Workaround IoVec upstream issue introduced by of Fetch implementation

[machineloop]

Master is broken for wasm32-unknown-unknown builds because of the Fetch implementation's use of Http Request/Response return types. @deniskolodin, we can avoid backing out Fetch's use of Http if we do something along the lines of this PR.

See #102 for more info, IoVec needs to cut a new release supporting Wasm and From<[u8]> impls.

There was a breaking change to remove the From<[u8]> impls that will be released with a version-bump eventually.

We can add these lines of code temporarily in the examples to pull a version of IoVec directly from my Github fork which cherry picks the commits that support Wasm while leaving out the breaking changes to the From<[u8]> impls.

Perhaps there's a more elegant way to do this without using [replace] in the cargo.toml files.

[therustmonk]

@machineloop This is a useful change and it's better than reverting Fetch service back. 👍 Thank you!
It seems not every example needs replace, because only dashboard uses Fetch service. Could you leave replace in dashboard demo only to keep this patch compact?

[machineloop]

Yeah, I'm not sure why this is the case, when I remove the [replace] from an example and cd into the its directory and try to compile with cargo web start --target-webasm, I still get this:

@deniskolodin, could you double check the other examples without a Fetch implementation compile without the [replace]?

[gabisurita]

@deniskolodin @machineloop Besides Fetch is not used on the examples, all of them will still try to compile IoVec as a dependecy, so you do need [replace] on all examples or on the yew package to compile them as wasm32-unknown-unknown.

[machineloop]

Thanks for taking a look @gabisurita, I've tried adding the [replace] directly to Yew's cargo.toml, also tried using newer [patch.crates-io], couldn't get either to work directly on Yew. Have you had any luck making a single change to the Yew lib to fix?

[therustmonk]

Ok, I'll examine that more deep. Also I have another fail for wasm32-unknown-unknown:

   Compiling dtoa v0.4.2
   Compiling unicode-xid v0.0.4
   Compiling itoa v0.3.4
   Compiling serde v1.0.27
   Compiling libc v0.2.36
   Compiling iovec v0.1.1 (https://github.com/machineloop/iovec?branch=wasm-support#c954f1d8)
   Compiling quote v0.3.15
   Compiling rustc-serialize v0.3.24
   Compiling byteorder v1.2.1
error[E0046]: not all trait items implemented, missing: `encode`
    --> /home/denis/.cargo/registry/src/github.com-1ecc6299db9ec823/rustc-serialize-0.3.24/src/serialize.rs:1358:1
     |
853  |     fn encode<S: Encoder>(&self, s: &mut S) -> Result<(), S::Error>;
     |     ---------------------------------------------------------------- `encode` from trait
...
1358 | impl Encodable for path::Path {
     | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ missing `encode` in implementation

error[E0046]: not all trait items implemented, missing: `decode`
    --> /home/denis/.cargo/registry/src/github.com-1ecc6299db9ec823/rustc-serialize-0.3.24/src/serialize.rs:1382:1
     |
904  |     fn decode<D: Decoder>(d: &mut D) -> Result<Self, D::Error>;
     |     ----------------------------------------------------------- `decode` from trait
...
1382 | impl Decodable for path::PathBuf {
     | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ missing `decode` in implementation

error: aborting due to 2 previous errors
error: Could not compile `rustc-serialize`.

warning: build failed, waiting for other jobs to finish...
error: build failed
error: build failed

[machineloop]

Interesting @deniskolodin... what example are you compiling and what version of Rust are you on?

[ctjhoa]

I've written a wasm backport for iovec 0.1.x
carllerche/iovec#13

[therustmonk]

@machineloop Thank you for the great help! IoVec works now. Probably should close this PR?

[machineloop]

Fixed, closing PR