Fix `rustc --unpretty=expanded` emit of `[const] [unsafe] impl Trait for`

diff --git a/compiler/rustc_ast_pretty/src/pprust/state/item.rs b/compiler/rustc_ast_pretty/src/pprust/state/item.rs
index 1dbd571..8602a21 100644
--- a/compiler/rustc_ast_pretty/src/pprust/state/item.rs
+++ b/compiler/rustc_ast_pretty/src/pprust/state/item.rs

@@ -344,9 +344,9 @@ pub(crate) fn print_item(&mut self, item: &ast::Item) {
                     let ast::TraitImplHeader { defaultness, safety, polarity, ref trait_ref } =
                         *of_trait;
                     self.print_defaultness(defaultness);
+                    self.print_constness(*constness);
                     self.print_safety(safety);
                     impl_generics(self);
-                    self.print_constness(*constness);
                     if let ast::ImplPolarity::Negative(_) = polarity {
                         self.word("!");
                     }

diff --git a/tests/ui/unpretty/exhaustive.expanded.stdout b/tests/ui/unpretty/exhaustive.expanded.stdout
index f555904..17995ca 100644
--- a/tests/ui/unpretty/exhaustive.expanded.stdout
+++ b/tests/ui/unpretty/exhaustive.expanded.stdout

@@ -449,7 +449,7 @@
         impl () {}
         impl<T> () {}
         impl Default for () {}
-        impl<T> const Default for () {}
+        const impl<T> Default for () {}
     }
     /// ItemKind::MacCall
     mod item_mac_call { }