C#: Add test case and expected output.

Author: michaelnebel

csharp/ql/test/library-tests/spans/Slice.cs

@@ -0,0 +1,19 @@
+using System;
+
+public class C
+{
+    public void M(int a)
+    {
+        var s = "hello world";
+        var sub1 = s[1..a];
+        var sub2 = s[..2];
+        var sub3 = s[3..];
+        var sub4 = s[..^4];
+
+        Span<int> sp = null;
+        var slice1 = sp[5..a];
+        var slice2 = sp[..6];
+        var slice3 = sp[7..];
+        var slice4 = sp[..^8];
+    }
+}

csharp/ql/test/library-tests/spans/slice.expected

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+methodCalls
+| Slice.cs:8:20:8:26 | call to method Substring | Substring(int, int) | 0 | 1 |
+| Slice.cs:8:20:8:26 | call to method Substring | Substring(int, int) | 1 | access to parameter a - 1 |
+| Slice.cs:9:20:9:25 | call to method Substring | Substring(int, int) | 0 | 0 |
+| Slice.cs:9:20:9:25 | call to method Substring | Substring(int, int) | 1 | 2 |
+| Slice.cs:10:20:10:25 | call to method Substring | Substring(int, int) | 0 | 3 |
+| Slice.cs:10:20:10:25 | call to method Substring | Substring(int, int) | 1 | access to property Length - 3 |
+| Slice.cs:11:20:11:26 | call to method Substring | Substring(int, int) | 0 | 0 |
+| Slice.cs:11:20:11:26 | call to method Substring | Substring(int, int) | 1 | access to property Length - 4 |
+| Slice.cs:14:22:14:29 | call to method Slice | Slice(int, int) | 0 | 5 |
+| Slice.cs:14:22:14:29 | call to method Slice | Slice(int, int) | 1 | access to parameter a - 5 |
+| Slice.cs:15:22:15:28 | call to method Slice | Slice(int, int) | 0 | 0 |
+| Slice.cs:15:22:15:28 | call to method Slice | Slice(int, int) | 1 | 6 |
+| Slice.cs:16:22:16:28 | call to method Slice | Slice(int, int) | 0 | 7 |
+| Slice.cs:16:22:16:28 | call to method Slice | Slice(int, int) | 1 | access to property Length - 7 |
+| Slice.cs:17:22:17:29 | call to method Slice | Slice(int, int) | 0 | 0 |
+| Slice.cs:17:22:17:29 | call to method Slice | Slice(int, int) | 1 | access to property Length - 8 |
+propertyCalls
+| Slice.cs:10:20:10:25 | access to property Length | Slice.cs:10:20:10:20 | access to local variable s |
+| Slice.cs:11:20:11:26 | access to property Length | Slice.cs:11:20:11:20 | access to local variable s |
+| Slice.cs:16:22:16:28 | access to property Length | Slice.cs:16:22:16:23 | access to local variable sp |
+| Slice.cs:17:22:17:29 | access to property Length | Slice.cs:17:22:17:23 | access to local variable sp |

csharp/ql/test/library-tests/spans/slice.ql

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+import csharp
+
+private string printExpr(Expr e) {
+  e =
+    any(SubExpr sub |
+      result = sub.getLeftOperand().toString() + " - " + sub.getRightOperand().toString()
+    )
+  or
+  not e instanceof SubExpr and
+  result = e.toString()
+}
+
+query predicate methodCalls(MethodCall mc, string m, int i, string arg) {
+  m = mc.getTarget().toStringWithTypes() and
+  arg = printExpr(mc.getArgument(i))
+}
+
+query predicate propertyCalls(PropertyCall p, Expr qualifier) { qualifier = p.getQualifier() }