Remove a Span from TokenKind::Interpolated.

This span records the declaration of the metavariable in the LHS of the macro.
It's used in a couple of error messages. Unfortunately, it gets in the way of
the long-term goal of removing `TokenKind::Interpolated`. So this commit
removes it, which degrades a couple of (obscure) error messages but makes
things simpler and enables the next commit.

compiler/rustc_ast/src/attr/mod.rs

@@ -345,7 +345,7 @@ impl MetaItem {
                 let span = span.with_hi(segments.last().unwrap().ident.span.hi());
                 Path { span, segments, tokens: None }
             }
-            Some(TokenTree::Token(Token { kind: token::Interpolated(nt), .. }, _)) => match &nt.0 {
+            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,

compiler/rustc_ast/src/mut_visit.rs

@@ -783,8 +783,6 @@ pub fn visit_token<T: MutVisitor>(t: &mut Token, vis: &mut T) {
         }
         token::Interpolated(nt) => {
             let nt = Lrc::make_mut(nt);
-            let (nt, sp) = (&mut nt.0, &mut nt.1);
-            vis.visit_span(sp);
             visit_nonterminal(nt, vis);
         }
         _ => {}

compiler/rustc_ast/src/token.rs

@@ -111,7 +111,7 @@ impl Lit {
             Ident(name, IdentIsRaw::No) if name.is_bool_lit() => Some(Lit::new(Bool, name, None)),
             Literal(token_lit) => Some(token_lit),
             Interpolated(ref nt)
-                if let NtExpr(expr) | NtLiteral(expr) = &nt.0
+                if let NtExpr(expr) | NtLiteral(expr) = &**nt
                     && let ast::ExprKind::Lit(token_lit) = expr.kind =>
             {
                 Some(token_lit)
@@ -333,7 +333,11 @@ pub enum TokenKind {
     /// - It prevents `Token` from implementing `Copy`.
     /// It adds complexity and likely slows things down. Please don't add new
     /// occurrences of this token kind!
-    Interpolated(Lrc<(Nonterminal, Span)>),
+    ///
+    /// The span in the surrounding `Token` is that of the metavariable in the
+    /// macro's RHS. The span within the Nonterminal is that of the fragment
+    /// passed to the macro at the call site.
+    Interpolated(Lrc<Nonterminal>),
 
