Auto merge of rust-lang#124141 - nnethercote:rm-Nonterminal-and-TokenKind-Interpolated, r=<try>

Remove `Nonterminal` and `TokenKind::Interpolated`

A third attempt at this; the first attempt was rust-lang#96724 and the second was rust-lang#114647.

r? `@ghost`

Author: bors

compiler/rustc_ast/src/ast_traits.rs

@@ -3,7 +3,6 @@
 //! The traits are not implemented exhaustively, only when actually necessary.
 
 use crate::ptr::P;
-use crate::token::Nonterminal;
 use crate::tokenstream::LazyAttrTokenStream;
 use crate::{Arm, Crate, ExprField, FieldDef, GenericParam, Param, PatField, Variant};
 use crate::{AssocItem, Expr, ForeignItem, Item, NodeId};
@@ -228,35 +227,6 @@ impl HasTokens for Attribute {
     }
 }
 
-impl HasTokens for Nonterminal {
-    fn tokens(&self) -> Option<&LazyAttrTokenStream> {
-        match self {
-            Nonterminal::NtItem(item) => item.tokens(),
-            Nonterminal::NtStmt(stmt) => stmt.tokens(),
-            Nonterminal::NtExpr(expr) | Nonterminal::NtLiteral(expr) => expr.tokens(),
-            Nonterminal::NtPat(pat) => pat.tokens(),
-            Nonterminal::NtTy(ty) => ty.tokens(),
-            Nonterminal::NtMeta(attr_item) => attr_item.tokens(),
-            Nonterminal::NtPath(path) => path.tokens(),
-            Nonterminal::NtVis(vis) => vis.tokens(),
-            Nonterminal::NtBlock(block) => block.tokens(),
-        }
-    }
-    fn tokens_mut(&mut self) -> Option<&mut Option<LazyAttrTokenStream>> {
-        match self {
-            Nonterminal::NtItem(item) => item.tokens_mut(),
-            Nonterminal::NtStmt(stmt) => stmt.tokens_mut(),
-            Nonterminal::NtExpr(expr) | Nonterminal::NtLiteral(expr) => expr.tokens_mut(),
-            Nonterminal::NtPat(pat) => pat.tokens_mut(),
-            Nonterminal::NtTy(ty) => ty.tokens_mut(),
-            Nonterminal::NtMeta(attr_item) => attr_item.tokens_mut(),
-            Nonterminal::NtPath(path) => path.tokens_mut(),
-            Nonterminal::NtVis(vis) => vis.tokens_mut(),
-            Nonterminal::NtBlock(block) => block.tokens_mut(),
-        }
-    }
-}
-
 /// A trait for AST nodes having (or not having) attributes.
 pub trait HasAttrs {
     /// This is `true` if this `HasAttrs` might support 'custom' (proc-macro) inner

compiler/rustc_ast/src/attr/mod.rs

@@ -7,7 +7,7 @@ use crate::ast::{DelimArgs, Expr, ExprKind, LitKind, MetaItemLit};
 use crate::ast::{MetaItem, MetaItemKind, NestedMetaItem, NormalAttr};
 use crate::ast::{Path, PathSegment, DUMMY_NODE_ID};
 use crate::ptr::P;
-use crate::token::{self, CommentKind, Delimiter, Token};
+use crate::token::{self, CommentKind, Delimiter, InvisibleOrigin, MetaVarKind, Token};
 use crate::tokenstream::{DelimSpan, Spacing, TokenTree};
 use crate::tokenstream::{LazyAttrTokenStream, TokenStream};
 use crate::util::comments;
@@ -327,7 +327,8 @@ impl MetaItem {
         I: Iterator<Item = &'a TokenTree>,
     {
         // FIXME: Share code with `parse_path`.
-        let path = match tokens.next().map(|tt| TokenTree::uninterpolate(tt)).as_deref() {
+        let tt = tokens.next().map(|tt| TokenTree::uninterpolate(tt));
+        let path = match tt.as_deref() {
             Some(&TokenTree::Token(
                 Token { kind: ref kind @ (token::Ident(..) | token::PathSep), span },
                 _,
@@ -363,11 +364,23 @@ 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 {
-                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 | MetaVarKind::Path,
+                )),
+                _stream,
+            )) => {
+                // This path is currently unreachable in the test suite.
+                unreachable!()
+            }
+            Some(TokenTree::Token(
+                Token { kind: token::OpenDelim(_) | token::CloseDelim(_), .. },
+                _,
+            )) => {
+                panic!("Should be `AttrTokenTree::Delimited`, not delim tokens: {:?}", tt);
+            }
             _ => return None,
         };
         let list_closing_paren_pos = tokens.peek().map(|tt| tt.span().hi());
@@ -404,7 +417,7 @@ impl MetaItemKind {
         tokens: &mut impl Iterator<Item = &'a TokenTree>,
     ) -> Option<MetaItemKind> {
         match tokens.next() {
-            Some(TokenTree::Delimited(.., Delimiter::Invisible, inner_tokens)) => {
+            Some(TokenTree::Delimited(.., Delimiter::Invisible(_), inner_tokens)) => {
                 MetaItemKind::name_value_from_tokens(&mut inner_tokens.trees())
             }
             Some(TokenTree::Token(token, _)) => {
@@ -542,7 +555,7 @@ impl NestedMetaItem {
                 tokens.next();
                 return Some(NestedMetaItem::Lit(lit));
             }
-            Some(TokenTree::Delimited(.., Delimiter::Invisible, inner_tokens)) => {
+            Some(TokenTree::Delimited(.., Delimiter::Invisible(_), inner_tokens)) => {
                 tokens.next();
                 return NestedMetaItem::from_tokens(&mut inner_tokens.trees().peekable());
             }

