Release 1.0.59

Transparent attribute to specify that representation is the same as its only field

serde/Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "serde"
-version = "1.0.56" # remember to update html_root_url
+version = "1.0.59" # remember to update html_root_url
 authors = ["Erick Tryzelaar <erick.tryzelaar@gmail.com>", "David Tolnay <dtolnay@gmail.com>"]
 license = "MIT/Apache-2.0"
 description = "A generic serialization/deserialization framework"

serde/src/de/from_primitive.rs

@@ -39,12 +39,10 @@ macro_rules! uint_to {
 }
 
 pub trait FromPrimitive: Sized {
-    fn from_isize(n: isize) -> Option<Self>;
     fn from_i8(n: i8) -> Option<Self>;
     fn from_i16(n: i16) -> Option<Self>;
     fn from_i32(n: i32) -> Option<Self>;
     fn from_i64(n: i64) -> Option<Self>;
-    fn from_usize(n: usize) -> Option<Self>;
     fn from_u8(n: u8) -> Option<Self>;
     fn from_u16(n: u16) -> Option<Self>;
     fn from_u32(n: u32) -> Option<Self>;
@@ -54,10 +52,6 @@ pub trait FromPrimitive: Sized {
 macro_rules! impl_from_primitive_for_int {
     ($t:ident) => {
         impl FromPrimitive for $t {
-            #[inline]
-            fn from_isize(n: isize) -> Option<Self> {
-                int_to_int!($t, n)
-            }
             #[inline]
             fn from_i8(n: i8) -> Option<Self> {
                 int_to_int!($t, n)
@@ -75,10 +69,6 @@ macro_rules! impl_from_primitive_for_int {
                 int_to_int!($t, n)
             }
             #[inline]
-            fn from_usize(n: usize) -> Option<Self> {
-                uint_to!($t, n)
-            }
-            #[inline]
             fn from_u8(n: u8) -> Option<Self> {
                 uint_to!($t, n)
             }
@@ -101,10 +91,6 @@ macro_rules! impl_from_primitive_for_int {
 macro_rules! impl_from_primitive_for_uint {
     ($t:ident) => {
         impl FromPrimitive for $t {
-            #[inline]
-            fn from_isize(n: isize) -> Option<Self> {
-                int_to_uint!($t, n)
-            }
             #[inline]
             fn from_i8(n: i8) -> Option<Self> {
                 int_to_uint!($t, n)
@@ -122,10 +108,6 @@ macro_rules! impl_from_primitive_for_uint {
                 int_to_uint!($t, n)
             }
             #[inline]
-            fn from_usize(n: usize) -> Option<Self> {
-                uint_to!($t, n)
-            }
-            #[inline]
             fn from_u8(n: u8) -> Option<Self> {
                 uint_to!($t, n)
             }
@@ -148,10 +130,6 @@ macro_rules! impl_from_primitive_for_uint {
 macro_rules! impl_from_primitive_for_float {
     ($t:ident) => {
         impl FromPrimitive for $t {
-            #[inline]
-            fn from_isize(n: isize) -> Option<Self> {
-                Some(n as Self)
-            }
             #[inline]
             fn from_i8(n: i8) -> Option<Self> {
                 Some(n as Self)
@@ -169,10 +147,6 @@ macro_rules! impl_from_primitive_for_float {
                 Some(n as Self)
             }
             #[inline]
-            fn from_usize(n: usize) -> Option<Self> {
-                Some(n as Self)
-            }
-            #[inline]
             fn from_u8(n: u8) -> Option<Self> {
                 Some(n as Self)
             }

serde/src/de/impls.rs

@@ -1411,7 +1411,8 @@ impl<'de> Visitor<'de> for OsStringVisitor {
         use std::os::windows::ffi::OsStringExt;
 
         match try!(data.variant()) {
-            (OsStringKind::Windows, v) => v.newtype_variant::<Vec<u16>>()
+            (OsStringKind::Windows, v) => v
+                .newtype_variant::<Vec<u16>>()
                 .map(|vec| OsString::from_wide(&vec)),
             (OsStringKind::Unix, _) => Err(Error::custom(
                 "cannot deserialize Unix OS string on Windows",
@@ -2005,24 +2006,6 @@ where
 
 ////////////////////////////////////////////////////////////////////////////////
 
-#[cfg(feature = "unstable")]
-#[allow(deprecated)]
-impl<'de, T> Deserialize<'de> for NonZero<T>
-where
-    T: Deserialize<'de> + Zeroable,
-{
-    fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
-    where
-        D: Deserializer<'de>,
-    {
-        let value = try!(Deserialize::deserialize(deserializer));
-        match NonZero::new(value) {
-            Some(nonzero) => Ok(nonzero),
-            None => Err(Error::custom("expected a non-zero value")),
-        }
-    }
-}
-
 macro_rules! nonzero_integers {
     ( $( $T: ty, )+ ) => {
         $(

serde/src/de/mod.rs

@@ -84,7 +84,6 @@
 //!    - LinkedList\<T\>
 //!    - VecDeque\<T\>
 //!    - Vec\<T\>
-//!    - EnumSet\<T\> (unstable)
 //!  - **Zero-copy types**:
 //!    - &str
 //!    - &[u8]
@@ -98,7 +97,6 @@
 //!    - Path
 //!    - PathBuf
 //!    - Range\<T\>
-//!    - NonZero\<T\> (unstable, deprecated)
 //!    - num::NonZero* (unstable)
 //!  - **Net types**:
 //!    - IpAddr

serde/src/lib.rs

@@ -79,14 +79,14 @@
 ////////////////////////////////////////////////////////////////////////////////
 
 // Serde types in rustdoc of other crates get linked to here.
-#![doc(html_root_url = "https://docs.rs/serde/1.0.56")]
+#![doc(html_root_url = "https://docs.rs/serde/1.0.59")]
 // Support using Serde without the standard library!
 #![cfg_attr(not(feature = "std"), no_std)]
 // Unstable functionality only if the user asks for it. For tracking and
 // discussion of these features please refer to this issue:
 //
 //    https://github.com/serde-rs/serde/issues/812
-#![cfg_attr(feature = "unstable", feature(nonzero, specialization))]
+#![cfg_attr(feature = "unstable", feature(specialization))]
 #![cfg_attr(feature = "alloc", feature(alloc))]
 #![cfg_attr(feature = "cargo-clippy", deny(clippy, clippy_pedantic))]
 // Whitelisted clippy lints
@@ -213,10 +213,6 @@ mod lib {
     #[cfg(feature = "std")]
     pub use std::time::{Duration, SystemTime, UNIX_EPOCH};
 
-    #[cfg(feature = "unstable")]
-    #[allow(deprecated)]
-    pub use core::nonzero::{NonZero, Zeroable};
-
     #[cfg(feature = "unstable")]
     pub use core::num::{NonZeroU16, NonZeroU32, NonZeroU64, NonZeroU8, NonZeroUsize};
 }

serde/src/private/de.rs

@@ -2323,7 +2323,8 @@ mod content {
             T: de::DeserializeSeed<'de>,
         {
             match self.iter.next() {
-                Some(value) => seed.deserialize(ContentRefDeserializer::new(value))
+                Some(value) => seed
+                    .deserialize(ContentRefDeserializer::new(value))
                     .map(Some),
                 None => Ok(None),
             }
@@ -2821,14 +2822,13 @@ where
             // about.  In case we do not know which fields we want, we take them all.
             let use_item = match *item {
                 None => false,
-                Some((ref c, _)) => {
-                    c.as_str()
-                        .map_or(self.fields.is_none(), |key| match self.fields {
-                            None => true,
-                            Some(fields) if fields.contains(&key) => true,
-                            _ => false,
-                        })
-                }
+                Some((ref c, _)) => c.as_str().map_or(self.fields.is_none(), |key| {
+                    match self.fields {
+                        None => true,
+                        Some(fields) if fields.contains(&key) => true,
+                        _ => false,
+                    }
+                }),
             };
 
             if use_item {

serde/src/private/ser.rs

@@ -947,7 +947,8 @@ mod content {
         where
             T: Serialize,
         {
-            let key = self.key
+            let key = self
+                .key
                 .take()
                 .expect("serialize_value called before serialize_key");
             let value = try!(value.serialize(ContentSerializer::<E>::new()));

serde/src/ser/impls.rs

@@ -408,20 +408,6 @@ where
 
 ////////////////////////////////////////////////////////////////////////////////
 
-#[cfg(feature = "unstable")]
-#[allow(deprecated)]
-impl<T> Serialize for NonZero<T>
-where
-    T: Serialize + Zeroable + Clone,
-{
-    fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
-    where
-        S: Serializer,
-    {
-        self.clone().get().serialize(serializer)
-    }
-}
-
 macro_rules! nonzero_integers {
     ( $( $T: ident, )+ ) => {
         $(
@@ -549,7 +535,8 @@ impl Serialize for SystemTime {
         S: Serializer,
     {
         use super::SerializeStruct;
-        let duration_since_epoch = self.duration_since(UNIX_EPOCH)
+        let duration_since_epoch = self
+            .duration_since(UNIX_EPOCH)
             .expect("SystemTime must be later than UNIX_EPOCH");
         let mut state = try!(serializer.serialize_struct("SystemTime", 2));
         try!(state.serialize_field("secs_since_epoch", &duration_since_epoch.as_secs()));

serde/src/ser/mod.rs

@@ -81,7 +81,6 @@
 //!    - LinkedList\<T\>
 //!    - VecDeque\<T\>
 //!    - Vec\<T\>
-//!    - EnumSet\<T\> (unstable)
 //!  - **FFI types**:
 //!    - CStr
 //!    - CString
@@ -93,7 +92,6 @@
 //!    - Path
 //!    - PathBuf
 //!    - Range\<T\>
-//!    - NonZero\<T\> (unstable, deprecated)
 //!    - num::NonZero* (unstable)
 //!  - **Net types**:
 //!    - IpAddr

serde_derive/Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "serde_derive"
-version = "1.0.56" # remember to update html_root_url
+version = "1.0.59" # remember to update html_root_url
 authors = ["Erick Tryzelaar <erick.tryzelaar@gmail.com>", "David Tolnay <dtolnay@gmail.com>"]
 license = "MIT/Apache-2.0"
 description = "Macros 1.1 implementation of #[derive(Serialize, Deserialize)]"
@@ -23,9 +23,9 @@ name = "serde_derive"
 proc-macro = true
 
 [dependencies]
-proc-macro2 = "0.3"
-quote = "0.5.2"
-syn = { version = "0.13", features = ["visit"] }
+proc-macro2 = "0.4"
+quote = "0.6"
+syn = { version = "0.14", features = ["visit"] }
 
