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attr.rs
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attr.rs
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use super::{FlatToken, Parser, PathStyle};
use rustc_ast as ast;
use rustc_ast::attr::{self, HasAttrs};
use rustc_ast::token::{self, Nonterminal, Token, TokenKind};
use rustc_ast::tokenstream::{
AttributesData, DelimSpan, PreexpTokenStream, PreexpTokenTree, Spacing, TokenStream,
};
use rustc_ast::{AttrVec, Attribute};
use rustc_ast_pretty::pprust;
use rustc_errors::{error_code, Handler, PResult};
use rustc_span::symbol::sym;
use rustc_span::{Span, DUMMY_SP};
use tracing::debug;
#[derive(Debug)]
pub(super) enum InnerAttrPolicy<'a> {
Permitted,
Forbidden { reason: &'a str, saw_doc_comment: bool, prev_attr_sp: Option<Span> },
}
const DEFAULT_UNEXPECTED_INNER_ATTR_ERR_MSG: &str = "an inner attribute is not \
permitted in this context";
pub struct CfgAttrItem {
pub item: ast::AttrItem,
pub span: Span,
pub tokens: TokenStream,
}
pub(super) const DEFAULT_INNER_ATTR_FORBIDDEN: InnerAttrPolicy<'_> = InnerAttrPolicy::Forbidden {
reason: DEFAULT_UNEXPECTED_INNER_ATTR_ERR_MSG,
saw_doc_comment: false,
prev_attr_sp: None,
};
impl<'a> Parser<'a> {
fn has_any_attributes(&mut self) -> bool {
self.check(&token::Pound) || matches!(self.token.kind, token::DocComment(..))
}
fn parse_outer_attributes_(&mut self) -> PResult<'a, Vec<ast::Attribute>> {
let mut attrs: Vec<ast::Attribute> = Vec::new();
let mut just_parsed_doc_comment = false;
loop {
let (attr, tokens) = self.collect_tokens_keep_in_stream(false, |this| {
debug!("parse_outer_attributes: self.token={:?}", this.token);
if this.check(&token::Pound) {
let inner_error_reason = if just_parsed_doc_comment {
"an inner attribute is not permitted following an outer doc comment"
} else if !attrs.is_empty() {
"an inner attribute is not permitted following an outer attribute"
} else {
DEFAULT_UNEXPECTED_INNER_ATTR_ERR_MSG
};
let inner_parse_policy = InnerAttrPolicy::Forbidden {
reason: inner_error_reason,
saw_doc_comment: just_parsed_doc_comment,
prev_attr_sp: attrs.last().map(|a| a.span),
};
let attr = this.parse_attribute_with_inner_parse_policy(inner_parse_policy)?;
just_parsed_doc_comment = false;
Ok((Some(attr), Vec::new())) // Attributes don't have their own attributes
} else if let token::DocComment(comment_kind, attr_style, data) = this.token.kind {
let attr =
attr::mk_doc_comment(comment_kind, attr_style, data, this.token.span);
if attr.style != ast::AttrStyle::Outer {
this.sess
.span_diagnostic
.struct_span_err_with_code(
this.token.span,
"expected outer doc comment",
error_code!(E0753),
)
.note(
"inner doc comments like this (starting with \
`//!` or `/*!`) can only appear before items",
)
.emit();
}
this.bump();
just_parsed_doc_comment = true;
Ok((Some(attr), Vec::new()))
} else {
Ok((None, Vec::new()))
}
})?;
if let Some(mut attr) = attr {
attr.tokens = Some(tokens.to_tokenstream());
attrs.push(attr);
} else {
break;
}
}
Ok(attrs)
}
pub(super) fn parse_or_use_outer_attributes<
R: HasAttrs,
F: FnOnce(&mut Self, AttrVec) -> PResult<'a, R>,
>(
&mut self,
already_parsed_attrs: Option<AttrVec>,
f: F,
) -> PResult<'a, (R, Option<PreexpTokenStream>)> {
let in_derive = self.in_derive;
let needs_tokens = |attrs: &[Attribute]| attrs_require_tokens(in_derive, attrs);
let make_capture_res = |this: &mut Self, f: F, attrs: AttrVec| {
let (res, tokens) = this.collect_tokens(|this| {
let mut new_attrs = attrs.clone().to_vec();
let old_in_derive = this.in_derive;
this.in_derive =
old_in_derive || new_attrs.iter().any(|attr| attr.has_name(sym::derive));
let res = f(this, attrs);
this.in_derive = old_in_derive;
let mut res = res?;
res.visit_attrs(|attrs| {
new_attrs = attrs.clone();
});
Ok((res, new_attrs))
})?;
Ok((res, Some(tokens)))
};
if let Some(attrs) = already_parsed_attrs {
if needs_tokens(&attrs) {
return make_capture_res(self, f, attrs);
} else {
return f(self, attrs).map(|res| (res, None));
}
} else {
// If we are already collecting tokens, we need to
// perform token collection here even if we have no
// outer attributes, since there may be inner attributes
// parsed by 'f'.
