code: public GenericsContext parameterTypeAs(final int pos, final Class<?> asType) {
          checkParameter(pos);
          return inlyingTypeAs(meth.getGenericParameterTypes()[pos], asType);
      }
docs: Create generics context for actual class, passed into parameter type (assuming you have access to that instance
  or know exact type). Context will contain correct generics for known declaration type (middle type in
  target type hierarchy). This is useful when analyzing object instance (introspecting actual object).
  <p>
  Other than target type, method is the same as {@link #parameterType(int)}.
  
  @param pos    parameter position (from 0)
  @param asType required target type to build generics context for (must include declared type as base class)
  @return generics context of requested type with known parameter generics
  @throws IllegalArgumentException if parameter index is incorrect
  @see #inlyingTypeAs(Type, Class)