vest_lib 0.2.2

Verified parser and serializer combinators in Verus
Documentation
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//! Correctness, termination, and ambiguity proofs for repetition.
use crate::combinators::length::AsLen;
use crate::combinators::Pair;
use crate::core::{proof::*, spec::*};
use vstd::{calc, prelude::*};

verus! {

impl<A> super::Star<A> where A: SPRoundTripDps + NonTailFmt {
    proof fn lemma_serialize_parse_roundtrip_rec(&self, vs: Seq<A::PVal>, obuf: Seq<u8>)
        requires
            self.0.serialize_dps_inv(),
            self.0.unambiguous(),
            parser_fails_on(self.0, obuf),
            self.consistent(vs),
        ensures
            self.spec_parse(self.spec_serialize_dps(vs, obuf)) == Some(
                ((self.spec_serialize_dps(vs, obuf).len() - obuf.len()) as int, vs),
            ),
        decreases vs.len(),
    {
        reveal(<super::Star::<_> as SpecParser>::spec_parse);
        reveal(<super::Star::<_> as SpecSerializerDps>::spec_serialize_dps);
        reveal(<super::Star::<_> as Consistency>::consistent);
        if vs.len() == 0 {
            assert(self.0.spec_parse(obuf) is None);
        } else {
            let v = vs[0];
            let rest = vs[1..];
            let rest_buf = self.spec_serialize_dps(rest, obuf);
            let serialized = self.spec_serialize_dps(vs, obuf);
            assert(serialized == self.0.spec_serialize_dps(v, rest_buf));

            // induction
            assert(self.consistent(rest));
            self.lemma_serialize_parse_roundtrip_rec(rest, obuf);

            // base
            assert(self.0.consistent(v));
            self.0.theorem_serialize_dps_parse_roundtrip(v, rest_buf);
            self.0.lemma_serialize_dps_prepend(v, rest_buf);
            self.0.lemma_serialize_dps_len(v, rest_buf);

            let n0 = (serialized.len() - rest_buf.len()) as int;
            assert(self.0.spec_parse(serialized) == Some((n0, v)));
            assert(serialized[n0..] == rest_buf);

            if 0 < n0 <= serialized.len() {
                assert(self.spec_parse(rest_buf) == Some(self.parse_rec(rest_buf)));
                let (n1, v1) = self.parse_rec(rest_buf);
                assert(self.spec_parse(serialized) == Some((n0 + n1, seq![v] + v1)));
            } else {
                assert(n0 == 0);
                assert(serialized == rest_buf);
                assert(self.0.spec_parse(rest_buf) == Some((0int, v)));

                // from the definition
                assert(self.parse_rec(rest_buf) == (0int, Seq::<A::PVal>::empty()));
                // from I.H.:
                assert(self.parse_rec(rest_buf) == (rest_buf.len() - obuf.len(), rest));
                self.lemma_serialize_dps_prepend(rest, obuf);

                // therefore:
                assert(rest_buf == obuf);
                assert(rest == Seq::<A::PVal>::empty());

                // contradiction
                assert(self.0.spec_parse(obuf) is Some);
                assert(self.0.spec_parse(obuf) is None);
            }
        }
    }
}

impl<A: NonMalleable + SafeParser> super::Star<A> {
    proof fn lemma_parse_non_malleable_rec(&self, buf1: Seq<u8>, buf2: Seq<u8>)
        requires
            self.nonmal_inv(),
        ensures
            ({
                let (n1, v1) = self.parse_rec(buf1);
                let (n2, v2) = self.parse_rec(buf2);
                v1 == v2 ==> buf1[0..n1] == buf2[0..n2]
            }),
        decreases buf1.len(),
    {
        reveal(<super::Star::<_> as SpecParser>::spec_parse);
        let (n1, v1) = self.parse_rec(buf1);
        let (n2, v2) = self.parse_rec(buf2);
        if v1 == v2 {
            match (self.0.spec_parse(buf1), self.0.spec_parse(buf2)) {
                (Some((m1, a1)), Some((m2, a2))) => {
                    if 0 < m1 <= buf1.len() && 0 < m2 <= buf2.len() {
                        let (n1_rest, rest1) = self.parse_rec(buf1[m1..]);
                        let (n2_rest, rest2) = self.parse_rec(buf2[m2..]);

