rust/compiler/rustc_ast/src/tokenstream.rs

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//! # Token Streams
//!
//! `TokenStream`s represent syntactic objects before they are converted into ASTs.
//! A `TokenStream` is, roughly speaking, a sequence of [`TokenTree`]s,
//! which are themselves a single [`Token`] or a `Delimited` subsequence of tokens.
//!
//! ## Ownership
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//!
//! `TokenStream`s are persistent data structures constructed as ropes with reference
//! counted-children. In general, this means that calling an operation on a `TokenStream`
//! (such as `slice`) produces an entirely new `TokenStream` from the borrowed reference to
//! the original. This essentially coerces `TokenStream`s into "views" of their subparts,
//! and a borrowed `TokenStream` is sufficient to build an owned `TokenStream` without taking
//! ownership of the original.
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use crate::token::{self, DelimToken, Token, TokenKind};
Implement token-based handling of attributes during expansion This PR modifies the macro expansion infrastructure to handle attributes in a fully token-based manner. As a result: * Derives macros no longer lose spans when their input is modified by eager cfg-expansion. This is accomplished by performing eager cfg-expansion on the token stream that we pass to the derive proc-macro * Inner attributes now preserve spans in all cases, including when we have multiple inner attributes in a row. This is accomplished through the following changes: * New structs `AttrAnnotatedTokenStream` and `AttrAnnotatedTokenTree` are introduced. These are very similar to a normal `TokenTree`, but they also track the position of attributes and attribute targets within the stream. They are built when we collect tokens during parsing. An `AttrAnnotatedTokenStream` is converted to a regular `TokenStream` when we invoke a macro. * Token capturing and `LazyTokenStream` are modified to work with `AttrAnnotatedTokenStream`. A new `ReplaceRange` type is introduced, which is created during the parsing of a nested AST node to make the 'outer' AST node aware of the attributes and attribute target stored deeper in the token stream. * When we need to perform eager cfg-expansion (either due to `#[derive]` or `#[cfg_eval]`), we tokenize and reparse our target, capturing additional information about the locations of `#[cfg]` and `#[cfg_attr]` attributes at any depth within the target. This is a performance optimization, allowing us to perform less work in the typical case where captured tokens never have eager cfg-expansion run.
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use crate::AttrVec;
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use rustc_data_structures::stable_hasher::{HashStable, StableHasher};
Rewrite `collect_tokens` implementations to use a flattened buffer Instead of trying to collect tokens at each depth, we 'flatten' the stream as we go allong, pushing open/close delimiters to our buffer just like regular tokens. One capturing is complete, we reconstruct a nested `TokenTree::Delimited` structure, producing a normal `TokenStream`. The reconstructed `TokenStream` is not created immediately - instead, it is produced on-demand by a closure (wrapped in a new `LazyTokenStream` type). This closure stores a clone of the original `TokenCursor`, plus a record of the number of calls to `next()/next_desugared()`. This is sufficient to reconstruct the tokenstream seen by the callback without storing any additional state. If the tokenstream is never used (e.g. when a captured `macro_rules!` argument is never passed to a proc macro), we never actually create a `TokenStream`. This implementation has a number of advantages over the previous one: * It is significantly simpler, with no edge cases around capturing the start/end of a delimited group. * It can be easily extended to allow replacing tokens an an arbitrary 'depth' by just using `Vec::splice` at the proper position. This is important for PR #76130, which requires us to track information about attributes along with tokens. * The lazy approach to `TokenStream` construction allows us to easily parse an AST struct, and then decide after the fact whether we need a `TokenStream`. This will be useful when we start collecting tokens for `Attribute` - we can discard the `LazyTokenStream` if the parsed attribute doesn't need tokens (e.g. is a builtin attribute). The performance impact seems to be neglibile (see https://github.com/rust-lang/rust/pull/77250#issuecomment-703960604). There is a small slowdown on a few benchmarks, but it only rises above 1% for incremental builds, where it represents a larger fraction of the much smaller instruction count. There a ~1% speedup on a few other incremental benchmarks - my guess is that the speedups and slowdowns will usually cancel out in practice.
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use rustc_data_structures::sync::{self, Lrc};
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use rustc_macros::HashStable_Generic;
Rewrite `collect_tokens` implementations to use a flattened buffer Instead of trying to collect tokens at each depth, we 'flatten' the stream as we go allong, pushing open/close delimiters to our buffer just like regular tokens. One capturing is complete, we reconstruct a nested `TokenTree::Delimited` structure, producing a normal `TokenStream`. The reconstructed `TokenStream` is not created immediately - instead, it is produced on-demand by a closure (wrapped in a new `LazyTokenStream` type). This closure stores a clone of the original `TokenCursor`, plus a record of the number of calls to `next()/next_desugared()`. This is sufficient to reconstruct the tokenstream seen by the callback without storing any additional state. If the tokenstream is never used (e.g. when a captured `macro_rules!` argument is never passed to a proc macro), we never actually create a `TokenStream`. This implementation has a number of advantages over the previous one: * It is significantly simpler, with no edge cases around capturing the start/end of a delimited group. * It can be easily extended to allow replacing tokens an an arbitrary 'depth' by just using `Vec::splice` at the proper position. This is important for PR #76130, which requires us to track information about attributes along with tokens. * The lazy approach to `TokenStream` construction allows us to easily parse an AST struct, and then decide after the fact whether we need a `TokenStream`. This will be useful when we start collecting tokens for `Attribute` - we can discard the `LazyTokenStream` if the parsed attribute doesn't need tokens (e.g. is a builtin attribute). The performance impact seems to be neglibile (see https://github.com/rust-lang/rust/pull/77250#issuecomment-703960604). There is a small slowdown on a few benchmarks, but it only rises above 1% for incremental builds, where it represents a larger fraction of the much smaller instruction count. There a ~1% speedup on a few other incremental benchmarks - my guess is that the speedups and slowdowns will usually cancel out in practice.
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use rustc_serialize::{Decodable, Decoder, Encodable, Encoder};
use rustc_span::{Span, DUMMY_SP};
use smallvec::{smallvec, SmallVec};
use std::{fmt, iter, mem};
/// When the main Rust parser encounters a syntax-extension invocation, it
/// parses the arguments to the invocation as a token tree. This is a very
/// loose structure, such that all sorts of different AST fragments can
/// be passed to syntax extensions using a uniform type.
///
/// If the syntax extension is an MBE macro, it will attempt to match its
/// LHS token tree against the provided token tree, and if it finds a
/// match, will transcribe the RHS token tree, splicing in any captured
/// `macro_parser::matched_nonterminals` into the `SubstNt`s it finds.
///
/// The RHS of an MBE macro is the only place `SubstNt`s are substituted.
/// Nothing special happens to misnamed or misplaced `SubstNt`s.
#[derive(Debug, Clone, PartialEq, Encodable, Decodable, HashStable_Generic)]
pub enum TokenTree {
/// A single token.
Token(Token),
/// A delimited sequence of token trees.
Delimited(DelimSpan, DelimToken, TokenStream),
}
#[derive(Copy, Clone)]
pub enum CanSynthesizeMissingTokens {
Yes,
No,
}
// Ensure all fields of `TokenTree` is `Send` and `Sync`.
