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|
use proc_macro2::{Group, Ident, TokenStream, TokenTree};
use crate::iter::IteratorExt;
#[allow(clippy::module_name_repetitions)]
pub trait TokenStreamExt
{
/// Recursively replaces all occurences of a identifier with a token tree.
fn replace_ident(
&self,
target_ident: &Ident,
substitution: &TokenTree,
) -> TokenStream;
}
impl TokenStreamExt for TokenStream
{
fn replace_ident(&self, target_ident: &Ident, substitution: &TokenTree)
-> TokenStream
{
recurse_replace_ident(self.clone(), target_ident, substitution, '#')
}
}
fn recurse_replace_ident(
token_stream: TokenStream,
target_ident: &Ident,
substitution: &TokenTree,
prefix: char,
) -> TokenStream
{
let mut prev_token_was_prefix = false;
token_stream
.into_iter()
.windows()
.filter_map(|(token_tree, next_token_tree)| match token_tree {
TokenTree::Punct(punct) if punct.as_char() == prefix => {
if matches!(next_token_tree, Some(TokenTree::Ident(ident)) if &ident == target_ident) {
prev_token_was_prefix = true;
None
}
else {
prev_token_was_prefix = false;
Some(TokenTree::Punct(punct))
}
}
TokenTree::Ident(ident) if prev_token_was_prefix && &ident == target_ident => {
prev_token_was_prefix = false;
Some(substitution.clone())
}
TokenTree::Ident(_) if prev_token_was_prefix => {
prev_token_was_prefix = false;
Some(substitution.clone())
}
TokenTree::Group(group) => {
prev_token_was_prefix = false;
Some(TokenTree::Group(Group::new(
group.delimiter(),
recurse_replace_ident(group.stream(), target_ident, substitution, prefix),
)))
}
tt => {
prev_token_was_prefix = false;
Some(tt)
}
})
.collect()
}
#[cfg(test)]
mod tests
{
extern crate test;
use std::hint::black_box;
use proc_macro2::{Punct, Spacing, Span};
use quote::{format_ident, quote};
use test::Bencher;
use super::*;
#[test]
fn replace_ident_works()
{
let ht = Punct::new('#', Spacing::Alone);
assert_eq!(
quote! {
let abc = #ht xyz;
}
.replace_ident(
&format_ident!("xyz"),
&TokenTree::Ident(Ident::new("foo", Span::call_site())),
)
.to_string(),
quote! {
let abc = foo;
}
.to_string()
);
assert_eq!(
quote! {
let abc = (#ht xyz, "123");
}
.replace_ident(
&format_ident!("xyz"),
&TokenTree::Ident(Ident::new("foo", Span::call_site())),
)
.to_string(),
quote! {
let abc = (foo, "123");
}
.to_string()
);
assert_eq!(
quote! {
let abc = (hello, "123").iter_map(|_| #ht xyz);
}
.replace_ident(
&format_ident!("xyz"),
&TokenTree::Ident(Ident::new("foo", Span::call_site())),
)
.to_string(),
quote! {
let abc = (hello, "123").iter_map(|_| foo);
}
.to_string()
);
assert_eq!(
quote! {
fn #ht xyz(bar: &Bar) {
let foo = "baz";
foo
}
let xyz = "123";
println!("Hello {}", #ht xyz());
}
.replace_ident(
&format_ident!("xyz"),
&TokenTree::Ident(Ident::new("foo", Span::call_site())),
)
.to_string(),
quote! {
fn foo(bar: &Bar) {
let foo = "baz";
foo
}
let xyz = "123";
println!("Hello {}", foo());
}
.to_string()
);
}
#[bench]
fn bench_replace_ident(bencher: &mut Bencher)
{
let ht = Punct::new('#', Spacing::Alone);
let input_strem = quote! {
let #ht foo = |abc| {
let x = "foo";
let y = a_foo;
let #ht foo = "Hello";
#ht foo.to_string()
};
};
bencher.iter(|| {
input_strem.replace_ident(
black_box(&format_ident!("foo")),
black_box(&TokenTree::Ident(format_ident!("foobar"))),
)
});
}
}
|