                        assert(n1 == m1 + n1_rest);
                        assert(n2 == m2 + n2_rest);
                        assert(v1 == seq![a1] + rest1);
                        assert(v2 == seq![a2] + rest2);

                        assert(a1 == a2) by {
                            assert(a1 == v1[0] && a2 == v2[0]);
                        }
                        assert(rest1 == rest2) by {
                            assert(rest1 == v1[1..]);
                            assert(rest2 == v2[1..]);
                        }

                        // base
                        self.0.lemma_parse_non_malleable(buf1, buf2);
                        assert(buf1[0..m1] == buf2[0..m2]);

                        // induction
                        assert(self.safe_inv());
                        self.lemma_parse_non_malleable_rec(buf1[m1..], buf2[m2..]);
                        assert(buf1[m1..][0..n1_rest] == buf2[m2..][0..n2_rest]);

                        // need to show buf1[0..n1] == buf2[0..n2]
                        assert(self.safe_inv());
                        self.lemma_parse_safe(buf1[m1..]);
                        self.lemma_parse_safe(buf2[m2..]);
                        assert(buf1[0..n1] == buf1[0..m1] + buf1[m1..][0..n1_rest]);
                        assert(buf2[0..n2] == buf2[0..m2] + buf2[m2..][0..n2_rest]);
                    }
                },
                _ => {},
            }
        }
    }
}

impl<A: NonMalleable + SafeParser> NonMalleable for super::Star<A> {
    open spec fn nonmal_inv(&self) -> bool {
        &&& self.0.nonmal_inv()
        &&& self.0.safe_inv()
    }

    proof fn lemma_parse_non_malleable(&self, buf1: Seq<u8>, buf2: Seq<u8>) {
        reveal(<super::Star::<_> as SpecParser>::spec_parse);
        assert(self.nonmal_inv());
        assert(self.safe_inv());
        self.lemma_parse_non_malleable_rec(buf1, buf2);
    }
}

impl<A: SafeParser> Productive for super::Star<A> {
    open spec fn productive_inv(&self) -> bool {
        false
    }

    proof fn lemma_productive(&self, s: Seq<u8>) {
    }
}

impl<A: NoLookAhead> super::Star<A> {
    proof fn lemma_parse_rec_no_lookahead_conditional(&self, i1: Seq<u8>, i2: Seq<u8>)
        requires
            self.safe_inv(),
            self.0.no_lookahead_inv(),
            parser_fails_on(self.0, i2[self.parse_rec(i1).0..]),
        ensures
            ({
                let r = self.parse_rec(i1);
                0 <= r.0 <= i2.len() ==> i2[0..r.0] == i1[0..r.0] ==> self.parse_rec(i2) == r
            }),
        decreases i1.len(),
    {
        reveal(<super::Star::<_> as SpecParser>::spec_parse);
        use crate::combinators::tuple::proof::lemma_take_skip;
        broadcast use vstd::seq_lib::group_seq_properties;

        let (n, vs) = self.parse_rec(i1);
        match self.0.spec_parse(i1) {
            Some((m, v)) if 0 < m <= i1.len() => {
                let i1_rest = i1[m..];
                let i2_rest = i2[m..];
                let (n_rest, vs_rest) = self.parse_rec(i1_rest);
                assert(self.safe_inv());
                self.lemma_parse_safe(i1_rest);
                if 0 <= n <= i2.len() {
                    if i2[0..n] == i1[0..n] {
                        assert(i2[0..m] == i1[0..m]);
                        assert(self.0.safe_inv());
                        self.0.lemma_no_lookahead(i1, i2);
                        assert(i2_rest[0..n_rest] == i1_rest[0..n_rest]) by {
                            lemma_take_skip(i1, m, n_rest);
                            lemma_take_skip(i2, m, n_rest);
                        };
                        assert(parser_fails_on(self.0, i2_rest[n_rest..])) by {
                            broadcast use vstd::seq_lib::lemma_seq_skip_of_skip;

