; Iter 16e — `==` extends from Int-only to Int/Bool/Str/Unit (polymorphic
; dispatch). The builtin's declared type became
;   forall a. (a, a) -> Bool
; and codegen monomorphises on the resolved arg type:
;   Int  → icmp eq i64
;   Bool → icmp eq i1
;   Str  → @strcmp + icmp eq i32 0
;   Unit → constant i1 true (single-inhabitant type)
;   ADT/Fn → rejected at codegen with a clear error.
;
; This fixture exercises all four supported types, both directly via
; `(app == ...)` and indirectly via 16c's lit-pattern desugar (which
; rewrites `(pat-lit "hi")` → `(if (== sv "hi") body fall_k)` and
; therefore inherits 16e's polymorphic `==`).
;
; Expected stdout (one per line):
;   true   ; (== 5 5)
;   false  ; (== 5 6)
;   false  ; (== true false)
;   true   ; (== true true)
;   true   ; (== "hi" "hi")
;   false  ; (== "hi" "ho")
;   true   ; (== () ())
;   1      ; classify_str "hi"   (lit-pattern hits 1 arm)
;   2      ; classify_str "ho"   (lit-pattern hits 2 arm)
;   0      ; classify_str "??"   (default arm)
;
; Driver lowers via io/print_bool / io/print_int.

(module eq_demo

  (fn classify_str
    (doc "Lit-pattern over Str; exercises 16c's build_eq for non-Int.")
    (type (fn-type (params (con Str)) (ret (con Int))))
    (params s)
    (body
      (match s
        (case (pat-lit "hi") 1)
        (case (pat-lit "ho") 2)
        (case _ 0))))

  (fn main
    (doc "Drive == at Int/Bool/Str/Unit; then drive classify_str.")
    (type (fn-type (params) (ret (con Unit)) (effects IO)))
    (params)
    (body
      (seq (do io/print_bool (app == 5 5))
      (seq (do io/print_bool (app == 5 6))
      (seq (do io/print_bool (app == true false))
      (seq (do io/print_bool (app == true true))
      (seq (do io/print_bool (app == "hi" "hi"))
      (seq (do io/print_bool (app == "hi" "ho"))
      (seq (do io/print_bool (app == (lit-unit) (lit-unit)))
      (seq (do io/print_int (app classify_str "hi"))
      (seq (do io/print_int (app classify_str "ho"))
           (do io/print_int (app classify_str "??"))))))))))))))