Inconsistent clone() requirement when passing Classes to HTML elements vs. components (#3589)

[sshekhar563]

There is an inconsistency in how the Classes type is handled between component props and standard HTML element attributes.

When passing a Classes prop to a Yew component, it can be passed directly without needing to call .clone(). However, when passing the same Classes value to an HTML element's class attribute, the compiler fails with a trait bound error, forcing the developer to explicitly call .clone().

This behavior is unintuitive and inconsistent, as one would expect the html! macro to handle both cases similarly.

[github-actions]

Benchmark - core

Yew Master

vnode           fastest       │ slowest       │ median        │ mean          │ samples │ iters
╰─ vnode_clone  2.463 ns      │ 3.734 ns      │ 2.467 ns      │ 2.546 ns      │ 100     │ 1000000000

Pull Request

vnode           fastest       │ slowest       │ median        │ mean          │ samples │ iters
╰─ vnode_clone  2.31 ns       │ 2.345 ns      │ 2.315 ns      │ 2.316 ns      │ 100     │ 1000000000

[github-actions]

Benchmark - SSR

Yew Master

Details

Benchmark	Round	Min (ms)	Max (ms)	Mean (ms)	Standard Deviation
Baseline	10	310.535	312.108	310.853	0.485
Hello World	10	531.843	546.184	537.575	5.242
Function Router	10	1704.364	1746.592	1720.668	16.352
Concurrent Task	10	1005.259	1007.831	1006.664	0.855
Many Providers	10	1113.824	1148.390	1127.551	12.389

Pull Request

Details

Benchmark	Round	Min (ms)	Max (ms)	Mean (ms)	Standard Deviation
Baseline	10	310.565	313.683	311.068	0.932
Hello World	10	516.956	527.916	519.579	3.236
Function Router	10	1721.441	1744.502	1736.970	6.518
Concurrent Task	10	1005.599	1007.256	1006.597	0.568
Many Providers	10	1087.177	1147.965	1105.281	18.790

[github-actions]

Visit the preview URL for this PR (updated for commit 02efc44):

https://yew-rs-api--pr3931-fix-classes-implicit-y7ul53kb.web.app

_{(expires Wed, 29 Oct 2025 13:48:06 GMT)}

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[github-actions]

Size Comparison

Details

examples	master (KB)	pull request (KB)	diff (KB)	diff (%)
async_clock	98.325	98.325	0	0.000%
boids	167.644	167.644	0	0.000%
communication_child_to_parent	91.488	91.488	0	0.000%
communication_grandchild_with_grandparent	102.600	102.600	0	0.000%
communication_grandparent_to_grandchild	98.950	98.950	0	0.000%
communication_parent_to_child	88.812	88.812	0	0.000%
contexts	103.931	103.931	0	0.000%
counter	85.988	85.988	0	0.000%
counter_functional	86.129	86.129	0	0.000%
dyn_create_destroy_apps	88.907	88.907	0	0.000%
file_upload	97.851	97.851	0	0.000%
function_delayed_input	91.048	91.048	0	0.000%
function_memory_game	170.111	170.140	+0.028	+0.017%
function_router	330.215	330.242	+0.027	+0.008%
function_todomvc	162.543	162.571	+0.028	+0.017%
futures	237.354	237.354	0	0.000%
game_of_life	104.080	104.108	+0.028	+0.027%
immutable	194.814	194.814	0	0.000%
inner_html	79.844	79.844	0	0.000%
js_callback	107.788	107.788	0	0.000%
keyed_list	180.234	180.234	0	0.000%
mount_point	83.180	83.180	0	0.000%
nested_list	114.258	114.286	+0.028	+0.025%
node_refs	90.825	90.825	0	0.000%
password_strength	1751.711	1751.711	0	0.000%
portals	92.810	92.810	0	0.000%
router	303.848	303.876	+0.028	+0.009%
suspense	112.123	112.123	0	0.000%
timer	88.080	88.080	0	0.000%
timer_functional	95.812	95.812	0	0.000%
todomvc	142.688	142.716	+0.028	+0.020%
two_apps	85.218	85.218	0	0.000%
web_worker_fib	133.267	133.267	0	0.000%
web_worker_prime	185.155	185.155	0	0.000%
webgl	82.509	82.509	0	0.000%

✅ None of the examples has changed their size significantly.

[WorldSEnder]

Looks good. If implicit-clone ever gets a trait for Into that automatically uses ImplicitClone for references, that would make this less of a manual effort to keep track of the impls.

Thanks for the PR 🎉