                        };
                        self.lemma_parse_rec_no_lookahead_conditional(i1_rest, i2_rest);
                        assert(self.parse_rec(i2) == (m + n_rest, seq![v] + vs_rest));
                    }
                }
            },
            _ => {},
        }
    }
}

impl<A> super::Star<A> where A: EquivSerializersGeneral {
    proof fn lemma_serialize_equiv_rec(&self, vs: Seq<A::SVal>, obuf: Seq<u8>)
        requires
            self.0.equiv_general_inv(),
        ensures
            self.rfold_serialize_dps(vs, obuf) == self.spec_serialize(vs) + obuf,
        decreases vs.len(),
    {
        reveal(<super::Star::<_> as SpecSerializer>::spec_serialize);
        let f = |buf: Seq<u8>, elem: A::SVal| buf + self.0.spec_serialize(elem);

        if vs.len() == 0 {
        } else {
            let v0 = vs[0];
            let rest = vs[1..];

            let rest_foldr = self.rfold_serialize_dps(rest, obuf);
            let rest_foldl = rest.fold_left(Seq::empty(), f);

            calc! {
                (==)
                self.rfold_serialize_dps(vs, obuf); {  // definition
                }
                self.0.spec_serialize_dps(v0, rest_foldr); {
                    // base
                    self.0.lemma_serialize_equiv(v0, rest_foldr);
                }
                self.0.spec_serialize(v0) + rest_foldr; {
                    // induction
                    self.lemma_serialize_equiv_rec(rest, obuf);
                }
                self.0.spec_serialize(v0) + (rest_foldl + obuf); {}
                (self.0.spec_serialize(v0) + rest_foldl) + obuf;
            }

            // need to show: fold_left(vs, empty, f) == inner.spec_serialize(v0) + rest_foldl

            calc! {
                (==)
                vs.fold_left(Seq::empty(), f); {
                    vs.lemma_fold_left_alt(Seq::empty(), f);
                }
                vs.fold_left_alt(Seq::empty(), f); {}
                rest.fold_left_alt(f(Seq::empty(), v0), f); {}
                rest.fold_left_alt(self.0.spec_serialize(v0), f); {
                    rest.lemma_fold_left_alt(self.0.spec_serialize(v0), f);
                }
                rest.fold_left(self.0.spec_serialize(v0), f); {
                    assert forall|acc: Seq<u8>, x: Seq<u8>, y: A::SVal| #[trigger]
                        f(acc + x, y) == acc + #[trigger] f(x, y) by {}
                    lemma_fold_left_accumulate_seq(rest, self.0.spec_serialize(v0), f);
                }
                self.0.spec_serialize(v0) + rest_foldl;
            }
        }
    }
}

pub(crate) proof fn lemma_fold_left_accumulate_seq<T, U>(
    vs: Seq<T>,
    init: Seq<U>,
    f: spec_fn(Seq<U>, T) -> Seq<U>,
)
    requires
        forall|acc: Seq<U>, x: Seq<U>, y: T| #[trigger] f(acc + x, y) == acc + #[trigger] f(x, y),
    ensures
        vs.fold_left(init, f) == init + vs.fold_left(Seq::<U>::empty(), f),
    decreases vs.len(),
{
    if vs.len() == 0 {
    } else {
        let last = vs.last();
        let prefix = vs.drop_last();
        lemma_fold_left_accumulate_seq(prefix, init, f);
    }
}

pub(crate) proof fn lemma_fold_left_accumulate_nat<T>(
    vs: Seq<T>,
    init: nat,
    f: spec_fn(nat, T) -> nat,
)
    requires
        forall|acc: nat, x: nat, y: T| #[trigger] f(acc + x, y) == acc + #[trigger] f(x, y),
    ensures
        vs.fold_left(init, f) == init + vs.fold_left(0, f),
    decreases vs.len(),
{
    if vs.len() == 0 {
    } else {
        let last = vs.last();
        let prefix = vs.drop_last();
        lemma_fold_left_accumulate_nat(prefix, init, f);
    }
}