if !self.has_any_attributes() && !self.in_derive {
return Ok((f(self, AttrVec::new())?, None));
}
let attrs = self.parse_outer_attributes_()?;
if !needs_tokens(&attrs) {
return Ok((f(self, attrs.into())?, None));
}
return make_capture_res(self, f, attrs.into());
}
}
pub(super) fn parse_outer_attributes<R: HasAttrs>(
&mut self,
f: impl FnOnce(&mut Self, Vec<ast::Attribute>) -> PResult<'a, R>,
) -> PResult<'a, R> {
self.parse_outer_attributes_with_tokens(f).map(|(res, _tokens)| res)
}
/// Parses attributes that appear before an item.
pub(super) fn parse_outer_attributes_with_tokens<R: HasAttrs>(
&mut self,
f: impl FnOnce(&mut Self, Vec<ast::Attribute>) -> PResult<'a, R>,
) -> PResult<'a, (R, Option<PreexpTokenStream>)> {
self.parse_or_use_outer_attributes(None, |this, attrs| f(this, attrs.into()))
}
/// Matches `attribute = # ! [ meta_item ]`.
///
/// If `permit_inner` is `true`, then a leading `!` indicates an inner
/// attribute.
pub fn parse_attribute(&mut self, permit_inner: bool) -> PResult<'a, ast::Attribute> {
debug!("parse_attribute: permit_inner={:?} self.token={:?}", permit_inner, self.token);
let inner_parse_policy =
if permit_inner { InnerAttrPolicy::Permitted } else { DEFAULT_INNER_ATTR_FORBIDDEN };
self.parse_attribute_with_inner_parse_policy(inner_parse_policy)
}
/// The same as `parse_attribute`, except it takes in an `InnerAttrPolicy`
/// that prescribes how to handle inner attributes.
fn parse_attribute_with_inner_parse_policy(
&mut self,
inner_parse_policy: InnerAttrPolicy<'_>,
) -> PResult<'a, ast::Attribute> {
debug!(
"parse_attribute_with_inner_parse_policy: inner_parse_policy={:?} self.token={:?}",
inner_parse_policy, self.token
);
let lo = self.token.span;
let (span, item, style) = if self.eat(&token::Pound) {
let style =
if self.eat(&token::Not) { ast::AttrStyle::Inner } else { ast::AttrStyle::Outer };
self.expect(&token::OpenDelim(token::Bracket))?;
let item = self.parse_attr_item()?;
self.expect(&token::CloseDelim(token::Bracket))?;
let attr_sp = lo.to(self.prev_token.span);
// Emit error if inner attribute is encountered and forbidden.
