diff options
Diffstat (limited to 'compiler/rustc_parse/src/parser/attr_wrapper.rs')
| -rw-r--r-- | compiler/rustc_parse/src/parser/attr_wrapper.rs | 464 |
1 files changed, 464 insertions, 0 deletions
diff --git a/compiler/rustc_parse/src/parser/attr_wrapper.rs b/compiler/rustc_parse/src/parser/attr_wrapper.rs new file mode 100644 index 000000000..6c750ff42 --- /dev/null +++ b/compiler/rustc_parse/src/parser/attr_wrapper.rs @@ -0,0 +1,464 @@ +use super::{Capturing, FlatToken, ForceCollect, Parser, ReplaceRange, TokenCursor, TrailingToken}; +use rustc_ast::token::{self, Delimiter, Token, TokenKind}; +use rustc_ast::tokenstream::{AttrAnnotatedTokenStream, AttributesData, CreateTokenStream}; +use rustc_ast::tokenstream::{AttrAnnotatedTokenTree, DelimSpan, LazyTokenStream, Spacing}; +use rustc_ast::{self as ast}; +use rustc_ast::{AttrVec, Attribute, HasAttrs, HasTokens}; +use rustc_errors::PResult; +use rustc_span::{sym, Span}; + +use std::convert::TryInto; +use std::ops::Range; + +/// A wrapper type to ensure that the parser handles outer attributes correctly. +/// When we parse outer attributes, we need to ensure that we capture tokens +/// for the attribute target. This allows us to perform cfg-expansion on +/// a token stream before we invoke a derive proc-macro. +/// +/// This wrapper prevents direct access to the underlying `Vec<ast::Attribute>`. +/// Parsing code can only get access to the underlying attributes +/// by passing an `AttrWrapper` to `collect_tokens_trailing_tokens`. +/// This makes it difficult to accidentally construct an AST node +/// (which stores a `Vec<ast::Attribute>`) without first collecting tokens. +/// +/// This struct has its own module, to ensure that the parser code +/// cannot directly access the `attrs` field +#[derive(Debug, Clone)] +pub struct AttrWrapper { + attrs: AttrVec, + // The start of the outer attributes in the token cursor. + // This allows us to create a `ReplaceRange` for the entire attribute + // target, including outer attributes. + start_pos: usize, +} + +// This struct is passed around very frequently, +// so make sure it doesn't accidentally get larger +#[cfg(all(target_arch = "x86_64", target_pointer_width = "64"))] +rustc_data_structures::static_assert_size!(AttrWrapper, 16); + +impl AttrWrapper { + pub(super) fn new(attrs: AttrVec, start_pos: usize) -> AttrWrapper { + AttrWrapper { attrs, start_pos } + } + pub fn empty() -> AttrWrapper { + AttrWrapper { attrs: AttrVec::new(), start_pos: usize::MAX } + } + // FIXME: Delay span bug here? + pub(crate) fn take_for_recovery(self) -> AttrVec { + self.attrs + } + + // FIXME: require passing an NT to prevent misuse of this method + pub(crate) fn prepend_to_nt_inner(self, attrs: &mut Vec<Attribute>) { + let mut self_attrs: Vec<_> = self.attrs.into(); + std::mem::swap(attrs, &mut self_attrs); + attrs.extend(self_attrs); + } + + pub fn is_empty(&self) -> bool { + self.attrs.is_empty() + } + + pub fn maybe_needs_tokens(&self) -> bool { + crate::parser::attr::maybe_needs_tokens(&self.attrs) + } +} + +/// Returns `true` if `attrs` contains a `cfg` or `cfg_attr` attribute +fn has_cfg_or_cfg_attr(attrs: &[Attribute]) -> bool { + // NOTE: Builtin attributes like `cfg` and `cfg_attr` cannot be renamed via imports. + // Therefore, the absence of a literal `cfg` or `cfg_attr` guarantees that + // we don't need to do any eager expansion. + attrs.iter().any(|attr| { + attr.ident().map_or(false, |ident| ident.name == sym::cfg || ident.name == sym::cfg_attr) + }) +} + +// Produces a `TokenStream` on-demand. Using `cursor_snapshot` +// and `num_calls`, we can reconstruct the `TokenStream` seen +// by the callback. This allows us to avoid producing a `TokenStream` +// if it is never needed - for example, a captured `macro_rules!