#[cfg(parallel_compiler)]
fn _dummy()
where
Token: Send + Sync,
DelimSpan: Send + Sync,
DelimToken: Send + Sync,
TokenStream: Send + Sync,
{
}
impl TokenTree {
/// Checks if this `TokenTree` is equal to the other, regardless of span information.
pub fn eq_unspanned(&self, other: &TokenTree) -> bool {
match (self, other) {
(TokenTree::Token(token), TokenTree::Token(token2)) => token.kind == token2.kind,
(TokenTree::Delimited(_, delim, tts), TokenTree::Delimited(_, delim2, tts2)) => {
delim == delim2 && tts.eq_unspanned(&tts2)
}
_ => false,
}
}
/// Retrieves the `TokenTree`'s span.
pub fn span(&self) -> Span {
match self {
TokenTree::Token(token) => token.span,
TokenTree::Delimited(sp, ..) => sp.entire(),
}
}
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/// Modify the `TokenTree`'s span in-place.
pub fn set_span(&mut self, span: Span) {
match self {
TokenTree::Token(token) => token.span = span,
TokenTree::Delimited(dspan, ..) => *dspan = DelimSpan::from_single(span),
}
}
pub fn token(kind: TokenKind, span: Span) -> TokenTree {
TokenTree::Token(Token::new(kind, span))
}
pub fn uninterpolate(self) -> TokenTree {
match self {
TokenTree::Token(token) => TokenTree::Token(token.uninterpolate().into_owned()),
tt => tt,
}
}
}
impl<CTX> HashStable<CTX> for TokenStream
where
CTX: crate::HashStableContext,
{
fn hash_stable(&self, hcx: &mut CTX, hasher: &mut StableHasher) {
for sub_tt in self.trees() {
sub_tt.hash_stable(hcx, hasher);
}
}
}
pub trait CreateTokenStream: sync::Send + sync::Sync {
Implement token-based handling of attributes during expansion This PR modifies the macro expansion infrastructure to handle attributes in a fully token-based manner. As a result: * Derives macros no longer lose spans when their input is modified by eager cfg-expansion. This is accomplished by performing eager cfg-expansion on the token stream that we pass to the derive proc-macro * Inner attributes now preserve spans in all cases, including when we have multiple inner attributes in a row. This is accomplished through the following changes: * New structs `AttrAnnotatedTokenStream` and `AttrAnnotatedTokenTree` are introduced. These are very similar to a normal `TokenTree`, but they also track the position of attributes and attribute targets within the stream. They are built when we collect tokens during parsing. An `AttrAnnotatedTokenStream` is converted to a regular `TokenStream` when we invoke a macro. * Token capturing and `LazyTokenStream` are modified to work with `AttrAnnotatedTokenStream`. A new `ReplaceRange` type is introduced, which is created during the parsing of a nested AST node to make the 'outer' AST node aware of the attributes and attribute target stored deeper in the token stream. * When we need to perform eager cfg-expansion (either due to `#[derive]` or `#[cfg_eval]`), we tokenize and reparse our target, capturing additional information about the locations of `#[cfg]` and `#[cfg_attr]` attributes at any depth within the target. This is a performance optimization, allowing us to perform less work in the typical case where captured tokens never have eager cfg-expansion run.
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fn create_token_stream(&self) -> AttrAnnotatedTokenStream;
Rewrite `collect_tokens` implementations to use a flattened buffer Instead of trying to collect tokens at each depth, we 'flatten' the stream as we go allong, pushing open/close delimiters to our buffer just like regular tokens. One capturing is complete, we reconstruct a nested `TokenTree::Delimited` structure, producing a normal `TokenStream`. The reconstructed `TokenStream` is not created immediately - instead, it is produced on-demand by a closure (wrapped in a new `LazyTokenStream` type). This closure stores a clone of the original `TokenCursor`, plus a record of the number of calls to `next()/next_desugared()`. This is sufficient to reconstruct the tokenstream seen by the callback without storing any additional state. If the tokenstream is never used (e.g. when a captured `macro_rules!` argument is never passed to a proc macro), we never actually create a `TokenStream`. This implementation has a number of advantages over the previous one: * It is significantly simpler, with no edge cases around capturing the start/end of a delimited group. * It can be easily extended to allow replacing tokens an an arbitrary 'depth' by just using `Vec::splice` at the proper position. This is important for PR #76130, which requires us to track information about attributes along with tokens. * The lazy approach to `TokenStream` construction allows us to easily parse an AST struct, and then decide after the fact whether we need a `TokenStream`. This will be useful when we start collecting tokens for `Attribute` - we can discard the `LazyTokenStream` if the parsed attribute doesn't need tokens (e.g. is a builtin attribute). The performance impact seems to be neglibile (see https://github.com/rust-lang/rust/pull/77250#issuecomment-703960604). There is a small slowdown on a few benchmarks, but it only rises above 1% for incremental builds, where it represents a larger fraction of the much smaller instruction count. There a ~1% speedup on a few other incremental benchmarks - my guess is that the speedups and slowdowns will usually cancel out in practice.
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}
Implement token-based handling of attributes during expansion This PR modifies the macro expansion infrastructure to handle attributes in a fully token-based manner. As a result: * Derives macros no longer lose spans when their input is modified by eager cfg-expansion. This is accomplished by performing eager cfg-expansion on the token stream that we pass to the derive proc-macro * Inner attributes now preserve spans in all cases, including when we have multiple inner attributes in a row. This is accomplished through the following changes: * New structs `AttrAnnotatedTokenStream` and `AttrAnnotatedTokenTree` are introduced. These are very similar to a normal `TokenTree`, but they also track the position of attributes and attribute targets within the stream. They are built when we collect tokens during parsing. An `AttrAnnotatedTokenStream` is converted to a regular `TokenStream` when we invoke a macro. * Token capturing and `LazyTokenStream` are modified to work with `AttrAnnotatedTokenStream`. A new `ReplaceRange` type is introduced, which is created during the parsing of a nested AST node to make the 'outer' AST node aware of the attributes and attribute target stored deeper in the token stream. * When we need to perform eager cfg-expansion (either due to `#[derive]` or `#[cfg_eval]`), we tokenize and reparse our target, capturing additional information about the locations of `#[cfg]` and `#[cfg_attr]` attributes at any depth within the target. This is a performance optimization, allowing us to perform less work in the typical case where captured tokens never have eager cfg-expansion run.
