* 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>

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>

Normally, the span of a field has the same hygiene context as
`Span::call_site`. However, it's possible for a struct definition
to be 'constructed' via a `macro_rules` macro such that the field
has a different hygiene context. This will cause the expanded code
to be unable to resolve any references to `self`, resulting in a
compilation error.

This pull request uses `quote!` instead of `quote_spanned!` when
emitting a 'self' identifier. `quote_spanned!` is still used for
everything else in the emitted method, meaning that error messages
will still point to the proper field.

I've included a test case which triggers this issue on
Rust 1.43.1. It's current difficult to hit this issue
other than in this artificial case, but that will change
once rust-lang/rust#72622 is re-landed.

* add check for attribute and modify index attribute

* fmt

* improve doc

* improve doc

* add custom error message

* impl return error for decode_from in CompactAs trait

* update readme

* update doc test and readme

* add doc

Co-Authored-By: Bastian Köcher <bkchr@users.noreply.github.com>

* Increase version to `1.1` and release

* Use correct version format

* Fixes build and require explicit versions

* Update dependencies

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

* Update

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

* Revert some deps; Fix some warnings

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

* Improve utils of derive

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

* Bump bitvec to 0.15

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

* Improve utils of derive

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

* Implement `dumb_trait_bound` attribute

* Document derive attributes

* Update README

* few more type

* update versions

* Add `EncodeLike`

* Some stuff

* Make it work

* Review feedback

* Add example

* Update README

* Add bound

* impl bound to input_len

* typo

* fix + doc

* fix

* hide alloc

* address issues

* derive full single optimisation

* refactor

* fix io reader

* Revert "Implement min_encoded_len and required_len (#119)"

This reverts commit 2b66d2ce.

* Basic CompactAs derive

* Support single field named structs

* Extract function to wrap impl in dummy const

* Support single non-skipped field

* Restore original include_parity_scale_codec_crate function

* Add test for Compact<T> codec

* Rename to `parity-scale-codec` and revert version to 1.0

* Fix compilation after renaming

* Fix benchmarks

* Update src/lib.rs

Co-Authored-By: thiolliere <gui.thiolliere@gmail.com>

* Remove last parity-codec leftovers

We can not just use `usize`, because `quote!` converts `let i: usize =
0;` to `0usize` and this is not accepted as field accessor.

* release parity-codec v3.2

* impl skip fields and variants (#58)

* impl skip variants

* impl skip on fields

* reorganize code

* in code rename

Co-Authored-By: thiolliere <gui.thiolliere@gmail.com>

* in code rename

* code refactor

* refactor: variant filter

* new version of derive (#61)

* release codec-v3.3 that forward derive-v3.2 (#63)

* Implement derive for empty enums

* Bump version of parity-codec-derive to 3.3

* Fixes test

* impl skip fields and variants (#58)

* impl skip variants

* impl skip on fields

* reorganize code

* in code rename

Co-Authored-By: thiolliere <gui.thiolliere@gmail.com>

* in code rename

* code refactor

* refactor: variant filter

* impl skip variant and fields

* forward encoding for single field struct
* code refactor

* decode returns Result instead of Option

Fixes #33

* don't use String inside Error

* some fixes to formatting and error messages

* fix review

* implements std::error::Error and std::fmt::Display for Error
* removes implementation of ToString
* fixes error message for decoding Enum
* generate error messages with format!() outside of the quote!()

* refactors error message generation

* adds simple sanity tests

* adds from str implementation for error

* adds tests for named structs fields

* remove all the literal error messages from no_std builds

* brings back PartialEq lost along the way

* fix review v3

* Work around a compiler bug that does not like self recursive where
clauses

* Some code refactor

* Adds missing new lines

Bastian Köcher authored Feb 12, 2019 and thiolliere committed Feb 12, 2019

* Make use of `proc-macro-crate`

* use syntax of rust 2018

* Fixes test

* Refactors panics to compile errors