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.

5 files changed, 16 insertions, 20 deletions

diff --git a/compiler/rustc_ast/src/ast_traits.rs b/compiler/rustc_ast/src/ast_traits.rs
index 8b94d65c44e..30b8216df87 100644
--- a/compiler/rustc_ast/src/ast_traits.rs
+++ b/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(),
         }
diff --git a/compiler/rustc_ast/src/attr/mod.rs b/compiler/rustc_ast/src/attr/mod.rs
index df2f4b88712..be2e897e460 100644
--- a/compiler/rustc_ast/src/attr/mod.rs
+++ b/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(_), .. },
                 _,
diff --git a/compiler/rustc_ast/src/mut_visit.rs b/compiler/rustc_ast/src/mut_visit.rs
index 6ebe52738b9..27fab2a02ed 100644
--- a/compiler/rustc_ast/src/mut_visit.rs
+++ b/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),
     }
 }
diff --git a/compiler/rustc_ast/src/token.rs b/compiler/rustc_ast/src/token.rs
index ff8a68ff711..ff590df0d68 100644
--- a/compiler/rustc_ast/src/token.rs
+++ b/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(..)"),
         }
     }
diff --git a/compiler/rustc_ast/src/tokenstream.rs b/compiler/rustc_ast/src/tokenstream.rs
index 2b4c818fc32..489b5ad1a77 100644
--- a/compiler/rustc_ast/src/tokenstream.rs
+++ b/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),
         }