Remove NtMeta.

Note: there was an existing code path involving `Interpolated` in
`MetaItem::from_tokens` that was dead. This commit transfers that to the
new form, but puts an `unreachable!` call inside it.

compiler/rustc_ast/src/ast_traits.rs

@@ -202,7 +202,6 @@ impl HasTokens for Nonterminal {
             Nonterminal::NtItem(item) => item.tokens(),
             Nonterminal::NtStmt(stmt) => stmt.tokens(),
             Nonterminal::NtExpr(expr) | Nonterminal::NtLiteral(expr) => expr.tokens(),
-            Nonterminal::NtMeta(attr_item) => attr_item.tokens(),
             Nonterminal::NtPath(path) => path.tokens(),
             Nonterminal::NtBlock(block) => block.tokens(),
         }
@@ -212,7 +211,6 @@ impl HasTokens for Nonterminal {
             Nonterminal::NtItem(item) => item.tokens_mut(),
             Nonterminal::NtStmt(stmt) => stmt.tokens_mut(),
             Nonterminal::NtExpr(expr) | Nonterminal::NtLiteral(expr) => expr.tokens_mut(),
-            Nonterminal::NtMeta(attr_item) => attr_item.tokens_mut(),
             Nonterminal::NtPath(path) => path.tokens_mut(),
             Nonterminal::NtBlock(block) => block.tokens_mut(),
         }

compiler/rustc_ast/src/attr/mod.rs

@@ -14,7 +14,7 @@ use crate::ast::{
     PathSegment, Safety,
 };
 use crate::ptr::P;
-use crate::token::{self, CommentKind, Delimiter, Token};
+use crate::token::{self, CommentKind, Delimiter, InvisibleOrigin, MetaVarKind, Token};
 use crate::tokenstream::{
     DelimSpan, LazyAttrTokenStream, Spacing, TokenStream, TokenStreamIter, TokenTree,
 };
@@ -406,10 +406,18 @@ impl MetaItem {
                 Path { span, segments, tokens: None }
             }
             Some(TokenTree::Token(Token { kind: token::Interpolated(nt), .. }, _)) => match &**nt {
-                token::Nonterminal::NtMeta(item) => return item.meta(item.path.span),
                 token::Nonterminal::NtPath(path) => (**path).clone(),
                 _ => return None,
             },
+            Some(TokenTree::Delimited(
+                _span,
+                _spacing,
+                Delimiter::Invisible(InvisibleOrigin::MetaVar(MetaVarKind::Meta { .. })),
+                _stream,
+            )) => {
+                // This path is currently unreachable in the test suite.
+                unreachable!()
+            }
             Some(TokenTree::Token(
                 Token { kind: token::OpenDelim(_) | token::CloseDelim(_), .. },
                 _,

compiler/rustc_ast/src/mut_visit.rs

@@ -907,12 +907,6 @@ fn visit_nonterminal<T: MutVisitor>(vis: &mut T, nt: &mut token::Nonterminal) {
         }),
         token::NtExpr(expr) => vis.visit_expr(expr),
         token::NtLiteral(expr) => vis.visit_expr(expr),
-        token::NtMeta(item) => {
-            let AttrItem { unsafety: _, path, args, tokens } = item.deref_mut();
-            vis.visit_path(path);
-            visit_attr_args(vis, args);
-            visit_lazy_tts(vis, tokens);
-        }
         token::NtPath(path) => vis.visit_path(path),
     }
 }

