Remove NtTy.

Notes about tests:

- tests/ui/parser/macro/trait-object-macro-matcher.rs: the syntax error
  is duplicated, because it occurs now when parsing the decl macro
  input, and also when parsing the expanded decl macro. But this won't
  show up for normal users due to error de-duplication.

- tests/ui/associated-consts/issue-93835.rs: similar, plus there are
  some additional errors about this very broken code.

- The changes to metavariable descriptions in #132629 are now visible in
  error message for several tests.

compiler/rustc_parse/src/parser/path.rs

@@ -2,7 +2,7 @@ use std::mem;
 
 use ast::token::IdentIsRaw;
 use rustc_ast::ptr::P;
-use rustc_ast::token::{self, Delimiter, Token, TokenKind};
+use rustc_ast::token::{self, Delimiter, MetaVarKind, Token, TokenKind};
 use rustc_ast::{
     self as ast, AngleBracketedArg, AngleBracketedArgs, AnonConst, AssocItemConstraint,
     AssocItemConstraintKind, BlockCheckMode, GenericArg, GenericArgs, Generics, ParenthesizedArgs,
@@ -196,13 +196,14 @@ impl<'a> Parser<'a> {
 
         maybe_whole!(self, NtPath, |path| reject_generics_if_mod_style(self, path.into_inner()));
 
-        if let token::Interpolated(nt) = &self.token.kind {
-            if let token::NtTy(ty) = &**nt {
-                if let ast::TyKind::Path(None, path) = &ty.kind {
-                    let path = path.clone();
-                    self.bump();
-                    return Ok(reject_generics_if_mod_style(self, path));
-                }
+        if let Some(MetaVarKind::Ty) = self.token.is_metavar_seq() {
+            let mut snapshot = self.create_snapshot_for_diagnostic();
+            let ty = snapshot
+                .eat_metavar_seq(MetaVarKind::Ty, |this| this.parse_ty_no_question_mark_recover())
+                .expect("metavar seq ty");
+            if let ast::TyKind::Path(None, path) = ty.into_inner().kind {
+                self.restore_snapshot(snapshot);
+                return Ok(reject_generics_if_mod_style(self, path));
             }
         }