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impl CreateTokenStream for AttrAnnotatedTokenStream {
fn create_token_stream(&self) -> AttrAnnotatedTokenStream {
self.clone()
Rewrite `collect_tokens` implementations to use a flattened buffer Instead of trying to collect tokens at each depth, we 'flatten' the stream as we go allong, pushing open/close delimiters to our buffer just like regular tokens. One capturing is complete, we reconstruct a nested `TokenTree::Delimited` structure, producing a normal `TokenStream`. The reconstructed `TokenStream` is not created immediately - instead, it is produced on-demand by a closure (wrapped in a new `LazyTokenStream` type). This closure stores a clone of the original `TokenCursor`, plus a record of the number of calls to `next()/next_desugared()`. This is sufficient to reconstruct the tokenstream seen by the callback without storing any additional state. If the tokenstream is never used (e.g. when a captured `macro_rules!` argument is never passed to a proc macro), we never actually create a `TokenStream`. This implementation has a number of advantages over the previous one: * It is significantly simpler, with no edge cases around capturing the start/end of a delimited group. * It can be easily extended to allow replacing tokens an an arbitrary 'depth' by just using `Vec::splice` at the proper position. This is important for PR #76130, which requires us to track information about attributes along with tokens. * The lazy approach to `TokenStream` construction allows us to easily parse an AST struct, and then decide after the fact whether we need a `TokenStream`. This will be useful when we start collecting tokens for `Attribute` - we can discard the `LazyTokenStream` if the parsed attribute doesn't need tokens (e.g. is a builtin attribute). The performance impact seems to be neglibile (see https://github.com/rust-lang/rust/pull/77250#issuecomment-703960604). There is a small slowdown on a few benchmarks, but it only rises above 1% for incremental builds, where it represents a larger fraction of the much smaller instruction count. There a ~1% speedup on a few other incremental benchmarks - my guess is that the speedups and slowdowns will usually cancel out in practice.
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}
}
/// A lazy version of [`TokenStream`], which defers creation
Rewrite `collect_tokens` implementations to use a flattened buffer Instead of trying to collect tokens at each depth, we 'flatten' the stream as we go allong, pushing open/close delimiters to our buffer just like regular tokens. One capturing is complete, we reconstruct a nested `TokenTree::Delimited` structure, producing a normal `TokenStream`. The reconstructed `TokenStream` is not created immediately - instead, it is produced on-demand by a closure (wrapped in a new `LazyTokenStream` type). This closure stores a clone of the original `TokenCursor`, plus a record of the number of calls to `next()/next_desugared()`. This is sufficient to reconstruct the tokenstream seen by the callback without storing any additional state. If the tokenstream is never used (e.g. when a captured `macro_rules!` argument is never passed to a proc macro), we never actually create a `TokenStream`. This implementation has a number of advantages over the previous one: * It is significantly simpler, with no edge cases around capturing the start/end of a delimited group. * It can be easily extended to allow replacing tokens an an arbitrary 'depth' by just using `Vec::splice` at the proper position. This is important for PR #76130, which requires us to track information about attributes along with tokens. * The lazy approach to `TokenStream` construction allows us to easily parse an AST struct, and then decide after the fact whether we need a `TokenStream`. This will be useful when we start collecting tokens for `Attribute` - we can discard the `LazyTokenStream` if the parsed attribute doesn't need tokens (e.g. is a builtin attribute). The performance impact seems to be neglibile (see https://github.com/rust-lang/rust/pull/77250#issuecomment-703960604). There is a small slowdown on a few benchmarks, but it only rises above 1% for incremental builds, where it represents a larger fraction of the much smaller instruction count. There a ~1% speedup on a few other incremental benchmarks - my guess is that the speedups and slowdowns will usually cancel out in practice.
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/// of an actual `TokenStream` until it is needed.
/// `Box` is here only to reduce the structure size.
Rewrite `collect_tokens` implementations to use a flattened buffer Instead of trying to collect tokens at each depth, we 'flatten' the stream as we go allong, pushing open/close delimiters to our buffer just like regular tokens. One capturing is complete, we reconstruct a nested `TokenTree::Delimited` structure, producing a normal `TokenStream`. The reconstructed `TokenStream` is not created immediately - instead, it is produced on-demand by a closure (wrapped in a new `LazyTokenStream` type). This closure stores a clone of the original `TokenCursor`, plus a record of the number of calls to `next()/next_desugared()`. This is sufficient to reconstruct the tokenstream seen by the callback without storing any additional state. If the tokenstream is never used (e.g. when a captured `macro_rules!` argument is never passed to a proc macro), we never actually create a `TokenStream`. This implementation has a number of advantages over the previous one: * It is significantly simpler, with no edge cases around capturing the start/end of a delimited group. * It can be easily extended to allow replacing tokens an an arbitrary 'depth' by just using `Vec::splice` at the proper position. This is important for PR #76130, which requires us to track information about attributes along with tokens. * The lazy approach to `TokenStream` construction allows us to easily parse an AST struct, and then decide after the fact whether we need a `TokenStream`. This will be useful when we start collecting tokens for `Attribute` - we can discard the `LazyTokenStream` if the parsed attribute doesn't need tokens (e.g. is a builtin attribute). The performance impact seems to be neglibile (see https://github.com/rust-lang/rust/pull/77250#issuecomment-703960604). There is a small slowdown on a few benchmarks, but it only rises above 1% for incremental builds, where it represents a larger fraction of the much smaller instruction count. There a ~1% speedup on a few other incremental benchmarks - my guess is that the speedups and slowdowns will usually cancel out in practice.
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#[derive(Clone)]
pub struct LazyTokenStream(Lrc<Box<dyn CreateTokenStream>>);
Rewrite `collect_tokens` implementations to use a flattened buffer Instead of trying to collect tokens at each depth, we 'flatten' the stream as we go allong, pushing open/close delimiters to our buffer just like regular tokens. One capturing is complete, we reconstruct a nested `TokenTree::Delimited` structure, producing a normal `TokenStream`. The reconstructed `TokenStream` is not created immediately - instead, it is produced on-demand by a closure (wrapped in a new `LazyTokenStream` type). This closure stores a clone of the original `TokenCursor`, plus a record of the number of calls to `next()/next_desugared()`. This is sufficient to reconstruct the tokenstream seen by the callback without storing any additional state. If the tokenstream is never used (e.g. when a captured `macro_rules!` argument is never passed to a proc macro), we never actually create a `TokenStream`. This implementation has a number of advantages over the previous one: * It is significantly simpler, with no edge cases around capturing the start/end of a delimited group. * It can be easily extended to allow replacing tokens an an arbitrary 'depth' by just using `Vec::splice` at the proper position. This is important for PR #76130, which requires us to track information about attributes along with tokens. * The lazy approach to `TokenStream` construction allows us to easily parse an AST struct, and then decide after the fact whether we need a `TokenStream`. This will be useful when we start collecting tokens for `Attribute` - we can discard the `LazyTokenStream` if the parsed attribute doesn't need tokens (e.g. is a builtin attribute). The performance impact seems to be neglibile (see https://github.com/rust-lang/rust/pull/77250#issuecomment-703960604). There is a small slowdown on a few benchmarks, but it only rises above 1% for incremental builds, where it represents a larger fraction of the much smaller instruction count. There a ~1% speedup on a few other incremental benchmarks - my guess is that the speedups and slowdowns will usually cancel out in practice.
