Bug 1643201 - Cherry-pick some servo changes to derive_common.

Depends on D78199

Differential Revision: https://phabricator.services.mozilla.com/D78200

servo/components/derive_common/cg.rs

@@ -7,7 +7,7 @@ use proc_macro2::{Span, TokenStream};
 use quote::TokenStreamExt;
 use syn::{self, AngleBracketedGenericArguments, Binding, DeriveInput, Field};
 use syn::{GenericArgument, GenericParam, Ident, Path};
-use syn::{PathArguments, PathSegment, QSelf, Type, TypeArray};
+use syn::{PathArguments, PathSegment, QSelf, Type, TypeArray, TypeGroup};
 use syn::{TypeParam, TypeParen, TypePath, TypeSlice, TypeTuple};
 use syn::{Variant, WherePredicate};
 use synstructure::{self, BindStyle, BindingInfo, VariantAst, VariantInfo};
@@ -208,6 +208,10 @@ where
             elem: Box::new(map_type_params(&inner.elem, params, f)),
             ..inner.clone()
         }),
+        Type::Group(ref inner) => Type::from(TypeGroup {
+            elem: Box::new(map_type_params(&inner.elem, params, f)),
+            ..inner.clone()
+        }),
         ref ty => panic!("type {:?} cannot be mapped yet", ty),
     }
 }