C#: Add extensions test.

Author: michaelnebel

csharp/ql/test/library-tests/extension/extensionType.expected

@@ -0,0 +1,11 @@
+extensionTypeReceiverParameter
+| extensions.cs:6:5:17:5 | extension(String) | extensions.cs:6:22:6:22 | s |
+| extensions.cs:26:5:35:5 | extension(Object)<Object> | extensions.cs:26:20:26:20 | t |
+| extensions.cs:26:5:35:5 | extension(String)<String> | extensions.cs:26:20:26:20 | t |
+| extensions.cs:26:5:35:5 | extension(T)`1 | extensions.cs:26:20:26:20 | t |
+extensionTypeExtendedType
+| extensions.cs:6:5:17:5 | extension(String) | string |
+| extensions.cs:19:5:24:5 | extension(Object) | object |
+| extensions.cs:26:5:35:5 | extension(Object)<Object> | object |
+| extensions.cs:26:5:35:5 | extension(String)<String> | string |
+| extensions.cs:26:5:35:5 | extension(T)`1 | T |

csharp/ql/test/library-tests/extension/extensionType.ql

@@ -0,0 +1,11 @@
+import csharp
+
+query predicate extensionTypeReceiverParameter(ExtensionType et, Parameter p) {
+  et.getFile().getBaseName() = "extensions.cs" and
+  p = et.getReceiverParameter()
+}
+
+query predicate extensionTypeExtendedType(ExtensionType et, string t) {
+  et.getFile().getBaseName() = "extensions.cs" and
+  t = et.getExtendedType().toStringWithTypes()
+}

csharp/ql/test/library-tests/extension/extensions.cs

@@ -0,0 +1,107 @@
+using System;
+using System.Collections.Generic;
+
+public static class MyExtensions
+{
+    extension(string s)
+    {
+        public bool Prop1 => s.Length > 0;
+        public bool Prop2 { get { return true; } set { } }
+        public static bool StaticProp1 { get { return false; } }
+        public bool M1() => s is not null;
+        public string M2(string other) { return s + other; }
+        public static int StaticM1() { return 0; }
+        public static int StaticM2(string x) { return x.Length; }
+        public static string operator *(int a, string b) { return ""; }
+        public T StringGenericM1<T>(T t, object o) { return t; }
+    }
+
+    extension(object)
+    {
+        public static int StaticObjectM1() { return 0; }
+        public static int StaticObjectM2(string s) { return s.Length; }
+        public static bool StaticProp => true;
+    }
+
+    extension<T>(T t) where T : class
+    {
+        public bool GenericProp1 => t is not null;
+        public bool GenericProp2 { get { return true; } set { } }
+        public bool GenericM1() => t is not null;
+        public void GenericM2<S>(S other) { }
+        public void GenericStaticM1() { }
+        public static void GenericStaticM2<S>(S other) { }
+        public static T operator +(T a, T b) { return null; }
+    }
+}
+
+public static class ClassicExtensions
+{
+    public static bool M3(this string s) => s is not null;
+}
+
+public class C
+{
+    public static void CallingExtensions()
+    {
+        var s = "Hello World.";
+
+        // Calling the extensions properties
+        var x11 = s.Prop1;
+        var x12 = s.Prop2;
+        s.Prop2 = true;
+        var x13 = string.StaticProp1;
+        var x14 = object.StaticProp;
+
+        // Calling the extensions methods.
+        var x21 = s.M1();
+        var x22 = s.M2("!!!");
+        var x23 = string.StaticM1();
+        var x24 = string.StaticM2(s);
+        var x25 = object.StaticObjectM1();
+        var x26 = object.StaticObjectM2(s);
+
+        // Calling the extension operator.
+        var x30 = 3 * s;
+
+        // Calling the classic extension method.
+        var y = s.M3();
+
+        // Calling the compiler generated static extension methods.
+        MyExtensions.M1(s);
+        MyExtensions.M2(s, "!!!");
+        MyExtensions.StaticM1();
+        MyExtensions.StaticM2(s);
+        MyExtensions.StaticObjectM1();
+        MyExtensions.StaticObjectM2(s);
+
+        // Calling the compiler generated operator method.
+        MyExtensions.op_Multiply(3, s);
+
+        // Calling the compiler generated methods used by the extension property accessors.
+        MyExtensions.get_Prop1(s);
+        MyExtensions.get_Prop2(s);
+        MyExtensions.set_Prop2(s, false);
+        MyExtensions.get_StaticProp();
+    }
+
+    public static void CallingGenericExtensions()
+    {
+        var s = "Hello Generic World.";
+        var o = new object();
+
+        // Calling generic extension method
+        o.GenericM1();
+        s.GenericM1();
+
+        // Calling the compiler generated static extension methods.
+        MyExtensions.GenericM1(o);
+        MyExtensions.GenericM1(s);
+
+        o.GenericM2(42);
+        MyExtensions.GenericM2(o, 42);
+
+        s.StringGenericM1<int>(7, new object());
+        MyExtensions.StringGenericM1<string>(s, "test", new object());
+    }
+}