Switched to Box::new in many places.

Many of the modifications putting in `Box::new` calls also include a
pointer to Issue 22405, which tracks going back to `box <expr>` if
possible in the future.

(Still tried to use `Box<_>` where it sufficed; thus some tests still
have `box_syntax` enabled, as they use a mix of `box` and `Box::new`.)

Precursor for overloaded-`box` and placement-`in`; see Issue 22181.

1 files changed, 2 insertions, 1 deletions

diff --git a/src/test/auxiliary/plugin_args.rs b/src/test/auxiliary/plugin_args.rs
index 1775bbf4af2..20c84c4ba5b 100644
--- a/src/test/auxiliary/plugin_args.rs
+++ b/src/test/auxiliary/plugin_args.rs
@@ -46,5 +46,6 @@ impl TTMacroExpander for Expander {
 pub fn plugin_registrar(reg: &mut Registry) {
     let args = reg.args().clone();
     reg.register_syntax_extension(token::intern("plugin_args"),
-        NormalTT(box Expander { args: args, }, None));
+        // FIXME (#22405): Replace `Box::new` with `box` here when/if possible.
+        NormalTT(Box::new(Expander { args: args, }), None));
 }