;;;; The dev-build break loop — spec-conditions.md §2.
;;;;
;;;; An unhandled error used to kill the program. Here it stops instead, on the
;;;; frame that erred with nothing unwound, and waits for someone to pick a
;;;; restart. Two of them, and the run takes a different one each time, so a
;;;; break loop that always resumed the same way could not pass.
(import agent "vendor:agent")

(defstruct Missing [id i32])

(defn fetch [n i32] i32
  (restart-case
    (do (error (Missing {.id n})) 0)
    (use-placeholder [] :report "Answer -1 for the missing value" -1)
    (retry           [] 7)))

;;; Two frames offering the same name, which §4 says resolves to the inner one
;;; and only ever the inner one. The outer clause is therefore on every list a
;;; break loop prints and reachable from no name at all, which is why a restart
;;; is taken by *index* now. 900 is the proof: it is the only value in this
;;; file that by-name lookup cannot produce.
(defn shadowed [n i32] i32
  (restart-case
    (+ (restart-case (do (error (Missing {.id n})) 0)
         (retry [] 5))
       100)
    (retry [] 900)))

(defstruct Other [])

;;; A handler-case establishes a restart of its own, under a name nobody wrote,
;;; and a break loop inside it must not offer that one: it is reached through
;;; the form's handler, which carries the condition in. Only [keep] is listed.
(defn caught [n i32] i32
  (restart-case
    (handler-case (do (error (Missing {.id n})) 0)
      [(Other [_o] 5)])
    (keep [] :report "Answer 42" 42)))

(defn main [] i32
  (agent/start "/tmp/flan-break.sock")
  (print (fetch 1)) (println "")
  (print (fetch 2)) (println "")
  (print (shadowed 3)) (println "")
  (print (caught 4)) (println "")
  0)