if style == ast::AttrStyle::Inner {
self.error_on_forbidden_inner_attr(attr_sp, inner_parse_policy);
}
(attr_sp, item, style)
} else {
let token_str = pprust::token_to_string(&self.token);
let msg = &format!("expected `#`, found `{}`", token_str);
return Err(self.struct_span_err(self.token.span, msg));
};
Ok(attr::mk_attr_from_item(style, item, span))
}
pub(super) fn error_on_forbidden_inner_attr(&self, attr_sp: Span, policy: InnerAttrPolicy<'_>) {
if let InnerAttrPolicy::Forbidden { reason, saw_doc_comment, prev_attr_sp } = policy {
let prev_attr_note =
if saw_doc_comment { "previous doc comment" } else { "previous outer attribute" };
let mut diag = self.struct_span_err(attr_sp, reason);
if let Some(prev_attr_sp) = prev_attr_sp {
diag.span_label(attr_sp, "not permitted following an outer attribute")
.span_label(prev_attr_sp, prev_attr_note);
}
diag.note(
"inner attributes, like `#![no_std]`, annotate the item enclosing them, \
and are usually found at the beginning of source files. \
Outer attributes, like `#[test]`, annotate the item following them.",
)
.emit();
}
}
/// Parses an inner part of an attribute (the path and following tokens).
/// The tokens must be either a delimited token stream, or empty token stream,
/// or the "legacy" key-value form.
/// PATH `(` TOKEN_STREAM `)`
/// PATH `[` TOKEN_STREAM `]`
/// PATH `{` TOKEN_STREAM `}`
/// PATH
/// PATH `=` UNSUFFIXED_LIT
/// The delimiters or `=` are still put into the resulting token stream.
pub fn parse_attr_item(&mut self) -> PResult<'a, ast::AttrItem> {
let item = match self.token.kind {
token::Interpolated(ref nt) => match **nt {
Nonterminal::NtMeta(ref item) => Some(item.clone().into_inner()),
_ => None,
},
_ => None,
};
Ok(if let Some(item) = item {
self.bump();
item
} else {
let path = self.parse_path(PathStyle::Mod)?;
let args = self.parse_attr_args()?;
ast::AttrItem { path, args, tokens: None }
})
}
/// Parses attributes that appear after the opening of an item. These should
/// be preceded by an exclamation mark, but we accept and warn about one
/// terminated by a semicolon.
///
/// Matches `inner_attrs*`.
crate fn parse_inner_attributes(&mut self) -> PResult<'a, Vec<ast::Attribute>> {
let mut attrs: Vec<ast::Attribute> = vec![];
loop {
let (attr, tokens) = self.collect_tokens_no_attrs(|this| {
// Only try to parse if it is an inner attribute (has `!`).
if this.check(&token::Pound) && this.look_ahead(1, |t| t == &token::Not) {
let attr = this.parse_attribute(true)?;
assert_eq!(attr.style, ast::AttrStyle::Inner);
Ok(Some(attr))
} else if let token::DocComment(comment_kind, attr_style, data) = this.token.kind {
// We need to get the position of this token before we bump.
let attr =
attr::mk_doc_comment(comment_kind, attr_style, data, this.token.span);
if attr.style == ast::AttrStyle::Inner {
this.bump();
Ok(Some(attr))
} else {
Ok(None)
}
} else {
Ok(None)
}
})?;
if let Some(mut attr) = attr {
attr.tokens = Some(tokens.to_tokenstream());
attrs.push(attr)
} else {
break;
}
}
Ok(attrs)
}
crate fn parse_unsuffixed_lit(&mut self) -> PResult<'a, ast::Lit> {
let lit = self.parse_lit()?;
debug!("checking if {:?} is unusuffixed", lit);
if !lit.kind.is_unsuffixed() {
self.struct_span_err(lit.span, "suffixed literals are not allowed in attributes")
.help(
"instead of using a suffixed literal (`1u8`, `1.0f32`, etc.), \
use an unsuffixed version (`1`, `1.0`, etc.)",
)
.emit();
}
Ok(lit)
}
/// Parses `cfg_attr(pred, attr_item_list)` where `attr_item_list` is comma-delimited.
pub fn parse_cfg_attr(&mut self) -> PResult<'a, (ast::MetaItem, Vec<CfgAttrItem>)> {
let cfg_predicate = self.parse_meta_item()?;
self.expect(&token::Comma)?;
// Presumably, the majority of the time there will only be one attr.
