Add a test to check String/Bytes equivalence

testsuite/tests/lib-stdlib/string_bytes_equiv.ml

@@ -0,0 +1,83 @@
+(* TEST
+   ocaml_script_as_argument = "true"
+   * toplevel
+*)
+
+(* This test trips if Bytes and String don't have equivalent interfaces. The
+   response to this test's failure is either to make the modules equivalent
+   again or code an exception below which ignores it, typically by adding a
+   val declaration to STRING or BYTES. If an item must differ (e.g. an external
+   declaration), then it may be overidden in the EXTERNALS signature. *)
+
+[@@@ocaml.alert "-deprecated"]
+
+(* Load the signatures of String and Bytes as STRING and BYTES where *)
+type bytes = string;;
+
+#sig_use "string.mli"
+#sig_use "bytes.mli"
+
+(* Convert external declarations to val *)
+module type EXTERNALS = sig
+  val length : string -> int
+  val get : string -> int -> char
+  val set : string -> int -> char
+  val create : int -> string
+  val unsafe_get : string -> int -> char
+  val unsafe_set : string -> int -> char
+  val unsafe_fill : string -> int -> int -> char -> unit
+end
+
+module type STRING = sig
+  include STRING
+
+  include EXTERNALS
+
+  (* Strring obviously doesn't need {of,to}_string *)
+  val of_string : string -> bytes
+  val to_string : bytes -> string
+
+  val unsafe_to_string : bytes -> string
+  val unsafe_of_string : string -> bytes
+
+  (* Functions which make no sense in String *)
+  val blit_string : string -> int -> bytes -> int -> int -> unit
+  val extend : bytes -> int -> int -> bytes
+  val sub_string : bytes -> int -> int -> string
+
+  external unsafe_blit : bytes -> int -> bytes -> int -> int -> unit
+    = "caml_blit_bytes" [@@noalloc]
+  external unsafe_blit_string : string -> int -> bytes -> int -> int -> unit
+    = "caml_blit_string" [@@noalloc]
+
+  val set_uint8 : bytes -> int -> int -> unit
+  val set_int8 : bytes -> int -> int -> unit
+  val set_uint16_ne : bytes -> int -> int -> unit
+  val set_uint16_be : bytes -> int -> int -> unit
+  val set_uint16_le : bytes -> int -> int -> unit
+  val set_int16_ne : bytes -> int -> int -> unit
+  val set_int16_be : bytes -> int -> int -> unit
+  val set_int16_le : bytes -> int -> int -> unit
+  val set_int32_ne : bytes -> int -> int32 -> unit
+  val set_int32_be : bytes -> int -> int32 -> unit
+  val set_int32_le : bytes -> int -> int32 -> unit
+  val set_int64_ne : bytes -> int -> int64 -> unit
+  val set_int64_be : bytes -> int -> int64 -> unit
+  val set_int64_le : bytes -> int -> int64 -> unit
+end
+
+module type BYTES = sig
+  include BYTES
+
+  include EXTERNALS
+
+  (* Bytes obviously doesn't need {of,to}_bytes *)
+  val of_bytes : bytes -> string
+  val to_bytes : string -> bytes
+end
+
+(* Check that the two signatures are equivalent *)
+module String_includes(_ : BYTES) = struct end
+module M(Bytes: STRING) = String_includes(Bytes)
+module Bytes_includes(_: STRING) = struct end
+module M(String: BYTES) = Bytes_includes(String)