     /// A doc comment token.
     /// `Symbol` is the doc comment's data excluding its "quotes" (`///`, `/**`, etc)
@@ -441,7 +445,7 @@ impl Token {
     /// if they keep spans or perform edition checks.
     pub fn uninterpolated_span(&self) -> Span {
         match &self.kind {
-            Interpolated(nt) => nt.0.use_span(),
+            Interpolated(nt) => nt.use_span(),
             _ => self.span,
         }
     }
@@ -486,7 +490,7 @@ impl Token {
             PathSep                            | // global path
             Lifetime(..)                      | // labeled loop
             Pound                             => true, // expression attributes
-            Interpolated(ref nt) => matches!(&nt.0, NtLiteral(..) |
+            Interpolated(ref nt) => matches!(&**nt, NtLiteral(..) |
                 NtExpr(..)    |
                 NtBlock(..)   |
                 NtPath(..)),
@@ -510,7 +514,7 @@ impl Token {
             | DotDot | DotDotDot | DotDotEq      // ranges
             | Lt | BinOp(Shl)                    // associated path
             | PathSep                    => true, // global path
-            Interpolated(ref nt) => matches!(&nt.0, NtLiteral(..) |
+            Interpolated(ref nt) => matches!(&**nt, NtLiteral(..) |
                 NtPat(..)     |
                 NtBlock(..)   |
                 NtPath(..)),
@@ -533,7 +537,7 @@ impl Token {
             Lifetime(..)                | // lifetime bound in trait object
             Lt | BinOp(Shl)             | // associated path
             PathSep                      => true, // global path
-            Interpolated(ref nt) => matches!(&nt.0, NtTy(..) | NtPath(..)),
+            Interpolated(ref nt) => matches!(&**nt, NtTy(..) | NtPath(..)),
             // For anonymous structs or unions, which only appear in specific positions
             // (type of struct fields or union fields), we don't consider them as regular types
             _ => false,
@@ -544,7 +548,7 @@ impl Token {
     pub fn can_begin_const_arg(&self) -> bool {
         match self.kind {
             OpenDelim(Delimiter::Brace) => true,
-            Interpolated(ref nt) => matches!(&nt.0, NtExpr(..) | NtBlock(..) | NtLiteral(..)),
+            Interpolated(ref nt) => matches!(&**nt, NtExpr(..) | NtBlock(..) | NtLiteral(..)),
             _ => self.can_begin_literal_maybe_minus(),
         }
     }
@@ -589,7 +593,7 @@ impl Token {
         match self.uninterpolate().kind {
             Literal(..) | BinOp(Minus) => true,
             Ident(name, IdentIsRaw::No) if name.is_bool_lit() => true,
-            Interpolated(ref nt) => match &nt.0 {
+            Interpolated(ref nt) => match &**nt {
                 NtLiteral(_) => true,
                 NtExpr(e) => match &e.kind {
                     ast::ExprKind::Lit(_) => true,
@@ -610,7 +614,7 @@ impl Token {
     /// otherwise returns the original token.
     pub fn uninterpolate(&self) -> Cow<'_, Token> {
         match &self.kind {
-            Interpolated(nt) => match &nt.0 {
+            Interpolated(nt) => match &**nt {
                 NtIdent(ident, is_raw) => {
                     Cow::Owned(Token::new(Ident(ident.name, *is_raw), ident.span))
                 }
@@ -627,7 +631,7 @@ impl Token {
         // We avoid using `Token::uninterpolate` here because it's slow.
         match &self.kind {
             &Ident(name, is_raw) => Some((Ident::new(name, self.span), is_raw)),
-            Interpolated(nt) => match &nt.0 {
+            Interpolated(nt) => match &**nt {
                 NtIdent(ident, is_raw) => Some((*ident, *is_raw)),
                 _ => None,
             },
@@ -641,7 +645,7 @@ impl Token {
         // We avoid using `Token::uninterpolate` here because it's slow.
         match &self.kind {
             &Lifetime(name) => Some(Ident::new(name, self.span)),
-            Interpolated(nt) => match &nt.0 {
+            Interpolated(nt) => match &**nt {
                 NtLifetime(ident) => Some(*ident),
                 _ => None,
             },
@@ -668,7 +672,7 @@ impl Token {
     /// Returns `true` if the token is an interpolated path.
     fn is_whole_path(&self) -> bool {
         if let Interpolated(nt) = &self.kind
-            && let NtPath(..) = &nt.0
+            && let NtPath(..) = &**nt
         {
             return true;
         }
@@ -681,7 +685,7 @@ impl Token {
     /// (which happens while parsing the result of macro expansion)?
     pub fn is_whole_expr(&self) -> bool {
         if let Interpolated(nt) = &self.kind
-            && let NtExpr(_) | NtLiteral(_) | NtPath(_) | NtBlock(_) = &nt.0
+            && let NtExpr(_) | NtLiteral(_) | NtPath(_) | NtBlock(_) = &**nt
         {
             return true;
         }
@@ -692,7 +696,7 @@ impl Token {
     /// Is the token an interpolated block (`$b:block`)?
     pub fn is_whole_block(&self) -> bool {
         if let Interpolated(nt) = &self.kind
-            && let NtBlock(..) = &nt.0
+            && let NtBlock(..) = &**nt
         {
             return true;
         }
@@ -857,6 +861,7 @@ pub enum Nonterminal {
     NtPat(P<ast::Pat>),
     NtExpr(P<ast::Expr>),
     NtTy(P<ast::Ty>),
+    /// The span is for the identifier argument passed to the macro.
     NtIdent(Ident, IdentIsRaw),
     NtLifetime(Ident),
     NtLiteral(P<ast::Expr>),

compiler/rustc_ast/src/tokenstream.rs

@@ -490,14 +490,14 @@ impl TokenStream {
 
     fn flatten_token(token: &Token, spacing: Spacing) -> TokenTree {
         match &token.kind {
-            token::Interpolated(nt) if let token::NtIdent(ident, is_raw) = nt.0 => {
-                TokenTree::Token(Token::new(token::Ident(ident.name, is_raw), ident.span), spacing)
+            token::Interpolated(nt) if let token::NtIdent(ident, is_raw) = &**nt => {
+                TokenTree::Token(Token::new(token::Ident(ident.name, *is_raw), ident.span), spacing)
             }
             token::Interpolated(nt) => TokenTree::Delimited(
                 DelimSpan::from_single(token.span),
                 DelimSpacing::new(Spacing::JointHidden, spacing),
                 Delimiter::Invisible,
-                TokenStream::from_nonterminal_ast(&nt.0).flattened(),
+                TokenStream::from_nonterminal_ast(&nt).flattened(),
             ),
             _ => TokenTree::Token(token.clone(), spacing),
         }

compiler/rustc_ast_pretty/src/pprust/state.rs

@@ -926,7 +926,7 @@ pub trait PrintState<'a>: std::ops::Deref<Target = pp::Printer> + std::ops::Dere
             }
             token::Eof => "<eof>".into(),
 
