Report unexpected verbatim literals in test

Author: dtolnay

tests/test_precedence.rs

@@ -385,7 +385,9 @@ fn librustc_parenthesize(mut librustc_expr: Box<ast::Expr>) -> Box<ast::Expr> {
 
 fn syn_parenthesize(syn_expr: syn::Expr) -> syn::Expr {
     use syn::fold::{fold_expr, fold_generic_argument, Fold};
-    use syn::{token, BinOp, Expr, ExprParen, GenericArgument, MetaNameValue, Pat, Stmt, Type};
+    use syn::{
+        token, BinOp, Expr, ExprParen, GenericArgument, Lit, MetaNameValue, Pat, Stmt, Type,
+    };
 
     struct FullyParenthesize;
 
@@ -463,6 +465,13 @@ fn syn_parenthesize(syn_expr: syn::Expr) -> syn::Expr {
         fn fold_type(&mut self, ty: Type) -> Type {
             ty
         }
+
+        fn fold_lit(&mut self, lit: Lit) -> Lit {
+            if let Lit::Verbatim(lit) = &lit {
+                panic!("unexpected verbatim literal: {lit}");
+            }
+            lit
+        }
     }
 
     let mut folder = FullyParenthesize;