[PV] Ambiguous field access

[jschneider-bensch]

If we have the following Rust items, the PV backend will generate ambiguous accessors for them

struct Foo(Vec<u8>);
struct Bar(Vec<u8>);

fn qux(a: Foo, b: Bar) -> bool{
    a.0 == b.0
}

The generated PV shows that the backend generates the same destructor accessor_mwe__0 for both types, which is not supported by ProVerif.

type mwe__t_Foo.

[...]
fun mwe__Foo(bitstring)
    : mwe__t_Foo [data].
reduc forall mwe__0: bitstring;
    accessor_mwe__0(mwe__Foo(mwe__0)) = mwe__0.

type mwe__t_Bar.

[...]
fun mwe__Bar(bitstring)
    : mwe__t_Bar [data].
reduc forall mwe__0: bitstring;
    accessor_mwe__0(mwe__Bar(mwe__0)) = mwe__0.


letfun mwe__qux(a : mwe__t_Foo, b : mwe__t_Bar) =
       core__cmp__f_eq(accessor_mwe__0(a), accessor_mwe__0(b)).