Address review comments

src/librustc/ty/print/pretty.rs

@@ -1019,7 +1019,7 @@ pub trait PrettyPrinter<'tcx>:
                 )?;
             }
             // For function type zsts just printing the type is enough
-            (Scalar::Raw { size: 0, .. }, ty::FnDef(..)) => p!(print(ty)),
+            (Scalar::Raw { size: 0, .. }, ty::FnDef(d, s)) => p!(print_value_path(*d, s)),
             // Empty tuples are frequently occurring, so don't print the fallback.
             (Scalar::Raw { size: 0, .. }, ty::Tuple(ts)) if ts.is_empty() => p!(write("()")),
             // Zero element arrays have a trivial representation.