mirage 4.5.0 errors report sometimes off-by-one

[hannesm]

Hey,

so I have the following generated file -- :

# 171 "mirage/main.ml"

let mirage_runtime__11 = lazy (
  let __struct_end__2 = Lazy.force struct_end__2 in
  let __printexc__3 = Lazy.force printexc__3 in
  let __hashtbl__4 = Lazy.force hashtbl__4 in
  let __gc__5 = Lazy.force gc__5 in
  let __mirage_runtime__6 = Lazy.force mirage_runtime__6 in
  let __mirage_logs_make__8 = Lazy.force mirage_logs_make__8 in
  let __unikernel_hello__10 = Lazy.force unikernel_hello__10 in
  __struct_end__2 >>= fun _struct_end__2 ->
  __printexc__3 >>= fun _printexc__3 ->
  __hashtbl__4 >>= fun _hashtbl__4 ->
  __gc__5 >>= fun _gc__5 ->
  __mirage_runtime__6 >>= fun _mirage_runtime__6 ->
  __mirage_logs_make__8 >>= fun _mirage_logs_make__8 ->
  __unikernel_hello__10 >>|= fun _unikernel_hello__10 ->
# 384 "lib/mirage.ml"
  return ()
);;
# 191 "mirage/main.ml"

Emacs agrees with the line number: the directive # 171 is on line 171, the directive # 191 on line 191.

When I run a make build, I get:

File "mirage/main.ml", line 186, characters 24-28:
Error: Unbound value >>|=
Hint: Did you mean >>= or >|=?

But the use of >>|= is in line 187, characters 24-28. How can that be?

If you need a full example, the above is from mirage-skeleton/tutorial/hello with a mirage configure -t hvt and then a manual edit of the file (to inject bad syntax).

[hannesm]

AFAICT all mirage/main line number directives are off-by-one.