compiler/rustc_ast/src/token.rs

@@ -90,7 +90,10 @@ pub enum MetaVarKind {
     Ident,
     Lifetime,
     Literal,
-    Meta,
+    Meta {
+        /// Will `AttrItem::meta` succeed on this, if reparsed?
+        has_meta_form: bool,
+    },
     Path,
     Vis,
     TT,
@@ -110,7 +113,7 @@ impl fmt::Display for MetaVarKind {
             MetaVarKind::Ident => sym::ident,
             MetaVarKind::Lifetime => sym::lifetime,
             MetaVarKind::Literal => sym::literal,
-            MetaVarKind::Meta => sym::meta,
+            MetaVarKind::Meta { .. } => sym::meta,
             MetaVarKind::Path => sym::path,
             MetaVarKind::Vis => sym::vis,
             MetaVarKind::TT => sym::tt,
@@ -658,13 +661,12 @@ impl Token {
                 matches!(&**nt,
                     | NtExpr(..)
                     | NtLiteral(..)
-                    | NtMeta(..)
                     | NtPath(..)
                 ),
             OpenDelim(Delimiter::Invisible(InvisibleOrigin::MetaVar(
                 MetaVarKind::Expr { .. } |
                 MetaVarKind::Literal |
-                MetaVarKind::Meta |
+                MetaVarKind::Meta { .. } |
                 MetaVarKind::Pat(_) |
                 MetaVarKind::Path |
                 MetaVarKind::Ty { .. }
@@ -1076,8 +1078,6 @@ pub enum Nonterminal {
     NtStmt(P<ast::Stmt>),
     NtExpr(P<ast::Expr>),
     NtLiteral(P<ast::Expr>),
-    /// Stuff inside brackets for attributes
-    NtMeta(P<ast::AttrItem>),
     NtPath(P<ast::Path>),
 }
 
@@ -1171,7 +1171,6 @@ impl Nonterminal {
             NtBlock(block) => block.span,
             NtStmt(stmt) => stmt.span,
             NtExpr(expr) | NtLiteral(expr) => expr.span,
-            NtMeta(attr_item) => attr_item.span(),
             NtPath(path) => path.span,
         }
     }
@@ -1183,7 +1182,6 @@ impl Nonterminal {
             NtStmt(..) => "statement",
             NtExpr(..) => "expression",
             NtLiteral(..) => "literal",
-            NtMeta(..) => "attribute",
             NtPath(..) => "path",
         }
     }
@@ -1207,7 +1205,6 @@ impl fmt::Debug for Nonterminal {
             NtStmt(..) => f.pad("NtStmt(..)"),
             NtExpr(..) => f.pad("NtExpr(..)"),
             NtLiteral(..) => f.pad("NtLiteral(..)"),
-            NtMeta(..) => f.pad("NtMeta(..)"),
             NtPath(..) => f.pad("NtPath(..)"),
         }
     }

compiler/rustc_ast/src/tokenstream.rs

@@ -468,7 +468,6 @@ impl TokenStream {
                 TokenStream::token_alone(token::Semi, stmt.span)
             }
             Nonterminal::NtStmt(stmt) => TokenStream::from_ast(stmt),
-            Nonterminal::NtMeta(attr) => TokenStream::from_ast(attr),
             Nonterminal::NtPath(path) => TokenStream::from_ast(path),
             Nonterminal::NtExpr(expr) | Nonterminal::NtLiteral(expr) => TokenStream::from_ast(expr),
         }

compiler/rustc_attr_parsing/src/parser.rs

@@ -481,15 +481,6 @@ impl<'a> MetaItemListParserContext<'a> {
                 self.inside_delimiters.peek()
             {
                 match &**nt {
-                    // or maybe a full nt meta including the path but we return immediately
-                    token::Nonterminal::NtMeta(item) => {
-                        self.inside_delimiters.next();
-
-                        return Some(MetaItemOrLitParser::MetaItemParser(MetaItemParser {
-                            path: PathParser::Ast(&item.path),
-                            args: ArgParser::from_attr_args(&item.args, self.dcx),
-                        }));
-                    }
                     // an already interpolated path from a macro expansion is a path, no need to parse
                     // one from tokens
                     token::Nonterminal::NtPath(path) => {

compiler/rustc_expand/src/mbe/transcribe.rs

@@ -336,6 +336,14 @@ pub(super) fn transcribe<'a>(
                                 TokenStream::from_ast(ty),
                             )
                         }
+                        MatchedSingle(ParseNtResult::Meta(attr_item)) => {
+                            let has_meta_form = attr_item.meta_kind().is_some();
+                            mk_delimited(
+                                attr_item.span(),
+                                MetaVarKind::Meta { has_meta_form },
+                                TokenStream::from_ast(attr_item),
+                            )
+                        }
                         MatchedSingle(ParseNtResult::Vis(vis)) => {
                             mk_delimited(vis.span, MetaVarKind::Vis, TokenStream::from_ast(vis))
                         }

compiler/rustc_parse/messages.ftl

@@ -424,7 +424,7 @@ parse_invalid_logical_operator = `{$incorrect}` is not a logical operator
     .use_amp_amp_for_conjunction = use `&&` to perform logical conjunction
     .use_pipe_pipe_for_disjunction = use `||` to perform logical disjunction
 