impl<A> EquivSerializersGeneral for super::Star<A> where A: EquivSerializersGeneral {
    open spec fn equiv_general_inv(&self) -> bool {
        self.0.equiv_general_inv()
    }

    proof fn lemma_serialize_equiv(&self, v: Self::SVal, obuf: Seq<u8>) {
        reveal(<super::Star::<_> as SpecSerializerDps>::spec_serialize_dps);
        reveal(<super::Star::<_> as SpecSerializer>::spec_serialize);
        self.lemma_serialize_equiv_rec(v, obuf);
    }
}

impl<A> EquivSerializers for super::Star<A> where A: EquivSerializersGeneral {
    open spec fn equiv_inv(&self) -> bool {
        self.0.equiv_general_inv()
    }

    proof fn lemma_serialize_equiv_on_empty(&self, v: Self::SVal) {
        reveal(<super::Star::<_> as SpecSerializerDps>::spec_serialize_dps);
        reveal(<super::Star::<_> as SpecSerializer>::spec_serialize);
        assert(self.equiv_inv() == self.0.equiv_general_inv());
        self.lemma_serialize_equiv_rec(v, Seq::empty());
    }
}

impl<C, N> super::RepeatN<C, N> where C: SPRoundTripDps + NonTailFmt, N: AsLen {
    proof fn lemma_serialize_parse_roundtrip_rec(&self, vs: Seq<C::PVal>, count: nat, obuf: Seq<u8>)
        requires
            self.1.serialize_dps_inv(),
            self.1.unambiguous(),
            vs.len() == count,
            (super::Star(self.1).consistent(vs)),
        ensures
            self.parse_n_rec(count, self.spec_serialize_dps(vs, obuf)) == Some(
                ((self.spec_serialize_dps(vs, obuf).len() - obuf.len()) as int, vs),
            ),
        decreases count,
    {
        reveal(<super::Star::<_> as SpecSerializerDps>::spec_serialize_dps);
        reveal(<super::Star::<_> as Consistency>::consistent);
        if count == 0 {
        } else {
            let v0 = vs[0];
            let rest = vs[1..];
            let rest_buf = self.spec_serialize_dps(rest, obuf);
            let serialized = self.spec_serialize_dps(vs, obuf);

            self.lemma_serialize_parse_roundtrip_rec(rest, (count - 1) as nat, obuf);

            self.1.theorem_serialize_dps_parse_roundtrip(v0, rest_buf);
            self.1.lemma_serialize_dps_prepend(v0, rest_buf);
            self.1.lemma_serialize_dps_len(v0, rest_buf);

            let n0 = (serialized.len() - rest_buf.len()) as int;
            assert(serialized[n0..] == rest_buf);
        }
    }
}

impl<C, N> SPRoundTripDps for super::RepeatN<C, N> where C: SPRoundTripDps + NonTailFmt, N: AsLen {
    open spec fn unambiguous(&self) -> bool {
        &&& self.1.serialize_dps_inv()
        &&& self.1.unambiguous()
    }

    proof fn theorem_serialize_dps_parse_roundtrip(&self, v: Self::T, obuf: Seq<u8>) {
        self.lemma_serialize_parse_roundtrip_rec(v, self.0.as_nat(), obuf);
        self.lemma_serialize_dps_len(v, obuf);
    }
}

impl<C: NonMalleable, N: AsLen> super::RepeatN<C, N> {
    #[verusfmt::skip]
    proof fn lemma_parse_non_malleable_rec(&self, count: nat, buf1: Seq<u8>, buf2: Seq<u8>)
        requires
            self.1.nonmal_inv(),
            self.1.safe_inv(),
        ensures
            self.parse_n_rec(count, buf1) matches Some((n1, v1)) ==>
            self.parse_n_rec(count, buf2) matches Some((n2, v2)) ==>
            v1 == v2 ==> buf1[0..n1] == buf2[0..n2],
        decreases count,
    {
        broadcast use vstd::seq_lib::group_seq_properties;