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impl LazyTokenStream {
pub fn new(inner: impl CreateTokenStream + 'static) -> LazyTokenStream {
LazyTokenStream(Lrc::new(Box::new(inner)))
}
Implement token-based handling of attributes during expansion This PR modifies the macro expansion infrastructure to handle attributes in a fully token-based manner. As a result: * Derives macros no longer lose spans when their input is modified by eager cfg-expansion. This is accomplished by performing eager cfg-expansion on the token stream that we pass to the derive proc-macro * Inner attributes now preserve spans in all cases, including when we have multiple inner attributes in a row. This is accomplished through the following changes: * New structs `AttrAnnotatedTokenStream` and `AttrAnnotatedTokenTree` are introduced. These are very similar to a normal `TokenTree`, but they also track the position of attributes and attribute targets within the stream. They are built when we collect tokens during parsing. An `AttrAnnotatedTokenStream` is converted to a regular `TokenStream` when we invoke a macro. * Token capturing and `LazyTokenStream` are modified to work with `AttrAnnotatedTokenStream`. A new `ReplaceRange` type is introduced, which is created during the parsing of a nested AST node to make the 'outer' AST node aware of the attributes and attribute target stored deeper in the token stream. * When we need to perform eager cfg-expansion (either due to `#[derive]` or `#[cfg_eval]`), we tokenize and reparse our target, capturing additional information about the locations of `#[cfg]` and `#[cfg_attr]` attributes at any depth within the target. This is a performance optimization, allowing us to perform less work in the typical case where captured tokens never have eager cfg-expansion run.
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pub fn create_token_stream(&self) -> AttrAnnotatedTokenStream {
self.0.create_token_stream()
Rewrite `collect_tokens` implementations to use a flattened buffer Instead of trying to collect tokens at each depth, we 'flatten' the stream as we go allong, pushing open/close delimiters to our buffer just like regular tokens. One capturing is complete, we reconstruct a nested `TokenTree::Delimited` structure, producing a normal `TokenStream`. The reconstructed `TokenStream` is not created immediately - instead, it is produced on-demand by a closure (wrapped in a new `LazyTokenStream` type). This closure stores a clone of the original `TokenCursor`, plus a record of the number of calls to `next()/next_desugared()`. This is sufficient to reconstruct the tokenstream seen by the callback without storing any additional state. If the tokenstream is never used (e.g. when a captured `macro_rules!` argument is never passed to a proc macro), we never actually create a `TokenStream`. This implementation has a number of advantages over the previous one: * It is significantly simpler, with no edge cases around capturing the start/end of a delimited group. * It can be easily extended to allow replacing tokens an an arbitrary 'depth' by just using `Vec::splice` at the proper position. This is important for PR #76130, which requires us to track information about attributes along with tokens. * The lazy approach to `TokenStream` construction allows us to easily parse an AST struct, and then decide after the fact whether we need a `TokenStream`. This will be useful when we start collecting tokens for `Attribute` - we can discard the `LazyTokenStream` if the parsed attribute doesn't need tokens (e.g. is a builtin attribute). The performance impact seems to be neglibile (see https://github.com/rust-lang/rust/pull/77250#issuecomment-703960604). There is a small slowdown on a few benchmarks, but it only rises above 1% for incremental builds, where it represents a larger fraction of the much smaller instruction count. There a ~1% speedup on a few other incremental benchmarks - my guess is that the speedups and slowdowns will usually cancel out in practice.
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}
}
impl fmt::Debug for LazyTokenStream {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
Implement token-based handling of attributes during expansion This PR modifies the macro expansion infrastructure to handle attributes in a fully token-based manner. As a result: * Derives macros no longer lose spans when their input is modified by eager cfg-expansion. This is accomplished by performing eager cfg-expansion on the token stream that we pass to the derive proc-macro * Inner attributes now preserve spans in all cases, including when we have multiple inner attributes in a row. This is accomplished through the following changes: * New structs `AttrAnnotatedTokenStream` and `AttrAnnotatedTokenTree` are introduced. These are very similar to a normal `TokenTree`, but they also track the position of attributes and attribute targets within the stream. They are built when we collect tokens during parsing. An `AttrAnnotatedTokenStream` is converted to a regular `TokenStream` when we invoke a macro. * Token capturing and `LazyTokenStream` are modified to work with `AttrAnnotatedTokenStream`. A new `ReplaceRange` type is introduced, which is created during the parsing of a nested AST node to make the 'outer' AST node aware of the attributes and attribute target stored deeper in the token stream. * When we need to perform eager cfg-expansion (either due to `#[derive]` or `#[cfg_eval]`), we tokenize and reparse our target, capturing additional information about the locations of `#[cfg]` and `#[cfg_attr]` attributes at any depth within the target. This is a performance optimization, allowing us to perform less work in the typical case where captured tokens never have eager cfg-expansion run.
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write!(f, "LazyTokenStream({:?})", self.create_token_stream())
Rewrite `collect_tokens` implementations to use a flattened buffer Instead of trying to collect tokens at each depth, we 'flatten' the stream as we go allong, pushing open/close delimiters to our buffer just like regular tokens. One capturing is complete, we reconstruct a nested `TokenTree::Delimited` structure, producing a normal `TokenStream`. The reconstructed `TokenStream` is not created immediately - instead, it is produced on-demand by a closure (wrapped in a new `LazyTokenStream` type). This closure stores a clone of the original `TokenCursor`, plus a record of the number of calls to `next()/next_desugared()`. This is sufficient to reconstruct the tokenstream seen by the callback without storing any additional state. If the tokenstream is never used (e.g. when a captured `macro_rules!` argument is never passed to a proc macro), we never actually create a `TokenStream`. This implementation has a number of advantages over the previous one: * It is significantly simpler, with no edge cases around capturing the start/end of a delimited group. * It can be easily extended to allow replacing tokens an an arbitrary 'depth' by just using `Vec::splice` at the proper position. This is important for PR #76130, which requires us to track information about attributes along with tokens. * The lazy approach to `TokenStream` construction allows us to easily parse an AST struct, and then decide after the fact whether we need a `TokenStream`. This will be useful when we start collecting tokens for `Attribute` - we can discard the `LazyTokenStream` if the parsed attribute doesn't need tokens (e.g. is a builtin attribute). The performance impact seems to be neglibile (see https://github.com/rust-lang/rust/pull/77250#issuecomment-703960604). There is a small slowdown on a few benchmarks, but it only rises above 1% for incremental builds, where it represents a larger fraction of the much smaller instruction count. There a ~1% speedup on a few other incremental benchmarks - my guess is that the speedups and slowdowns will usually cancel out in practice.
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}
}
impl<S: Encoder> Encodable<S> for LazyTokenStream {
fn encode(&self, s: &mut S) -> Result<(), S::Error> {
// Used by AST json printing.
Encodable::encode(&self.create_token_stream(), s)
Rewrite `collect_tokens` implementations to use a flattened buffer Instead of trying to collect tokens at each depth, we 'flatten' the stream as we go allong, pushing open/close delimiters to our buffer just like regular tokens. One capturing is complete, we reconstruct a nested `TokenTree::Delimited` structure, producing a normal `TokenStream`. The reconstructed `TokenStream` is not created immediately - instead, it is produced on-demand by a closure (wrapped in a new `LazyTokenStream` type). This closure stores a clone of the original `TokenCursor`, plus a record of the number of calls to `next()/next_desugared()`. This is sufficient to reconstruct the tokenstream seen by the callback without storing any additional state. If the tokenstream is never used (e.g. when a captured `macro_rules!` argument is never passed to a proc macro), we never actually create a `TokenStream`. This implementation has a number of advantages over the previous one: * It is significantly simpler, with no edge cases around capturing the start/end of a delimited group. * It can be easily extended to allow replacing tokens an an arbitrary 'depth' by just using `Vec::splice` at the proper position. This is important for PR #76130, which requires us to track information about attributes along with tokens. * The lazy approach to `TokenStream` construction allows us to easily parse an AST struct, and then decide after the fact whether we need a `TokenStream`. This will be useful when we start collecting tokens for `Attribute` - we can discard the `LazyTokenStream` if the parsed attribute doesn't need tokens (e.g. is a builtin attribute). The performance impact seems to be neglibile (see https://github.com/rust-lang/rust/pull/77250#issuecomment-703960604). There is a small slowdown on a few benchmarks, but it only rises above 1% for incremental builds, where it represents a larger fraction of the much smaller instruction count. There a ~1% speedup on a few other incremental benchmarks - my guess is that the speedups and slowdowns will usually cancel out in practice.
