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perf: reduce allocations using Cow #39

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Merged
ShapelessCat merged 1 commit into from
Jan 30, 2026
Merged

perf: reduce allocations using Cow #39

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23 changes: 15 additions & 8 deletions patchable-macro/src/context.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -7,6 +7,7 @@
//! macro can emit the companion patch struct plus the `Patchable` and `Patch`
//! trait implementations.

use std::borrow::Cow;
use std::collections::HashMap;

use proc_macro_crate::{FoundCrate, crate_name};
Expand Down Expand Up @@ -80,7 +81,7 @@ impl<'a> MacroContext<'a> {

for (index, field) in stateful_fields.enumerate() {
let member = if let Some(field_name) = field.ident.as_ref() {
FieldMember::Named(field_name.clone())
FieldMember::Named(Cow::Borrowed(field_name))
} else {
FieldMember::Unnamed(Index::from(index))
};
Expand Down Expand Up @@ -326,11 +327,11 @@ impl<'a> MacroContext<'a> {
)
}

fn collect_patch_generics(&self) -> Vec<Ident> {
fn collect_patch_generics(&self) -> Vec<Cow<'_, Ident>> {
let mut generics = Vec::new();
for param in self.generics.type_params() {
if self.preserved_types.contains_key(&param.ident) {
generics.push(param.ident.clone());
generics.push(Cow::Borrowed(&param.ident));
}
}
generics
Expand Down Expand Up @@ -434,12 +435,12 @@ impl<'a> MacroContext<'a> {
}
}

enum FieldMember {
Named(Ident),
enum FieldMember<'a> {
Named(Cow<'a, Ident>),
Unnamed(Index),
}

impl ToTokens for FieldMember {
impl<'a> ToTokens for FieldMember<'a> {
fn to_tokens(&self, tokens: &mut TokenStream2) {
match self {
FieldMember::Named(ident) => ident.to_tokens(tokens),
Expand All @@ -449,8 +450,14 @@ impl ToTokens for FieldMember {
}

enum FieldAction<'a> {
Keep { member: FieldMember, ty: &'a Type },
Patch { member: FieldMember, ty: &'a Type },
Keep {
member: FieldMember<'a>,
ty: &'a Type,
},
Patch {
member: FieldMember<'a>,
ty: &'a Type,
},
}

pub fn use_site_crate_path() -> TokenStream2 {
Expand Down