compiler/rustc_ast/src/mut_visit.rs

@@ -764,9 +764,9 @@ fn visit_lazy_tts<T: MutVisitor>(lazy_tts: &mut Option<LazyAttrTokenStream>, vis
     visit_lazy_tts_opt_mut(lazy_tts.as_mut(), vis);
 }
 
-/// Applies ident visitor if it's an ident; applies other visits to interpolated nodes.
-/// In practice the ident part is not actually used by specific visitors right now,
-/// but there's a test below checking that it works.
+/// Applies ident visitor if it's an ident. In practice this is not actually
+/// used by specific visitors right now, but there's a test below checking that
+/// it works.
 // No `noop_` prefix because there isn't a corresponding method in `MutVisitor`.
 pub fn visit_token<T: MutVisitor>(t: &mut Token, vis: &mut T) {
     let Token { kind, span } = t;
@@ -784,69 +784,11 @@ pub fn visit_token<T: MutVisitor>(t: &mut Token, vis: &mut T) {
         token::NtLifetime(ident) => {
             vis.visit_ident(ident);
         }
-        token::Interpolated(nt) => {
-            let nt = Lrc::make_mut(nt);
-            visit_nonterminal(nt, vis);
-        }
         _ => {}
     }
     vis.visit_span(span);
 }
 
-// No `noop_` prefix because there isn't a corresponding method in `MutVisitor`.
-/// Applies the visitor to elements of interpolated nodes.
-//
-// N.B., this can occur only when applying a visitor to partially expanded
-// code, where parsed pieces have gotten implanted ito *other* macro
-// invocations. This is relevant for macro hygiene, but possibly not elsewhere.
-//
-// One problem here occurs because the types for flat_map_item, flat_map_stmt,
-// etc., allow the visitor to return *multiple* items; this is a problem for the
-// nodes here, because they insist on having exactly one piece. One solution
-// would be to mangle the MutVisitor trait to include one-to-many and
-// one-to-one versions of these entry points, but that would probably confuse a
-// lot of people and help very few. Instead, I'm just going to put in dynamic
-// checks. I think the performance impact of this will be pretty much
-// nonexistent. The danger is that someone will apply a `MutVisitor` to a
-// partially expanded node, and will be confused by the fact that their
-// `flat_map_item` or `flat_map_stmt` isn't getting called on `NtItem` or `NtStmt`
-// nodes. Hopefully they'll wind up reading this comment, and doing something
-// appropriate.
-//
-// BTW, design choice: I considered just changing the type of, e.g., `NtItem` to
-// contain multiple items, but decided against it when I looked at
-// `parse_item_or_view_item` and tried to figure out what I would do with
-// multiple items there....
-fn visit_nonterminal<T: MutVisitor>(nt: &mut token::Nonterminal, vis: &mut T) {
-    match nt {
-        token::NtItem(item) => visit_clobber(item, |item| {
-            // This is probably okay, because the only visitors likely to
-            // peek inside interpolated nodes will be renamings/markings,
-            // which map single items to single items.
-            vis.flat_map_item(item).expect_one("expected visitor to produce exactly one item")
-        }),
-        token::NtBlock(block) => vis.visit_block(block),
-        token::NtStmt(stmt) => visit_clobber(stmt, |stmt| {
-            // See reasoning above.
-            stmt.map(|stmt| {
-                vis.flat_map_stmt(stmt).expect_one("expected visitor to produce exactly one item")
-            })
-        }),
-        token::NtPat(pat) => vis.visit_pat(pat),
-        token::NtExpr(expr) => vis.visit_expr(expr),
-        token::NtTy(ty) => vis.visit_ty(ty),
-        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(args, vis);
-            visit_lazy_tts(tokens, vis);
-        }
-        token::NtPath(path) => vis.visit_path(path),
-        token::NtVis(visib) => vis.visit_vis(visib),
-    }
-}
-
 // No `noop_` prefix because there isn't a corresponding method in `MutVisitor`.
 fn visit_defaultness<T: MutVisitor>(defaultness: &mut Defaultness, vis: &mut T) {
     match defaultness {