2020-09-26 20:56:29 -05:00
}
}
impl<D: Decoder> Decodable<D> for LazyTokenStream {
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fn decode(_d: &mut D) -> Self {
Rewrite `collect_tokens` implementations to use a flattened buffer Instead of trying to collect tokens at each depth, we 'flatten' the stream as we go allong, pushing open/close delimiters to our buffer just like regular tokens. One capturing is complete, we reconstruct a nested `TokenTree::Delimited` structure, producing a normal `TokenStream`. The reconstructed `TokenStream` is not created immediately - instead, it is produced on-demand by a closure (wrapped in a new `LazyTokenStream` type). This closure stores a clone of the original `TokenCursor`, plus a record of the number of calls to `next()/next_desugared()`. This is sufficient to reconstruct the tokenstream seen by the callback without storing any additional state. If the tokenstream is never used (e.g. when a captured `macro_rules!` argument is never passed to a proc macro), we never actually create a `TokenStream`. This implementation has a number of advantages over the previous one: * It is significantly simpler, with no edge cases around capturing the start/end of a delimited group. * It can be easily extended to allow replacing tokens an an arbitrary 'depth' by just using `Vec::splice` at the proper position. This is important for PR #76130, which requires us to track information about attributes along with tokens. * The lazy approach to `TokenStream` construction allows us to easily parse an AST struct, and then decide after the fact whether we need a `TokenStream`. This will be useful when we start collecting tokens for `Attribute` - we can discard the `LazyTokenStream` if the parsed attribute doesn't need tokens (e.g. is a builtin attribute). The performance impact seems to be neglibile (see https://github.com/rust-lang/rust/pull/77250#issuecomment-703960604). There is a small slowdown on a few benchmarks, but it only rises above 1% for incremental builds, where it represents a larger fraction of the much smaller instruction count. There a ~1% speedup on a few other incremental benchmarks - my guess is that the speedups and slowdowns will usually cancel out in practice.
2020-09-26 20:56:29 -05:00
panic!("Attempted to decode LazyTokenStream");
}
}
impl<CTX> HashStable<CTX> for LazyTokenStream {
Rewrite `collect_tokens` implementations to use a flattened buffer Instead of trying to collect tokens at each depth, we 'flatten' the stream as we go allong, pushing open/close delimiters to our buffer just like regular tokens. One capturing is complete, we reconstruct a nested `TokenTree::Delimited` structure, producing a normal `TokenStream`. The reconstructed `TokenStream` is not created immediately - instead, it is produced on-demand by a closure (wrapped in a new `LazyTokenStream` type). This closure stores a clone of the original `TokenCursor`, plus a record of the number of calls to `next()/next_desugared()`. This is sufficient to reconstruct the tokenstream seen by the callback without storing any additional state. If the tokenstream is never used (e.g. when a captured `macro_rules!` argument is never passed to a proc macro), we never actually create a `TokenStream`. This implementation has a number of advantages over the previous one: * It is significantly simpler, with no edge cases around capturing the start/end of a delimited group. * It can be easily extended to allow replacing tokens an an arbitrary 'depth' by just using `Vec::splice` at the proper position. This is important for PR #76130, which requires us to track information about attributes along with tokens. * The lazy approach to `TokenStream` construction allows us to easily parse an AST struct, and then decide after the fact whether we need a `TokenStream`. This will be useful when we start collecting tokens for `Attribute` - we can discard the `LazyTokenStream` if the parsed attribute doesn't need tokens (e.g. is a builtin attribute). The performance impact seems to be neglibile (see https://github.com/rust-lang/rust/pull/77250#issuecomment-703960604). There is a small slowdown on a few benchmarks, but it only rises above 1% for incremental builds, where it represents a larger fraction of the much smaller instruction count. There a ~1% speedup on a few other incremental benchmarks - my guess is that the speedups and slowdowns will usually cancel out in practice.
2020-09-26 20:56:29 -05:00
fn hash_stable(&self, _hcx: &mut CTX, _hasher: &mut StableHasher) {
panic!("Attempted to compute stable hash for LazyTokenStream");
}
}
Implement token-based handling of attributes during expansion This PR modifies the macro expansion infrastructure to handle attributes in a fully token-based manner. As a result: * Derives macros no longer lose spans when their input is modified by eager cfg-expansion. This is accomplished by performing eager cfg-expansion on the token stream that we pass to the derive proc-macro * Inner attributes now preserve spans in all cases, including when we have multiple inner attributes in a row. This is accomplished through the following changes: * New structs `AttrAnnotatedTokenStream` and `AttrAnnotatedTokenTree` are introduced. These are very similar to a normal `TokenTree`, but they also track the position of attributes and attribute targets within the stream. They are built when we collect tokens during parsing. An `AttrAnnotatedTokenStream` is converted to a regular `TokenStream` when we invoke a macro. * Token capturing and `LazyTokenStream` are modified to work with `AttrAnnotatedTokenStream`. A new `ReplaceRange` type is introduced, which is created during the parsing of a nested AST node to make the 'outer' AST node aware of the attributes and attribute target stored deeper in the token stream. * When we need to perform eager cfg-expansion (either due to `#[derive]` or `#[cfg_eval]`), we tokenize and reparse our target, capturing additional information about the locations of `#[cfg]` and `#[cfg_attr]` attributes at any depth within the target. This is a performance optimization, allowing us to perform less work in the typical case where captured tokens never have eager cfg-expansion run.
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/// A `AttrAnnotatedTokenStream` is similar to a `TokenStream`, but with extra
/// information about the tokens for attribute targets. This is used
/// during expansion to perform early cfg-expansion, and to process attributes
/// during proc-macro invocations.
#[derive(Clone, Debug, Default, Encodable, Decodable)]
pub struct AttrAnnotatedTokenStream(pub Lrc<Vec<(AttrAnnotatedTokenTree, Spacing)>>);
/// Like `TokenTree`, but for `AttrAnnotatedTokenStream`
#[derive(Clone, Debug, Encodable, Decodable)]
pub enum AttrAnnotatedTokenTree {
Token(Token),
Delimited(DelimSpan, DelimToken, AttrAnnotatedTokenStream),
/// Stores the attributes for an attribute target,
/// along with the tokens for that attribute target.
/// See `AttributesData` for more information
Attributes(AttributesData),
}
impl AttrAnnotatedTokenStream {
pub fn new(tokens: Vec<(AttrAnnotatedTokenTree, Spacing)>) -> AttrAnnotatedTokenStream {
AttrAnnotatedTokenStream(Lrc::new(tokens))
}
/// Converts this `AttrAnnotatedTokenStream` to a plain `TokenStream
/// During conversion, `AttrAnnotatedTokenTree::Attributes` get 'flattened'
/// back to a `TokenStream` of the form `outer_attr attr_target`.
