Fix destructuring async props

[mc1098]

Fixes #410

This PR fixes support in the #[component] macro for destructured struct patterns of props.

I added a single test to trybuild using the existing prop struct with generics and lifetimes to show it handles those too :)

I started trying to do what I think was discussed here only to find that trying to match on fields that themselves might also be destructured was a rabbit hole I didn't want to go down :)

So instead this change simply alters the new sync function that we create to wrap around the async one - it takes the type from the destructured pattern and converts it into a syn::PatType (i.e. props: MyProps) then we just have to add this ident to the args we supply the async function and the pattern the user uses will work if valid and all the errors associated with incorrect patterns will be well formed from rustc.

I added the more eager parser check for the first argument to be syn::Ident instead of the unwrap that was there before as this should give a better error message that will be consistent across both types of components.

Moved most of the change to its own function as it got bit messy and used a struct for named fields so it is hopefully more clear :)

[codecov]

Codecov Report

Merging #419 (9493584) into master (49135bd) will increase coverage by 0.23%.
The diff coverage is 90.47%.

@@            Coverage Diff             @@
##           master     #419      +/-   ##
==========================================
+ Coverage   64.48%   64.72%   +0.23%     
==========================================
  Files          49       49              
  Lines        7958     8022      +64     
==========================================
+ Hits         5132     5192      +60     
- Misses       2826     2830       +4     

Impacted Files	Coverage Δ
packages/sycamore-macro/src/component/mod.rs	96.01% <90.47%> (-1.07%)	⬇️

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[danielalvsaaker]

This looks very nice, but I think you're doing more work than necessary. Here's my proposed solution. It's okay to reuse the destructured struct as input to the inner async function.

Actually, ignore the previous statement. It won't handle partially destructured assignments. Your solution looks good!

[mc1098]

This looks very nice, but I think you're doing more work than necessary. Here's my proposed solution. It's okay to reuse the destructured struct as input to the inner async function.

Actually, ignore the previous statement. It won't handle partially destructured assignments. Your solution looks good!

Yeah, I don't know how likely someone will use partial destructured patterns for props but good to include it if we can :)

Also, I'm sorry! I didn't realise you were working on the issue and now I feel like I've stepped on your toes - if you want I can close this PR and allow you to continue working on the issue.

[danielalvsaaker]

No, that's okay, I was just testing an alternative solution. 🙂

[lukechu10]

Looks great thanks!