` +// argument that is never passed to a proc macro. +// In practice token stream creation happens rarely compared to +// calls to `collect_tokens` (see some statistics in #78736), +// so we are doing as little up-front work as possible. +// +// This also makes `Parser` very cheap to clone, since +// there is no intermediate collection buffer to clone. +#[derive(Clone)] +struct LazyTokenStreamImpl { + start_token: (Token, Spacing), + cursor_snapshot: TokenCursor, + num_calls: usize, + break_last_token: bool, + replace_ranges: Box<[ReplaceRange]>, +} + +#[cfg(all(target_arch = "x86_64", target_pointer_width = "64"))] +rustc_data_structures::static_assert_size!(LazyTokenStreamImpl, 144); + +impl CreateTokenStream for LazyTokenStreamImpl { + fn create_token_stream(&self) -> AttrAnnotatedTokenStream { + // The token produced by the final call to `{,inlined_}next` was not + // actually consumed by the callback. The combination of chaining the + // initial token and using `take` produces the desired result - we + // produce an empty `TokenStream` if no calls were made, and omit the + // final token otherwise. + let mut cursor_snapshot = self.cursor_snapshot.clone(); + let tokens = + std::iter::once((FlatToken::Token(self.start_token.0.clone()), self.start_token.1)) + .chain((0..self.num_calls).map(|_| { + let token = cursor_snapshot.next(cursor_snapshot.desugar_doc_comments); + (FlatToken::Token(token.0), token.1) + })) + .take(self.num_calls); + + if !self.replace_ranges.is_empty() { + let mut tokens: Vec<_> = tokens.collect(); + let mut replace_ranges = self.replace_ranges.clone(); + replace_ranges.sort_by_key(|(range, _)| range.start); + + #[cfg(debug_assertions)] + { + for [(range, tokens), (next_range, next_tokens)] in replace_ranges.array_windows() { + assert!( + range.end <= next_range.start || range.end >= next_range.end, + "Replace ranges should either be disjoint or nested: ({:?}, {:?}) ({:?}, {:?})", + range, + tokens, + next_range, + next_tokens, + ); + } + } + + // Process the replace ranges, starting from the highest start + // position and working our way back. If have tokens like: + // + // `#[cfg(FALSE)]` struct Foo { #[cfg(FALSE)] field: bool }` + // + // Then we will generate replace ranges for both + // the `#[cfg(FALSE)] field: bool` and the entire + // `#[cfg(FALSE)]` struct Foo { #[cfg(FALSE)] field: bool }` + // + // By starting processing from the replace range with the greatest + // start position, we ensure that any replace range which encloses + // another replace range will capture the *replaced* tokens for the inner + // range, not the original tokens. + for (range, new_tokens) in replace_ranges.iter().rev() { + assert!(!range.is_empty(), "Cannot replace an empty range: {:?}", range); + // Replace ranges are only allowed to decrease the number of tokens. + assert!( + range.len() >= new_tokens.len(), + "Range {:?} has greater len than {:?}", + range, + new_tokens + ); + + // Replace any removed tokens with `FlatToken::Empty`. + // This keeps the total length of `tokens` constant throughout the + // replacement process, allowing us to use all of the `ReplaceRanges` entries + // without adjusting indices. + let filler = std::iter::repeat((FlatToken::Empty, Spacing::Alone)) + .take(range.len() - new_tokens.len()); + + tokens.splice( + (range.start as usize)..