 [dev-dependencies]
 serde = { version = "1.0", path = "../serde" }

serde_derive/src/bound.rs

@@ -55,7 +55,8 @@ pub fn with_where_predicates_from_fields(
     generics: &syn::Generics,
     from_field: fn(&attr::Field) -> Option<&[syn::WherePredicate]>,
 ) -> syn::Generics {
-    let predicates = cont.data
+    let predicates = cont
+        .data
         .all_fields()
         .flat_map(|field| from_field(&field.attrs))
         .flat_map(|predicates| predicates.to_vec());
@@ -139,9 +140,9 @@ pub fn with_bound(
                 }
             }
             if path.leading_colon.is_none() && path.segments.len() == 1 {
-                let id = path.segments[0].ident;
-                if self.all_type_params.contains(&id) {
-                    self.relevant_type_params.insert(id);
+                let id = &path.segments[0].ident;
+                if self.all_type_params.contains(id) {
+                    self.relevant_type_params.insert(id.clone());
                 }
             }
             visit::visit_path(self, path);
@@ -156,7 +157,7 @@ pub fn with_bound(
         fn visit_macro(&mut self, _mac: &'ast syn::Macro) {}
     }
 
-    let all_type_params = generics.type_params().map(|param| param.ident).collect();
+    let all_type_params = generics.type_params().map(|param| param.ident.clone()).collect();
 
     let mut visitor = FindTyParams {
         all_type_params: all_type_params,
@@ -184,7 +185,7 @@ pub fn with_bound(
     let associated_type_usage = visitor.associated_type_usage;
     let new_predicates = generics
         .type_params()
-        .map(|param| param.ident)
+        .map(|param| param.ident.clone())
         .filter(|id| relevant_type_params.contains(id))
         .map(|id| syn::TypePath {
             qself: None,
@@ -246,7 +247,7 @@ pub fn with_lifetime_bound(generics: &syn::Generics, lifetime: &str) -> syn::Gen
     let bound = syn::Lifetime::new(lifetime, Span::call_site());
     let def = syn::LifetimeDef {
         attrs: Vec::new(),
-        lifetime: bound,
+        lifetime: bound.clone(),
         colon_token: None,
         bounds: Punctuated::new(),
     };
@@ -256,10 +257,10 @@ pub fn with_lifetime_bound(generics: &syn::Generics, lifetime: &str) -> syn::Gen
         .chain(generics.params.iter().cloned().map(|mut param| {
             match param {
                 syn::GenericParam::Lifetime(ref mut param) => {
-                    param.bounds.push(bound);
+                    param.bounds.push(bound.clone());
                 }
                 syn::GenericParam::Type(ref mut param) => {
-                    param.bounds.push(syn::TypeParamBound::Lifetime(bound));
+                    param.bounds.push(syn::TypeParamBound::Lifetime(bound.clone()));
                 }
                 syn::GenericParam::Const(_) => {}
             }
@@ -279,23 +280,24 @@ fn type_of_item(cont: &Container) -> syn::Type {
         path: syn::Path {
             leading_colon: None,
             segments: vec![syn::PathSegment {
-                ident: cont.ident,
+                ident: cont.ident.clone(),
                 arguments: syn::PathArguments::AngleBracketed(
                     syn::AngleBracketedGenericArguments {
                         colon2_token: None,
                         lt_token: Default::default(),
-                        args: cont.generics
+                        args: cont
+                            .generics
                             .params
                             .iter()
                             .map(|param| match *param {
                                 syn::GenericParam::Type(ref param) => {
                                     syn::GenericArgument::Type(syn::Type::Path(syn::TypePath {
                                         qself: None,
-                                        path: param.ident.into(),
+                                        path: param.ident.clone().into(),
                                     }))
                                 }
                                 syn::GenericParam::Lifetime(ref param) => {
-                                    syn::GenericArgument::Lifetime(param.lifetime)
+                                    syn::GenericArgument::Lifetime(param.lifetime.clone())
                                 }
                                 syn::GenericParam::Const(_) => {
                                     panic!("Serde does not support const generics yet");

serde_derive/src/de.rs

@@ -6,8 +6,8 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-use proc_macro2::{Literal, Span};
-use quote::{ToTokens, Tokens};
+use proc_macro2::{Literal, Span, TokenStream};
+use quote::ToTokens;
 use syn::punctuated::Punctuated;
 use syn::spanned::Spanned;
 use syn::{self, Ident, Index, Member};
@@ -15,19 +15,19 @@ use syn::{self, Ident, Index, Member};
 use bound;
 use fragment::{Expr, Fragment, Match, Stmts};
 use internals::ast::{Container, Data, Field, Style, Variant};
-use internals::{attr, Ctxt};
+use internals::{attr, Ctxt, Derive};
 use pretend;
 use try;
 
 use std::collections::BTreeSet;
 
-pub fn expand_derive_deserialize(input: &syn::DeriveInput) -> Result<Tokens, String> {
+pub fn expand_derive_deserialize(input: &syn::DeriveInput) -> Result<TokenStream, String> {
     let ctxt = Ctxt::new();
-    let cont = Container::from_ast(&ctxt, input);
+    let cont = Container::from_ast(&ctxt, input, Derive::Deserialize);
     precondition(&ctxt, &cont);
     try!(ctxt.check());
 
-    let ident = cont.ident;
+    let ident = &cont.ident;
     let params = Parameters::new(&cont);
     let (de_impl_generics, _, ty_generics, where_clause) = split_with_de_lifetime(&params);
     let dummy_const = Ident::new(
@@ -130,10 +130,10 @@ struct Parameters {
 
 impl Parameters {
     fn new(cont: &Container) -> Self {
-        let local = cont.ident;
+        let local = cont.ident.clone();
         let this = match cont.attrs.remote() {
             Some(remote) => remote.clone(),
-            None => cont.ident.into(),
+            None => cont.ident.clone().into(),
         };
         let borrowed = borrowed_lifetimes(cont);
         let generics = build_generics(cont, &borrowed);
@@ -150,8 +150,8 @@ impl Parameters {
 
     /// Type name to use in error messages and `&'static str` arguments to
     /// various Deserializer methods.
-    fn type_name(&self) -> &str {
-        self.this.segments.last().unwrap().value().ident.as_ref()
+    fn type_name(&self) -> String {
+        self.this.segments.last().unwrap().value().ident.to_string()
     }
 }
 
@@ -203,7 +203,8 @@ fn build_generics(cont: &Container, borrowed: &BorrowedLifetimes) -> syn::Generi
 fn needs_deserialize_bound(field: &attr::Field, variant: Option<&attr::Variant>) -> bool {
     !field.skip_deserializing() && field.deserialize_with().is_none() && field.de_bound().is_none()
         && variant.map_or(true, |variant| {
-            !variant.skip_deserializing() && variant.deserialize_with().is_none()
+            !variant.skip_deserializing()
+                && variant.deserialize_with().is_none()
                 && variant.de_bound().is_none()
         })
 }
@@ -268,21 +269,17 @@ fn borrowed_lifetimes(cont: &Container) -> BorrowedLifetimes {
 }
 
 fn deserialize_body(cont: &Container, params: &Parameters) -> Fragment {
-    if let Some(type_from) = cont.attrs.type_from() {
+    if cont.attrs.transparent() {
+        deserialize_transparent(cont, params)
+    } else if let Some(type_from) = cont.attrs.type_from() {
         deserialize_from(type_from)
     } else if let attr::Identifier::No = cont.attrs.identifier() {
         match cont.data {
             Data::Enum(ref variants) => deserialize_enum(params, variants, &cont.attrs),
             Data::Struct(Style::Struct, ref fields) => {
-                if fields.iter().any(|field| field.ident.is_none()) {
-                    panic!("struct has unnamed fields");
-                }
                 deserialize_struct(None, params, fields, &cont.attrs, None, &Untagged::No)
             }
             Data::Struct(Style::Tuple, ref fields) | Data::Struct(Style::Newtype, ref fields) => {
-                if fields.iter().any(|field| field.ident.is_some()) {
-                    panic!("tuple struct has named fields");
-                }
                 deserialize_tuple(None, params, fields, &cont.attrs, None)
             }
             Data::Struct(Style::Unit, _) => deserialize_unit_struct(params, &cont.attrs),
@@ -303,8 +300,11 @@ fn deserialize_in_place_body(cont: &Container, params: &Parameters) -> Option<St
     // deserialize_in_place for remote derives.
     assert!(!params.has_getter);
 
-    if cont.attrs.type_from().is_some() || cont.attrs.identifier().is_some()
-        || cont.data
+    if cont.attrs.transparent()
+        || cont.attrs.type_from().is_some()
+        || cont.attrs.identifier().is_some()
+        || cont
+            .data
             .all_fields()
             .all(|f| f.attrs.deserialize_with().is_some())
     {
@@ -348,6 +348,41 @@ fn deserialize_in_place_body(_cont: &Container, _params: &Parameters) -> Option<
     None
 }
 
