Forbid function redefinitions in an OCaml module

[leostera]

This OCaml source code:

let f 0 = true
let f _ = false

should result in a compilation error explaining that module functions can only be defined once, and multi-clause functions are achievable by the use of the function | pattern_1 -> expr_1 | pattern_2 -> expr_2 syntax.

This currently yields a function redefinition:

f(0) -> true.
f(_) -> false.

Which is not valid Erlang.

All of the modules are available as we translate them (see OCaml_to_erlang.Fun.mk_functions) but unfortunately we do not do this with every function.

Instead we are mapping over them so they are unaware of each other.

Changing this to a fold would allow us to carry around the list of functions that have already been defined, and we could check that any is being defined twice.