fixup rest of backend to compile tests

Author: SteveBronder

src/middle/Expr.ml

@@ -43,7 +43,8 @@ module Fixed = struct
             indices
       | EAnd (l, r) -> Fmt.pf ppf "%a && %a" pp_e l pp_e r
       | EOr (l, r) -> Fmt.pf ppf "%a || %a" pp_e l pp_e r
-      | Promotion (from, ut) -> Fmt.pf ppf "%a -> %a" pp_e from UnsizedType.pp ut
+      | Promotion (from, ut) ->
+          Fmt.pf ppf "%a -> %a" pp_e from UnsizedType.pp ut
 
     include Foldable.Make (struct
       type nonrec 'a t = 'a t

src/stan_math_backend/Expression_gen.ml

@@ -527,7 +527,9 @@ and pp_expr ppf Expr.Fixed.({pattern; meta} as e) =
   | Lit (Str, s) -> pf ppf "\"%s\"" (Cpp_str.escaped s)
   | Lit (Imaginary, s) -> pf ppf "to_complex(0, %s)" s
   | Lit ((Real | Int), s) -> pf ppf "%s" s
-  | Promotion (expr, ut) -> pf ppf "stan::math::promote_scalar_t<%a>(%a)" pp_unsizedtype_local (meta.adlevel, ut) pp_expr expr
+  | Promotion (expr, ut) ->
+      pf ppf "stan::math::promote_scalar_t<%a>(%a)" pp_unsizedtype_local
+        (meta.adlevel, ut) pp_expr expr
   | FunApp
       ( StanLib (op, _, _)
       , [ { meta= {type_= URowVector; _}