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|
(* TEST
expect;
*)
type inkind = [ `Link | `Nonlink ]
type _ inline_t =
| Text: string -> [< inkind > `Nonlink ] inline_t
| Bold: 'a inline_t list -> 'a inline_t
| Link: string -> [< inkind > `Link ] inline_t
| Mref: string * [ `Nonlink ] inline_t list -> [< inkind > `Link ] inline_t
;;
let uppercase seq =
let rec process: type a. a inline_t -> a inline_t = function
| Text txt -> Text (String.uppercase_ascii txt)
| Bold xs -> Bold (List.map process xs)
| Link lnk -> Link lnk
| Mref (lnk, xs) -> Mref (lnk, List.map process xs)
in List.map process seq
;;
[%%expect{|
type inkind = [ `Link | `Nonlink ]
type _ inline_t =
Text : string -> [< inkind > `Nonlink ] inline_t
| Bold : 'a inline_t list -> 'a inline_t
| Link : string -> [< inkind > `Link ] inline_t
| Mref : string *
[ `Nonlink ] inline_t list -> [< inkind > `Link ] inline_t
val uppercase : 'a inline_t list -> 'a inline_t list = <fun>
|}];;
type ast_t =
| Ast_Text of string
| Ast_Bold of ast_t list
| Ast_Link of string
| Ast_Mref of string * ast_t list
;;
let inlineseq_from_astseq seq =
let rec process_nonlink = function
| Ast_Text txt -> Text txt
| Ast_Bold xs -> Bold (List.map process_nonlink xs)
| _ -> assert false in
let rec process_any = function
| Ast_Text txt -> Text txt
| Ast_Bold xs -> Bold (List.map process_any xs)
| Ast_Link lnk -> Link lnk
| Ast_Mref (lnk, xs) -> Mref (lnk, List.map process_nonlink xs)
in List.map process_any seq
;;
[%%expect{|
type ast_t =
Ast_Text of string
| Ast_Bold of ast_t list
| Ast_Link of string
| Ast_Mref of string * ast_t list
val inlineseq_from_astseq : ast_t list -> inkind inline_t list = <fun>
|}];;
(* OK *)
type _ linkp =
| Nonlink : [ `Nonlink ] linkp
| Maylink : inkind linkp
;;
let inlineseq_from_astseq seq =
let rec process : type a. a linkp -> ast_t -> a inline_t =
fun allow_link ast ->
match (allow_link, ast) with
| (Maylink, Ast_Text txt) -> Text txt
| (Nonlink, Ast_Text txt) -> Text txt
| (x, Ast_Bold xs) -> Bold (List.map (process x) xs)
| (Maylink, Ast_Link lnk) -> Link lnk
| (Nonlink, Ast_Link _) -> assert false
| (Maylink, Ast_Mref (lnk, xs)) ->
Mref (lnk, List.map (process Nonlink) xs)
| (Nonlink, Ast_Mref _) -> assert false
in List.map (process Maylink) seq
;;
[%%expect{|
type _ linkp = Nonlink : [ `Nonlink ] linkp | Maylink : inkind linkp
val inlineseq_from_astseq : ast_t list -> inkind inline_t list = <fun>
|}];;
(* Bad *)
type _ linkp2 = Kind : 'a linkp -> ([< inkind ] as 'a) linkp2
;;
let inlineseq_from_astseq seq =
let rec process : type a. a linkp2 -> ast_t -> a inline_t =
fun allow_link ast ->
match (allow_link, ast) with
| (Kind _, Ast_Text txt) -> Text txt
| (x, Ast_Bold xs) -> Bold (List.map (process x) xs)
| (Kind Maylink, Ast_Link lnk) -> Link lnk
| (Kind Nonlink, Ast_Link _) -> assert false
| (Kind Maylink, Ast_Mref (lnk, xs)) ->
Mref (lnk, List.map (process (Kind Nonlink)) xs)
| (Kind Nonlink, Ast_Mref _) -> assert false
in List.map (process (Kind Maylink)) seq
;;
[%%expect{|
type _ linkp2 = Kind : 'a linkp -> ([< inkind ] as 'a) linkp2
Line 7, characters 35-43:
7 | | (Kind _, Ast_Text txt) -> Text txt
^^^^^^^^
Error: This expression has type [< inkind > `Nonlink ] inline_t
but an expression was expected of type a inline_t
Type [< inkind > `Nonlink ] = [< `Link | `Nonlink > `Nonlink ]
is not compatible with type a = [< `Link | `Nonlink ]
The second variant type is bound to $'a,
it may not allow the tag(s) `Nonlink
|}];;
|
