libocaml-compiler-libs-ocaml-dev - 0.12.3-1 main

This package simply repackages the OCaml compiler libraries so they
don’t expose everything at toplevel. For instance Ast_helper is now
Ocaml_common.Ast_helper.
.
The special library ocaml_shadow adds a deprecation warning on all
modules from the compiler libraries, to force the user to use the
prefixed names.