        if count == 0 {
        } else {
            if let Some((n1, v1)) = self.parse_n_rec(count, buf1) {
                if let Some((n2, v2)) = self.parse_n_rec(count, buf2) {
                    if v1 == v2 {
                        let (m1, a1) = self.1.spec_parse(buf1)->0;
                        let (m2, a2) = self.1.spec_parse(buf2)->0;
                        let (r1, rest1) = self.parse_n_rec((count - 1) as nat, buf1[m1..])->0;
                        let (r2, rest2) = self.parse_n_rec((count - 1) as nat, buf2[m2..])->0;
                        assert(v1 == seq![a1] + rest1);
                        assert(v2 == seq![a2] + rest2);
                        assert(a1 == a2) by {
                            assert(a1 == v1[0]);
                            assert(a2 == v2[0]);
                        }
                        assert(rest1 == rest2) by {
                            assert(rest1 == v1[1..]);
                            assert(rest2 == v2[1..]);
                        }

                        self.1.lemma_parse_safe(buf1);
                        self.1.lemma_parse_safe(buf2);
                        self.lemma_parse_n_len_bound((count - 1) as nat, buf1[m1..]);
                        self.lemma_parse_n_len_bound((count - 1) as nat, buf2[m2..]);
                        self.1.lemma_parse_non_malleable(buf1, buf2);
                        assert(buf1[0..m1] == buf2[0..m2]);

                        self.lemma_parse_non_malleable_rec((count - 1) as nat, buf1[m1..], buf2[m2..]);
                        assert(buf1[m1..][0..r1] == buf2[m2..][0..r2]);

                        assert(n1 == m1 + r1);
                        assert(n2 == m2 + r2);
                        assert(buf1[0..n1] == buf1[0..m1] + buf1[m1..][0..r1]);
                        assert(buf2[0..n2] == buf2[0..m2] + buf2[m2..][0..r2]);
                    }
                }
            }
        }
    }
}

impl<C: NonMalleable + SafeParser, N: AsLen> NonMalleable for super::RepeatN<C, N> {
    open spec fn nonmal_inv(&self) -> bool {
        &&& self.1.nonmal_inv()
        &&& self.1.safe_inv()
    }

    proof fn lemma_parse_non_malleable(&self, buf1: Seq<u8>, buf2: Seq<u8>) {
        assert(self.nonmal_inv());
        self.lemma_parse_non_malleable_rec(self.0.as_nat(), buf1, buf2);
    }
}

impl<C: NoLookAhead, N: AsLen> super::RepeatN<C, N> {
    proof fn lemma_no_lookahead_rec(&self, count: nat, i1: Seq<u8>, i2: Seq<u8>)
        requires
            self.1.safe_inv(),
            self.1.no_lookahead_inv(),
        ensures
            self.parse_n_rec(count, i1) matches Some((n, v)) ==> 0 <= n <= i2.len() ==> i2[0..n]
                == i1[0..n] ==> self.parse_n_rec(count, i2) == Some((n, v)),
        decreases count,
    {
        use crate::combinators::tuple::proof::lemma_take_skip;
        broadcast use vstd::seq_lib::group_seq_properties;

        if count == 0 {
        } else {
            if let Some((n, v)) = self.parse_n_rec(count, i1) {
                if 0 <= n <= i2.len() {
                    if i2[0..n] == i1[0..n] {
                        let (m, a) = self.1.spec_parse(i1)->0;
                        let (r, rest) = self.parse_n_rec((count - 1) as nat, i1[m..])->0;
                        assert(v == seq![a] + rest);
                        assert(n == m + r);
                        self.1.lemma_parse_safe(i1);
                        self.lemma_parse_n_len_bound((count - 1) as nat, i1[m..]);
                        assert(0 <= m <= n);
                        assert(i2[0..m] == i1[0..m]);
                        self.1.lemma_no_lookahead(i1, i2);
                        assert(i2[m..][0..r] == i1[m..][0..r]) by {
                            lemma_take_skip(i1, m, r);
                            lemma_take_skip(i2, m, r);
                        };
                        self.lemma_no_lookahead_rec((count - 1) as nat, i1[m..], i2[m..]);
                    }
                }
            }
        }
    }
}