+fn deserialize_transparent(cont: &Container, params: &Parameters) -> Fragment {
+    let fields = match cont.data {
+        Data::Struct(_, ref fields) => fields,
+        Data::Enum(_) => unreachable!(),
+    };
+
+    let this = &params.this;
+    let transparent_field = fields.iter().find(|f| f.attrs.transparent()).unwrap();
+
+    let path = match transparent_field.attrs.deserialize_with() {
+        Some(path) => quote!(#path),
+        None => quote!(_serde::Deserialize::deserialize),
+    };
+
+    let assign = fields.iter().map(|field| {
+        let member = &field.member;
+        if field as *const Field == transparent_field as *const Field {
+            quote!(#member: __transparent)
+        } else {
+            let value = match *field.attrs.default() {
+                attr::Default::Default => quote!(_serde::export::Default::default()),
+                attr::Default::Path(ref path) => quote!(#path()),
+                attr::Default::None => quote!(_serde::export::PhantomData),
+            };
+            quote!(#member: #value)
+        }
+    });
+
+    quote_block! {
+        _serde::export::Result::map(
+            #path(__deserializer),
+            |__transparent| #this { #(#assign),* })
+    }
+}
+
 fn deserialize_from(type_from: &syn::Type) -> Fragment {
     quote_block! {
         _serde::export::Result::map(
@@ -386,11 +421,11 @@ fn deserialize_unit_struct(params: &Parameters, cattrs: &attr::Container) -> Fra
 }
 
 fn deserialize_tuple(
-    variant_ident: Option<syn::Ident>,
+    variant_ident: Option<&syn::Ident>,
     params: &Parameters,
     fields: &[Field],
     cattrs: &attr::Container,
-    deserializer: Option<Tokens>,
+    deserializer: Option<TokenStream>,
 ) -> Fragment {
     let this = &params.this;
     let (de_impl_generics, de_ty_generics, ty_generics, where_clause) =
@@ -403,7 +438,7 @@ fn deserialize_tuple(
     // and use an `Into` conversion to get the remote type. If there are no
     // getters then construct the target type directly.
     let construct = if params.has_getter {
-        let local = params.local;
+        let local = &params.local;
         quote!(#local)
     } else {
         quote!(#this)
@@ -411,7 +446,7 @@ fn deserialize_tuple(
 
     let is_enum = variant_ident.is_some();
     let type_path = match variant_ident {
-        Some(variant_ident) => quote!(#construct::#variant_ident),
+        Some(ref variant_ident) => quote!(#construct::#variant_ident),
         None => construct,
     };
     let expecting = match variant_ident {
@@ -490,7 +525,7 @@ fn deserialize_tuple_in_place(
     params: &Parameters,
     fields: &[Field],
     cattrs: &attr::Container,
-    deserializer: Option<Tokens>,
+    deserializer: Option<TokenStream>,
 ) -> Fragment {
     let this = &params.this;
     let (de_impl_generics, de_ty_generics, ty_generics, where_clause) =
@@ -574,7 +609,7 @@ fn deserialize_tuple_in_place(
 }
 
 fn deserialize_seq(
-    type_path: &Tokens,
+    type_path: &TokenStream,
     params: &Parameters,
     fields: &[Field],
     is_struct: bool,
@@ -583,8 +618,6 @@ fn deserialize_seq(
 ) -> Fragment {
     let vars = (0..fields.len()).map(field_i as fn(_) -> _);
 
-    // XXX: do we need an error for flattening here?
-
     let deserialized_count = fields
         .iter()
         .filter(|field| !field.attrs.skip_deserializing())
@@ -635,7 +668,7 @@ fn deserialize_seq(
     });
 
     let mut result = if is_struct {
-        let names = fields.iter().map(|f| &f.ident);
+        let names = fields.iter().map(|f| &f.member);
         quote! {
             #type_path { #( #names: #vars ),* }
         }
@@ -680,10 +713,6 @@ fn deserialize_seq_in_place(
     cattrs: &attr::Container,
     expecting: &str,
 ) -> Fragment {
-    let vars = (0..fields.len()).map(field_i as fn(_) -> _);
-
-    // XXX: do we need an error for flattening here?
-
     let deserialized_count = fields
         .iter()
         .filter(|field| !field.attrs.skip_deserializing())
@@ -695,57 +724,47 @@ fn deserialize_seq_in_place(
     };
 
     let mut index_in_seq = 0usize;
-    let write_values = vars.clone()
-        .zip(fields)
-        .enumerate()
-        .map(|(field_index, (_, field))| {
-            // If there's no field name, assume we're a tuple-struct and use a numeric index
-            let field_name = field.ident.map(Member::Named).unwrap_or_else(|| {
-                Member::Unnamed(Index {
-                    index: field_index as u32,
-                    span: Span::call_site(),
-                })
-            });
+    let write_values = fields.iter().map(|field| {
+        let member = &field.member;
 
-            if field.attrs.skip_deserializing() {
-                let default = Expr(expr_is_missing(field, cattrs));
-                quote! {
-                    self.place.#field_name = #default;
-                }
-            } else {
-                let return_invalid_length = quote! {
-                    return _serde::export::Err(_serde::de::Error::invalid_length(#index_in_seq, &#expecting));
-                };
-                let write = match field.attrs.deserialize_with() {
-                    None => {
-                        quote! {
-                            if let _serde::export::None = try!(_serde::de::SeqAccess::next_element_seed(&mut __seq,
-                                _serde::private::de::InPlaceSeed(&mut self.place.#field_name)))
-                            {
-                                #return_invalid_length
-                            }
+        if field.attrs.skip_deserializing() {
+            let default = Expr(expr_is_missing(field, cattrs));
+            quote! {
+                self.place.#member = #default;
+            }
+        } else {
+            let return_invalid_length = quote! {
+                return _serde::export::Err(_serde::de::Error::invalid_length(#index_in_seq, &#expecting));
+            };
+            let write = match field.attrs.deserialize_with() {
+                None => {
+                    quote! {
+                        if let _serde::export::None = try!(_serde::de::SeqAccess::next_element_seed(&mut __seq,
+                            _serde::private::de::InPlaceSeed(&mut self.place.#member)))
+                        {
+                            #return_invalid_length
                         }
                     }
-                    Some(path) => {
-                        let (wrapper, wrapper_ty) =
-                            wrap_deserialize_field_with(params, field.ty, path);
-                        quote!({
+                }
+                Some(path) => {
+                    let (wrapper, wrapper_ty) = wrap_deserialize_field_with(params, field.ty, path);
+                    quote!({
                             #wrapper
                             match try!(_serde::de::SeqAccess::next_element::<#wrapper_ty>(&mut __seq)) {
                                 _serde::export::Some(__wrap) => {
-                                    self.place.#field_name = __wrap.value;
+                                    self.place.#member = __wrap.value;
                                 }
                                 _serde::export::None => {
                                     #return_invalid_length
                                 }
                             }
                         })
-                    }
-                };
-                index_in_seq += 1;
-                write
-            }
-        });
+                }
+            };
+            index_in_seq += 1;
+            write
+        }
+    });
 
     let this = &params.this;
     let (_, ty_generics, _) = params.generics.split_for_impl();
@@ -770,7 +789,7 @@ fn deserialize_seq_in_place(
     }
 }
 
-fn deserialize_newtype_struct(type_path: &Tokens, params: &Parameters, field: &Field) -> Tokens {
+fn deserialize_newtype_struct(type_path: &TokenStream, params: &Parameters, field: &Field) -> TokenStream {
     let delife = params.borrowed.de_lifetime();
     let field_ty = field.ty;
 
@@ -808,7 +827,7 @@ fn deserialize_newtype_struct(type_path: &Tokens, params: &Parameters, field: &F
 }
 
 #[cfg(feature = "deserialize_in_place")]
-fn deserialize_newtype_struct_in_place(params: &Parameters, field: &Field) -> Tokens {
+fn deserialize_newtype_struct_in_place(params: &Parameters, field: &Field) -> TokenStream {
     // We do not generate deserialize_in_place if every field has a deserialize_with.
     assert!(field.attrs.deserialize_with().is_none());
 
@@ -831,11 +850,11 @@ enum Untagged {
 }
 
 fn deserialize_struct(
-    variant_ident: Option<syn::Ident>,
+    variant_ident: Option<&syn::Ident>,
     params: &Parameters,
     fields: &[Field],
     cattrs: &attr::Container,
-    deserializer: Option<Tokens>,
+    deserializer: Option<TokenStream>,
     untagged: &Untagged,
 ) -> Fragment {
     let is_enum = variant_ident.is_some();
@@ -849,14 +868,14 @@ fn deserialize_struct(
     // and use an `Into` conversion to get the remote type. If there are no
     // getters then construct the target type directly.
     let construct = if params.has_getter {
-        let local = params.local;
+        let local = &params.local;
         quote!(#local)
     } else {
         quote!(#this)
     };
 
     let type_path = match variant_ident {
-        Some(variant_ident) => quote!(#construct::#variant_ident),
+        Some(ref variant_ident) => quote!(#construct::#variant_ident),
         None => construct,
     };
     let expecting = match variant_ident {
@@ -985,7 +1004,7 @@ fn deserialize_struct_in_place(
     params: &Parameters,
     fields: &[Field],
     cattrs: &attr::Container,
-    deserializer: Option<Tokens>,
+    deserializer: Option<TokenStream>,
 ) -> Option<Fragment> {
     let is_enum = variant_ident.is_some();
 
@@ -1370,7 +1389,7 @@ fn deserialize_adjacently_tagged_enum(
             .filter(|&(_, variant)| !variant.attrs.skip_deserializing() && is_unit(variant))
             .map(|(i, variant)| {
                 let variant_index = field_i(i);
-                let variant_ident = variant.ident;
+                let variant_ident = &variant.ident;
                 quote! {
                     __Field::#variant_index => _serde::export::Ok(#this::#variant_ident),
                 }
@@ -1634,7 +1653,7 @@ fn deserialize_externally_tagged_variant(
         };
     }
 
-    let variant_ident = variant.ident;
+    let variant_ident = &variant.ident;
 
     match variant.style {
         Style::Unit => {
@@ -1665,19 +1684,19 @@ fn deserialize_internally_tagged_variant(
     params: &Parameters,
     variant: &Variant,
     cattrs: &attr::Container,
-    deserializer: Tokens,
+    deserializer: TokenStream,
 ) -> Fragment {
     if variant.attrs.deserialize_with().is_some() {
         return deserialize_untagged_variant(params, variant, cattrs, deserializer);
     }
 
-    let variant_ident = variant.ident;
+    let variant_ident = &variant.ident;
 
     match variant.style {
         Style::Unit => {
             let this = &params.this;
             let type_name = params.type_name();
-            let variant_name = variant.ident.as_ref();
+            let variant_name = variant.ident.to_string();
             quote_block! {
                 try!(_serde::Deserializer::deserialize_any(#deserializer, _serde::private::de::InternallyTaggedUnitVisitor::new(#type_name, #variant_name)));
                 _serde::export::Ok(#this::#variant_ident)
@@ -1705,7 +1724,7 @@ fn deserialize_untagged_variant(
     params: &Parameters,
     variant: &Variant,
     cattrs: &attr::Container,
-    deserializer: Tokens,
+    deserializer: TokenStream,
 ) -> Fragment {
     if let Some(path) = variant.attrs.deserialize_with() {
         let (wrapper, wrapper_ty, unwrap_fn) = wrap_deserialize_variant_with(params, variant, path);
@@ -1716,13 +1735,13 @@ fn deserialize_untagged_variant(
         };
     }
 