-            token::Interpolated(ref nt) => self.nonterminal_to_string(&nt.0).into(),
+            token::Interpolated(ref nt) => self.nonterminal_to_string(&nt).into(),
         }
     }
 

compiler/rustc_expand/src/mbe/diagnostics.rs

@@ -73,12 +73,6 @@ pub(super) fn failed_to_match_macro<'cx>(
         && (matches!(expected_token.kind, TokenKind::Interpolated(_))
             || matches!(token.kind, TokenKind::Interpolated(_)))
     {
-        if let TokenKind::Interpolated(node) = &expected_token.kind {
-            err.span_label(node.1, "");
-        }
-        if let TokenKind::Interpolated(node) = &token.kind {
-            err.span_label(node.1, "");
-        }
         err.note("captured metavariables except for `:tt`, `:ident` and `:lifetime` cannot be compared to other tokens");
         err.note("see <https://doc.rust-lang.org/nightly/reference/macros-by-example.html#forwarding-a-matched-fragment> for more information");
 

compiler/rustc_expand/src/mbe/macro_parser.rs

@@ -75,10 +75,9 @@ pub(crate) use ParseResult::*;
 
 use crate::mbe::{macro_rules::Tracker, KleeneOp, TokenTree};
 
-use rustc_ast::token::{self, DocComment, Nonterminal, NonterminalKind, Token};
+use rustc_ast::token::{self, DocComment, NonterminalKind, Token};
 use rustc_ast_pretty::pprust;
 use rustc_data_structures::fx::FxHashMap;
-use rustc_data_structures::sync::Lrc;
 use rustc_errors::ErrorGuaranteed;
 use rustc_lint_defs::pluralize;
 use rustc_parse::parser::{ParseNtResult, Parser};
@@ -392,7 +391,7 @@ pub(super) fn count_metavar_decls(matcher: &[TokenTree]) -> usize {
 #[derive(Debug, Clone)]
 pub(crate) enum NamedMatch {
     MatchedSeq(Vec<NamedMatch>),
-    MatchedSingle(ParseNtResult<Lrc<(Nonterminal, Span)>>),
+    MatchedSingle(ParseNtResult),
 }
 
 /// Performs a token equality check, ignoring syntax context (that is, an unhygienic comparison)
@@ -686,11 +685,7 @@ impl TtParser {
                             }
                             Ok(nt) => nt,
                         };
-                        mp.push_match(
-                            next_metavar,
-                            seq_depth,
-                            MatchedSingle(nt.map_nt(|nt| (Lrc::new((nt, span))))),
-                        );
+                        mp.push_match(next_metavar, seq_depth, MatchedSingle(nt));
                         mp.idx += 1;
                     } else {
                         unreachable!()

compiler/rustc_expand/src/proc_macro.rs

@@ -127,7 +127,7 @@ impl MultiItemModifier for DeriveProcMacro {
                 Annotatable::Stmt(stmt) => token::NtStmt(stmt),
                 _ => unreachable!(),
             };
-            TokenStream::token_alone(token::Interpolated(Lrc::new((nt, span))), DUMMY_SP)
+            TokenStream::token_alone(token::Interpolated(Lrc::new(nt)), DUMMY_SP)
         } else {
             item.to_tokens()
         };

compiler/rustc_expand/src/proc_macro_server.rs

@@ -259,7 +259,7 @@ impl FromInternal<(TokenStream, &mut Rustc<'_, '_>)> for Vec<TokenTree<TokenStre
                     }));
                 }
 
