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Do not convert doc comments into #[doc = "..."] form unless necessary for macros #60935
Description
Keep them as tokens in AST, this may partially mitigate the perf impact from turning normal comments into doc comments (#60930).
pub struct Attribute {
pub id: AttrId,
pub style: AttrStyle,
pub path: Path,
pub tokens: TokenStream,
pub is_sugared_doc: bool,
pub span: Span,
}=>
pub struct Attribute {
pub kind: AttrKind,
pub span: Span,
pub id: AttrId,
}
pub enum AttrKind {
Normal(Path, TokenStream, AttrStyle),
Doc(Symbol),
}Reacted by Esteban Kuber and Mazdak Farrokhzad
Activity
nnethercote commentedon Oct 23, 2019
Because
TokenStreamcontains aLrc<Vec<TreeAndJoint>>, this would avoid two allocations per doc comment line: one for theLrcand one for theVec. That would get a big chunk of the potential saving. (We would still need one symbol interning per line, which involves a TLS access and a hash table.)nnethercote commentedon Oct 23, 2019
I have a local patch that changes
TokenStreamto aLrc<SmallVec<[TreeAndJoint; 2]>>. It's a clear win, but it only gets rid of one of the allocations, so the approach suggested in this PR has a greater potential.nnethercote commentedon Oct 24, 2019
I have implemented this idea in #65750. It works well!
Make doc comments cheaper with `AttrKind`.
Auto merge of #65750 - nnethercote:cheaper-doc-comments, r=petrochenkov