Macro p 

macro_rules! p {
    (#parse_base(
        $action:ident($($action_args:tt)*),
        input(
            // A deref of a potentially-complex place expression.
            (*$($place:tt)*)
            $($rest:tt)*
        )
    )) => { ... };
    (#parse_base(
        $action:ident($($action_args:tt)*),
        input(
            // A deref of a local, with no projections.
            *$local:ident
        )
    )) => { ... };
    (#parse_base(
        $action:ident($($action_args:tt)*),
        input(
            // A postfix deref
            $local:ident.*
            $($rest:tt)*
        )
    )) => { ... };
    (#parse_base(
        $action:ident($($action_args:tt)*),
        input(
            // Not a deref so we remove the parens (to support `(x.a).b`).
            ($($place:tt)*)
            $($rest:tt)*
        )
    )) => { ... };
    (#parse_proj(
        $action:ident($($action_args:tt)*),
        $start:ident($($start_args:tt)*),
        project($($fields:tt)*),
        input(
            . * // postfix deref
            $($input:tt)*
        )
    )) => { ... };
    (#parse_proj(
        $action:ident($($action_args:tt)*),
        $start:ident($($start_args:tt)*),
        project($($fields:tt)*),
        input(
            .$field:ident
            $($rest:tt)*
        )
    )) => { ... };
    (#parse_proj(
        $action:ident($($action_args:tt)*),
        $start:ident($($start_args:tt)*),
        project($($fields:tt)*),
        input(
            $(= $rvalue:expr)?
        )
    )) => { ... };
    (#parse_assign(
        read_or_write(),
        $start:ident($($start_args:tt)*),
        project($($proj_args:tt)*),
        input(
            = $rvalue:expr
        )
    )) => { ... };
    (#parse_assign(
        read_or_write(),
        $start:ident($($start_args:tt)*),
        project($($proj_args:tt)*),
        input()
    )) => { ... };
    (#parse_assign(
        $action:ident($($action_args:tt)*),
        $start:ident($($start_args:tt)*),
        project($($proj_args:tt)*),
        input()
    )) => { ... };
    (#compose_projs()) => { ... };
    (#compose_projs(.$field:ident $($rest:tt)*)) => { ... };
    (#build_start(deref($ptr:ident))) => { ... };
    (#build_start(deref($($place:tt)*))) => { ... };
    (#build(
        $action:ident($($action_args:tt)*),
        ptr($ptr:expr),
        project($($proj_args:tt)*),
    )) => { ... };
    (#do_action(
        read(),
        base($ptr:expr),
        project($proj:expr),
    )) => { ... };
    (#do_action(
        deref(),
        base($ptr:expr),
        project($proj:expr),
    )) => { ... };
    (#do_action(
        write($rvalue:expr),
        base($ptr:expr),
        project($proj:expr),
    )) => { ... };
    (#do_action(
        borrow($($ptr_ty:tt)*),
        base($ptr:expr),
        project($proj:expr),
    )) => { ... };
    (#$($rest:tt)*) => { ... };
    (@_ $($place:tt)*) => { ... };
    (@$ptr:ident<$($ty:ty),*> $($place:tt)*) => { ... };
    (@$ptr:ident $($place:tt)*) => { ... };
    ($($place:tt)*) => { ... };
}

Macro that simulates the proposed new syntax. Derefs must be explicit and the identifiers used for field projections must actually be values of some Projection type, e.g. built with mk_field_proj.

Examples:

(*p).a
-> a.read(&raw const p)
(*p).a.b
-> a.compose(b).read(&raw const p)
(**p).a
-> a.read(NoopProj::default().deref(&raw const p))
(*(*p).ptr_a).b
-> b.read(ptr_a.deref(&raw const p))
(*p).a = foo()
-> a.write(&raw const p, foo())
@R *p
-> NoopProj::default().borrow::<_, R<_>>(&raw const p)
@R (*p).a
-> a.borrow::<_, R<_>>(&raw const p)
@R (**p).a
-> a.borrow::<_, R<_>>(NoopProj::default().deref(&raw const p))