[Super errors] Specialize error msgs for Reason syntax when needed (#2616)

See the updated error/warning msgs

As per feedback, we're gonna do it for Reason syntax for now. We'll add
back the support for OCaml syntax later.

Author: chenglou

jscomp/super_errors/super_typecore.ml

@@ -228,8 +228,19 @@ let report_error env ppf = function
             type_expr typ;
           fprintf ppf "@ @[It only accepts %i %s; here, it's called with more.@]@]"
                       acceptsCount (if acceptsCount == 1 then "argument" else "arguments")
-      | Tconstr ((Path.Pdot (((Pdot (Path.Pident {name="Js"}, "Internal", _))| (Pident {name="Js_internal"})), ("fn" | "meth"), _)), _, _)
-        -> fprintf ppf "This is an uncurried bucklescript function. It must be applied with [@bs]."
+      | Tconstr (
+          (Path.Pdot (((Pdot (Path.Pident {name="Js"}, "Internal", _)) | (Pident {name="Js_internal"})), ("fn" | "meth"), _)),
+          _,
+          _
+        )
+        ->
+          fprintf
+            ppf
+            "@[<v>This is an uncurried BuckleScript function. @{<info>It must be applied with a dot@}.@,@,\
+            Like this: @{<info>foo(. a, b)@}@,\
+            Not like this: @{<dim>foo(a, b)@}@,@,\
+            This guarantees that your function is fully applied. More info here:@,\
+            https://bucklescript.github.io/docs/en/function.html#solution-guaranteed-uncurrying@]"
       | _ ->
           fprintf ppf "@[<v>@[<2>This expression has type@ %a@]@ %s@]"
             type_expr typ

jscomp/super_errors/super_warnings.ml

@@ -18,5 +18,7 @@ let message (warning : Warnings.t)  =
       "This file's name is potentially invalid. The build systems conventionally turn a file name into a module name by upper-casing the first letter. " ^ modname ^ " isn't a valid module name.\n" ^
       "Note: some build systems might e.g. turn kebab-case into CamelCase module, which is why this isn't a hard error."
   | Statement_type -> "This expression returns a value, but you're not doing anything with it. If this is on purpose, put `|> ignore` at the end."
+  | Useless_record_with ->
+      "All the fields are already explicitly listed in this record. You can remove the `...` spread."
   | _ -> Warnings.message warning
 ;;