-                Interpolated(ref nt) if let NtIdent(ident, is_raw) = &nt.0 => {
+                Interpolated(ref nt) if let NtIdent(ident, is_raw) = &**nt => {
                     trees.push(TokenTree::Ident(Ident {
                         sym: ident.name,
                         is_raw: matches!(is_raw, IdentIsRaw::Yes),
@@ -268,14 +268,14 @@ impl FromInternal<(TokenStream, &mut Rustc<'_, '_>)> for Vec<TokenTree<TokenStre
                 }
 
                 Interpolated(nt) => {
-                    let stream = TokenStream::from_nonterminal_ast(&nt.0);
+                    let stream = TokenStream::from_nonterminal_ast(&nt);
                     // A hack used to pass AST fragments to attribute and derive
                     // macros as a single nonterminal token instead of a token
                     // stream. Such token needs to be "unwrapped" and not
                     // represented as a delimited group.
                     // FIXME: It needs to be removed, but there are some
                     // compatibility issues (see #73345).
-                    if crate::base::nt_pretty_printing_compatibility_hack(&nt.0, rustc.ecx.sess) {
+                    if crate::base::nt_pretty_printing_compatibility_hack(&nt, rustc.ecx.sess) {
                         trees.extend(Self::from_internal((stream, rustc)));
                     } else {
                         trees.push(TokenTree::Group(Group {

compiler/rustc_parse/src/parser/attr.rs

@@ -363,7 +363,7 @@ impl<'a> Parser<'a> {
         // We can't use `maybe_whole` here because it would bump in the `None`
         // case, which we don't want.
         if let token::Interpolated(nt) = &self.token.kind
-            && let token::NtMeta(attr_item) = &nt.0
+            && let token::NtMeta(attr_item) = &**nt
         {
             match attr_item.meta(attr_item.path.span) {
                 Some(meta) => {

compiler/rustc_parse/src/parser/diagnostics.rs

@@ -2372,9 +2372,9 @@ impl<'a> Parser<'a> {
         // in a subsequent macro invocation (#71039).
         let mut tok = self.token.clone();
         let mut labels = vec![];
-        while let TokenKind::Interpolated(node) = &tok.kind {
-            let tokens = node.0.tokens();
-            labels.push(node.clone());
+        while let TokenKind::Interpolated(nt) = &tok.kind {
+            let tokens = nt.tokens();
+            labels.push(nt.clone());
             if let Some(tokens) = tokens
                 && let tokens = tokens.to_attr_token_stream()
                 && let tokens = tokens.0.deref()
@@ -2387,27 +2387,20 @@ impl<'a> Parser<'a> {
         }
         let mut iter = labels.into_iter().peekable();
         let mut show_link = false;
-        while let Some(node) = iter.next() {
-            let descr = node.0.descr();
+        while let Some(nt) = iter.next() {
+            let descr = nt.descr();
             if let Some(next) = iter.peek() {
-                let next_descr = next.0.descr();
+                let next_descr = next.descr();
                 if next_descr != descr {
-                    err.span_label(next.1, format!("this macro fragment matcher is {next_descr}"));
-                    err.span_label(node.1, format!("this macro fragment matcher is {descr}"));
+                    err.span_label(next.use_span(), format!("this is expected to be {next_descr}"));
                     err.span_label(
-                        next.0.use_span(),
-                        format!("this is expected to be {next_descr}"),
-                    );
-                    err.span_label(
-                        node.0.use_span(),
+                        nt.use_span(),
                         format!(
                             "this is interpreted as {}, but it is expected to be {}",
                             next_descr, descr,
                         ),
                     );
                     show_link = true;
-                } else {
-                    err.span_label(node.1, "");
                 }
             }
         }

compiler/rustc_parse/src/parser/expr.rs

@@ -45,7 +45,7 @@ use thin_vec::{thin_vec, ThinVec};
 macro_rules! maybe_whole_expr {
     ($p:expr) => {
         if let token::Interpolated(nt) = &$p.token.kind {
-            match &nt.0 {
+            match &**nt {
                 token::NtExpr(e) | token::NtLiteral(e) => {
                     let e = e.clone();
                     $p.bump();

compiler/rustc_parse/src/parser/item.rs

@@ -2841,7 +2841,7 @@ impl<'a> Parser<'a> {
 
     fn is_named_param(&self) -> bool {
         let offset = match &self.token.kind {
-            token::Interpolated(nt) => match &nt.0 {
+            token::Interpolated(nt) => match &**nt {
                 token::NtPat(..) => return self.look_ahead(1, |t| t == &token::Colon),
                 _ => 0,
             },