code: protected void appendConstrainedExtends(
  			GenerationContext context,
  			JvmGenericType owner, Class<?> defaultJvmType,
  			Class<? extends XtendTypeDeclaration> defaultSarlType,
  			JvmParameterizedTypeReference supertype) {
  		final List<? extends JvmParameterizedTypeReference> supertypes;
  		if (supertype == null) {
  			supertypes = Collections.emptyList();
  		} else {
  			supertypes = Collections.singletonList(supertype);
  		}
  		appendConstrainedExtends(context, owner, defaultJvmType, defaultSarlType, supertypes);
  	}
docs: Generate the extended types for the given SARL statement.
  
  @param context the context of the generation.
  @param owner the JVM element to change.
  @param defaultJvmType the default JVM type.
  @param defaultSarlType the default SARL type.
  @param supertype the supertype.