-    let variant_ident = variant.ident;
+    let variant_ident = &variant.ident;
 
     match variant.style {
         Style::Unit => {
             let this = &params.this;
             let type_name = params.type_name();
-            let variant_name = variant.ident.as_ref();
+            let variant_name = variant.ident.to_string();
             quote_expr! {
                 match _serde::Deserializer::deserialize_any(
                     #deserializer,
@@ -1758,7 +1777,7 @@ fn deserialize_untagged_variant(
 }
 
 fn deserialize_externally_tagged_newtype_variant(
-    variant_ident: syn::Ident,
+    variant_ident: &syn::Ident,
     params: &Parameters,
     field: &Field,
 ) -> Fragment {
@@ -1785,10 +1804,10 @@ fn deserialize_externally_tagged_newtype_variant(
 }
 
 fn deserialize_untagged_newtype_variant(
-    variant_ident: syn::Ident,
+    variant_ident: &syn::Ident,
     params: &Parameters,
     field: &Field,
-    deserializer: &Tokens,
+    deserializer: &TokenStream,
 ) -> Fragment {
     let this = &params.this;
     let field_ty = field.ty;
@@ -1802,10 +1821,8 @@ fn deserialize_untagged_newtype_variant(
         }
         Some(path) => {
             quote_block! {
-                let __value: #field_ty = _serde::export::Result::map(
-                    #path(#deserializer),
-                    #this::#variant_ident);
-                __value
+                let __value: _serde::export::Result<#field_ty, _> = #path(#deserializer);
+                _serde::export::Result::map(__value, #this::#variant_ident)
             }
         }
     }
@@ -1887,7 +1904,7 @@ fn deserialize_custom_identifier(
     let this = quote!(#this);
 
     let (ordinary, fallthrough) = if let Some(last) = variants.last() {
-        let last_ident = last.ident;
+        let last_ident = &last.ident;
         if last.attrs.other() {
             let ordinary = &variants[..variants.len() - 1];
             let fallthrough = quote!(_serde::export::Ok(#this::#last_ident));
@@ -1910,7 +1927,7 @@ fn deserialize_custom_identifier(
 
     let names_idents: Vec<_> = ordinary
         .iter()
-        .map(|variant| (variant.attrs.name().deserialize_name(), variant.ident))
+        .map(|variant| (variant.attrs.name().deserialize_name(), variant.ident.clone()))
         .collect();
 
     let names = names_idents.iter().map(|&(ref name, _)| name);
@@ -1963,10 +1980,10 @@ fn deserialize_custom_identifier(
 }
 
 fn deserialize_identifier(
-    this: &Tokens,
+    this: &TokenStream,
     fields: &[(String, Ident)],
     is_variant: bool,
-    fallthrough: Option<Tokens>,
+    fallthrough: Option<TokenStream>,
     collect_other_fields: bool,
 ) -> Fragment {
     let field_strs = fields.iter().map(|&(ref name, _)| name);
@@ -2220,7 +2237,7 @@ fn deserialize_identifier(
 }
 
 fn deserialize_struct_as_struct_visitor(
-    struct_path: &Tokens,
+    struct_path: &TokenStream,
     params: &Parameters,
     fields: &[Field],
     cattrs: &attr::Container,
@@ -2249,7 +2266,7 @@ fn deserialize_struct_as_struct_visitor(
 }
 
 fn deserialize_struct_as_map_visitor(
-    struct_path: &Tokens,
+    struct_path: &TokenStream,
     params: &Parameters,
     fields: &[Field],
     cattrs: &attr::Container,
@@ -2269,7 +2286,7 @@ fn deserialize_struct_as_map_visitor(
 }
 
 fn deserialize_map(
-    struct_path: &Tokens,
+    struct_path: &TokenStream,
     params: &Parameters,
     fields: &[Field],
     cattrs: &attr::Container,
@@ -2424,12 +2441,12 @@ fn deserialize_map(
     };
 
     let result = fields_names.iter().map(|&(field, ref name)| {
-        let ident = field.ident.expect("struct contains unnamed fields");
+        let member = &field.member;
         if field.attrs.skip_deserializing() {
             let value = Expr(expr_is_missing(field, cattrs));
-            quote!(#ident: #value)
+            quote!(#member: #value)
         } else {
-            quote!(#ident: #name)
+            quote!(#member: #name)
         }
     });
 
@@ -2534,19 +2551,19 @@ fn deserialize_map_in_place(
         .filter(|&&(field, _)| !field.attrs.skip_deserializing())
         .map(|&(field, ref name)| {
             let deser_name = field.attrs.name().deserialize_name();
-            let field_name = field.ident;
+            let member = &field.member;
 
             let visit = match field.attrs.deserialize_with() {
                 None => {
                     quote! {
-                        try!(_serde::de::MapAccess::next_value_seed(&mut __map, _serde::private::de::InPlaceSeed(&mut self.place.#field_name)))
+                        try!(_serde::de::MapAccess::next_value_seed(&mut __map, _serde::private::de::InPlaceSeed(&mut self.place.#member)))
                     }
                 }
                 Some(path) => {
                     let (wrapper, wrapper_ty) = wrap_deserialize_field_with(params, field.ty, path);
                     quote!({
                         #wrapper
-                        self.place.#field_name = try!(_serde::de::MapAccess::next_value::<#wrapper_ty>(&mut __map)).value
+                        self.place.#member = try!(_serde::de::MapAccess::next_value::<#wrapper_ty>(&mut __map)).value
                     })
                 }
             };
@@ -2598,7 +2615,8 @@ fn deserialize_map_in_place(
             let missing_expr = expr_is_missing(field, cattrs);
             // If missing_expr unconditionally returns an error, don't try
             // to assign its value to self.place.
-            if field.attrs.default().is_none() && cattrs.default().is_none()
+            if field.attrs.default().is_none()
+                && cattrs.default().is_none()
                 && field.attrs.deserialize_with().is_some()
             {
                 let missing_expr = Stmts(missing_expr);
@@ -2608,11 +2626,11 @@ fn deserialize_map_in_place(
                     }
                 }
             } else {
-                let field_name = field.ident;
+                let member = &field.member;
                 let missing_expr = Expr(missing_expr);
                 quote! {
                     if !#name {
-                        self.place.#field_name = #missing_expr;
+                        self.place.#member = #missing_expr;
                     };
                 }
             }
@@ -2656,9 +2674,9 @@ fn field_i(i: usize) -> Ident {
 /// in a trait to prevent it from accessing the internal `Deserialize` state.
 fn wrap_deserialize_with(
     params: &Parameters,
-    value_ty: &Tokens,
+    value_ty: &TokenStream,
     deserialize_with: &syn::ExprPath,
-) -> (Tokens, Tokens) {
+) -> (TokenStream, TokenStream) {
     let this = &params.this;
     let (de_impl_generics, de_ty_generics, ty_generics, where_clause) =
         split_with_de_lifetime(params);
@@ -2694,7 +2712,7 @@ fn wrap_deserialize_field_with(
     params: &Parameters,
     field_ty: &syn::Type,
     deserialize_with: &syn::ExprPath,
-) -> (Tokens, Tokens) {
+) -> (TokenStream, TokenStream) {
     wrap_deserialize_with(params, &quote!(#field_ty), deserialize_with)
 }
 
@@ -2702,9 +2720,9 @@ fn wrap_deserialize_variant_with(
     params: &Parameters,
     variant: &Variant,
     deserialize_with: &syn::ExprPath,
-) -> (Tokens, Tokens, Tokens) {
+) -> (TokenStream, TokenStream, TokenStream) {
     let this = &params.this;
-    let variant_ident = variant.ident;
+    let variant_ident = &variant.ident;
 
     let field_tys = variant.fields.iter().map(|field| field.ty);
     let (wrapper, wrapper_ty) =
@@ -2718,18 +2736,15 @@ fn wrap_deserialize_variant_with(
     });
     let unwrap_fn = match variant.style {
         Style::Struct if variant.fields.len() == 1 => {
-            let field_ident = variant.fields[0].ident.unwrap();
+            let member = &variant.fields[0].member;
             quote! {
-                |__wrap| #this::#variant_ident { #field_ident: __wrap.value }
+                |__wrap| #this::#variant_ident { #member: __wrap.value }
             }
         }
         Style::Struct => {
-            let field_idents = variant
-                .fields
-                .iter()
-                .map(|field| field.ident.as_ref().unwrap());
+            let members = variant.fields.iter().map(|field| &field.member);
             quote! {
-                |__wrap| #this::#variant_ident { #(#field_idents: __wrap.value.#field_access),* }
+                |__wrap| #this::#variant_ident { #(#members: __wrap.value.#field_access),* }
             }
         }
         Style::Tuple => quote! {
@@ -2759,8 +2774,8 @@ fn expr_is_missing(field: &Field, cattrs: &attr::Container) -> Fragment {
 
     match *cattrs.default() {
         attr::Default::Default | attr::Default::Path(_) => {
-            let ident = field.ident;
-            return quote_expr!(__default.#ident);
+            let member = &field.member;
+            return quote_expr!(__default.#member);
         }
         attr::Default::None => { /* below */ }
     }
@@ -2787,7 +2802,7 @@ struct DeImplGenerics<'a>(&'a Parameters);
 struct InPlaceImplGenerics<'a>(&'a Parameters);
 
 impl<'a> ToTokens for DeImplGenerics<'a> {
-    fn to_tokens(&self, tokens: &mut Tokens) {
+    fn to_tokens(&self, tokens: &mut TokenStream) {
         let mut generics = self.0.generics.clone();
         if let Some(de_lifetime) = self.0.borrowed.de_lifetime_def() {
             generics.params = Some(syn::GenericParam::Lifetime(de_lifetime))
@@ -2802,7 +2817,7 @@ impl<'a> ToTokens for DeImplGenerics<'a> {
 
 #[cfg(feature = "deserialize_in_place")]
 impl<'a> ToTokens for InPlaceImplGenerics<'a> {
-    fn to_tokens(&self, tokens: &mut Tokens) {
+    fn to_tokens(&self, tokens: &mut TokenStream) {
         let place_lifetime = place_lifetime();
         let mut generics = self.0.generics.clone();
 
@@ -2810,12 +2825,12 @@ impl<'a> ToTokens for InPlaceImplGenerics<'a> {
         for param in &mut generics.params {
             match *param {
                 syn::GenericParam::Lifetime(ref mut param) => {
-                    param.bounds.push(place_lifetime.lifetime);
+                    param.bounds.push(place_lifetime.lifetime.clone());
                 }
                 syn::GenericParam::Type(ref mut param) => {
                     param
                         .bounds
-                        .push(syn::TypeParamBound::Lifetime(place_lifetime.lifetime));
+                        .push(syn::TypeParamBound::Lifetime(place_lifetime.lifetime.clone()));
                 }
                 syn::GenericParam::Const(_) => {}
             }
@@ -2847,7 +2862,7 @@ struct DeTypeGenerics<'a>(&'a Parameters);
 struct InPlaceTypeGenerics<'a>(&'a Parameters);
 
 impl<'a> ToTokens for DeTypeGenerics<'a> {
-    fn to_tokens(&self, tokens: &mut Tokens) {
+    fn to_tokens(&self, tokens: &mut TokenStream) {
         let mut generics = self.0.generics.clone();
         if self.0.borrowed.de_lifetime_def().is_some() {
             let def = syn::LifetimeDef {
@@ -2868,7 +2883,7 @@ impl<'a> ToTokens for DeTypeGenerics<'a> {
 
