Merge pull request github#11593 from michaelnebel/csharp/patternmatchspan

C#: Pattern match Span<char> and ReadOnlySpan<char> against a constant string.

Author: michaelnebel

csharp/ql/test/library-tests/csharp11/PatternMatchSpan.cs

@@ -0,0 +1,19 @@
+using System;
+
+class PatternMatchSpan
+{
+
+    public void M1(ReadOnlySpan<char> x1)
+    {
+        if (x1 is "ABC") { }
+    }
+
+    public void M2(Span<char> x2)
+    {
+        switch (x2)
+        {
+            case "DEF": { break; }
+            default: { break; }
+        }
+    }
+}

csharp/ql/test/library-tests/csharp11/patternMatchSpan.expected

@@ -0,0 +1,2 @@
+| ReadOnlySpan<Char> | PatternMatchSpan.cs:8:19:8:23 | "ABC" | String |
+| Span<Char> | PatternMatchSpan.cs:15:18:15:22 | "DEF" | String |

csharp/ql/test/library-tests/csharp11/patternMatchSpan.ql

@@ -0,0 +1,5 @@
+import csharp
+
+from PatternMatch pm
+where pm.getFile().getStem() = "PatternMatchSpan"
+select pm.getExpr().getType().getName(), pm.getPattern(), pm.getPattern().getType().getName()