impl<C: NoLookAhead, N: AsLen> NoLookAhead for super::RepeatN<C, N> {
    open spec fn no_lookahead_inv(&self) -> bool {
        self.1.no_lookahead_inv()
    }

    proof fn lemma_no_lookahead(&self, i1: Seq<u8>, i2: Seq<u8>) {
        self.lemma_no_lookahead_rec(self.0.as_nat(), i1, i2);
    }
}

impl<A: SpecParser> super::Star<A> {
    proof fn lemma_parse_rec_nonnegative(&self, ibuf: Seq<u8>)
        ensures
            0 <= self.parse_rec(ibuf).0,
        decreases ibuf.len(),
    {
        if let Some((n, _v)) = self.0.spec_parse(ibuf) {
            if 0 < n <= ibuf.len() {
                self.lemma_parse_rec_nonnegative(ibuf[n..]);
            }
        }
    }
}

impl<C: Productive, N: AsLen> super::RepeatN<C, N> {
    proof fn lemma_parse_n_positive(&self, count: nat, ibuf: Seq<u8>)
        requires
            self.1.productive_inv(),
            self.1.safe_inv(),
            count > 0,
        ensures
            self.parse_n_rec(count, ibuf) matches Some((n, _)) ==> n > 0,
        decreases count,
    {
        if let Some((n0, _v0)) = self.1.spec_parse(ibuf) {
            self.1.lemma_productive(ibuf);
            if let Some((n1, _rest)) = self.parse_n_rec((count - 1) as nat, ibuf[n0..]) {
                if count - 1 > 0 {
                    self.lemma_parse_n_positive((count - 1) as nat, ibuf[n0..]);
                    assert(n1 > 0);
                } else {
                    assert(n1 == 0);
                }
                assert(n0 > 0);
                assert(n0 + n1 > 0);
            }
        }
    }
}

impl<C: Productive, N: AsLen> Productive for super::RepeatN<C, N> {
    open spec fn productive_inv(&self) -> bool {
        &&& self.0.as_nat() > 0
        &&& self.1.productive_inv()
    }

    proof fn lemma_productive(&self, s: Seq<u8>) {
        if let Some((n, _v)) = self.spec_parse(s) {
            self.lemma_parse_n_positive(self.0.as_nat(), s);
            assert(n > 0);
        }
    }
}

impl<C: EquivSerializersGeneral, N: AsLen> EquivSerializersGeneral for super::RepeatN<C, N> {
    open spec fn equiv_general_inv(&self) -> bool {
        self.1.equiv_general_inv()
    }

    proof fn lemma_serialize_equiv(&self, v: Self::SVal, obuf: Seq<u8>) {
        reveal(<super::Star::<_> as SpecSerializerDps>::spec_serialize_dps);
        reveal(<super::Star::<_> as SpecSerializer>::spec_serialize);
        super::Star(self.1).lemma_serialize_equiv(v, obuf);
    }
}

impl<C: EquivSerializersGeneral, N: AsLen> EquivSerializers for super::RepeatN<C, N> {
    open spec fn equiv_inv(&self) -> bool {
        self.1.equiv_general_inv()
    }

    proof fn lemma_serialize_equiv_on_empty(&self, v: Self::SVal) {
        reveal(<super::Star::<_> as SpecSerializerDps>::spec_serialize_dps);
        reveal(<super::Star::<_> as SpecSerializer>::spec_serialize);
        super::Star(self.1).lemma_serialize_equiv_on_empty(v);
    }
}

