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Defer calls to proc_macro::TokenStream::extend #199

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Merged
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Oct 4, 2019
Merged

Defer calls to proc_macro::TokenStream::extend #199

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79 changes: 61 additions & 18 deletions src/wrapper.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -10,10 +10,20 @@ use crate::{fallback, Delimiter, Punct, Spacing, TokenTree};

#[derive(Clone)]
pub enum TokenStream {
Compiler(proc_macro::TokenStream),
Compiler(DeferredTokenStream),
Fallback(fallback::TokenStream),
}

// Work around https://github.com/rust-lang/rust/issues/65080.
// In `impl Extend<TokenTree> for TokenStream` which is used heavily by quote,
// we hold on to the appended tokens and do proc_macro::TokenStream::extend as
// late as possible to batch together consecutive uses of the Extend impl.
#[derive(Clone)]
pub struct DeferredTokenStream {
stream: proc_macro::TokenStream,
extra: Vec<proc_macro::TokenTree>,
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Cannot all of this be put into a single vector?

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That has different performance characteristics when converting between proc_macro::TokenStream and proc_macro2::TokenStream.

}

pub enum LexError {
Compiler(proc_macro::LexError),
Fallback(fallback::LexError),
Expand Down Expand Up @@ -80,10 +90,32 @@ fn mismatch() -> ! {
panic!("stable/nightly mismatch")
}

impl DeferredTokenStream {
fn new(stream: proc_macro::TokenStream) -> Self {
DeferredTokenStream {
stream,
extra: Vec::new(),
}
}

fn is_empty(&self) -> bool {
self.stream.is_empty() && self.extra.is_empty()
}

fn evaluate_now(&mut self) {
self.stream.extend(self.extra.drain(..));
}

fn into_token_stream(mut self) -> proc_macro::TokenStream {
self.evaluate_now();
self.stream
}
}

impl TokenStream {
pub fn new() -> TokenStream {
if nightly_works() {
TokenStream::Compiler(proc_macro::TokenStream::new())
TokenStream::Compiler(DeferredTokenStream::new(proc_macro::TokenStream::new()))
} else {
TokenStream::Fallback(fallback::TokenStream::new())
}
Expand All @@ -98,7 +130,7 @@ impl TokenStream {

fn unwrap_nightly(self) -> proc_macro::TokenStream {
match self {
TokenStream::Compiler(s) => s,
TokenStream::Compiler(s) => s.into_token_stream(),
TokenStream::Fallback(_) => mismatch(),
}
}
Expand All @@ -116,7 +148,9 @@ impl FromStr for TokenStream {

fn from_str(src: &str) -> Result<TokenStream, LexError> {
if nightly_works() {
Ok(TokenStream::Compiler(src.parse()?))
Ok(TokenStream::Compiler(DeferredTokenStream::new(
src.parse()?,
)))
} else {
Ok(TokenStream::Fallback(src.parse()?))
}
Expand All @@ -126,22 +160,22 @@ impl FromStr for TokenStream {
impl fmt::Display for TokenStream {
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
match self {
TokenStream::Compiler(tts) => tts.fmt(f),
TokenStream::Compiler(tts) => tts.clone().into_token_stream().fmt(f),
TokenStream::Fallback(tts) => tts.fmt(f),
}
}
}

impl From<proc_macro::TokenStream> for TokenStream {
fn from(inner: proc_macro::TokenStream) -> TokenStream {
TokenStream::Compiler(inner)
TokenStream::Compiler(DeferredTokenStream::new(inner))
}
}