 #[cfg(feature = "deserialize_in_place")]
 impl<'a> ToTokens for InPlaceTypeGenerics<'a> {
-    fn to_tokens(&self, tokens: &mut Tokens) {
+    fn to_tokens(&self, tokens: &mut TokenStream) {
         let mut generics = self.0.generics.clone();
         generics.params = Some(syn::GenericParam::Lifetime(place_lifetime()))
             .into_iter()

serde_derive/src/fragment.rs

@@ -6,15 +6,16 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-use quote::{ToTokens, Tokens};
+use quote::ToTokens;
 use syn::token;
+use proc_macro2::TokenStream;
 
 pub enum Fragment {
     /// Tokens that can be used as an expression.
-    Expr(Tokens),
+    Expr(TokenStream),
     /// Tokens that can be used inside a block. The surrounding curly braces are
     /// not part of these tokens.
-    Block(Tokens),
+    Block(TokenStream),
 }
 
 macro_rules! quote_expr {
@@ -33,7 +34,7 @@ macro_rules! quote_block {
 /// Block fragments in curly braces.
 pub struct Expr(pub Fragment);
 impl ToTokens for Expr {
-    fn to_tokens(&self, out: &mut Tokens) {
+    fn to_tokens(&self, out: &mut TokenStream) {
         match self.0 {
             Fragment::Expr(ref expr) => expr.to_tokens(out),
             Fragment::Block(ref block) => {
@@ -46,7 +47,7 @@ impl ToTokens for Expr {
 /// Interpolate a fragment as the statements of a block.
 pub struct Stmts(pub Fragment);
 impl ToTokens for Stmts {
-    fn to_tokens(&self, out: &mut Tokens) {
+    fn to_tokens(&self, out: &mut TokenStream) {
         match self.0 {
             Fragment::Expr(ref expr) => expr.to_tokens(out),
             Fragment::Block(ref block) => block.to_tokens(out),
@@ -58,7 +59,7 @@ impl ToTokens for Stmts {
 /// involves putting a comma after expressions and curly braces around blocks.
 pub struct Match(pub Fragment);
 impl ToTokens for Match {
-    fn to_tokens(&self, out: &mut Tokens) {
+    fn to_tokens(&self, out: &mut TokenStream) {
         match self.0 {
             Fragment::Expr(ref expr) => {
                 expr.to_tokens(out);
@@ -71,8 +72,8 @@ impl ToTokens for Match {
     }
 }
 
-impl AsRef<Tokens> for Fragment {
-    fn as_ref(&self) -> &Tokens {
+impl AsRef<TokenStream> for Fragment {
+    fn as_ref(&self) -> &TokenStream {
         match *self {
             Fragment::Expr(ref expr) => expr,
             Fragment::Block(ref block) => block,

serde_derive/src/internals/ast.rs

@@ -8,7 +8,7 @@
 
 use internals::attr;
 use internals::check;
-use internals::Ctxt;
+use internals::{Ctxt, Derive};
 use syn;
 use syn::punctuated::Punctuated;
 
@@ -32,7 +32,7 @@ pub struct Variant<'a> {
 }
 
 pub struct Field<'a> {
-    pub ident: Option<syn::Ident>,
+    pub member: syn::Member,
     pub attrs: attr::Field,
     pub ty: &'a syn::Type,
     pub original: &'a syn::Field,
@@ -47,7 +47,7 @@ pub enum Style {
 }
 
 impl<'a> Container<'a> {
-    pub fn from_ast(cx: &Ctxt, item: &'a syn::DeriveInput) -> Container<'a> {
+    pub fn from_ast(cx: &Ctxt, item: &'a syn::DeriveInput, derive: Derive) -> Container<'a> {
         let mut attrs = attr::Container::from_ast(cx, item);
 
         let mut data = match item.data {
@@ -86,13 +86,13 @@ impl<'a> Container<'a> {
             attrs.mark_has_flatten();
         }
 
-        let item = Container {
-            ident: item.ident,
+        let mut item = Container {
+            ident: item.ident.clone(),
             attrs: attrs,
             data: data,
             generics: &item.generics,
         };
-        check::check(cx, &item);
+        check::check(cx, &mut item, derive);
         item
     }
 }
@@ -124,7 +124,7 @@ fn enum_from_ast<'a>(
             let (style, fields) =
                 struct_from_ast(cx, &variant.fields, Some(&attrs), container_default);
             Variant {
-                ident: variant.ident,
+                ident: variant.ident.clone(),
                 attrs: attrs,
                 style: style,
                 fields: fields,
@@ -166,7 +166,10 @@ fn fields_from_ast<'a>(
         .iter()
         .enumerate()
         .map(|(i, field)| Field {
-            ident: field.ident,
+            member: match field.ident {
+                Some(ref ident) => syn::Member::Named(ident.clone()),
+                None => syn::Member::Unnamed(i.into()),
+            },
             attrs: attr::Field::from_ast(cx, i, field, attrs, container_default),
             ty: &field.ty,
             original: field,

serde_derive/src/internals/attr.rs

@@ -105,6 +105,7 @@ impl Name {
 /// Represents container (e.g. struct) attribute information
 pub struct Container {
     name: Name,
+    transparent: bool,
     deny_unknown_fields: bool,
     default: Default,
     rename_all: RenameRule,
@@ -181,6 +182,7 @@ impl Container {
     pub fn from_ast(cx: &Ctxt, item: &syn::DeriveInput) -> Self {
         let mut ser_name = Attr::none(cx, "rename");
         let mut de_name = Attr::none(cx, "rename");
+        let mut transparent = BoolAttr::none(cx, "transparent");
         let mut deny_unknown_fields = BoolAttr::none(cx, "deny_unknown_fields");
         let mut default = Attr::none(cx, "default");
         let mut rename_all = Attr::none(cx, "rename_all");
@@ -200,7 +202,7 @@ impl Container {
                 match meta_item {
                     // Parse `#[serde(rename = "foo")]`
                     Meta(NameValue(ref m)) if m.ident == "rename" => {
-                        if let Ok(s) = get_lit_str(cx, m.ident.as_ref(), m.ident.as_ref(), &m.lit) {
+                        if let Ok(s) = get_lit_str(cx, &m.ident, &m.ident, &m.lit) {
                             ser_name.set(s.value());
                             de_name.set(s.value());
                         }
@@ -216,7 +218,7 @@ impl Container {
 
                     // Parse `#[serde(rename_all = "foo")]`
                     Meta(NameValue(ref m)) if m.ident == "rename_all" => {
-                        if let Ok(s) = get_lit_str(cx, m.ident.as_ref(), m.ident.as_ref(), &m.lit) {
+                        if let Ok(s) = get_lit_str(cx, &m.ident, &m.ident, &m.lit) {
                             match RenameRule::from_str(&s.value()) {
                                 Ok(rename_rule) => rename_all.set(rename_rule),
                                 Err(()) => cx.error(format!(
@@ -228,13 +230,18 @@ impl Container {
                         }
                     }
 
+                    // Parse `#[serde(transparent)]`
+                    Meta(Word(ref word)) if word == "transparent" => {
+                        transparent.set_true();
+                    }
+
                     // Parse `#[serde(deny_unknown_fields)]`
-                    Meta(Word(word)) if word == "deny_unknown_fields" => {
+                    Meta(Word(ref word)) if word == "deny_unknown_fields" => {
                         deny_unknown_fields.set_true();
                     }
 
                     // Parse `#[serde(default)]`
-                    Meta(Word(word)) if word == "default" => match item.data {
+                    Meta(Word(ref word)) if word == "default" => match item.data {
                         syn::Data::Struct(syn::DataStruct {
                             fields: syn::Fields::Named(_),
                             ..
@@ -249,7 +256,7 @@ impl Container {
 
                     // Parse `#[serde(default = "...")]`
                     Meta(NameValue(ref m)) if m.ident == "default" => {
-                        if let Ok(path) = parse_lit_into_expr_path(cx, m.ident.as_ref(), &m.lit) {
+                        if let Ok(path) = parse_lit_into_expr_path(cx, &m.ident, &m.lit) {
                             match item.data {
                                 syn::Data::Struct(syn::DataStruct {
                                     fields: syn::Fields::Named(_),
@@ -268,7 +275,7 @@ impl Container {
                     // Parse `#[serde(bound = "D: Serialize")]`
                     Meta(NameValue(ref m)) if m.ident == "bound" => {
                         if let Ok(where_predicates) =
-                            parse_lit_into_where(cx, m.ident.as_ref(), m.ident.as_ref(), &m.lit)
+                            parse_lit_into_where(cx, &m.ident, &m.ident, &m.lit)
                         {
                             ser_bound.set(where_predicates.clone());
                             de_bound.set(where_predicates);
@@ -284,7 +291,7 @@ impl Container {
                     }
 
                     // Parse `#[serde(untagged)]`
-                    Meta(Word(word)) if word == "untagged" => match item.data {
+                    Meta(Word(ref word)) if word == "untagged" => match item.data {
                         syn::Data::Enum(_) => {
                             untagged.set_true();
                         }
@@ -295,7 +302,7 @@ impl Container {
 
                     // Parse `#[serde(tag = "type")]`
                     Meta(NameValue(ref m)) if m.ident == "tag" => {
-                        if let Ok(s) = get_lit_str(cx, m.ident.as_ref(), m.ident.as_ref(), &m.lit) {
+                        if let Ok(s) = get_lit_str(cx, &m.ident, &m.ident, &m.lit) {
                             match item.data {
                                 syn::Data::Enum(_) => {
                                     internal_tag.set(s.value());
@@ -309,7 +316,7 @@ impl Container {
 
                     // Parse `#[serde(content = "c")]`
                     Meta(NameValue(ref m)) if m.ident == "content" => {
-                        if let Ok(s) = get_lit_str(cx, m.ident.as_ref(), m.ident.as_ref(), &m.lit) {
+                        if let Ok(s) = get_lit_str(cx, &m.ident, &m.ident, &m.lit) {
                             match item.data {
                                 syn::Data::Enum(_) => {
                                     content.set(s.value());
@@ -324,23 +331,23 @@ impl Container {
 
