; Fieldtest mut-local #1 — factorial 5! via straight-line mut updates.
;
; Task: print 5! (= 120) using a `mut` block that names a running
; product and unrolls five multiplications as straight-line statements.
; This is the most direct possible use of mut-local: no helper fn, no
; iteration, just a sequence of in-block updates terminated by reading
; the var. The LLM-author's mental model of "I want a local accumulator"
; maps 1:1 onto the surface here.
;
; Why this fits mut-local's scope: the milestone supplies only sealed
; lexically-scoped mutables, with no `while` or `for`. Straight-line
; unroll is the *only* shape inside one mut block that needs no helper.
;
; Expected stdout: 120

(module mut-local_1_factorial

  (fn main
    (type (fn-type (params) (ret (con Unit)) (effects IO)))
    (params)
    (body
      (app print
        (mut
          (var prod (con Int) 1)
          (assign prod (app * prod 1))
          (assign prod (app * prod 2))
          (assign prod (app * prod 3))
          (assign prod (app * prod 4))
          (assign prod (app * prod 5))
          prod)))))