-parse_invalid_meta_item = expected unsuffixed literal, found `{$token}`
+parse_invalid_meta_item = expected unsuffixed literal, found {$descr}
     .quote_ident_sugg = surround the identifier with quotation marks to make it into a string literal
 
 parse_invalid_offset_of = offset_of expects dot-separated field and variant names

compiler/rustc_parse/src/errors.rs

@@ -1024,7 +1024,7 @@ pub(crate) struct SuffixedLiteralInAttribute {
 pub(crate) struct InvalidMetaItem {
     #[primary_span]
     pub span: Span,
-    pub token: Token,
+    pub descr: String,
     #[subdiagnostic]
     pub quote_ident_sugg: Option<InvalidMetaItemQuoteIdentSugg>,
 }

compiler/rustc_parse/src/parser/attr.rs

@@ -1,4 +1,6 @@
-use rustc_ast::{self as ast, Attribute, attr, token};
+use rustc_ast as ast;
+use rustc_ast::token::{self, MetaVarKind};
+use rustc_ast::{Attribute, attr};
 use rustc_errors::codes::*;
 use rustc_errors::{Diag, PResult};
 use rustc_span::{BytePos, Span};
@@ -9,7 +11,7 @@ use super::{
     AttrWrapper, Capturing, FnParseMode, ForceCollect, Parser, ParserRange, PathStyle, Trailing,
     UsePreAttrPos,
 };
-use crate::{errors, exp, fluent_generated as fluent, maybe_whole};
+use crate::{errors, exp, fluent_generated as fluent};
 
 // Public for rustfmt usage
 #[derive(Debug)]
@@ -269,7 +271,12 @@ impl<'a> Parser<'a> {
     ///     PATH `=` UNSUFFIXED_LIT
     /// The delimiters or `=` are still put into the resulting token stream.
     pub fn parse_attr_item(&mut self, force_collect: ForceCollect) -> PResult<'a, ast::AttrItem> {
-        maybe_whole!(self, NtMeta, |attr| attr.into_inner());
+        if let Some(item) = self.eat_metavar_seq_with_matcher(
+            |mv_kind| matches!(mv_kind, MetaVarKind::Meta { .. }),
+            |this| this.parse_attr_item(force_collect),
+        ) {
+            return Ok(item);
+        }
 
         // Attr items don't have attributes.
         self.collect_tokens(None, AttrWrapper::empty(), force_collect, |this, _empty_attrs| {
@@ -396,18 +403,17 @@ impl<'a> Parser<'a> {
         &mut self,
         unsafe_allowed: AllowLeadingUnsafe,
     ) -> PResult<'a, ast::MetaItem> {
-        // We can't use `maybe_whole` here because it would bump in the `None`
+        if let Some(MetaVarKind::Meta { has_meta_form }) = self.token.is_metavar_seq() {
-        // case, which we don't want.
+            return if has_meta_form {
-        if let token::Interpolated(nt) = &self.token.kind
+                let attr_item = self
-            && let token::NtMeta(attr_item) = &**nt
+                    .eat_metavar_seq(MetaVarKind::Meta { has_meta_form: true }, |this| {
-        {
+                        this.parse_attr_item(ForceCollect::No)
-            match attr_item.meta(attr_item.path.span) {
+                    })
-                Some(meta) => {
+                    .unwrap();
-                    self.bump();
+                Ok(attr_item.meta(attr_item.path.span).unwrap())
-                    return Ok(meta);
+            } else {
-                }
+                self.unexpected_any()
-                None => self.unexpected()?,
+            };
-            }
         }
 
