fix(ppx): stop printing extra @ characters (#951)

ppx/ast_external_process.ml

@@ -26,7 +26,7 @@ open Import
 module External_arg_spec = Melange_ffi.External_arg_spec
 module External_ffi_types = Melange_ffi.External_ffi_types
 
-(* record pattern match complete checker*)
+(* record pattern match complete checker *)
 
 let rec variant_can_unwrap_aux (row_fields : Parsetree.row_field list) : bool =
   match row_fields with
@@ -158,8 +158,7 @@ let refine_obj_arg_type ~(nolabel : bool) (ptyp : Parsetree.core_type) :
     let result = Ast_attributes.iter_process_mel_string_or_int_as ptyp_attrs in
     (* when ppx start dropping attributes
        we should warn, there is a trade off whether
-       we should warn dropped non bs attribute or not
-    *)
+       we should warn dropped non bs attribute or not *)
     Mel_ast_invariant.warn_discarded_unused_attributes ptyp_attrs;
     match result with
     | None -> Error.err ~loc:ptyp.ptyp_loc Invalid_underscore_type_in_external
@@ -179,8 +178,7 @@ let refine_obj_arg_type ~(nolabel : bool) (ptyp : Parsetree.core_type) :
     {[
       external f : hi:([ `hi | `lo ] [@string]) -> unit -> _ = "" [@@obj]
     ]}
-    The result type would be [ hi:string ]
-*)
+    The result type would be [ hi:string ] *)
 let get_opt_arg_type ~(nolabel : bool) (ptyp : Parsetree.core_type) :
     External_arg_spec.attr =
   if ptyp.ptyp_desc = Ptyp_any then

ppx/error.ml

@@ -63,13 +63,13 @@ let pp_error fmt err =
         "`@mel.return' directive *_to_opt expects the return type to be an \
          option literal type (`_ option')"
     | Not_supported_directive_in_mel_return ->
-        "Unsupported `@mel.return' directive. Supported directives are one of:@\n\
-         - undefined_to_opt@\n\
-         - null_to_opt@\n\
-         - nullable / null_undefined_to_opt@\n\
+        "Unsupported `@mel.return' directive. Supported directives are one of:\n\
+         - undefined_to_opt\n\
+         - null_to_opt\n\
+         - nullable / null_undefined_to_opt\n\
          - identity"
     | Cannot_infer_arity_by_syntax ->
-        "Cannot infer arity through syntax.@\n\
+        "Cannot infer arity through syntax.\n\
          Use either `[@mel.uncurry n]' or the full arrow type"
     | Inconsistent_arity { uncurry_attribute; real } ->
         Printf.sprintf