Add Usexp.Loc.in_file

Moved from Loc

src/loc.ml

@@ -51,17 +51,7 @@ let fail_opt t fmt =
   | None -> die fmt
   | Some t -> fail t fmt
 
-let in_file fn =
+let in_file = Usexp.Loc.in_file
-  let pos : Lexing.position =
-    { pos_fname = fn
-    ; pos_lnum  = 1
-    ; pos_cnum  = 0
-    ; pos_bol   = 0
-    }
-  in
-  { start = pos
-  ; stop = pos
-  }
 
 let of_pos (fname, lnum, cnum, enum) =
   let pos : Lexing.position =

src/usexp/usexp.ml

@@ -240,7 +240,21 @@ let prepare_formatter ppf =
            | _ -> n))
     }
 
-module Loc = Sexp_ast.Loc
+module Loc = struct
+  include Sexp_ast.Loc
+
+  let in_file fn =
+    let pos : Lexing.position =
+      { pos_fname = fn
+      ; pos_lnum  = 1
+      ; pos_cnum  = 0
+      ; pos_bol   = 0
+      }
+    in
+    { start = pos
+    ; stop = pos
+    }
+end
 
 module Ast = struct
   type t = Sexp_ast.t =

src/usexp/usexp.mli

@@ -28,6 +28,8 @@ module Loc : sig
     { start : Lexing.position
     ; stop  : Lexing.position
     }
+
+  val in_file : string -> t
 end
 
 (** The S-expression type *)