Yokota Yuki

Allegro Common Lisp does not have `truly-the` operator, but has `excl:trusted-type` declaration for similar purpose. https://franz.com/support/documentation/10.1/doc/compiling.htm#trusted-type-2

There is [atomics](https://github.com/Shinmera/atomics) as a compatibility layer.

[trivial-cltl2](https://github.com/Zulu-Inuoe/trivial-cltl2) works as a compatibility layer about `declaration-information` and `define-declaration`.

Allegro Common Lisp extends `#A` reader macro for similar purpose, but its syntax is very different from the one discussed here. See https://franz.com/support/documentation/10.1/doc/implementation.htm#sharpsign-a-2