Box rustc_parse_format::Piece::NextArgument

This makes both variants closer together in size (previously they were
different by 208 bytes -- 16 vs 224). This may make things worse, but
it's worth a try.

compiler/rustc_parse_format/src/lib.rs

@@ -58,13 +58,13 @@ impl InnerOffset {
 
 /// A piece is a portion of the format string which represents the next part
 /// to emit. These are emitted as a stream by the `Parser` class.
-#[derive(Copy, Clone, Debug, PartialEq)]
+#[derive(Clone, Debug, PartialEq)]
 pub enum Piece<'a> {
     /// A literal string which should directly be emitted
     String(&'a str),
     /// This describes that formatting should process the next argument (as
     /// specified inside) for emission.
-    NextArgument(Argument<'a>),
+    NextArgument(Box<Argument<'a>>),
 }
 
 /// Representation of an argument specification.
@@ -244,7 +244,7 @@ impl<'a> Iterator for Parser<'a> {
                         } else {
                             self.suggest_positional_arg_instead_of_captured_arg(arg);
                         }
-                        Some(NextArgument(arg))
+                        Some(NextArgument(Box::new(arg)))
                     }
                 }
                 '}' => {