67 lines
2.1 KiB
OCaml
67 lines
2.1 KiB
OCaml
open Ppxlib
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let payload : unit -> (structure_item, label list -> 'a, 'a) Ast_pattern.t =
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fun () ->
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Ast_pattern.(
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pstr_eval (elist (pexp_constant (pconst_string __ drop drop))) drop)
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let make_payload ~loc labels =
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let open Ast_builder.Make (struct
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let loc = loc
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end) in
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pstr_eval (elist (List.map estring labels)) []
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let expand ~loc ident recurse =
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let open Ast_builder.Make (struct
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let loc = loc
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end) in
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let ident =
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Located.mk
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(match ident with
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| Lident x -> Lident (x ^ "x")
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| _ -> Location.raise_errorf ~loc "ident must be simple")
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in
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match recurse with
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| [] -> pexp_ident ident
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| "%ext" :: recurse ->
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pexp_extension
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( Located.mk "ext",
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PStr [ pstr_eval (pexp_ident ident) []; make_payload ~loc recurse ] )
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| "@attr" :: recurse ->
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{
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pexp_desc = Pexp_ident ident;
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pexp_attributes =
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[
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attribute ~name:(Located.mk "attr")
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~payload:(PStr [ make_payload ~loc recurse ]);
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];
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pexp_loc = loc;
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pexp_loc_stack = [];
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}
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| hd :: _ -> Location.raise_errorf ~loc "invalid rewrite: %s" hd
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let () =
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Driver.register_transformation "recursive"
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~rules:
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[
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Context_free.Rule.extension
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(Extension.V3.declare "ext" Extension.Context.expression
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Ast_pattern.(
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pstr (pstr_eval (pexp_ident __) drop ^:: payload () ^:: nil))
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(fun ~ctxt ident recurse ->
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let loc = Expansion_context.Extension.extension_point_loc ctxt in
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let loc = { loc with loc_ghost = true } in
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expand ~loc ident recurse));
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Context_free.Rule.attr_replace "attr" Extension.Context.expression
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(Attribute.declare "attr" Attribute.Context.Expression
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Ast_pattern.(pstr (payload () ^:: nil))
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(fun x -> x))
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(fun ~ctxt:_ x recurse ->
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match x.pexp_desc with
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| Pexp_ident ident -> expand ~loc:x.pexp_loc ident.txt recurse
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| _ ->
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Location.raise_errorf ~loc:x.pexp_loc
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"rewrite must be applied to an identifier");
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]
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let () = Driver.standalone ()
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