/// If there are inner attributes, they are inserted into the proper
/// place in the attribute target tokens.
pub fn to_tokenstream(&self) -> TokenStream {
let trees: Vec<_> = self
.0
.iter()
.flat_map(|tree| match &tree.0 {
AttrAnnotatedTokenTree::Token(inner) => {
smallvec![(TokenTree::Token(inner.clone()), tree.1)].into_iter()
}
AttrAnnotatedTokenTree::Delimited(span, delim, stream) => smallvec![(
TokenTree::Delimited(*span, *delim, stream.to_tokenstream()),
tree.1,
)]
.into_iter(),
AttrAnnotatedTokenTree::Attributes(data) => {
let mut outer_attrs = Vec::new();
let mut inner_attrs = Vec::new();
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for attr in &data.attrs {
Implement token-based handling of attributes during expansion This PR modifies the macro expansion infrastructure to handle attributes in a fully token-based manner. As a result: * Derives macros no longer lose spans when their input is modified by eager cfg-expansion. This is accomplished by performing eager cfg-expansion on the token stream that we pass to the derive proc-macro * Inner attributes now preserve spans in all cases, including when we have multiple inner attributes in a row. This is accomplished through the following changes: * New structs `AttrAnnotatedTokenStream` and `AttrAnnotatedTokenTree` are introduced. These are very similar to a normal `TokenTree`, but they also track the position of attributes and attribute targets within the stream. They are built when we collect tokens during parsing. An `AttrAnnotatedTokenStream` is converted to a regular `TokenStream` when we invoke a macro. * Token capturing and `LazyTokenStream` are modified to work with `AttrAnnotatedTokenStream`. A new `ReplaceRange` type is introduced, which is created during the parsing of a nested AST node to make the 'outer' AST node aware of the attributes and attribute target stored deeper in the token stream. * When we need to perform eager cfg-expansion (either due to `#[derive]` or `#[cfg_eval]`), we tokenize and reparse our target, capturing additional information about the locations of `#[cfg]` and `#[cfg_attr]` attributes at any depth within the target. This is a performance optimization, allowing us to perform less work in the typical case where captured tokens never have eager cfg-expansion run.
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match attr.style {
crate::AttrStyle::Outer => {
outer_attrs.push(attr);
}
crate::AttrStyle::Inner => {
inner_attrs.push(attr);
}
}
}
let mut target_tokens: Vec<_> = data
.tokens
.create_token_stream()
.to_tokenstream()
.0
.iter()
.cloned()
.collect();
if !inner_attrs.is_empty() {
let mut found = false;
// Check the last two trees (to account for a trailing semi)
for (tree, _) in target_tokens.iter_mut().rev().take(2) {
if let TokenTree::Delimited(span, delim, delim_tokens) = tree {
// Inner attributes are only supported on extern blocks, functions, impls,
// and modules. All of these have their inner attributes placed at
// the beginning of the rightmost outermost braced group:
// e.g. fn foo() { #![my_attr} }
//
// Therefore, we can insert them back into the right location
// without needing to do any extra position tracking.
//
// Note: Outline modules are an exception - they can
// have attributes like `#![my_attr]` at the start of a file.
// Support for custom attributes in this position is not
// properly implemented - we always synthesize fake tokens,
// so we never reach this code.
let mut builder = TokenStreamBuilder::new();
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for inner_attr in inner_attrs {
Implement token-based handling of attributes during expansion This PR modifies the macro expansion infrastructure to handle attributes in a fully token-based manner. As a result: * Derives macros no longer lose spans when their input is modified by eager cfg-expansion. This is accomplished by performing eager cfg-expansion on the token stream that we pass to the derive proc-macro * Inner attributes now preserve spans in all cases, including when we have multiple inner attributes in a row. This is accomplished through the following changes: * New structs `AttrAnnotatedTokenStream` and `AttrAnnotatedTokenTree` are introduced. These are very similar to a normal `TokenTree`, but they also track the position of attributes and attribute targets within the stream. They are built when we collect tokens during parsing. An `AttrAnnotatedTokenStream` is converted to a regular `TokenStream` when we invoke a macro. * Token capturing and `LazyTokenStream` are modified to work with `AttrAnnotatedTokenStream`. A new `ReplaceRange` type is introduced, which is created during the parsing of a nested AST node to make the 'outer' AST node aware of the attributes and attribute target stored deeper in the token stream. * When we need to perform eager cfg-expansion (either due to `#[derive]` or `#[cfg_eval]`), we tokenize and reparse our target, capturing additional information about the locations of `#[cfg]` and `#[cfg_attr]` attributes at any depth within the target. This is a performance optimization, allowing us to perform less work in the typical case where captured tokens never have eager cfg-expansion run.
2020-11-28 17:33:17 -06:00
builder.push(inner_attr.tokens().to_tokenstream());
}
builder.push(delim_tokens.clone());
*tree = TokenTree::Delimited(*span, *delim, builder.build());
found = true;
break;
}
}
assert!(
found,
"Failed to find trailing delimited group in: {:?}",
target_tokens
);
}
let mut flat: SmallVec<[_; 1]> = SmallVec::new();
for attr in outer_attrs {
// FIXME: Make this more efficient
flat.extend(attr.tokens().to_tokenstream().0.clone().iter().cloned());
}
flat.extend(target_tokens);
flat.into_iter()
}
})
.collect();
TokenStream::new(trees)
}
}
/// Stores the tokens for an attribute target, along
/// with its attributes.
///
/// This is constructed during parsing when we need to capture
/// tokens.
///
/// For example, `#[cfg(FALSE)] struct Foo {}` would
2021-04-19 07:57:08 -05:00
/// have an `attrs` field containing the `#[cfg(FALSE)]` attr,
/// and a `tokens` field storing the (unparsed) tokens `struct Foo {}`
Implement token-based handling of attributes during expansion This PR modifies the macro expansion infrastructure to handle attributes in a fully token-based manner. As a result: * Derives macros no longer lose spans when their input is modified by eager cfg-expansion. This is accomplished by performing eager cfg-expansion on the token stream that we pass to the derive proc-macro * Inner attributes now preserve spans in all cases, including when we have multiple inner attributes in a row. This is accomplished through the following changes: * New structs `AttrAnnotatedTokenStream` and `AttrAnnotatedTokenTree` are introduced. These are very similar to a normal `TokenTree`, but they also track the position of attributes and attribute targets within the stream. They are built when we collect tokens during parsing. An `AttrAnnotatedTokenStream` is converted to a regular `TokenStream` when we invoke a macro. * Token capturing and `LazyTokenStream` are modified to work with `AttrAnnotatedTokenStream`. A new `ReplaceRange` type is introduced, which is created during the parsing of a nested AST node to make the 'outer' AST node aware of the attributes and attribute target stored deeper in the token stream. * When we need to perform eager cfg-expansion (either due to `#[derive]` or `#[cfg_eval]`), we tokenize and reparse our target, capturing additional information about the locations of `#[cfg]` and `#[cfg_attr]` attributes at any depth within the target. This is a performance optimization, allowing us to perform less work in the typical case where captured tokens never have eager cfg-expansion run.
