Simplify test predicates

Author: tamasvajk

csharp/ql/test/library-tests/csharp9/typeParameterNullability.ql

@@ -1,39 +1,17 @@
 import csharp
 
-private predicate isRealRefTypeConstraint(Type t) {
-  t instanceof RefType and
-  not t instanceof Interface
-}
-
 query predicate refType(TypeParameter tp) {
   tp.fromSource() and
-  (
-    not exists(tp.getConstraints())
-    or
-    tp.getConstraints().hasRefTypeConstraint()
-    or
-    tp.getConstraints().hasNullableRefTypeConstraint()
-    or
-    isRealRefTypeConstraint(tp.getConstraints().getATypeConstraint())
-  )
+  tp.isRefType()
 }
 
 query predicate valueType(TypeParameter tp) {
   tp.fromSource() and
-  (
-    not exists(tp.getConstraints()) or
-    tp.getConstraints().hasValueTypeConstraint() or
-    tp.getConstraints().getATypeConstraint() instanceof ValueType
-  )
+  tp.isValueType()
 }
 
 query predicate valueOrRefType(TypeParameter tp) {
   tp.fromSource() and
-  (
-    not exists(tp.getConstraints())
-    or
-    not tp.getConstraints().hasValueTypeConstraint() and
-    not tp.getConstraints().hasRefTypeConstraint() and
-    not isRealRefTypeConstraint(tp.getConstraints().getATypeConstraint())
-  )
+  not tp.isRefType() and
+  not tp.isValueType()
 }