Look inside of None-delimited groups when examining types

serde_derive/src/internals/attr.rs

@@ -1,5 +1,5 @@
 use internals::symbol::*;
-use internals::Ctxt;
+use internals::{ungroup, Ctxt};
 use proc_macro2::{Group, Span, TokenStream, TokenTree};
 use quote::ToTokens;
 use std::borrow::Cow;
@@ -1737,7 +1737,7 @@ fn is_implicitly_borrowed_reference(ty: &syn::Type) -> bool {
 //         cow: Cow<'a, str>,
 //     }
 fn is_cow(ty: &syn::Type, elem: fn(&syn::Type) -> bool) -> bool {
-    let path = match ty {
+    let path = match ungroup(ty) {
         syn::Type::Path(ty) => &ty.path,
         _ => {
             return false;
@@ -1764,7 +1764,7 @@ fn is_cow(ty: &syn::Type, elem: fn(&syn::Type) -> bool) -> bool {
 }
 
 fn is_option(ty: &syn::Type, elem: fn(&syn::Type) -> bool) -> bool {
-    let path = match ty {
+    let path = match ungroup(ty) {
         syn::Type::Path(ty) => &ty.path,
         _ => {
             return false;
@@ -1811,7 +1811,7 @@ fn is_option(ty: &syn::Type, elem: fn(&syn::Type) -> bool) -> bool {
 //         r: &'a str,
 //     }
 fn is_reference(ty: &syn::Type, elem: fn(&syn::Type) -> bool) -> bool {
-    match ty {
+    match ungroup(ty) {
         syn::Type::Reference(ty) => ty.mutability.is_none() && elem(&ty.elem),
         _ => false,
     }
@@ -1822,14 +1822,14 @@ fn is_str(ty: &syn::Type) -> bool {
 }
 
 fn is_slice_u8(ty: &syn::Type) -> bool {
-    match ty {
+    match ungroup(ty) {
         syn::Type::Slice(ty) => is_primitive_type(&ty.elem, "u8"),
         _ => false,
     }
 }
 
 fn is_primitive_type(ty: &syn::Type, primitive: &str) -> bool {
-    match ty {
+    match ungroup(ty) {
         syn::Type::Path(ty) => ty.qself.is_none() && is_primitive_path(&ty.path, primitive),
         _ => false,
     }

serde_derive/src/internals/check.rs

@@ -1,6 +1,6 @@
 use internals::ast::{Container, Data, Field, Style};
 use internals::attr::{Identifier, TagType};
-use internals::{Ctxt, Derive};
+use internals::{ungroup, Ctxt, Derive};
 use syn::{Member, Type};
 
 /// Cross-cutting checks that require looking at more than a single attrs
@@ -396,7 +396,7 @@ fn member_message(member: &Member) -> String {
 }
 
 fn allow_transparent(field: &Field, derive: Derive) -> bool {
-    if let Type::Path(ty) = field.ty {
+    if let Type::Path(ty) = ungroup(&field.ty) {
         if let Some(seg) = ty.path.segments.last() {
             if seg.ident == "PhantomData" {
                 return false;

serde_derive/src/internals/mod.rs

@@ -8,8 +8,17 @@ mod case;
 mod check;
 mod symbol;
 
+use syn::Type;
+
 #[derive(Copy, Clone)]
 pub enum Derive {
     Serialize,
     Deserialize,
 }
+
+pub fn ungroup(mut ty: &Type) -> &Type {
+    while let Type::Group(group) = ty {
+        ty = &group.elem;
+    }
+    ty
+}