Ruby: add RbiInstantiatedType

ruby/ql/lib/codeql/ruby/experimental/Rbi.qll

@@ -132,6 +132,9 @@ module Rbi {
       }
     }
 
+    /**
+     * A use of `T::Hash`.
+     */
     class RbiHashType extends RbiType, ConstantReadAccessFromT {
       RbiHashType() { this.getName() = "Hash" }
 
@@ -144,6 +147,11 @@ module Rbi {
       Expr getValueType() { result = this.getRefNode().getArgument(1) }
     }
 
+    /** A type instantiated with type arguments, such as `T::Array[String]`. */
+    class RbiInstantiatedType extends RbiType, ElementReference {
+      RbiInstantiatedType() { getReceiver() instanceof RbiType }
+    }
+
     /**
      * A call to `T.proc`. This defines a type signature for a proc or block
      */