                     // Parse `#[serde(from = "Type")]
                     Meta(NameValue(ref m)) if m.ident == "from" => {
-                        if let Ok(from_ty) = parse_lit_into_ty(cx, m.ident.as_ref(), &m.lit) {
+                        if let Ok(from_ty) = parse_lit_into_ty(cx, &m.ident, &m.lit) {
                             type_from.set_opt(Some(from_ty));
                         }
                     }
 
                     // Parse `#[serde(into = "Type")]
                     Meta(NameValue(ref m)) if m.ident == "into" => {
-                        if let Ok(into_ty) = parse_lit_into_ty(cx, m.ident.as_ref(), &m.lit) {
+                        if let Ok(into_ty) = parse_lit_into_ty(cx, &m.ident, &m.lit) {
                             type_into.set_opt(Some(into_ty));
                         }
                     }
 
                     // Parse `#[serde(remote = "...")]`
                     Meta(NameValue(ref m)) if m.ident == "remote" => {
-                        if let Ok(path) = parse_lit_into_path(cx, m.ident.as_ref(), &m.lit) {
+                        if let Ok(path) = parse_lit_into_path(cx, &m.ident, &m.lit) {
                             if is_primitive_path(&path, "Self") {
-                                remote.set(item.ident.into());
+                                remote.set(item.ident.clone().into());
                             } else {
                                 remote.set(path);
                             }
@@ -348,12 +355,12 @@ impl Container {
                     }
 
                     // Parse `#[serde(field_identifier)]`
-                    Meta(Word(word)) if word == "field_identifier" => {
+                    Meta(Word(ref word)) if word == "field_identifier" => {
                         field_identifier.set_true();
                     }
 
                     // Parse `#[serde(variant_identifier)]`
-                    Meta(Word(word)) if word == "variant_identifier" => {
+                    Meta(Word(ref word)) if word == "variant_identifier" => {
                         variant_identifier.set_true();
                     }
 
@@ -376,6 +383,7 @@ impl Container {
                 serialize: ser_name.get().unwrap_or_else(|| item.ident.to_string()),
                 deserialize: de_name.get().unwrap_or_else(|| item.ident.to_string()),
             },
+            transparent: transparent.get(),
             deny_unknown_fields: deny_unknown_fields.get(),
             default: default.get().unwrap_or(Default::None),
             rename_all: rename_all.get().unwrap_or(RenameRule::None),
@@ -398,6 +406,10 @@ impl Container {
         &self.rename_all
     }
 
+    pub fn transparent(&self) -> bool {
+        self.transparent
+    }
+
     pub fn deny_unknown_fields(&self) -> bool {
         self.deny_unknown_fields
     }
@@ -556,7 +568,7 @@ impl Variant {
                 match meta_item {
                     // Parse `#[serde(rename = "foo")]`
                     Meta(NameValue(ref m)) if m.ident == "rename" => {
-                        if let Ok(s) = get_lit_str(cx, m.ident.as_ref(), m.ident.as_ref(), &m.lit) {
+                        if let Ok(s) = get_lit_str(cx, &m.ident, &m.ident, &m.lit) {
                             ser_name.set(s.value());
                             de_name.set(s.value());
                         }
@@ -572,7 +584,7 @@ impl Variant {
 
                     // Parse `#[serde(rename_all = "foo")]`
                     Meta(NameValue(ref m)) if m.ident == "rename_all" => {
-                        if let Ok(s) = get_lit_str(cx, m.ident.as_ref(), m.ident.as_ref(), &m.lit) {
+                        if let Ok(s) = get_lit_str(cx, &m.ident, &m.ident, &m.lit) {
                             match RenameRule::from_str(&s.value()) {
                                 Ok(rename_rule) => rename_all.set(rename_rule),
                                 Err(()) => cx.error(format!(
@@ -585,30 +597,30 @@ impl Variant {
                     }
 
                     // Parse `#[serde(skip)]`
-                    Meta(Word(word)) if word == "skip" => {
+                    Meta(Word(ref word)) if word == "skip" => {
                         skip_serializing.set_true();
                         skip_deserializing.set_true();
                     }
 
                     // Parse `#[serde(skip_deserializing)]`
-                    Meta(Word(word)) if word == "skip_deserializing" => {
+                    Meta(Word(ref word)) if word == "skip_deserializing" => {
                         skip_deserializing.set_true();
                     }
 
                     // Parse `#[serde(skip_serializing)]`
-                    Meta(Word(word)) if word == "skip_serializing" => {
+                    Meta(Word(ref word)) if word == "skip_serializing" => {
                         skip_serializing.set_true();
                     }
 
                     // Parse `#[serde(other)]`
-                    Meta(Word(word)) if word == "other" => {
+                    Meta(Word(ref word)) if word == "other" => {
                         other.set_true();
                     }
 
                     // Parse `#[serde(bound = "D: Serialize")]`
                     Meta(NameValue(ref m)) if m.ident == "bound" => {
                         if let Ok(where_predicates) =
-                            parse_lit_into_where(cx, m.ident.as_ref(), m.ident.as_ref(), &m.lit)
+                            parse_lit_into_where(cx, &m.ident, &m.ident, &m.lit)
                         {
                             ser_bound.set(where_predicates.clone());
                             de_bound.set(where_predicates);
@@ -625,7 +637,7 @@ impl Variant {
 
                     // Parse `#[serde(with = "...")]`
                     Meta(NameValue(ref m)) if m.ident == "with" => {
-                        if let Ok(path) = parse_lit_into_expr_path(cx, m.ident.as_ref(), &m.lit) {
+                        if let Ok(path) = parse_lit_into_expr_path(cx, &m.ident, &m.lit) {
                             let mut ser_path = path.clone();
                             ser_path
                                 .path
@@ -643,14 +655,14 @@ impl Variant {
 
                     // Parse `#[serde(serialize_with = "...")]`
                     Meta(NameValue(ref m)) if m.ident == "serialize_with" => {
-                        if let Ok(path) = parse_lit_into_expr_path(cx, m.ident.as_ref(), &m.lit) {
+                        if let Ok(path) = parse_lit_into_expr_path(cx, &m.ident, &m.lit) {
                             serialize_with.set(path);
                         }
                     }
 
                     // Parse `#[serde(deserialize_with = "...")]`
                     Meta(NameValue(ref m)) if m.ident == "deserialize_with" => {
-                        if let Ok(path) = parse_lit_into_expr_path(cx, m.ident.as_ref(), &m.lit) {
+                        if let Ok(path) = parse_lit_into_expr_path(cx, &m.ident, &m.lit) {
                             deserialize_with.set(path);
                         }
                     }
@@ -764,6 +776,7 @@ pub struct Field {
     borrowed_lifetimes: BTreeSet<syn::Lifetime>,
     getter: Option<syn::ExprPath>,
     flatten: bool,
+    transparent: bool,
 }
 
 /// Represents the default to use for a field when deserializing.
@@ -777,7 +790,6 @@ pub enum Default {
 }
 
 impl Default {
-    #[cfg(feature = "deserialize_in_place")]
     pub fn is_none(&self) -> bool {
         match *self {
             Default::None => true,
@@ -828,7 +840,7 @@ impl Field {
                 match meta_item {
                     // Parse `#[serde(rename = "foo")]`
                     Meta(NameValue(ref m)) if m.ident == "rename" => {
-                        if let Ok(s) = get_lit_str(cx, m.ident.as_ref(), m.ident.as_ref(), &m.lit) {
+                        if let Ok(s) = get_lit_str(cx, &m.ident, &m.ident, &m.lit) {
                             ser_name.set(s.value());
                             de_name.set(s.value());
                         }
@@ -843,57 +855,57 @@ impl Field {
                     }
 
                     // Parse `#[serde(default)]`
-                    Meta(Word(word)) if word == "default" => {
+                    Meta(Word(ref word)) if word == "default" => {
                         default.set(Default::Default);
                     }
 
                     // Parse `#[serde(default = "...")]`
                     Meta(NameValue(ref m)) if m.ident == "default" => {
-                        if let Ok(path) = parse_lit_into_expr_path(cx, m.ident.as_ref(), &m.lit) {
+                        if let Ok(path) = parse_lit_into_expr_path(cx, &m.ident, &m.lit) {
                             default.set(Default::Path(path));
                         }
                     }
 
                     // Parse `#[serde(skip_serializing)]`
-                    Meta(Word(word)) if word == "skip_serializing" => {
+                    Meta(Word(ref word)) if word == "skip_serializing" => {
                         skip_serializing.set_true();
                     }
 
                     // Parse `#[serde(skip_deserializing)]`
-                    Meta(Word(word)) if word == "skip_deserializing" => {
+                    Meta(Word(ref word)) if word == "skip_deserializing" => {
                         skip_deserializing.set_true();
                     }
 
                     // Parse `#[serde(skip)]`
-                    Meta(Word(word)) if word == "skip" => {
+                    Meta(Word(ref word)) if word == "skip" => {
                         skip_serializing.set_true();
                         skip_deserializing.set_true();
                     }
 
                     // Parse `#[serde(skip_serializing_if = "...")]`
                     Meta(NameValue(ref m)) if m.ident == "skip_serializing_if" => {
-                        if let Ok(path) = parse_lit_into_expr_path(cx, m.ident.as_ref(), &m.lit) {
+                        if let Ok(path) = parse_lit_into_expr_path(cx, &m.ident, &m.lit) {
                             skip_serializing_if.set(path);
                         }
                     }
 
                     // Parse `#[serde(serialize_with = "...")]`
                     Meta(NameValue(ref m)) if m.ident == "serialize_with" => {
-                        if let Ok(path) = parse_lit_into_expr_path(cx, m.ident.as_ref(), &m.lit) {
+                        if let Ok(path) = parse_lit_into_expr_path(cx, &m.ident, &m.lit) {
                             serialize_with.set(path);
                         }
                     }
 
                     // Parse `#[serde(deserialize_with = "...")]`
                     Meta(NameValue(ref m)) if m.ident == "deserialize_with" => {
-                        if let Ok(path) = parse_lit_into_expr_path(cx, m.ident.as_ref(), &m.lit) {
+                        if let Ok(path) = parse_lit_into_expr_path(cx, &m.ident, &m.lit) {
                             deserialize_with.set(path);
                         }
                     }
 
