Avoid unnecessary `TokenTree` to `TokenStream` conversions #65455
Make `TokenStream::from_iter` less general and more efficient.
The current code has this impl: ``` impl<T: Into<TokenStream>> iter::FromIterator<T> for TokenStream ``` If given an `IntoIterator<Item = TokenTree>`, it will convert each individual `TokenTree` to a `TokenStream` (at the cost of two allocations: a `Vec` and an `Lrc`). It will then merge those `TokenStream`s into a single `TokenStream`. This is inefficient. This commit changes the impl to this less general one: ``` impl iter::FromIterator<TokenTree> for TokenStream ``` It collects the `TokenTree`s into a single `Vec` first and then converts that to a `TokenStream` by wrapping it in a single `Lrc`. The previous generality was unnecessary; no other code needs changing. This change speeds up several benchmarks by up to 4%.
- Loading branch information
ProTip! Use n and p to navigate between commits in a pull request.
Add this suggestion to a batch that can be applied as a single commit. This suggestion is invalid because no changes were made to the code. Suggestions cannot be applied while the pull request is closed. Suggestions cannot be applied while viewing a subset of changes. Only one suggestion per line can be applied in a batch. Add this suggestion to a batch that can be applied as a single commit. Applying suggestions on deleted lines is not supported. You must change the existing code in this line in order to create a valid suggestion. Outdated suggestions cannot be applied. This suggestion has been applied or marked resolved. Suggestions cannot be applied from pending reviews. Suggestions cannot be applied on multi-line comments.