impl<const N: usize, C> SPRoundTripDps for super::Array<N, C> where C: SPRoundTripDps + NonTailFmt {
    open spec fn unambiguous(&self) -> bool {
        super::RepeatN(N, self.0).unambiguous()
    }

    proof fn theorem_serialize_dps_parse_roundtrip(&self, v: Self::T, obuf: Seq<u8>) {
        super::RepeatN(N, self.0).theorem_serialize_dps_parse_roundtrip(v, obuf);
    }
}

impl<const N: usize, C: NonMalleable> NonMalleable for super::Array<N, C> {
    open spec fn nonmal_inv(&self) -> bool {
        super::RepeatN(N, self.0).nonmal_inv()
    }

    proof fn lemma_parse_non_malleable(&self, buf1: Seq<u8>, buf2: Seq<u8>) {
        super::RepeatN(N, self.0).lemma_parse_non_malleable(buf1, buf2);
    }
}

impl<const N: usize, C: NoLookAhead> NoLookAhead for super::Array<N, C> {
    open spec fn no_lookahead_inv(&self) -> bool {
        self.0.no_lookahead_inv()
    }

    proof fn lemma_no_lookahead(&self, i1: Seq<u8>, i2: Seq<u8>) {
        super::RepeatN(N, self.0).lemma_no_lookahead(i1, i2);
    }
}

impl<const N: usize, C: Productive> Productive for super::Array<N, C> {
    open spec fn productive_inv(&self) -> bool {
        super::RepeatN(N, self.0).productive_inv()
    }

    proof fn lemma_productive(&self, s: Seq<u8>) {
        super::RepeatN(N, self.0).lemma_productive(s);
    }
}

impl<const N: usize, C: EquivSerializersGeneral> EquivSerializersGeneral for super::Array<N, C> {
    open spec fn equiv_general_inv(&self) -> bool {
        self.0.equiv_general_inv()
    }

    proof fn lemma_serialize_equiv(&self, v: Self::SVal, obuf: Seq<u8>) {
        super::RepeatN(N, self.0).lemma_serialize_equiv(v, obuf);
    }
}

impl<const N: usize, C: EquivSerializersGeneral> EquivSerializers for super::Array<N, C> {
    open spec fn equiv_inv(&self) -> bool {
        self.0.equiv_general_inv()
    }

    proof fn lemma_serialize_equiv_on_empty(&self, v: Self::SVal) {
        super::RepeatN(N, self.0).lemma_serialize_equiv_on_empty(v);
    }
}

impl<A: SPRoundTripDps + NonTailFmt, B: SPRoundTripDps> SPRoundTripDps for super::Repeat<A, B> {
    open spec fn unambiguous(&self) -> bool {
        &&& self.0.serialize_dps_inv()
        &&& self.0.unambiguous()
        &&& self.1.unambiguous()
        &&& disjoint_domains(self.0, self.1)
    }

    proof fn theorem_serialize_dps_parse_roundtrip(&self, v: Self::T, obuf: Seq<u8>) {
        assert(self.unambiguous());
        reveal(<super::Star::<_> as SpecSerializerDps>::spec_serialize_dps);
        let star = super::Star(self.0);
        let serialized1 = self.1.spec_serialize_dps(v.1, obuf);
        self.1.theorem_serialize_dps_parse_roundtrip(v.1, obuf);
        assert(parser_fails_on(self.0, serialized1)) by {
            reveal(disjoint_domains);
            assert(self.1.spec_parse(serialized1) is Some);
        }
        let serialized0 = star.spec_serialize_dps(v.0, serialized1);
        star.lemma_serialize_parse_roundtrip_rec(v.0, serialized1);
        let n0 = serialized0.len() - serialized1.len();
        star.lemma_serialize_dps_prepend(v.0, serialized1);
        star.lemma_serialize_dps_len(v.0, serialized1);
        assert(serialized0[n0..] == serialized1);
    }
}

