests/locations/A.cs

@@ -0,0 +1,18 @@
+using System;
+
+public abstract class A<T>
+{
+    public void Apply(T t) { }
+    public abstract object ToObject(T t);
+}
+
+public class A2 : A<string>
+{
+    public override object ToObject(string t) => t;
+
+    public void M()
+    {
+        A2 other = new();
+        other.Apply("");
+    }
+}

csharp/ql/test/library-tests/locations/B.cs

@@ -0,0 +1,6 @@
+using System;
+
+public class B : A<int>
+{
+    public override object ToObject(int t) => t;
+}

csharp/ql/test/library-tests/locations/C.cs

@@ -0,0 +1,12 @@
+using System;
+
+class C
+{
+    public void M()
+    {
+        B b = new B();
+        b.Apply(0);
+        A2 a2 = new A2();
+        a2.Apply("");
+    }
+}

csharp/ql/test/library-tests/locations/locations.expected

@@ -0,0 +1,6 @@
+| A.cs:3:23:3:26 | A`1 | A.cs:5:17:5:21 | Apply | A.cs:5:17:5:21 | A.cs:5:17:5:21 |
+| A.cs:3:23:3:26 | A`1 | A.cs:6:28:6:35 | ToObject | A.cs:6:28:6:35 | A.cs:6:28:6:35 |
+| A.cs:9:14:9:15 | A2 | A.cs:11:28:11:35 | ToObject | A.cs:11:28:11:35 | A.cs:11:28:11:35 |
+| A.cs:9:14:9:15 | A2 | A.cs:13:17:13:17 | M | A.cs:13:17:13:17 | A.cs:13:17:13:17 |
+| B.cs:3:14:3:14 | B | B.cs:5:28:5:35 | ToObject | B.cs:5:28:5:35 | B.cs:5:28:5:35 |
+| C.cs:3:7:3:7 | C | C.cs:5:17:5:17 | M | C.cs:5:17:5:17 | C.cs:5:17:5:17 |

csharp/ql/test/library-tests/locations/locations.ql

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+import csharp
+
+from Type t, Method m, SourceLocation l
+where t = m.getDeclaringType() and l = m.getLocation() and not l instanceof EmptyLocation
+select t, m, l

csharp/ql/test/library-tests/locations/options

@@ -0,0 +1 @@
+semmle-extractor-options: --standalone