(range.end as usize), + new_tokens.clone().into_iter().chain(filler), + ); + } + make_token_stream(tokens.into_iter(), self.break_last_token) + } else { + make_token_stream(tokens, self.break_last_token) + } + } +} + +impl<'a> Parser<'a> { + /// Records all tokens consumed by the provided callback, + /// including the current token. These tokens are collected + /// into a `LazyTokenStream`, and returned along with the result + /// of the callback. + /// + /// Note: If your callback consumes an opening delimiter + /// (including the case where you call `collect_tokens` + /// when the current token is an opening delimiter), + /// you must also consume the corresponding closing delimiter. + /// + /// That is, you can consume + /// `something ([{ }])` or `([{}])`, but not `([{}]` + /// + /// This restriction shouldn't be an issue in practice, + /// since this function is used to record the tokens for + /// a parsed AST item, which always has matching delimiters. + pub fn collect_tokens_trailing_token<R: HasAttrs + HasTokens>( + &mut self, + attrs: AttrWrapper, + force_collect: ForceCollect, + f: impl FnOnce(&mut Self, Vec<ast::Attribute>) -> PResult<'a, (R, TrailingToken)>, + ) -> PResult<'a, R> { + // We only bail out when nothing could possibly observe the collected tokens: + // 1. We cannot be force collecting tokens (since force-collecting requires tokens + // by definition + if matches!(force_collect, ForceCollect::No) + // None of our outer attributes can require tokens (e.g. a proc-macro) + && !attrs.maybe_needs_tokens() + // If our target supports custom inner attributes, then we cannot bail + // out early, since we may need to capture tokens for a custom inner attribute + // invocation. + && !R::SUPPORTS_CUSTOM_INNER_ATTRS + // Never bail out early in `capture_cfg` mode, since there might be `#[cfg]` + // or `#[cfg_attr]` attributes. + && !self.capture_cfg + { + return Ok(f(self, attrs.attrs.into())?.0); + } + + let start_token = (self.token.clone(), self.token_spacing); + let cursor_snapshot = self.token_cursor.clone(); + + let has_outer_attrs = !attrs.attrs.is_empty(); + let prev_capturing = std::mem::replace(&mut self.capture_state.capturing, Capturing::Yes); + let replace_ranges_start = self.capture_state.replace_ranges.len(); + + let ret = f(self, attrs.attrs.into()); + + self.capture_state.capturing = prev_capturing; + + let (mut ret, trailing) = ret?; + + // When we're not in `capture-cfg` mode, then bail out early if: + // 1. Our target doesn't support tokens at all (e.g we're parsing an `NtIdent`) + // so there's nothing for us to do. + // 2. Our target already has tokens set (e.g. we've parsed something + // like `#[my_attr] $item`. The actual parsing code takes care of prepending + // any attributes to the nonterminal, so we don't need to modify the + // already captured tokens. + // Note that this check is independent of `force_collect`- if we already + // have tokens, or can't even store them, then there's never a need to + // force collection of new tokens. + if !self.capture_cfg && matches!(ret.tokens_mut(), None | Some(Some(_))) { + return Ok(ret); + } + + // This is very similar to the bail out check at the start of this function. + // Now that we've parsed an AST node, we have more information available. + if matches!(force_collect, ForceCollect::No) + // We now have inner attributes available, so this check is more precise + // than `attrs.maybe_needs_tokens()` at the start of the function. + // As a result, we don't need to check `R::SUPPORTS_CUSTOM_INNER_ATTRS` + && !crate::parser::attr::maybe_needs_tokens(ret.attrs()) + // Subtle: We call `has_cfg_or_cfg_attr` with the attrs from `ret`. + // This ensures that we consider inner attributes (e.g. `#![cfg]`), + // which require us to have tokens available + // We also call `has_cfg_or_cfg_attr` at the beginning of this function, + // but we only bail out if there's no possibility of inner attributes + // (!R::SUPPORTS_CUSTOM_INNER_ATTRS) + // We only capture about `#[cfg]` or `#[cfg_attr]` in `capture_cfg` + // mode - during normal parsing, we don't need any special capturing + // for those attributes, since they're builtin. + && !