                     // Parse `#[serde(with = "...")]`
                     Meta(NameValue(ref m)) if m.ident == "with" => {
-                        if let Ok(path) = parse_lit_into_expr_path(cx, m.ident.as_ref(), &m.lit) {
+                        if let Ok(path) = parse_lit_into_expr_path(cx, &m.ident, &m.lit) {
                             let mut ser_path = path.clone();
                             ser_path
                                 .path
@@ -912,7 +924,7 @@ impl Field {
                     // Parse `#[serde(bound = "D: Serialize")]`
                     Meta(NameValue(ref m)) if m.ident == "bound" => {
                         if let Ok(where_predicates) =
-                            parse_lit_into_where(cx, m.ident.as_ref(), m.ident.as_ref(), &m.lit)
+                            parse_lit_into_where(cx, &m.ident, &m.ident, &m.lit)
                         {
                             ser_bound.set(where_predicates.clone());
                             de_bound.set(where_predicates);
@@ -928,7 +940,7 @@ impl Field {
                     }
 
                     // Parse `#[serde(borrow)]`
-                    Meta(Word(word)) if word == "borrow" => {
+                    Meta(Word(ref word)) if word == "borrow" => {
                         if let Ok(borrowable) = borrowable_lifetimes(cx, &ident, &field.ty) {
                             borrowed_lifetimes.set(borrowable);
                         }
@@ -937,7 +949,7 @@ impl Field {
                     // Parse `#[serde(borrow = "'a + 'b")]`
                     Meta(NameValue(ref m)) if m.ident == "borrow" => {
                         if let Ok(lifetimes) =
-                            parse_lit_into_lifetimes(cx, m.ident.as_ref(), &m.lit)
+                            parse_lit_into_lifetimes(cx, &m.ident, &m.lit)
                         {
                             if let Ok(borrowable) = borrowable_lifetimes(cx, &ident, &field.ty) {
                                 for lifetime in &lifetimes {
@@ -955,13 +967,13 @@ impl Field {
 
                     // Parse `#[serde(getter = "...")]`
                     Meta(NameValue(ref m)) if m.ident == "getter" => {
-                        if let Ok(path) = parse_lit_into_expr_path(cx, m.ident.as_ref(), &m.lit) {
+                        if let Ok(path) = parse_lit_into_expr_path(cx, &m.ident, &m.lit) {
                             getter.set(path);
                         }
                     }
 
                     // Parse `#[serde(flatten)]`
-                    Meta(Word(word)) if word == "flatten" => {
+                    Meta(Word(ref word)) if word == "flatten" => {
                         flatten.set_true();
                     }
 
@@ -1066,6 +1078,7 @@ impl Field {
             borrowed_lifetimes: borrowed_lifetimes,
             getter: getter.get(),
             flatten: flatten.get(),
+            transparent: false,
         }
     }
 
@@ -1125,6 +1138,14 @@ impl Field {
     pub fn flatten(&self) -> bool {
         self.flatten
     }
+
+    pub fn transparent(&self) -> bool {
+        self.transparent
+    }
+
+    pub fn mark_transparent(&mut self) {
+        self.transparent = true;
+    }
 }
 
 type SerAndDe<T> = (Option<T>, Option<T>);
@@ -1137,21 +1158,22 @@ fn get_ser_and_de<'a, T, F>(
 ) -> Result<SerAndDe<T>, ()>
 where
     T: 'a,
-    F: Fn(&Ctxt, &str, &str, &'a syn::Lit) -> Result<T, ()>,
+    F: Fn(&Ctxt, &Ident, &Ident, &'a syn::Lit) -> Result<T, ()>,
 {
     let mut ser_meta = Attr::none(cx, attr_name);
     let mut de_meta = Attr::none(cx, attr_name);
+    let attr_name = Ident::new(attr_name, Span::call_site());
 
     for meta in metas {
         match *meta {
             Meta(NameValue(ref meta)) if meta.ident == "serialize" => {
-                if let Ok(v) = f(cx, attr_name, meta.ident.as_ref(), &meta.lit) {
+                if let Ok(v) = f(cx, &attr_name, &meta.ident, &meta.lit) {
                     ser_meta.set(v);
                 }
             }
 
             Meta(NameValue(ref meta)) if meta.ident == "deserialize" => {
-                if let Ok(v) = f(cx, attr_name, meta.ident.as_ref(), &meta.lit) {
+                if let Ok(v) = f(cx, &attr_name, &meta.ident, &meta.lit) {
                     de_meta.set(v);
                 }
             }
@@ -1200,8 +1222,8 @@ pub fn get_serde_meta_items(attr: &syn::Attribute) -> Option<Vec<syn::NestedMeta
 
 fn get_lit_str<'a>(
     cx: &Ctxt,
-    attr_name: &str,
-    meta_item_name: &str,
+    attr_name: &Ident,
+    meta_item_name: &Ident,
     lit: &'a syn::Lit,
 ) -> Result<&'a syn::LitStr, ()> {
     if let syn::Lit::Str(ref lit) = *lit {
@@ -1215,7 +1237,7 @@ fn get_lit_str<'a>(
     }
 }
 
-fn parse_lit_into_path(cx: &Ctxt, attr_name: &str, lit: &syn::Lit) -> Result<syn::Path, ()> {
+fn parse_lit_into_path(cx: &Ctxt, attr_name: &Ident, lit: &syn::Lit) -> Result<syn::Path, ()> {
     let string = try!(get_lit_str(cx, attr_name, attr_name, lit));
     parse_lit_str(string)
         .map_err(|_| cx.error(format!("failed to parse path: {:?}", string.value())))
@@ -1223,7 +1245,7 @@ fn parse_lit_into_path(cx: &Ctxt, attr_name: &str, lit: &syn::Lit) -> Result<syn
 
 fn parse_lit_into_expr_path(
     cx: &Ctxt,
-    attr_name: &str,
+    attr_name: &Ident,
     lit: &syn::Lit,
 ) -> Result<syn::ExprPath, ()> {
     let string = try!(get_lit_str(cx, attr_name, attr_name, lit));
@@ -1233,8 +1255,8 @@ fn parse_lit_into_expr_path(
 
 fn parse_lit_into_where(
     cx: &Ctxt,
-    attr_name: &str,
-    meta_item_name: &str,
+    attr_name: &Ident,
+    meta_item_name: &Ident,
     lit: &syn::Lit,
 ) -> Result<Vec<syn::WherePredicate>, ()> {
     let string = try!(get_lit_str(cx, attr_name, meta_item_name, lit));
@@ -1249,7 +1271,7 @@ fn parse_lit_into_where(
         .map_err(|err| cx.error(err))
 }
 
-fn parse_lit_into_ty(cx: &Ctxt, attr_name: &str, lit: &syn::Lit) -> Result<syn::Type, ()> {
+fn parse_lit_into_ty(cx: &Ctxt, attr_name: &Ident, lit: &syn::Lit) -> Result<syn::Type, ()> {
     let string = try!(get_lit_str(cx, attr_name, attr_name, lit));
 
     parse_lit_str(string).map_err(|_| {
@@ -1265,7 +1287,7 @@ fn parse_lit_into_ty(cx: &Ctxt, attr_name: &str, lit: &syn::Lit) -> Result<syn::
 // lifetimes separated by `+`.
 fn parse_lit_into_lifetimes(
     cx: &Ctxt,
-    attr_name: &str,
+    attr_name: &Ident,
     lit: &syn::Lit,
 ) -> Result<BTreeSet<syn::Lifetime>, ()> {
     let string = try!(get_lit_str(cx, attr_name, attr_name, lit));
@@ -1286,7 +1308,7 @@ fn parse_lit_into_lifetimes(
     if let Ok(BorrowedLifetimes(lifetimes)) = parse_lit_str(string) {
         let mut set = BTreeSet::new();
         for lifetime in lifetimes {
-            if !set.insert(lifetime) {
+            if !set.insert(lifetime.clone()) {
                 cx.error(format!("duplicate borrowed lifetime `{}`", lifetime));
             }
         }
@@ -1426,7 +1448,9 @@ fn is_primitive_type(ty: &syn::Type, primitive: &str) -> bool {
 }
 
 fn is_primitive_path(path: &syn::Path, primitive: &str) -> bool {
-    path.leading_colon.is_none() && path.segments.len() == 1 && path.segments[0].ident == primitive
+    path.leading_colon.is_none()
+        && path.segments.len() == 1
+        && path.segments[0].ident == primitive
         && path.segments[0].arguments.is_empty()
 }
 

serde_derive/src/internals/check.rs

@@ -8,17 +8,19 @@
 
 use internals::ast::{Container, Data, Field, Style};
 use internals::attr::{EnumTag, Identifier};
-use internals::Ctxt;
+use internals::{Ctxt, Derive};
+use syn::{Member, Type};
 
 /// Cross-cutting checks that require looking at more than a single attrs
 /// object. Simpler checks should happen when parsing and building the attrs.
-pub fn check(cx: &Ctxt, cont: &Container) {
+pub fn check(cx: &Ctxt, cont: &mut Container, derive: Derive) {
     check_getter(cx, cont);
     check_flatten(cx, cont);
     check_identifier(cx, cont);
     check_variant_skip_attrs(cx, cont);
     check_internal_tag_field_name_conflict(cx, cont);
     check_adjacent_tag_conflict(cx, cont);
+    check_transparent(cx, cont, derive);
 }
 
 /// Getters are only allowed inside structs (not enums) with the `remote`
@@ -171,17 +173,14 @@ fn check_variant_skip_attrs(cx: &Ctxt, cont: &Container) {
                 ));
             }
 
-            for (i, field) in variant.fields.iter().enumerate() {
-                let ident = field
-                    .ident
-                    .as_ref()
-                    .map_or_else(|| format!("{}", i), |ident| format!("`{}`", ident));
+            for field in &variant.fields {
+                let member = member_message(&field.member);
 
                 if field.attrs.skip_serializing() {
                     cx.error(format!(
                         "variant `{}` cannot have both #[serde(serialize_with)] and \
                          a field {} marked with #[serde(skip_serializing)]",
-                        variant.ident, ident
+                        variant.ident, member
                     ));
                 }
 
@@ -189,7 +188,7 @@ fn check_variant_skip_attrs(cx: &Ctxt, cont: &Container) {
                     cx.error(format!(
                         "variant `{}` cannot have both #[serde(serialize_with)] and \
                          a field {} marked with #[serde(skip_serializing_if)]",
-                        variant.ident, ident
+                        variant.ident, member
                     ));
                 }
             }
@@ -204,17 +203,14 @@ fn check_variant_skip_attrs(cx: &Ctxt, cont: &Container) {
                 ));
             }
 
