Surround found token with `

Author: estebank

src/libsyntax/parse/attr.rs

@@ -285,7 +285,7 @@ impl<'a> Parser<'a> {
         }
 
         let found = self.this_token_to_string();
-        let msg = format!("expected unsuffixed literal or identifier, found {}", found);
+        let msg = format!("expected unsuffixed literal or identifier, found `{}`", found);
         Err(self.diagnostic().struct_span_err(self.span, &msg))
     }
 

src/test/ui/conditional-compilation/cfg-attr-syntax-validation.rs

@@ -28,7 +28,7 @@ struct S9;
 macro_rules! generate_s10 {
     ($expr: expr) => {
         #[cfg(feature = $expr)]
-        //~^ ERROR expected unsuffixed literal or identifier, found concat!("nonexistent")
+        //~^ ERROR expected unsuffixed literal or identifier, found `concat!("nonexistent")`
         struct S10;
     }
 }

src/test/ui/conditional-compilation/cfg-attr-syntax-validation.stderr

@@ -52,7 +52,7 @@ error[E0565]: literal in `cfg` predicate value must be a string
 LL | #[cfg(a = b"hi")]  //~ ERROR literal in `cfg` predicate value must be a string
    |           ^^^^^ help: consider removing the prefix: `"hi"`
 
-error: expected unsuffixed literal or identifier, found concat!("nonexistent")
+error: expected unsuffixed literal or identifier, found `concat!("nonexistent")`
   --> $DIR/cfg-attr-syntax-validation.rs:30:25
    |
 LL |         #[cfg(feature = $expr)]