let mut expanded_attrs = Vec::with_capacity(1);
while self.token.kind != token::Eof {
let lo = self.token.span;
let (item, tokens) =
self.collect_tokens(|this| this.parse_attr_item().map(|item| (item, Vec::new())))?;
expanded_attrs.push(CfgAttrItem {
item,
span: lo.to(self.prev_token.span),
tokens: tokens.to_tokenstream(),
});
if !self.eat(&token::Comma) {
break;
}
}
Ok((cfg_predicate, expanded_attrs))
}
/// Matches `COMMASEP(meta_item_inner)`.
crate fn parse_meta_seq_top(&mut self) -> PResult<'a, Vec<ast::NestedMetaItem>> {
// Presumably, the majority of the time there will only be one attr.
let mut nmis = Vec::with_capacity(1);
while self.token.kind != token::Eof {
nmis.push(self.parse_meta_item_inner()?);
if !self.eat(&token::Comma) {
break;
}
}
Ok(nmis)
}
/// Matches the following grammar (per RFC 1559).
///
/// meta_item : PATH ( '=' UNSUFFIXED_LIT | '(' meta_item_inner? ')' )? ;
/// meta_item_inner : (meta_item | UNSUFFIXED_LIT) (',' meta_item_inner)? ;
pub fn parse_meta_item(&mut self) -> PResult<'a, ast::MetaItem> {
let nt_meta = match self.token.kind {
token::Interpolated(ref nt) => match **nt {
token::NtMeta(ref e) => Some(e.clone()),
_ => None,
},
_ => None,
};
if let Some(item) = nt_meta {
return match item.meta(item.path.span) {
Some(meta) => {
self.bump();
Ok(meta)
}
None => self.unexpected(),
};
}
let lo = self.token.span;
let path = self.parse_path(PathStyle::Mod)?;
let kind = self.parse_meta_item_kind()?;
let span = lo.to(self.prev_token.span);
Ok(ast::MetaItem { path, kind, span })
}
crate fn parse_meta_item_kind(&mut self) -> PResult<'a, ast::MetaItemKind> {
Ok(if self.eat(&token::Eq) {
ast::MetaItemKind::NameValue(self.parse_unsuffixed_lit()?)
} else if self.check(&token::OpenDelim(token::Paren)) {
// Matches `meta_seq = ( COMMASEP(meta_item_inner) )`.
let (list, _) = self.parse_paren_comma_seq(|p| p.parse_meta_item_inner())?;
ast::MetaItemKind::List(list)
} else {
ast::MetaItemKind::Word
})
}
/// Matches `meta_item_inner : (meta_item | UNSUFFIXED_LIT) ;`.
fn parse_meta_item_inner(&mut self) -> PResult<'a, ast::NestedMetaItem> {
match self.parse_unsuffixed_lit() {
Ok(lit) => return Ok(ast::NestedMetaItem::Literal(lit)),
Err(ref mut err) => err.cancel(),
}
match self.parse_meta_item() {
Ok(mi) => return Ok(ast::NestedMetaItem::MetaItem(mi)),
Err(ref mut err) => err.cancel(),
}
let found = pprust::token_to_string(&self.token);
let msg = format!("expected unsuffixed literal or identifier, found `{}`", found);
Err(self.struct_span_err(self.token.span, &msg))
}
pub(super) fn collect_tokens_keep_in_stream<R>(
&mut self,
keep_in_stream: bool,
f: impl FnOnce(&mut Self) -> PResult<'a, (R, Vec<ast::Attribute>)>,
) -> PResult<'a, (R, PreexpTokenStream)> {
let start_pos = self.token_cursor.collecting_buf.len() - 1;
let prev_collecting = std::mem::replace(&mut self.token_cursor.is_collecting, true);
let ret = f(self);
let err_stream = if ret.is_err() {
// Rustdoc tries to parse an item, and then cancels the error
// if it fails.
