Update syn quote

[Robbepop]

This PR updates dependencies syn from 0.11.x to 0.15.x and quote from 0.3.x to 0.6.x.

Improvements to the documentation have been made. Also restructured and simplified some code.

[Robbepop]

Note that Travis CI fails because of some unstable features used in stable context. I currently do not know why this happens.

[pepyakin]

Before continuing work on that I would really love to see CI working again.

[Robbepop]

Before continuing work on that I would really love to see CI working again.

Master doesn't work either as far as I have tested. But it should be when adding +nightly to cargo command. I will test that.

[debris]

I see that there are no unit tests for generated token stream. As debugging syn && quote is extremely painful I suggest adding some tests for generated token streams 😉

e.g. we have something like this in ethabi

https://github.com/paritytech/ethabi/blob/523cb5bcb41607737e52da051d46e223cc54b212/derive/src/event.rs#L322-L344

    #[test]
    fn test_log_with_one_field() {
        let ethabi_event = ethabi::Event {
            name: "one".into(),
            inputs: vec![ethabi::EventParam {
                name: "foo".into(),
                kind: ethabi::ParamType::Address,
                indexed: false
            }],
            anonymous: false,
        };

        let e = Event::from(&ethabi_event);

        let expected = quote! {
            #[derive(Debug, Clone, PartialEq)]
            pub struct One {
                pub foo: ethabi::Address
            }
        };

        assert_eq!(expected.to_string(), e.generate_log().to_string());
    }

[Robbepop]

I see that there are no unit tests for generated token stream. As debugging syn && quote is extremely painful I suggest adding some tests for generated token streams wink

e.g. we have something like this in ethabi

https://github.com/paritytech/ethabi/blob/523cb5bcb41607737e52da051d46e223cc54b212/derive/src/event.rs#L322-L344

  #[test]
  fn test_log_with_one_field() {
      let ethabi_event = ethabi::Event {
          name: "one".into(),
          inputs: vec![ethabi::EventParam {
              name: "foo".into(),
              kind: ethabi::ParamType::Address,
              indexed: false
          }],
          anonymous: false,
      };

      let e = Event::from(&ethabi_event);

      let expected = quote! {
          #[derive(Debug, Clone, PartialEq)]
          pub struct One {
              pub foo: ethabi::Address
          }
      };

      assert_eq!(expected.to_string(), e.generate_log().to_string());
  }

Thank you very much for hinting that to me! I actually didn't know about this testing functionality but it sounds awesome.

Maybe we should implement the tests in another PR as this is already too big.

[Robbepop]

@fckt I hope I resolved the formatting issues to your satisfaction in the most recent commits.

Besides that I have added some proper documentation for the items defined in items.rs as well. I hope we can merge this asap so that this PR doesn't get even bigger.

[Robbepop]

Thank you all for the reviews and feedback! :)

[Robbepop]

@NikVolf I think we can also delete the syn-upgrade branch.