         let lo = self.token.span;
@@ -464,7 +470,7 @@ impl<'a> Parser<'a> {
 
         let mut err = errors::InvalidMetaItem {
             span: self.token.span,
-            token: self.token.clone(),
+            descr: super::token_descr(&self.token),
             quote_ident_sugg: None,
         };
 

compiler/rustc_parse/src/parser/mod.rs

@@ -1748,6 +1748,7 @@ pub enum ParseNtResult {
     Lifetime(Ident, IdentIsRaw),
     Pat(P<ast::Pat>, NtPatKind),
     Ty(P<ast::Ty>),
+    Meta(P<ast::AttrItem>),
     Vis(P<ast::Visibility>),
 
     /// This variant will eventually be removed, along with `Token::Interpolate`.

compiler/rustc_parse/src/parser/nonterminal.rs

@@ -32,7 +32,7 @@ impl<'a> Parser<'a> {
                 | MetaVarKind::Expr { .. }
                 | MetaVarKind::Ty { .. }
                 | MetaVarKind::Literal // `true`, `false`
-                | MetaVarKind::Meta
+                | MetaVarKind::Meta { .. }
                 | MetaVarKind::Path => true,
 
                 MetaVarKind::Item
@@ -51,7 +51,6 @@ impl<'a> Parser<'a> {
                 NtStmt(_)
                 | NtExpr(_)
                 | NtLiteral(_) // `true`, `false`
-                | NtMeta(_)
                 | NtPath(_) => true,
 
                 NtItem(_) | NtBlock(_) => false,
@@ -98,7 +97,7 @@ impl<'a> Parser<'a> {
                 token::NtLifetime(..) => true,
                 token::Interpolated(nt) => match &**nt {
                     NtBlock(_) | NtStmt(_) | NtExpr(_) | NtLiteral(_) => true,
-                    NtItem(_) | NtMeta(_) | NtPath(_) => false,
+                    NtItem(_) | NtPath(_) => false,
                 },
                 token::OpenDelim(Delimiter::Invisible(InvisibleOrigin::MetaVar(k))) => match k {
                     MetaVarKind::Block
@@ -108,7 +107,7 @@ impl<'a> Parser<'a> {
                     MetaVarKind::Item
                     | MetaVarKind::Pat(_)
                     | MetaVarKind::Ty { .. }
-                    | MetaVarKind::Meta
+                    | MetaVarKind::Meta { .. }
                     | MetaVarKind::Path
                     | MetaVarKind::Vis => false,
                     MetaVarKind::Lifetime | MetaVarKind::Ident | MetaVarKind::TT => {
@@ -207,7 +206,9 @@ impl<'a> Parser<'a> {
             NonterminalKind::Path => {
                 NtPath(P(self.collect_tokens_no_attrs(|this| this.parse_path(PathStyle::Type))?))
             }
-            NonterminalKind::Meta => NtMeta(P(self.parse_attr_item(ForceCollect::Yes)?)),
+            NonterminalKind::Meta => {
+                return Ok(ParseNtResult::Meta(P(self.parse_attr_item(ForceCollect::Yes)?)));
+            }
             NonterminalKind::Vis => {
                 return Ok(ParseNtResult::Vis(P(self.collect_tokens_no_attrs(|this| {
                     this.parse_visibility(FollowedByType::Yes)

tests/ui/attributes/nonterminal-expansion.rs

@@ -5,7 +5,7 @@
 macro_rules! pass_nonterminal {
     ($n:expr) => {
         #[repr(align($n))]
-        //~^ ERROR expected unsuffixed literal, found `n!()`
+        //~^ ERROR expected unsuffixed literal, found expression `n!()`
         //~^^ ERROR incorrect `repr(align)` attribute format: `align` expects a literal integer as argument [E0693]
         struct S;
     };

tests/ui/attributes/nonterminal-expansion.stderr

@@ -1,4 +1,4 @@
-error: expected unsuffixed literal, found `n!()`
+error: expected unsuffixed literal, found expression `n!()`
   --> $DIR/nonterminal-expansion.rs:7:22
    |
 LL |         #[repr(align($n))]