// FIXME: Come up with a better way of doing this
if !self.is_rustdoc {
self.sess
.span_diagnostic
.delay_span_bug(self.token.span, "Parse error during token collection");
}
Some(PreexpTokenStream::new(vec![]))
} else {
None
};
fn make_stream(
handler: &Handler,
iter: impl Iterator<Item = (FlatToken, Spacing)>,
err_stream: Option<PreexpTokenStream>,
) -> PreexpTokenStream {
err_stream.unwrap_or_else(|| make_preexp_stream(handler, iter))
}
let last_token = self.token_cursor.collecting_buf.pop().unwrap();
let mut stream = if prev_collecting {
if keep_in_stream {
make_stream(
&self.sess.span_diagnostic,
self.token_cursor.collecting_buf[start_pos..].iter().cloned(),
err_stream,
)
} else {
make_stream(
&self.sess.span_diagnostic,
self.token_cursor.collecting_buf.drain(start_pos..),
err_stream,
)
}
} else {
debug_assert_eq!(start_pos, 0);
make_stream(
&self.sess.span_diagnostic,
std::mem::take(&mut self.token_cursor.collecting_buf).into_iter(),
err_stream,
)
};
if let Ok((_, attrs)) = ret.as_ref() {
if !attrs.is_empty() {
let data = AttributesData { attrs: attrs.clone(), tokens: stream };
let tree = (PreexpTokenTree::OuterAttributes(data.clone()), Spacing::Alone);
stream = PreexpTokenStream::new(vec![tree]);
if prev_collecting {
assert!(keep_in_stream);
self.token_cursor.collecting_buf.splice(
start_pos..,
std::iter::once((FlatToken::OuterAttributes(data), Spacing::Alone)),
);
}
}
}
self.token_cursor.collecting_buf.push(last_token);
self.token_cursor.is_collecting = prev_collecting;
Ok((ret?.0, stream))
}
}
fn make_preexp_stream(
handler: &Handler,
tokens: impl Iterator<Item = (FlatToken, Spacing)>,
) -> PreexpTokenStream {
#[derive(Debug)]
struct FrameData {
open: Span,
inner: Vec<(PreexpTokenTree, Spacing)>,
}
let mut stack = vec![FrameData { open: DUMMY_SP, inner: vec![] }];
for tree in tokens {
match tree.0 {
FlatToken::Token(Token { kind: TokenKind::OpenDelim(_), span }) => {
stack.push(FrameData { open: span, inner: vec![] });
}
FlatToken::Token(Token { kind: TokenKind::CloseDelim(delim), span }) => {
let frame_data = stack.pop().expect("Token stack was empty!");
let dspan = DelimSpan::from_pair(frame_data.open, span);
let stream = PreexpTokenStream::new(frame_data.inner);
let delimited = PreexpTokenTree::Delimited(dspan, delim, stream);
stack
.last_mut()
.expect("Bottom token frame is missing!")
.inner
.push((delimited, Spacing::Alone));
}
FlatToken::Token(token) => stack
.last_mut()
.expect("Bottom token frame is missing!")
.inner
.push((PreexpTokenTree::Token(token), tree.1)),
FlatToken::OuterAttributes(data) => stack
.last_mut()
.expect("Bottom token frame is missing!")
.inner
.push((PreexpTokenTree::OuterAttributes(data), Spacing::Alone)),
}
}
let final_buf = stack.pop().expect("Missing final buf!");
if !stack.is_empty() {
handler.delay_span_bug(
stack[0].open,
&format!("Stack should be empty: final_buf={:?} stack={:?}", final_buf, stack),
);
}
PreexpTokenStream::new(final_buf.inner)
}
pub fn attrs_require_tokens(in_derive: bool, attrs: &[Attribute]) -> bool {
attrs.iter().any(|attr| {
if let Some(ident) = attr.ident() {
ident.name == sym::derive
// We only need tokens for 'cfgs' inside a derive,
// since cfg-stripping occurs before derive expansion
|| (ident.name == sym::cfg && in_derive)
// This might apply a custom attribute/derive
|| ident.name == sym::cfg_attr
|| !rustc_feature::is_builtin_attr_name(ident.name)
} else {
true
}
})
}