Handle the possibility that the class name is in its own Group (#2159)

* Handle the possibility that the class name is in its own Group

rust-lang/rust#72388 makes this happen

* Handle Groups in more places

* fmt!

* Add some functions to handle Groups

As suggested by @alexcrichton [here](https://gist.github.com/alexcrichton/3c93ab2547d45d9caa3b72309cd4262b).

crates/test-macro/src/lib.rs

@@ -43,10 +43,7 @@ pub fn wasm_bindgen_test(
             }
         }
     }
-    let ident = match body.next() {
-        Some(TokenTree::Ident(token)) => token,
-        _ => panic!("expected a function name"),
-    };
+    let ident = find_ident(&mut body).expect("expected a function name");
 
     let mut tokens = Vec::<TokenTree>::new();
 
@@ -78,3 +75,13 @@ pub fn wasm_bindgen_test(
 
     tokens.into_iter().collect::<TokenStream>().into()
 }
+
+fn find_ident(iter: &mut token_stream::IntoIter) -> Option<Ident> {
+    match iter.next()? {
+        TokenTree::Ident(i) => Some(i),
+        TokenTree::Group(g) if g.delimiter() == Delimiter::None => {
+            find_ident(&mut g.stream().into_iter())
+        }
+        _ => None,
+    }
+}