tests/ui/conditional-compilation/cfg-attr-syntax-validation.rs

@@ -28,8 +28,8 @@ struct S9;
 macro_rules! generate_s10 {
     ($expr: expr) => {
         #[cfg(feature = $expr)]
-        //~^ ERROR expected unsuffixed literal, found `concat!("nonexistent")`
+        //~^ ERROR expected unsuffixed literal, found expression `concat!("nonexistent")`
-        //~| ERROR expected unsuffixed literal, found `concat!("nonexistent")`
+        //~| ERROR expected unsuffixed literal, found expression `concat!("nonexistent")`
         struct S10;
     }
 }

tests/ui/conditional-compilation/cfg-attr-syntax-validation.stderr

@@ -54,7 +54,7 @@ LL | #[cfg(a = b"hi")]
    |           |
    |           help: consider removing the prefix
 
-error: expected unsuffixed literal, found `concat!("nonexistent")`
+error: expected unsuffixed literal, found expression `concat!("nonexistent")`
   --> $DIR/cfg-attr-syntax-validation.rs:30:25
    |
 LL |         #[cfg(feature = $expr)]
@@ -65,7 +65,7 @@ LL | generate_s10!(concat!("nonexistent"));
    |
    = note: this error originates in the macro `generate_s10` (in Nightly builds, run with -Z macro-backtrace for more info)
 
-error: expected unsuffixed literal, found `concat!("nonexistent")`
+error: expected unsuffixed literal, found expression `concat!("nonexistent")`
   --> $DIR/cfg-attr-syntax-validation.rs:30:25
    |
 LL |         #[cfg(feature = $expr)]

tests/ui/parser/attribute/attr-bad-meta-4.rs

@@ -1,8 +1,8 @@
 macro_rules! mac {
     ($attr_item: meta) => {
         #[cfg($attr_item)]
-        //~^ ERROR expected unsuffixed literal, found `an(arbitrary token stream)`
+        //~^ ERROR expected unsuffixed literal, found `meta` metavariable
-        //~| ERROR expected unsuffixed literal, found `an(arbitrary token stream)`
+        //~| ERROR expected unsuffixed literal, found `meta` metavariable
         struct S;
     }
 }

tests/ui/parser/attribute/attr-bad-meta-4.stderr

@@ -4,7 +4,7 @@ error: expected unsuffixed literal, found `-`
 LL | #[cfg(feature = -1)]
    |                 ^
 
-error: expected unsuffixed literal, found `an(arbitrary token stream)`
+error: expected unsuffixed literal, found `meta` metavariable
   --> $DIR/attr-bad-meta-4.rs:3:15
    |
 LL |         #[cfg($attr_item)]
@@ -15,7 +15,7 @@ LL | mac!(an(arbitrary token stream));
    |
    = note: this error originates in the macro `mac` (in Nightly builds, run with -Z macro-backtrace for more info)
 
-error: expected unsuffixed literal, found `an(arbitrary token stream)`
+error: expected unsuffixed literal, found `meta` metavariable
   --> $DIR/attr-bad-meta-4.rs:3:15
    |
 LL |         #[cfg($attr_item)]

tests/ui/parser/attribute/attr-unquoted-ident.rs

@@ -19,7 +19,7 @@ fn main() {
 
 macro_rules! make {
     ($name:ident) => { #[doc(alias = $name)] pub struct S; }
-    //~^ ERROR expected unsuffixed literal, found `nickname`
+    //~^ ERROR expected unsuffixed literal, found identifier `nickname`
 }
 
 make!(nickname); //~ NOTE in this expansion

tests/ui/parser/attribute/attr-unquoted-ident.stderr

@@ -20,7 +20,7 @@ help: surround the identifier with quotation marks to make it into a string lite
 LL |     #[cfg(key="foo bar baz")]
    |               +           +
 
-error: expected unsuffixed literal, found `nickname`
+error: expected unsuffixed literal, found identifier `nickname`
   --> $DIR/attr-unquoted-ident.rs:21:38
    |
 LL |     ($name:ident) => { #[doc(alias = $name)] pub struct S; }