Simplify Accepts.

There only needs to be one `Fn` per symbol, not multiple.

Author: nnethercote

compiler/rustc_attr_parsing/src/context.rs

@@ -28,7 +28,7 @@ macro_rules! attribute_groups {
 ) => {
 typeAccepts = BTreeMap<
 &'static[Symbol],
-Vec<Box<dyn Send + Sync + Fn(&AcceptContext<'_>,&ArgParser<'_>)>>
+Box<dyn Send + Sync + Fn(&AcceptContext<'_>,&ArgParser<'_>)>
  >;
 typeFinalizes = Vec<
 Box<dyn Send + Sync + Fn(&FinalizeContext<'_>) -> Option<AttributeKind>>
@@ -43,11 +43,12 @@ macro_rules! attribute_groups {
 };
 
 for(k, v) in <$names>::ATTRIBUTES{
- accepts.entry(*k).or_default().push(Box::new(|cx, args| {
+let old = accepts.insert(*k,Box::new(|cx, args| {
 STATE_OBJECT.with_borrow_mut(|s| {
  v(s, cx, args)
 })
 }));
+ assert!(old.is_none());
 }
 
  finalizes.push(Box::new(|cx| {
@@ -267,15 +268,11 @@ impl<'sess> AttributeParser<'sess> {
 let(path, args) = parser.deconstruct();
 let parts = path.segments().map(|i| i.name).collect::<Vec<_>>();
 
-ifletSome(accepts) = ATTRIBUTE_MAPPING.0.get(parts.as_slice()){
-for f in accepts {
-let cx = AcceptContext{
-group_cx:&group_cx,
-attr_span:lower_span(attr.span),
-};
+ifletSome(accept) = ATTRIBUTE_MAPPING.0.get(parts.as_slice()){
+let cx =
+AcceptContext{group_cx:&group_cx,attr_span:lower_span(attr.span)};
 
-f(&cx,&args)
-}
+accept(&cx,&args)
 }else{
 // if we're here, we must be compiling a tool attribute... Or someone forgot to
 // parse their fancy new attribute. Let's warn them in any case. If you are that