// impl<
//     A: PSRoundTrip + GoodSerializerDps + EquivSerializersGeneral,
//     B: PSRoundTrip,
// > PSRoundTrip for super::Repeat<A, B> {
// }
impl<A: NonMalleable, B: NonMalleable> NonMalleable for super::Repeat<A, B> {
    open spec fn nonmal_inv(&self) -> bool {
        Pair(super::Star(self.0), self.1).nonmal_inv()
    }

    proof fn lemma_parse_non_malleable(&self, buf1: Seq<u8>, buf2: Seq<u8>) {
        Pair(super::Star(self.0), self.1).lemma_parse_non_malleable(buf1, buf2);
    }
}

impl<A: NoLookAhead, B: NoLookAhead> NoLookAhead for super::Repeat<A, B> {
    open spec fn no_lookahead_inv(&self) -> bool {
        &&& self.0.no_lookahead_inv()
        &&& self.1.no_lookahead_inv()
        &&& disjoint_domains(self.0, self.1)
    }

    proof fn lemma_no_lookahead(&self, i1: Seq<u8>, i2: Seq<u8>) {
        reveal(disjoint_domains);
        reveal(<super::Star::<_> as SpecParser>::spec_parse);
        use crate::combinators::tuple::proof::lemma_take_skip;
        broadcast use vstd::seq_lib::group_seq_properties;

        let star = super::Star(self.0);
        self.lemma_parse_safe(i1);
        if let Some((n, v)) = self.spec_parse(i1) {
            if 0 <= n <= i2.len() {
                if i2[0..n] == i1[0..n] {
                    if let Some((n0, v0)) = star.spec_parse(i1) {
                        if let Some((n1, v1)) = self.1.spec_parse(i1[n0..]) {
                            star.lemma_parse_safe(i1);
                            self.1.lemma_parse_safe(i1[n0..]);
                            assert(i2[0..n0] == i1[0..n0]);
                            assert(i2[n0..][0..n1] == i1[n0..][0..n1]) by {
                                lemma_take_skip(i1, n0, n1);
                                lemma_take_skip(i2, n0, n1);
                            };
                            self.1.lemma_no_lookahead(i1[n0..], i2[n0..]);
                            assert(disjoint_domains(self.0, self.1));
                            star.lemma_parse_rec_no_lookahead_conditional(i1, i2);
                        }
                    }
                }
            }
        }
    }
}

impl<A: SafeParser, B: Productive> Productive for super::Repeat<A, B> {
    open spec fn productive_inv(&self) -> bool {
        self.1.productive_inv()
    }

    proof fn lemma_productive(&self, s: Seq<u8>) {
        reveal(<super::Star::<_> as SpecParser>::spec_parse);
        let star = super::Star(self.0);
        if let Some((n, _v)) = self.spec_parse(s) {
            let (n0, _vs) = star.spec_parse(s)->0;
            let (n1, _b) = self.1.spec_parse(s[n0..])->0;
            star.lemma_parse_rec_nonnegative(s);
            self.1.lemma_productive(s[n0..]);
            assert(n1 > 0);
            assert(n == n0 + n1);
            assert(n > 0);
        }
    }
}

impl<
    A: EquivSerializersGeneral,
    B: EquivSerializersGeneral,
> EquivSerializersGeneral for super::Repeat<A, B> {
    open spec fn equiv_general_inv(&self) -> bool {
        &&& self.0.equiv_general_inv()
        &&& self.1.equiv_general_inv()
    }

    proof fn lemma_serialize_equiv(&self, v: Self::SVal, obuf: Seq<u8>) {
        Pair(super::Star(self.0), self.1).lemma_serialize_equiv(v, obuf);
    }
}

impl<A: EquivSerializersGeneral, B: EquivSerializers> EquivSerializers for super::Repeat<A, B> {
    open spec fn equiv_inv(&self) -> bool {
        &&& self.0.equiv_general_inv()
        &&& self.1.equiv_inv()
    }

    proof fn lemma_serialize_equiv_on_empty(&self, v: Self::SVal) {
        assert(self.equiv_inv());
        Pair(super::Star(self.0), self.1).lemma_serialize_equiv_on_empty(v);
    }
}

} // verus!