(self.capture_cfg && has_cfg_or_cfg_attr(ret.attrs())) + { + return Ok(ret); + } + + let mut inner_attr_replace_ranges = Vec::new(); + // Take the captured ranges for any inner attributes that we parsed. + for inner_attr in ret.attrs().iter().filter(|a| a.style == ast::AttrStyle::Inner) { + if let Some(attr_range) = self.capture_state.inner_attr_ranges.remove(&inner_attr.id) { + inner_attr_replace_ranges.push(attr_range); + } else { + self.sess + .span_diagnostic + .delay_span_bug(inner_attr.span, "Missing token range for attribute"); + } + } + + let replace_ranges_end = self.capture_state.replace_ranges.len(); + + let cursor_snapshot_next_calls = cursor_snapshot.num_next_calls; + let mut end_pos = self.token_cursor.num_next_calls; + + // Capture a trailing token if requested by the callback 'f' + match trailing { + TrailingToken::None => {} + TrailingToken::Semi => { + assert_eq!(self.token.kind, token::Semi); + end_pos += 1; + } + TrailingToken::MaybeComma => { + if self.token.kind == token::Comma { + end_pos += 1; + } + } + } + + // If we 'broke' the last token (e.g. breaking a '>>' token to two '>' tokens), + // then extend the range of captured tokens to include it, since the parser + // was not actually bumped past it. When the `LazyTokenStream` gets converted + // into an `AttrAnnotatedTokenStream`, we will create the proper token. + if self.token_cursor.break_last_token { + assert_eq!( + trailing, + TrailingToken::None, + "Cannot set `break_last_token` and have trailing token" + ); + end_pos += 1; + } + + let num_calls = end_pos - cursor_snapshot_next_calls; + + // If we have no attributes, then we will never need to + // use any replace ranges. + let replace_ranges: Box<[ReplaceRange]> = if ret.attrs().is_empty() && !self.capture_cfg { + Box::new([]) + } else { + // Grab any replace ranges that occur *inside* the current AST node. + // We will perform the actual replacement when we convert the `LazyTokenStream` + // to an `AttrAnnotatedTokenStream` + let start_calls: u32 = cursor_snapshot_next_calls.try_into().unwrap(); + self.capture_state.replace_ranges[replace_ranges_start..replace_ranges_end] + .iter() + .cloned() + .chain(inner_attr_replace_ranges.clone().into_iter()) + .map(|(range, tokens)| { + ((range.start - start_calls)..(range.end - start_calls), tokens) + }) + .collect() + }; + + let tokens = LazyTokenStream::new(LazyTokenStreamImpl { + start_token, + num_calls, + cursor_snapshot, + break_last_token: self.token_cursor.break_last_token, + replace_ranges, + }); + + // If we support tokens at all + if let Some(target_tokens) = ret.tokens_mut() { + if target_tokens.is_none() { + // Store se our newly captured tokens into the AST node + *target_tokens = Some(tokens.clone()); + } + } + + let final_attrs = ret.attrs(); + + // If `capture_cfg` is set and we're inside a recursive call to + // `collect_tokens_trailing_token`, then we need to register a replace range + // if we have `#[cfg]` or `#[cfg_attr]`. This allows us to run eager cfg-expansion + // on the captured token stream. + if self.capture_cfg + && matches!(self.capture_state.capturing, Capturing::Yes) + && has_cfg_or_cfg_attr(&final_attrs) + { + let attr_data = AttributesData { attrs: final_attrs.to_vec().into(), tokens }; + + // Replace the entire AST node that we just parsed, including attributes, + // with a `FlatToken::AttrTarget`. If this AST node is inside an item + // that has `#[derive]`, then this will allow us to cfg-expand this + // AST node. + let start_pos = + if has_outer_attrs { attrs.start_pos } else { cursor_snapshot_next_calls }; + let new_tokens = vec![(FlatToken::AttrTarget(attr_data), Spacing::Alone)]; + + assert!