* Hide `trait MaxEncodedLen` behind the new `max-encoded-len` feature

* Bump versions to 2.2.0

* Shuffle some cfg feature directives

* ci: Test also using the new feature flag

* Support custom trait bounds on MaxEncodedLen derive macro

* Bump version to 2.2.0-rc.3

* Reorder error messaging

* Improve `#[codec(crate = path)]` attribute: path, not string literal

Accepting a path instead of a string literal makes life easier for
the downstream macros which need to actually use that attribute.

* actually test the pass test

Cargo will automatically strip dev-dependency for us, which removes the
need for manually doing so before publishing the crates.

See https://github.com/rust-lang/cargo/pull/7333

* Mention new #[codec(crate = ...)] attribute for MaxEncodedLen derive

* Update CHANGELOG.md

Co-authored-by: Peter Goodspeed-Niklaus <coriolinus@users.noreply.github.com>

* Update CHANGELOG.md

Co-authored-by: Bastian Köcher <bkchr@users.noreply.github.com>

Co-authored-by: Peter Goodspeed-Niklaus <coriolinus@users.noreply.github.com>
Co-authored-by: Bastian Köcher <bkchr@users.noreply.github.com>

* move MaxEncodedLen trait from Substrate

* Move derive macro and tests from Substrate

* only run ui tests when derive feature enabled

* reduce note-taking documentation

Co-authored-by: Bastian Köcher <bkchr@users.noreply.github.com>

* Bless trybuild `tests/max_encoded_len_ui/union.rs` test

* Update docs (these files are not part of substrate)

Co-authored-by: Andronik Ordian <write@reusable.software>

* Mention new `MaxEncodedLen` trait in the CHANGELOG.md

* Prepare a 2.2.0-rc.1 release

This is a pre-release rather than a full release in order to help shape
the new `MaxEncodedLen` trait used in Substrate in case some more
involved changes are found out to be required.
The API did not change since its introduction until now so chances are
slim but it's good to leave some leeway.

* incorporate changes made to Substrate version of MaxEncodedLen

Note: doesn't include the MaxEncodedLen impl for H160, H256, H512.
A substrate companion will be necessary to re-add those.

* remove redundant no_std

* Rewrite fn max_encoded_len_trait for clarity

* simplify logic checking for invalid attr

Co-authored-by: Bastian Köcher <bkchr@users.noreply.github.com>

* remove bogus whitespace

Co-authored-by: Bastian Köcher <bkchr@users.noreply.github.com>

* use Path::is_ident() helper

Co-authored-by: Bastian Köcher <bkchr@users.noreply.github.com>

* rm unused import

Co-authored-by: Bastian Köcher <bkchr@users.noreply.github.com>
Co-authored-by: Igor Matuszewski <Xanewok@gmail.com>
Co-authored-by: Andronik Ordian <write@reusable.software>

* Bump proc-macro-crate to v1.0.0

Signed-off-by: koushiro <koushiro.cqx@gmail.com>

* Bump honggfuzz and arbitrary

Signed-off-by: koushiro <koushiro.cqx@gmail.com>

* Bump quickcheck to v1.0

Signed-off-by: koushiro <koushiro.cqx@gmail.com>

* Impl Decode/Encode for Range/RangeInclusive

* Typo

* Adds support for custom where bounds

The user can now specify a custom where bound when using the derive
macros:

- `#[codec(encode_bound(T: Encode))]` for `Encode`
- `#[codec(decode_bound(T: Encode))]` for `Decode`

If nothing is specified (`encode_bound()`) the where bounds will be empty.

* Apply suggestions from code review

* Apply suggestions from code review

Co-authored-by: Gavin Wood <gavin@parity.io>

* Switch array impls to const generics

* addr comments

Co-authored-by: Bastian Köcher <bkchr@users.noreply.github.com>

Co-authored-by: David <dvdplm@gmail.com>

Co-authored-by: Guillaume Thiolliere <gui.thiolliere@gmail.com>
Co-authored-by: Bastian Köcher <bkchr@users.noreply.github.com>

Co-authored-by: Andronik Ordian <write@reusable.software>
Co-authored-by: Bastian Köcher <bkchr@users.noreply.github.com>

Co-authored-by: Bastian Köcher <bkchr@users.noreply.github.com>
Co-authored-by: David <dvdplm@gmail.com>

* CI: add miri test; new phase; remoe CARGO_HOME cache

* add miri and falgs to test

* Update .gitlab-ci.yml

Co-authored-by: Guillaume Thiolliere <gui.thiolliere@gmail.com>

Co-authored-by: Cheme
Co-authored-by: Brian Anderson <andersrb@gmail.com>
Co-authored-by: Bastian Köcher <bkchr@users.noreply.github.com>
Co-authored-by: David <dvdplm@gmail.com>

* change (CI): cache pre-population script; use of cargo home and cargo target caches; rules instead only

* fix (CI): wrong pasta

* fix (CI): persimmons to the pre_pop script

This makes it easier to write code that uses `Error` with or without `std`.