added --help-metas

main.ml

@@ -1046,6 +1046,37 @@ try
 			loop 0;
 			did_something := true
 		),": print help for all compiler specific defines");
+		("--help-metas", Arg.Unit (fun() ->
+			let rec loop i =
+				let d = Obj.magic i in
+				if d <> Meta.Last then begin
+					let t, (doc,flags) = MetaInfo.to_string d in
+					let params = ref [] and used = ref [] and pfs = ref [] in
+					List.iter (function
+						| MetaInfo.HasParam s -> params := s :: !params
+						| MetaInfo.Platform f -> pfs := f :: !pfs
+						| MetaInfo.Platforms fl -> pfs := fl @ !pfs
+						| MetaInfo.UsedOn u -> used := u :: !used
+						| MetaInfo.UsedOnEither ul -> used := ul @ !used
+					) flags;
+					let params = (match List.rev !params with
+						| [] -> ""
+						| l -> "(" ^ String.concat "," l ^ ")"
+					) in
+					let pfs = (match List.rev !pfs with
+						| [] -> ""
+						| [p] -> " (" ^ platform_name p ^ " only)"
+						| pl -> " (for " ^ String.concat "," (List.map platform_name pl) ^ ")"
+					) in
+					let str = "@" ^ t ^ params ^ " : " ^ doc ^ pfs in
+					str :: loop (i + 1)
+				end else
+					[]
+			in
+			let all = List.sort String.compare (loop 0) in
+			List.iter (fun msg -> message ctx msg Ast.null_pos) all;
+			did_something := true
+		),": print help for all compiler metadatas");
 	] in
 	let args_callback cl = classes := make_path cl :: !classes in
 	let process args =