bjoernager/rust
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Improve spans on evaluated cfg_attrs.

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When converting something like `#![cfg_attr(cond, attr)]` into
`#![attr]`, we currently duplicate the `#` token and the `!` token. But
weirdly, there is also this comment:

// We don't really have a good span to use for the synthesized `[]`
// in `#[attr]`, so just use the span of the `#` token.

Maybe that comment used to be true? But now it is false: we can
duplicate the existing delimiters (and their spans and spacing), much
like we do for the `#` and `!`.

This commit does that, thus removing the incorrect comment, and
improving the spans on `Group`s in a few proc-macro tests.
This commit is contained in:
Nicholas Nethercote 2024-07-24 20:29:28 +10:00
parent 08a9ca7c18
commit ac26b883bf
7 changed files with 40 additions and 40 deletions
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54
compiler/rustc_expand/src/config.rs
View file

@ -6,7 +6,7 @@ use crate::errors::{
};
use rustc_ast::ptr::P;
use rustc_ast::token::{Delimiter, Token, TokenKind};
use rustc_ast::tokenstream::{AttrTokenStream, AttrTokenTree, DelimSpacing, DelimSpan, Spacing};
use rustc_ast::tokenstream::{AttrTokenStream, AttrTokenTree, Spacing};
use rustc_ast::tokenstream::{LazyAttrTokenStream, TokenTree};
use rustc_ast::NodeId;
use rustc_ast::{self as ast, AttrStyle, Attribute, HasAttrs, HasTokens, MetaItem};
@ -298,47 +298,47 @@ impl<'a> StripUnconfigured<'a> {
cfg_attr: &Attribute,
(item, item_span): (ast::AttrItem, Span),
) -> Attribute {
// We are taking an attribute of the form `#[cfg_attr(pred, attr)]`
// and producing an attribute of the form `#[attr]`. We
// have captured tokens for `attr` itself, but we need to
// synthesize tokens for the wrapper `#` and `[]`, which
// we do below.
// Convert `#[cfg_attr(pred, attr)]` to `#[attr]`.
// Use the `#` in `#[cfg_attr(pred, attr)]` as the `#` token
// for `attr` when we expand it to `#[attr]`
// Use the `#` from `#[cfg_attr(pred, attr)]` in the result `#[attr]`.
let mut orig_trees = cfg_attr.token_trees().into_iter();
let TokenTree::Token(pound_token @ Token { kind: TokenKind::Pound, .. }, _) =
orig_trees.next().unwrap().clone()
let Some(TokenTree::Token(pound_token @ Token { kind: TokenKind::Pound, .. }, _)) =
orig_trees.next()
else {
panic!("Bad tokens for attribute {cfg_attr:?}");
};
// We don't really have a good span to use for the synthesized `[]`
// in `#[attr]`, so just use the span of the `#` token.
let bracket_group = AttrTokenTree::Delimited(
DelimSpan::from_single(pound_token.span),
DelimSpacing::new(Spacing::JointHidden, Spacing::Alone),
Delimiter::Bracket,
item.tokens
.as_ref()
.unwrap_or_else(|| panic!("Missing tokens for {item:?}"))
.to_attr_token_stream(),
);
let trees = if cfg_attr.style == AttrStyle::Inner {
// For inner attributes, we do the same thing for the `!` in `#![some_attr]`
let TokenTree::Token(bang_token @ Token { kind: TokenKind::Not, .. }, _) =
orig_trees.next().unwrap().clone()
// For inner attributes, we do the same thing for the `!` in `#![attr]`.
let mut trees = if cfg_attr.style == AttrStyle::Inner {
let Some(TokenTree::Token(bang_token @ Token { kind: TokenKind::Not, .. }, _)) =
orig_trees.next()
else {
panic!("Bad tokens for attribute {cfg_attr:?}");
};
vec![
AttrTokenTree::Token(pound_token, Spacing::Joint),
AttrTokenTree::Token(bang_token, Spacing::JointHidden),
bracket_group,
]
} else {
vec![AttrTokenTree::Token(pound_token, Spacing::JointHidden), bracket_group]
vec![AttrTokenTree::Token(pound_token, Spacing::JointHidden)]
};
// And the same thing for the `[`/`]` delimiters in `#[attr]`.
let Some(TokenTree::Delimited(delim_span, delim_spacing, Delimiter::Bracket, _)) =
orig_trees.next()
else {
panic!("Bad tokens for attribute {cfg_attr:?}");
};
trees.push(AttrTokenTree::Delimited(
delim_span,
delim_spacing,
Delimiter::Bracket,
item.tokens
.as_ref()
.unwrap_or_else(|| panic!("Missing tokens for {item:?}"))
.to_attr_token_stream(),
));
let tokens = Some(LazyAttrTokenStream::new(AttrTokenStream::new(trees)));
let attr = attr::mk_attr_from_item(
&self.sess.psess.attr_id_generator,