Hypothetical sketch of a system for adding rewrite rules to APIs.

rewrite-rule-idea.rkt

;; This is a hypothetical syntax for defining rewrite rules that can be used to create custom optimizations and
;; refactoring suggestions. This example assumes there's some sort of geometry library that accepts angles in terms of
;; either degrees or radians using wrapper structs like `(struct degrees (value))` and `(struct radians (value))`. If
;; the wrapping is done right where the function is called, it allocates garbage that specialized degree-specific and
;; radian-specific functions wouldn't allocate. But we don't want to double the API surface, so we instead create inlining
;; rules that fire when the wrapping is done at the call site.

(define-rewrite-rule rotate-degrees-specialization
  @explanation{Using the @racket[rotate-degrees] function avoids allocating the intermediate @racket[degrees] value.}
  #:surface-as hidden-optimization
  #:from (rotate (degrees 270))
  #:to (rotate-degrees 270))