( + !self.token_cursor.break_last_token, + "Should not have unglued last token with cfg attr" + ); + let range: Range<u32> = (start_pos.try_into().unwrap())..(end_pos.try_into().unwrap()); + self.capture_state.replace_ranges.push((range, new_tokens)); + self.capture_state.replace_ranges.extend(inner_attr_replace_ranges); + } + + // Only clear our `replace_ranges` when we're finished capturing entirely. + if matches!(self.capture_state.capturing, Capturing::No) { + self.capture_state.replace_ranges.clear(); + // We don't clear `inner_attr_ranges`, as doing so repeatedly + // had a measurable performance impact. Most inner attributes that + // we insert will get removed - when we drop the parser, we'll free + // up the memory used by any attributes that we didn't remove from the map. + } + Ok(ret) + } +} + +/// Converts a flattened iterator of tokens (including open and close delimiter tokens) +/// into a `TokenStream`, creating a `TokenTree::Delimited` for each matching pair +/// of open and close delims. +fn make_token_stream( + mut iter: impl Iterator<Item = (FlatToken, Spacing)>, + break_last_token: bool, +) -> AttrAnnotatedTokenStream { + #[derive(Debug)] + struct FrameData { + // This is `None` for the first frame, `Some` for all others. + open_delim_sp: Option<(Delimiter, Span)>, + inner: Vec<(AttrAnnotatedTokenTree, Spacing)>, + } + let mut stack = vec![FrameData { open_delim_sp: None, inner: vec![] }]; + let mut token_and_spacing = iter.next(); + while let Some((token, spacing)) = token_and_spacing { + match token { + FlatToken::Token(Token { kind: TokenKind::OpenDelim(delim), span }) => { + stack.push(FrameData { open_delim_sp: Some((delim, span)), inner: vec![] }); + } + FlatToken::Token(Token { kind: TokenKind::CloseDelim(delim), span }) => { + let frame_data = stack + .pop() + .unwrap_or_else(|| panic!("Token stack was empty for token: {:?}", token)); + + let (open_delim, open_sp) = frame_data.open_delim_sp.unwrap(); + assert_eq!( + open_delim, delim, + "Mismatched open/close delims: open={:?} close={:?}", + open_delim, span + ); + let dspan = DelimSpan::from_pair(open_sp, span); + let stream = AttrAnnotatedTokenStream::new(frame_data.inner); + let delimited = AttrAnnotatedTokenTree::Delimited(dspan, delim, stream); + stack + .last_mut() + .unwrap_or_else(|| { + panic!("Bottom token frame is missing for token: {:?}", token) + }) + .inner + .push((delimited, Spacing::Alone)); + } + FlatToken::Token(token) => stack + .last_mut() + .expect("Bottom token frame is missing!") + .inner + .push((AttrAnnotatedTokenTree::Token(token), spacing)), + FlatToken::AttrTarget(data) => stack + .last_mut() + .expect("Bottom token frame is missing!") + .inner + .push((AttrAnnotatedTokenTree::Attributes(data), spacing)), + FlatToken::Empty => {} + } + token_and_spacing = iter.next(); + } + let mut final_buf = stack.pop().expect("Missing final buf!"); + if break_last_token { + let (last_token, spacing) = final_buf.inner.pop().unwrap(); + if let AttrAnnotatedTokenTree::Token(last_token) = last_token { + let unglued_first = last_token.kind.break_two_token_op().unwrap().0; + + // An 'unglued' token is always two ASCII characters + let mut first_span = last_token.span.shrink_to_lo(); + first_span = first_span.with_hi(first_span.lo() + rustc_span::BytePos(1)); + + final_buf.inner.push(( + AttrAnnotatedTokenTree::Token(Token::new(unglued_first, first_span)), + spacing, + )); + } else { + panic!("Unexpected last token {:?}", last_token) + } + } + assert!(stack.is_empty(), "Stack should be empty: final_buf={:?} stack={:?}", final_buf, stack); + AttrAnnotatedTokenStream::new(final_buf.inner) +} |