2020-11-28 17:33:17 -06:00
#[derive(Clone, Debug, Encodable, Decodable)]
pub struct AttributesData {
/// Attributes, both outer and inner.
/// These are stored in the original order that they were parsed in.
pub attrs: AttrVec,
/// The underlying tokens for the attribute target that `attrs`
/// are applied to
pub tokens: LazyTokenStream,
}
/// A `TokenStream` is an abstract sequence of tokens, organized into [`TokenTree`]s.
///
2017-01-17 21:27:09 -06:00
/// The goal is for procedural macros to work with `TokenStream`s and `TokenTree`s
/// instead of a representation of the abstract syntax tree.
/// Today's `TokenTree`s can still contain AST via `token::Interpolated` for
2021-04-05 15:58:07 -05:00
/// backwards compatibility.
#[derive(Clone, Debug, Default, Encodable, Decodable)]
pub struct TokenStream(pub(crate) Lrc<Vec<TreeAndSpacing>>);
pub type TreeAndSpacing = (TokenTree, Spacing);
// `TokenStream` is used a lot. Make sure it doesn't unintentionally get bigger.
#[cfg(all(target_arch = "x86_64", target_pointer_width = "64"))]
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rustc_data_structures::static_assert_size!(TokenStream, 8);
#[derive(Clone, Copy, Debug, PartialEq, Encodable, Decodable)]
pub enum Spacing {
Alone,
Joint,
}
impl TokenStream {
/// Given a `TokenStream` with a `Stream` of only two arguments, return a new `TokenStream`
/// separating the two arguments with a comma for diagnostic suggestions.
pub fn add_comma(&self) -> Option<(TokenStream, Span)> {
// Used to suggest if a user writes `foo!(a b);`
let mut suggestion = None;
let mut iter = self.0.iter().enumerate().peekable();
while let Some((pos, ts)) = iter.next() {
if let Some((_, next)) = iter.peek() {
let sp = match (&ts, &next) {
(_, (TokenTree::Token(Token { kind: token::Comma, .. }), _)) => continue,
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(
(TokenTree::Token(token_left), Spacing::Alone),
(TokenTree::Token(token_right), _),
) if ((token_left.is_ident() && !token_left.is_reserved_ident())
|| token_left.is_lit())
&& ((token_right.is_ident() && !token_right.is_reserved_ident())
|| token_right.is_lit()) =>
2019-12-22 16:42:04 -06:00
{
token_left.span
2019-12-22 16:42:04 -06:00
}
((TokenTree::Delimited(sp, ..), Spacing::Alone), _) => sp.entire(),
_ => continue,
};
let sp = sp.shrink_to_hi();
let comma = (TokenTree::token(token::Comma, sp), Spacing::Alone);
suggestion = Some((pos, comma, sp));
}
}
if let Some((pos, comma, sp)) = suggestion {
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let mut new_stream = Vec::with_capacity(self.0.len() + 1);
let parts = self.0.split_at(pos + 1);
new_stream.extend_from_slice(parts.0);
new_stream.push(comma);
new_stream.extend_from_slice(parts.1);
return Some((TokenStream::new(new_stream), sp));
}
None
}
}
Implement token-based handling of attributes during expansion This PR modifies the macro expansion infrastructure to handle attributes in a fully token-based manner. As a result: * Derives macros no longer lose spans when their input is modified by eager cfg-expansion. This is accomplished by performing eager cfg-expansion on the token stream that we pass to the derive proc-macro * Inner attributes now preserve spans in all cases, including when we have multiple inner attributes in a row. This is accomplished through the following changes: * New structs `AttrAnnotatedTokenStream` and `AttrAnnotatedTokenTree` are introduced. These are very similar to a normal `TokenTree`, but they also track the position of attributes and attribute targets within the stream. They are built when we collect tokens during parsing. An `AttrAnnotatedTokenStream` is converted to a regular `TokenStream` when we invoke a macro. * Token capturing and `LazyTokenStream` are modified to work with `AttrAnnotatedTokenStream`. A new `ReplaceRange` type is introduced, which is created during the parsing of a nested AST node to make the 'outer' AST node aware of the attributes and attribute target stored deeper in the token stream. * When we need to perform eager cfg-expansion (either due to `#[derive]` or `#[cfg_eval]`), we tokenize and reparse our target, capturing additional information about the locations of `#[cfg]` and `#[cfg_attr]` attributes at any depth within the target. This is a performance optimization, allowing us to perform less work in the typical case where captured tokens never have eager cfg-expansion run.
2020-11-28 17:33:17 -06:00
impl From<(AttrAnnotatedTokenTree, Spacing)> for AttrAnnotatedTokenStream {
fn from((tree, spacing): (AttrAnnotatedTokenTree, Spacing)) -> AttrAnnotatedTokenStream {
AttrAnnotatedTokenStream::new(vec![(tree, spacing)])
}
}
2017-01-17 21:27:09 -06:00
impl From<TokenTree> for TokenStream {
fn from(tree: TokenTree) -> TokenStream {
TokenStream::new(vec![(tree, Spacing::Alone)])
}
}
impl From<TokenTree> for TreeAndSpacing {
fn from(tree: TokenTree) -> TreeAndSpacing {
(tree, Spacing::Alone)
}
}
impl iter::FromIterator<TokenTree> for TokenStream {
fn from_iter<I: IntoIterator<Item = TokenTree>>(iter: I) -> Self {
TokenStream::new(iter.into_iter().map(Into::into).collect::<Vec<TreeAndSpacing>>())
2018-08-12 14:45:48 -05:00
}
}
2017-01-17 21:27:09 -06:00
impl Eq for TokenStream {}
impl PartialEq<TokenStream> for TokenStream {
fn eq(&self, other: &TokenStream) -> bool {
2017-01-17 21:27:09 -06:00
self.trees().eq(other.trees())
}
}
impl TokenStream {
pub fn new(streams: Vec<TreeAndSpacing>) -> TokenStream {
TokenStream(Lrc::new(streams))
}
pub fn is_empty(&self) -> bool {
self.0.is_empty()
}
pub fn len(&self) -> usize {
self.0.len()
}
2019-10-10 03:26:10 -05:00
pub fn from_streams(mut streams: SmallVec<[TokenStream; 2]>) -> TokenStream {
match streams.len() {
0 => TokenStream::default(),
1 => streams.pop().unwrap(),
_ => {
// We are going to extend the first stream in `streams` with
// the elements from the subsequent streams. This requires
// using `make_mut()` on the first stream, and in practice this
// doesn't cause cloning 99.9% of the time.
//
// One very common use case is when `streams` has two elements,
// where the first stream has any number of elements within
// (often 1, but sometimes many more) and the second stream has
// a single element within.
// Determine how much the first stream will be extended.
// Needed to avoid quadratic blow up from on-the-fly
// reallocations (#57735).
let num_appends = streams.iter().skip(1).map(|ts| ts.len()).sum();
// Get the first stream. If it's `None`, create an empty
// stream.
