Add comment + move derive helper

src/rustdoc-json-types/lib.rs

@@ -282,8 +282,8 @@ pub enum StructType {
 }
 
 #[non_exhaustive]
-#[serde(rename_all = "snake_case")]
 #[derive(Clone, Debug, Serialize, Deserialize, PartialEq)]
+#[serde(rename_all = "snake_case")]
 pub enum Modifiers {
     Const,
     Unsafe,

src/test/rustdoc-json/fns/header.rs

@@ -18,3 +18,5 @@ pub async unsafe fn async_unsafe_fn() {}
 // @has - "$.index[*][?(@.name=='const_unsafe_fn')].inner.header[*]" '"const"'
 // @has - "$.index[*][?(@.name=='const_unsafe_fn')].inner.header[*]" '"unsafe"'
 pub const unsafe fn const_unsafe_fn() {}
+
+// It's impossible for a function to be both const and async, so no test for that

src/test/rustdoc-json/methods/header.rs

@@ -21,4 +21,6 @@ impl Foo {
     // @has - "$.index[*][?(@.name=='const_unsafe_meth')].inner.header[*]" '"const"'
     // @has - "$.index[*][?(@.name=='const_unsafe_meth')].inner.header[*]" '"unsafe"'
     pub const unsafe fn const_unsafe_meth() {}
+
+    // It's impossible for a method to be both const and async, so no test for that
 }