Add DB upgrade script to change generic type names to undecorated ones

csharp/ql/src/semmle/code/csharp/Type.qll

@@ -56,7 +56,7 @@ private predicate isObjectClass(Class c) { c instanceof ObjectType }
  */
 class ValueOrRefType extends DotNet::ValueOrRefType, Type, Attributable, @value_or_ref_type {
   /**
-   * DEPRECATED: use `getUndecoratedName()` instead
+   * DEPRECATED: use `getUndecoratedName()` instead.
    *
    * Gets the name of this type without `<...>` brackets, in case it is a generic type.
    */

csharp/ql/src/semmlecode.csharp.dbscheme

@@ -1,3 +1,13 @@
+/* This is a dummy line to alter the dbscheme, so we can make a database upgrade
+ * without actually changing any of the dbscheme predicates. It contains a date
+ * to allow for such updates in the future as well.
+ *
+ * 2021-07-14
+ *
+ * DO NOT remove this comment carelessly, since it can revert the dbscheme back to a
+ * previously seen state (matching a previously seen SHA), which would make the upgrade
+ * mechanism not work properly.
+ */
 
 /**
  * An invocation of the compiler. Note that more than one file may be

csharp/upgrades/770f844243d5a2282861b33fd201d0a02e3528d9/types.ql

@@ -0,0 +1,27 @@
+class Type extends @type {
+  string toString() { none() }
+
+  string getNewName() {
+    not this instanceof Generic and
+    types(this, _, result)
+    or
+    result = this.(Generic).getUndecoratedName()
+  }
+}
+
+class Generic extends Type {
+  Generic() {
+    type_parameters(_, _, this, _) or
+    type_arguments(_, _, this)
+  }
+
+  string getUndecoratedName() {
+    exists(string oldName |
+      types(this, _, oldName) and result = oldName.prefix(min(int i | i = oldName.indexOf("<")))
+    )
+  }
+}
+
+from Type type, int kind
+where types(type, kind, _)
+select type, kind, type.getNewName()

csharp/upgrades/770f844243d5a2282861b33fd201d0a02e3528d9/upgrade.properties

@@ -0,0 +1,4 @@
+description: Extractor changed to not include angle brackets in generic type names.
+compatibility: backwards
+
+types.rel: run types.qlo