A struct value's printed head comes from Render.head, which every renderer shares

lib/render.ml

@@ -103,6 +103,12 @@ let print_refusal _loc t =
   Printf.sprintf "no printer for %s — print the values you want out of it"
     (Types.to_string t)
 
+(* The head a struct value prints under: its name, or for a generic struct's
+   copy the template and its arguments, [Pair i32], so the value reads
+   [(Pair i32 {.a 1 .b 2})] the way its type is written. Every renderer of a
+   struct value goes through this, so they all print the same text. *)
+let head n = Types.struct_head n
+
 let rec render ?(refuse = print_refusal) c depth (e : Tast.expr) : Tast.expr list =
   let render c depth e = render ~refuse c depth e in
   let loc = e.Tast.loc in
@@ -333,7 +339,7 @@ let rec render ?(refuse = print_refusal) c depth (e : Tast.expr) : Tast.expr lis
                    @ render c (depth + 1) v)
                 shown)
          in
-         [ do_ ((lit ("(" ^ Types.struct_head n ^ " {") :: parts)
+         [ do_ ((lit ("(" ^ head n ^ " {") :: parts)
                 @ (if List.length fields > max_span then [ lit " ..." ] else [])
                 @ [ lit "})" ]) ])
     (* A fixed array's length is in its type, so it unrolls — capped, because