* @Nullable X>, then users might pass a TypeParameter<Y>, where Y is a subtype of X, while still
   * passing a TypeToken<X>. This would be invalid. Maybe we could accept a TypeParameter<@PolyNull
   * X> if we support such a thing? It would be weird or misleading for users to be able to pass
   * `new TypeParameter<@Nullable T>() {}` and have it act as a plain `TypeParameter<T>`, but

	origX := *px
	*px = ast.NewIdent(fmt.Sprintf("_cgoBase%d", i))
	fmt.Fprintf(sb, "_cgo%d := %s; ", i, gofmtPos(arg, arg.Pos()))
	*px = origX

	// Use "0 == 0" to do the right thing in the unlikely event
	// that "true" is shadowed.
	fmt.Fprintf(sbCheck, "_cgoCheckPointer(_cgoBase%d, 0 == 0); ", i)

	return true
}

// checkSlice checks whether arg has the form x[i:j], possibly inside