impl From<TokenStream> for proc_macro::TokenStream {
fn from(inner: TokenStream) -> proc_macro::TokenStream {
match inner {
TokenStream::Compiler(inner) => inner,
TokenStream::Compiler(inner) => inner.into_token_stream(),
TokenStream::Fallback(inner) => inner.to_string().parse().unwrap(),
}
}
Expand Down Expand Up @@ -174,7 +208,7 @@ fn into_compiler_token(token: TokenTree) -> proc_macro::TokenTree {
impl From<TokenTree> for TokenStream {
fn from(token: TokenTree) -> TokenStream {
if nightly_works() {
TokenStream::Compiler(into_compiler_token(token).into())
TokenStream::Compiler(DeferredTokenStream::new(into_compiler_token(token).into()))
} else {
TokenStream::Fallback(token.into())
}
Expand All @@ -184,7 +218,9 @@ impl From<TokenTree> for TokenStream {
impl iter::FromIterator<TokenTree> for TokenStream {
fn from_iter<I: IntoIterator<Item = TokenTree>>(trees: I) -> Self {
if nightly_works() {
TokenStream::Compiler(trees.into_iter().map(into_compiler_token).collect())
TokenStream::Compiler(DeferredTokenStream::new(
trees.into_iter().map(into_compiler_token).collect(),
))
} else {
TokenStream::Fallback(trees.into_iter().collect())
}
Expand All @@ -196,8 +232,9 @@ impl iter::FromIterator<TokenStream> for TokenStream {
let mut streams = streams.into_iter();
match streams.next() {
Some(TokenStream::Compiler(mut first)) => {
first.extend(streams.map(|s| match s {
TokenStream::Compiler(s) => s,
first.evaluate_now();
first.stream.extend(streams.map(|s| match s {
TokenStream::Compiler(s) => s.into_token_stream(),
TokenStream::Fallback(_) => mismatch(),
}));
TokenStream::Compiler(first)
Expand All @@ -218,7 +255,9 @@ impl Extend<TokenTree> for TokenStream {
fn extend<I: IntoIterator<Item = TokenTree>>(&mut self, streams: I) {
match self {
TokenStream::Compiler(tts) => {
tts.extend(streams.into_iter().map(into_compiler_token));
// Here is the reason for DeferredTokenStream.
tts.extra
.extend(streams.into_iter().map(into_compiler_token));
}
TokenStream::Fallback(tts) => tts.extend(streams),
}
Expand All @@ -229,7 +268,9 @@ impl Extend<TokenStream> for TokenStream {
fn extend<I: IntoIterator<Item = TokenStream>>(&mut self, streams: I) {
match self {
TokenStream::Compiler(tts) => {
tts.extend(streams.into_iter().map(|stream| stream.unwrap_nightly()));
tts.evaluate_now();
tts.stream
.extend(streams.into_iter().map(|stream| stream.unwrap_nightly()));
}
TokenStream::Fallback(tts) => {
tts.extend(streams.into_iter().map(|stream| stream.unwrap_stable()));
Expand All @@ -241,7 +282,7 @@ impl Extend<TokenStream> for TokenStream {
impl fmt::Debug for TokenStream {
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
match self {
TokenStream::Compiler(tts) => tts.fmt(f),
TokenStream::Compiler(tts) => tts.clone().into_token_stream().fmt(f),
TokenStream::Fallback(tts) => tts.fmt(f),
}
}
Expand Down Expand Up @@ -280,7 +321,9 @@ impl IntoIterator for TokenStream {

fn into_iter(self) -> TokenTreeIter {
match self {
TokenStream::Compiler(tts) => TokenTreeIter::Compiler(tts.into_iter()),
TokenStream::Compiler(tts) => {
TokenTreeIter::Compiler(tts.into_token_stream().into_iter())
}
TokenStream::Fallback(tts) => TokenTreeIter::Fallback(tts.into_iter()),
}
}
Expand Down Expand Up @@ -526,14 +569,14 @@ pub enum Group {
impl Group {
pub fn new(delimiter: Delimiter, stream: TokenStream) -> Group {
match stream {
TokenStream::Compiler(stream) => {
TokenStream::Compiler(tts) => {
let delimiter = match delimiter {
Delimiter::Parenthesis => proc_macro::Delimiter::Parenthesis,
Delimiter::Bracket => proc_macro::Delimiter::Bracket,
Delimiter::Brace => proc_macro::Delimiter::Brace,
Delimiter::None => proc_macro::Delimiter::None,
};
Group::Compiler(proc_macro::Group::new(delimiter, stream))
Group::Compiler(proc_macro::Group::new(delimiter, tts.into_token_stream()))
}
TokenStream::Fallback(stream) => {
Group::Fallback(fallback::Group::new(delimiter, stream))
Expand All @@ -555,7 +598,7 @@ impl Group {

pub fn stream(&self) -> TokenStream {
match self {
Group::Compiler(g) => TokenStream::Compiler(g.stream()),
Group::Compiler(g) => TokenStream::Compiler(DeferredTokenStream::new(g.stream())),
Group::Fallback(g) => TokenStream::Fallback(g.stream()),
}
}
Expand Down