当使用衬底的decl_event时，我如何隐藏来自Clippy的关于“不需要的单元表达式”的警告？

Question

具有类似于底层框架的源代码：

decl_event!(
    pub enum Event<T>
    where
        AccountId = <T as frame_system::Config>::AccountId,
        ChipBalance = <T as Config>::ChipBalance,
    {
        /// Buy chips event
        BuyChips(AccountId, ChipBalance),
        /// Redemption amount with chips event
        Redemption(AccountId, ChipBalance),
        /// Pledge chips
        Reserve(AccountId, ChipBalance),
        /// Cancel pledge chips
        Unreserve(AccountId, ChipBalance),
        /// Transfer the chips in the pledge to others
        RepatriateReserved(AccountId, AccountId, ChipBalance),
    }
);

从cargo clippy我得到了：

warning: unneeded unit expression
  --> pallets/gamecenter/src/lib.rs:58:1
   |
58 | / decl_event!(
59 | |     pub enum Event<T>
60 | |     where
61 | |         AccountId = <T as frame_system::Config>::AccountId,
...  |
66 | |     }
67 | | );
   | |__^
   |
   = note: `#[warn(clippy::unused_unit)]` on by default
   = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#unused_unit
   = note: this warning originates in the macro `$crate::__decl_generic_event` (in Nightly builds, run with -Z macro-backtrace for more info)

有没有更好的解决方案来隐藏为Clippy lints创建自定义规则的警告？

Answer 1

我猜测这是由于From<Event> for ()实现中的单元造成的。这可以解决这个问题：

diff --git a/frame/support/procedural/src/pallet/expand/event.rs b/frame/support/procedural/src/pallet/expand/event.rs
index c4f7aeffa7..ec38c83b8b 100644
--- a/frame/support/procedural/src/pallet/expand/event.rs
+++ b/frame/support/procedural/src/pallet/expand/event.rs
@@ -133,7 +133,7 @@ pub fn expand_event(def: &mut Def) -> proc_macro2::TokenStream {
                #deposit_event
 
                impl<#event_impl_gen> From<#event_ident<#event_use_gen>> for () #event_where_clause {
-                       fn from(_: #event_ident<#event_use_gen>) -> () { () }
+                       fn from(_: #event_ident<#event_use_gen>) -> () {}
                }
 
                impl<#event_impl_gen> #event_ident<#event_use_gen> #event_where_clause {
diff --git a/frame/support/src/event.rs b/frame/support/src/event.rs
index eb666b6f02..b11166d1c6 100644
--- a/frame/support/src/event.rs
+++ b/frame/support/src/event.rs
@@ -140,7 +140,7 @@ macro_rules! decl_event {
                        )*
                }
                impl From<Event> for () {
-                       fn from(_: Event) -> () { () }
+                       fn from(_: Event) -> () {}
                }
                impl Event {
                        #[allow(dead_code)]