bjoernager/rust
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Add metavariables to TokenDescription.

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Pasted metavariables are wrapped in invisible delimiters, which
pretty-print as empty strings, and changing that can break some proc
macros. But error messages saying "expected identifer, found ``" are
bad. So this commit adds support for metavariables in `TokenDescription`
so they print as "metavariable" in error messages, instead of "``".

It's not used meaningfully yet, but will be needed to get rid of
interpolated tokens.
This commit is contained in:
Nicholas Nethercote 2024-04-18 08:58:06 +10:00
parent afe238f66f
commit cfafa9380b
3 changed files with 58 additions and 16 deletions
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39
compiler/rustc_parse/src/parser/mod.rs
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@ -21,7 +21,9 @@ pub(crate) use item::FnParseMode;
pub use pat::{CommaRecoveryMode, RecoverColon, RecoverComma};
use path::PathStyle;
use rustc_ast::ptr::P;
use rustc_ast::token::{self, Delimiter, IdentIsRaw, Nonterminal, Token, TokenKind};
use rustc_ast::token::{
self, Delimiter, IdentIsRaw, InvisibleOrigin, MetaVarKind, Nonterminal, Token, TokenKind,
};
use rustc_ast::tokenstream::{
AttrsTarget, DelimSpacing, DelimSpan, Spacing, TokenStream, TokenTree, TokenTreeCursor,
};
@ -410,6 +412,12 @@ pub(super) enum TokenDescription {
Keyword,
ReservedKeyword,
DocComment,
// Expanded metavariables are wrapped in invisible delimiters which aren't
// pretty-printed. In error messages we must handle these specially
// otherwise we get confusing things in messages like "expected `(`, found
// ``". It's better to say e.g. "expected `(`, found type metavariable".
MetaVar(MetaVarKind),
}
impl TokenDescription {
@ -419,26 +427,29 @@ impl TokenDescription {
_ if token.is_used_keyword() => Some(TokenDescription::Keyword),
_ if token.is_unused_keyword() => Some(TokenDescription::ReservedKeyword),
token::DocComment(..) => Some(TokenDescription::DocComment),
token::OpenDelim(Delimiter::Invisible(InvisibleOrigin::MetaVar(kind))) => {
Some(TokenDescription::MetaVar(kind))
}
_ => None,
}
}
}
pub fn token_descr(token: &Token) -> String {
let name = pprust::token_to_string(token).to_string();
let s = pprust::token_to_string(token).to_string();
let kind = match (TokenDescription::from_token(token), &token.kind) {
(Some(TokenDescription::ReservedIdentifier), _) => Some("reserved identifier"),
(Some(TokenDescription::Keyword), _) => Some("keyword"),
(Some(TokenDescription::ReservedKeyword), _) => Some("reserved keyword"),
(Some(TokenDescription::DocComment), _) => Some("doc comment"),
(None, TokenKind::NtIdent(..)) => Some("identifier"),
(None, TokenKind::NtLifetime(..)) => Some("lifetime"),
(None, TokenKind::Interpolated(node)) => Some(node.descr()),
(None, _) => None,
};
if let Some(kind) = kind { format!("{kind} `{name}`") } else { format!("`{name}`") }
match (TokenDescription::from_token(token), &token.kind) {
(Some(TokenDescription::ReservedIdentifier), _) => format!("reserved identifier `{s}`"),
(Some(TokenDescription::Keyword), _) => format!("keyword `{s}`"),
(Some(TokenDescription::ReservedKeyword), _) => format!("reserved keyword `{s}`"),
(Some(TokenDescription::DocComment), _) => format!("doc comment `{s}`"),
// Deliberately doesn't print `s`, which is empty.
(Some(TokenDescription::MetaVar(kind)), _) => format!("`{kind}` metavariable"),
(None, TokenKind::NtIdent(..)) => format!("identifier `{s}`"),
(None, TokenKind::NtLifetime(..)) => format!("lifetime `{s}`"),
(None, TokenKind::Interpolated(node)) => format!("{} `{s}`", node.descr()),
(None, _) => format!("`{s}`"),
}
}
impl<'a> Parser<'a> {