rc.4 crypto-bigint compat regression: `NonZero` missing for `invert_mod`

[pinkforest]

Just checked from rustls-rustcrypto downstream trying to use rc.4:

$ cargo tree -i -p crypto-bigint@0.7.0-rc.1

crypto-bigint v0.7.0-rc.1
├── crypto-primes v0.7.0-pre.1
│   └── rsa v0.10.0-rc.4
│       └── rustls-rustcrypto v0.0.2-alpha (/home/foobar/code2/fork/rustls-rustcrypto)
└── rsa v0.10.0-rc.4 (*)

error[E0308]: mismatched types
   --> /home/foobar/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/rsa-0.10.0-rc.4/src/algorithms/rsa.rs:351:26
    |
351 |     match exp.invert_mod(&totient).into_option() {
    |               ---------- ^^^^^^^^ expected `&NonZero<BoxedUint>`, found `&BoxedUint`
    |               |
    |               arguments to this method are incorrect
    |
    = note: expected reference `&crypto_bigint::NonZero<BoxedUint>`
               found reference `&BoxedUint`
note: method defined here
   --> /home/foobar/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/crypto-bigint-0.7.0-rc.1/src/uint/boxed/invert_mod.rs:138:12
    |
138 |     pub fn invert_mod(&self, modulus: &NonZero<Self>) -> CtOption<Self> {
    |            ^^^^^^^^^^

error[E0308]: mismatched types
   --> /home/foobar/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/rsa-0.10.0-rc.4/src/algorithms/rsa.rs:379:37
    |
379 |     if let Some(d) = exp.invert_mod(&lcm).into() {
    |                          ---------- ^^^^ expected `&NonZero<BoxedUint>`, found `&BoxedUint`
    |                          |
    |                          arguments to this method are incorrect
    |
    = note: expected reference `&crypto_bigint::NonZero<BoxedUint>`
               found reference `&BoxedUint`
note: method defined here
   --> /home/foobar/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/crypto-bigint-0.7.0-rc.1/src/uint/boxed/invert_mod.rs:138:12
    |
138 |     pub fn invert_mod(&self, modulus: &NonZero<Self>) -> CtOption<Self> {
    |            ^^^^^^^^^^

   Compiling ed25519-dalek v2.1.1
error[E0308]: mismatched types
   --> /home/foobar/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/rsa-0.10.0-rc.4/src/key.rs:507:35
    |
507 |         Option::from(q.invert_mod(p))
    |                        ---------- ^ expected `&NonZero<BoxedUint>`, found `&BoxedUint`
    |                        |
    |                        arguments to this method are incorrect
    |
    = note: expected reference `&crypto_bigint::NonZero<BoxedUint>`
               found reference `&BoxedUint`
note: method defined here
   --> /home/foobar/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/crypto-bigint-0.7.0-rc.1/src/uint/boxed/invert_mod.rs:138:12
    |
138 |     pub fn invert_mod(&self, modulus: &NonZero<Self>) -> CtOption<Self> {
    |            ^^^^^^^^^^

[tarcieri]

I think that was all fixed in #558, but needs another release

[tarcieri]

I should also cut another release of crypto-bigint first, there were some additional changes we needed in elliptic-curve that came out of this

[tarcieri]

Fixed in v0.10.0-rc.5