A let in a form cut from inside a body stays local when the editor sends it, and the printer forgets one file's class names before the next.

lib/indent_printer.ml

@@ -1267,6 +1267,7 @@ let program ?source ?macros:m (fs : Form.t list) : string =
   in
   spelling := (fun _ -> None);
   inside := (fun _ -> false);
+  classes := [];
   (* With the source, its comments go back where they were; without it the
      tags come out and nothing goes in. *)
   Source_text.weave ~starts:(Source_text.form_starts fs)

lib/source.ml

@@ -72,9 +72,11 @@ let read_paren ?(line = 1) ?(col = 1) ~file src =
   in
   go []
 
-(** Editor code, in the request's syntax and at its position. With [expr], an
-    indented snippet of several statements is one expression, [(do ...)]: a
-    block of lines means its lines in order. *)
+(** Editor code, in the request's syntax and at its position. With [expr],
+    an indented snippet of several statements is one expression,
+    [(do ...)]: a block of lines means its lines in order. A [let] is a
+    global only in code from column 1 that is not an expression: a form cut
+    from inside a body, for a macroexpansion say, keeps its lets local. *)
 let read_code ?(expr = false) ~file code =
   let line, col =
     match !code_at with Some (l, c) -> (l, c) | None -> (1, 1)
@@ -82,7 +84,7 @@ let read_code ?(expr = false) ~file code =
   match !code_syntax with
   | Paren -> read_paren ~line ~col ~file code
   | Indented ->
-    (match Indent_reader.read_all ~line ~col ?indent:!code_indent ~global_let:(not expr)
+    (match Indent_reader.read_all ~line ~col ?indent:!code_indent ~global_let:(not expr && col = 1)
              ~file code with
      | (first :: _ :: _ as forms) when expr ->
        let last = List.nth forms (List.length forms - 1) in