fixpoint "--rewrite"

data Field 1 = [
  | FBool {}
  | FInt {}
  ]

constant add : (func(0, [int; int; int]))
constant proj : (func(1, [Field @(0); @(0); @(0)]))

define add (x:int, y:int): int = {
  x + y 
}
define proj (lq1 : (Field a),  lq2 : a): a = {
  if (is$FInt lq1) 
    then (coerce (int  ~ a) (add (coerce (a ~ int) lq2) 1)) 
    else (coerce (bool ~ a) (not ((coerce (a ~ bool) lq2))))
} 

match is$FInt FInt = (true)

constraint:
  env []
  lhs {v : int | true }
  rhs {v : int | proj FInt 10 == 11 }
  id 1 tag []

expand [1 : True]