Pattern linearity check is broken

The linearity check for patterns is broken. For example:

$ cat wat.mligo
module A = struct

  let (x, x) = (1, "string")

end

let y = A.x ^ "1"

$ dune exec ligo -- print ast-core ./wat.mligo
module A = struct                           
           let ((x,x)) = ( 1 , "string" )
           end
let (y) = CONCAT(A.x , "1")