2019-11-04 08:59:09 -06:00
let mut iter = streams.drain(..);
let mut first_stream_lrc = iter.next().unwrap().0;
// Append the elements to the first stream, after reserving
// space for them.
let first_vec_mut = Lrc::make_mut(&mut first_stream_lrc);
first_vec_mut.reserve(num_appends);
for stream in iter {
first_vec_mut.extend(stream.0.iter().cloned());
}
// Create the final `TokenStream`.
TokenStream(first_stream_lrc)
}
}
}
pub fn trees(&self) -> Cursor {
self.clone().into_trees()
}
pub fn into_trees(self) -> Cursor {
2017-01-17 21:27:09 -06:00
Cursor::new(self)
}
/// Compares two `TokenStream`s, checking equality without regarding span information.
pub fn eq_unspanned(&self, other: &TokenStream) -> bool {
let mut t1 = self.trees();
let mut t2 = other.trees();
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for (t1, t2) in iter::zip(&mut t1, &mut t2) {
if !t1.eq_unspanned(&t2) {
return false;
}
}
t1.next().is_none() && t2.next().is_none()
}
pub fn map_enumerated<F: FnMut(usize, &TokenTree) -> TokenTree>(self, mut f: F) -> TokenStream {
TokenStream(Lrc::new(
self.0
.iter()
.enumerate()
.map(|(i, (tree, is_joint))| (f(i, tree), *is_joint))
.collect(),
))
}
}
// 99.5%+ of the time we have 1 or 2 elements in this vector.
#[derive(Clone)]
pub struct TokenStreamBuilder(SmallVec<[TokenStream; 2]>);
impl TokenStreamBuilder {
2017-06-04 20:41:33 -05:00
pub fn new() -> TokenStreamBuilder {
TokenStreamBuilder(SmallVec::new())
2017-06-04 20:41:33 -05:00
}
pub fn push<T: Into<TokenStream>>(&mut self, stream: T) {
let mut stream = stream.into();
// If `self` is not empty and the last tree within the last stream is a
// token tree marked with `Joint`...
if let Some(TokenStream(ref mut last_stream_lrc)) = self.0.last_mut()
&& let Some((TokenTree::Token(last_token), Spacing::Joint)) = last_stream_lrc.last()
// ...and `stream` is not empty and the first tree within it is
// a token tree...
&& let TokenStream(ref mut stream_lrc) = stream
&& let Some((TokenTree::Token(token), spacing)) = stream_lrc.first()
// ...and the two tokens can be glued together...
&& let Some(glued_tok) = last_token.glue(&token)
{
// ...then do so, by overwriting the last token
// tree in `self` and removing the first token tree
// from `stream`. This requires using `make_mut()`
// on the last stream in `self` and on `stream`,
// and in practice this doesn't cause cloning 99.9%
// of the time.
// Overwrite the last token tree with the merged
// token.
let last_vec_mut = Lrc::make_mut(last_stream_lrc);
*last_vec_mut.last_mut().unwrap() = (TokenTree::Token(glued_tok), *spacing);
// Remove the first token tree from `stream`. (This
// is almost always the only tree in `stream`.)
let stream_vec_mut = Lrc::make_mut(stream_lrc);
stream_vec_mut.remove(0);
// Don't push `stream` if it's empty -- that could
// block subsequent token gluing, by getting
// between two token trees that should be glued
// together.
if !stream.is_empty() {
self.0.push(stream);
}
return;
}
self.0.push(stream);
}
pub fn build(self) -> TokenStream {
TokenStream::from_streams(self.0)
}
}
/// By-reference iterator over a [`TokenStream`].
#[derive(Clone)]
pub struct CursorRef<'t> {
stream: &'t TokenStream,
index: usize,
}
impl<'t> CursorRef<'t> {
fn next_with_spacing(&mut self) -> Option<&'t TreeAndSpacing> {
self.stream.0.get(self.index).map(|tree| {
self.index += 1;
tree
})
}
}
impl<'t> Iterator for CursorRef<'t> {
type Item = &'t TokenTree;
fn next(&mut self) -> Option<&'t TokenTree> {
self.next_with_spacing().map(|(tree, _)| tree)
}
}
/// Owning by-value iterator over a [`TokenStream`].
// FIXME: Many uses of this can be replaced with by-reference iterator to avoid clones.
#[derive(Clone)]
pub struct Cursor {
pub stream: TokenStream,
index: usize,
2017-01-17 21:27:09 -06:00
}
impl Iterator for Cursor {
type Item = TokenTree;
fn next(&mut self) -> Option<TokenTree> {
self.next_with_spacing().map(|(tree, _)| tree)
}
}
impl Cursor {
fn new(stream: TokenStream) -> Self {
Cursor { stream, index: 0 }
}
pub fn next_with_spacing(&mut self) -> Option<TreeAndSpacing> {
self.stream.0.get(self.index).map(|tree| {
self.index += 1;
tree.clone()
})
2017-03-28 20:55:01 -05:00
}
Implement token-based handling of attributes during expansion This PR modifies the macro expansion infrastructure to handle attributes in a fully token-based manner. As a result: * Derives macros no longer lose spans when their input is modified by eager cfg-expansion. This is accomplished by performing eager cfg-expansion on the token stream that we pass to the derive proc-macro * Inner attributes now preserve spans in all cases, including when we have multiple inner attributes in a row. This is accomplished through the following changes: * New structs `AttrAnnotatedTokenStream` and `AttrAnnotatedTokenTree` are introduced. These are very similar to a normal `TokenTree`, but they also track the position of attributes and attribute targets within the stream. They are built when we collect tokens during parsing. An `AttrAnnotatedTokenStream` is converted to a regular `TokenStream` when we invoke a macro. * Token capturing and `LazyTokenStream` are modified to work with `AttrAnnotatedTokenStream`. A new `ReplaceRange` type is introduced, which is created during the parsing of a nested AST node to make the 'outer' AST node aware of the attributes and attribute target stored deeper in the token stream. * When we need to perform eager cfg-expansion (either due to `#[derive]` or `#[cfg_eval]`), we tokenize and reparse our target, capturing additional information about the locations of `#[cfg]` and `#[cfg_attr]` attributes at any depth within the target. This is a performance optimization, allowing us to perform less work in the typical case where captured tokens never have eager cfg-expansion run.
2020-11-28 17:33:17 -06:00
pub fn index(&self) -> usize {
self.index
}
pub fn append(&mut self, new_stream: TokenStream) {
if new_stream.is_empty() {
return;
}
let index = self.index;
let stream = mem::take(&mut self.stream);
*self = TokenStream::from_streams(smallvec![stream, new_stream]).into_trees();
self.index = index;
}
pub fn look_ahead(&self, n: usize) -> Option<&TokenTree> {
self.stream.0[self.index..].get(n).map(|(tree, _)| tree)
}
}
#[derive(Debug, Copy, Clone, PartialEq, Encodable, Decodable, HashStable_Generic)]
pub struct DelimSpan {
pub open: Span,
pub close: Span,
}
impl DelimSpan {
pub fn from_single(sp: Span) -> Self {
DelimSpan { open: sp, close: sp }
}
pub fn from_pair(open: Span, close: Span) -> Self {
DelimSpan { open, close }
}
pub fn dummy() -> Self {
Self::from_single(DUMMY_SP)
}
pub fn entire(self) -> Span {
self.open.with_hi(self.close.hi())
}
}