-            for (i, field) in variant.fields.iter().enumerate() {
+            for field in &variant.fields {
                 if field.attrs.skip_deserializing() {
-                    let ident = field
-                        .ident
-                        .as_ref()
-                        .map_or_else(|| format!("{}", i), |ident| format!("`{}`", ident));
+                    let member = member_message(&field.member);
 
                     cx.error(format!(
                         "variant `{}` cannot have both #[serde(deserialize_with)] \
                          and a field {} marked with #[serde(skip_deserializing)]",
-                        variant.ident, ident
+                        variant.ident, member
                     ));
                 }
             }
@@ -282,3 +278,76 @@ fn check_adjacent_tag_conflict(cx: &Ctxt, cont: &Container) {
         cx.error(message);
     }
 }
+
+/// Enums and unit structs cannot be transparent.
+fn check_transparent(cx: &Ctxt, cont: &mut Container, derive: Derive) {
+    if !cont.attrs.transparent() {
+        return;
+    }
+
+    if cont.attrs.type_from().is_some() {
+        cx.error("#[serde(transparent)] is not allowed with #[serde(from = \"...\")]");
+    }
+
+    if cont.attrs.type_into().is_some() {
+        cx.error("#[serde(transparent)] is not allowed with #[serde(into = \"...\")]");
+    }
+
+    let fields = match cont.data {
+        Data::Enum(_) => {
+            cx.error("#[serde(transparent)] is not allowed on an enum");
+            return;
+        }
+        Data::Struct(Style::Unit, _) => {
+            cx.error("#[serde(transparent)] is not allowed on a unit struct");
+            return;
+        }
+        Data::Struct(_, ref mut fields) => fields,
+    };
+
+    let mut transparent_field = None;
+
+    for field in fields {
+        if allow_transparent(field, derive) {
+            if transparent_field.is_some() {
+                cx.error("#[serde(transparent)] requires struct to have at most one transparent field");
+                return;
+            }
+            transparent_field = Some(field);
+        }
+    }
+
+    match transparent_field {
+        Some(transparent_field) => transparent_field.attrs.mark_transparent(),
+        None => match derive {
+            Derive::Serialize => {
+                cx.error("#[serde(transparent)] requires at least one field that is not skipped");
+            }
+            Derive::Deserialize => {
+                cx.error("#[serde(transparent)] requires at least one field that is neither skipped nor has a default");
+            }
+        }
+    }
+}
+
+fn member_message(member: &Member) -> String {
+    match *member {
+        Member::Named(ref ident) => format!("`{}`", ident),
+        Member::Unnamed(ref i) => i.index.to_string(),
+    }
+}
+
+fn allow_transparent(field: &Field, derive: Derive) -> bool {
+    if let Type::Path(ref ty) = *field.ty {
+        if let Some(seg) = ty.path.segments.last() {
+            if seg.into_value().ident == "PhantomData" {
+                return false;
+            }
+        }
+    }
+
+    match derive {
+        Derive::Serialize => !field.attrs.skip_serializing(),
+        Derive::Deserialize => !field.attrs.skip_deserializing() && field.attrs.default().is_none(),
+    }
+}

serde_derive/src/internals/mod.rs

@@ -14,3 +14,9 @@ pub use self::ctxt::Ctxt;
 
 mod case;
 mod check;
+
+#[derive(Copy, Clone)]
+pub enum Derive {
+    Serialize,
+    Deserialize,
+}

serde_derive/src/lib.rs

@@ -22,7 +22,7 @@
 //!
 //! [https://serde.rs/derive.html]: https://serde.rs/derive.html
 
-#![doc(html_root_url = "https://docs.rs/serde_derive/1.0.56")]
+#![doc(html_root_url = "https://docs.rs/serde_derive/1.0.59")]
 #![cfg_attr(feature = "cargo-clippy", deny(clippy, clippy_pedantic))]
 // Whitelisted clippy lints
 #![cfg_attr(

serde_derive/src/pretend.rs

@@ -1,5 +1,4 @@
-use proc_macro2::Span;
-use quote::Tokens;
+use proc_macro2::{Span, TokenStream};
 use syn::Ident;
 
 use internals::ast::{Container, Data, Field, Style};
@@ -21,7 +20,7 @@ use internals::ast::{Container, Data, Field, Style};
 //     8 | enum EnumDef { V }
 //       |                ^
 //
-pub fn pretend_used(cont: &Container) -> Tokens {
+pub fn pretend_used(cont: &Container) -> TokenStream {
     let pretend_fields = pretend_fields_used(cont);
     let pretend_variants = pretend_variants_used(cont);
 
@@ -49,8 +48,8 @@ pub fn pretend_used(cont: &Container) -> Tokens {
 // The `ref` is important in case the user has written a Drop impl on their
 // type. Rust does not allow destructuring a struct or enum that has a Drop
 // impl.
-fn pretend_fields_used(cont: &Container) -> Tokens {
-    let type_ident = cont.ident;
+fn pretend_fields_used(cont: &Container) -> TokenStream {
+    let type_ident = &cont.ident;
     let (_, ty_generics, _) = cont.generics.split_for_impl();
 
     let patterns = match cont.data {
@@ -58,7 +57,7 @@ fn pretend_fields_used(cont: &Container) -> Tokens {
             .iter()
             .filter_map(|variant| match variant.style {
                 Style::Struct => {
-                    let variant_ident = variant.ident;
+                    let variant_ident = &variant.ident;
                     let pat = struct_pattern(&variant.fields);
                     Some(quote!(#type_ident::#variant_ident #pat))
                 }
@@ -93,7 +92,7 @@ fn pretend_fields_used(cont: &Container) -> Tokens {
 //         _ => {}
 //     }
 //
-fn pretend_variants_used(cont: &Container) -> Tokens {
+fn pretend_variants_used(cont: &Container) -> TokenStream {
     let variants = match cont.data {
         Data::Enum(ref variants) => variants,
         Data::Struct(_, _) => {
@@ -101,20 +100,20 @@ fn pretend_variants_used(cont: &Container) -> Tokens {
         }
     };
 
-    let type_ident = cont.ident;
+    let type_ident = &cont.ident;
     let (_, ty_generics, _) = cont.generics.split_for_impl();
     let turbofish = ty_generics.as_turbofish();
 
     let cases = variants.iter().map(|variant| {
-        let variant_ident = variant.ident;
+        let variant_ident = &variant.ident;
         let placeholders = &(0..variant.fields.len())
             .map(|i| Ident::new(&format!("__v{}", i), Span::call_site()))
             .collect::<Vec<_>>();
 
         let pat = match variant.style {
             Style::Struct => {
-                let names = variant.fields.iter().map(|field| field.ident);
-                quote!({ #(#names: #placeholders),* })
+                let members = variant.fields.iter().map(|field| &field.member);
+                quote!({ #(#members: #placeholders),* })
             }
             Style::Tuple | Style::Newtype => quote!(( #(#placeholders),* )),
             Style::Unit => quote!(),
@@ -133,9 +132,9 @@ fn pretend_variants_used(cont: &Container) -> Tokens {
     quote!(#(#cases)*)
 }
 
-fn struct_pattern(fields: &[Field]) -> Tokens {
-    let names = fields.iter().map(|field| field.ident);
+fn struct_pattern(fields: &[Field]) -> TokenStream {
+    let members = fields.iter().map(|field| &field.member);
     let placeholders =
         (0..fields.len()).map(|i| Ident::new(&format!("__v{}", i), Span::call_site()));
-    quote!({ #(#names: ref #placeholders),* })
+    quote!({ #(#members: ref #placeholders),* })
 }

serde_derive/src/ser.rs

@@ -6,25 +6,24 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-use proc_macro2::Span;
-use quote::Tokens;
+use proc_macro2::{Span, TokenStream};
 use syn::spanned::Spanned;
 use syn::{self, Ident, Index, Member};
 
 use bound;
 use fragment::{Fragment, Match, Stmts};
 use internals::ast::{Container, Data, Field, Style, Variant};
-use internals::{attr, Ctxt};
+use internals::{attr, Ctxt, Derive};
 use pretend;
 use try;
 
-pub fn expand_derive_serialize(input: &syn::DeriveInput) -> Result<Tokens, String> {
+pub fn expand_derive_serialize(input: &syn::DeriveInput) -> Result<TokenStream, String> {
     let ctxt = Ctxt::new();
-    let cont = Container::from_ast(&ctxt, input);
+    let cont = Container::from_ast(&ctxt, input, Derive::Serialize);
     precondition(&ctxt, &cont);
     try!(ctxt.check());
 
-    let ident = cont.ident;
+    let ident = &cont.ident;
     let params = Parameters::new(&cont);
     let (impl_generics, ty_generics, where_clause) = params.generics.split_for_impl();
     let dummy_const = Ident::new(&format!("_IMPL_SERIALIZE_FOR_{}", ident), Span::call_site());
@@ -110,7 +109,7 @@ impl Parameters {
 
         let this = match cont.attrs.remote() {
             Some(remote) => remote.clone(),
-            None => cont.ident.into(),
+            None => cont.ident.clone().into(),
         };
 
         let generics = build_generics(cont);
@@ -125,8 +124,8 @@ impl Parameters {
 
     /// Type name to use in error messages and `&'static str` arguments to
     /// various Serializer methods.
-    fn type_name(&self) -> &str {
-        self.this.segments.last().unwrap().value().ident.as_ref()
+    fn type_name(&self) -> String {
+        self.this.segments.last().unwrap().value().ident.to_string()
     }
 }
 
@@ -160,27 +159,24 @@ fn build_generics(cont: &Container) -> syn::Generics {
 fn needs_serialize_bound(field: &attr::Field, variant: Option<&attr::Variant>) -> bool {
     !field.skip_serializing() && field.serialize_with().is_none() && field.ser_bound().is_none()
         && variant.map_or(true, |variant| {
-            !variant.skip_serializing() && variant.serialize_with().is_none()
+            !variant.skip_serializing()
+                && variant.serialize_with().is_none()
                 && variant.ser_bound().is_none()
         })
 }
 
 fn serialize_body(cont: &Container, params: &Parameters) -> Fragment {
-    if let Some(type_into) = cont.attrs.type_into() {
+    if cont.attrs.transparent() {
+        serialize_transparent(cont, params)
+    } else if let Some(type_into) = cont.attrs.type_into() {
         serialize_into(params, type_into)
     } else {
         match cont.data {
             Data::Enum(ref variants) => serialize_enum(params, variants, &cont.attrs),
             Data::Struct(Style::Struct, ref fields) => {
-                if fields.iter().any(|field| field.ident.is_none()) {
-                    panic!("struct has unnamed fields");
-                }
                 serialize_struct(params, fields, &cont.attrs)
             }
             Data::Struct(Style::Tuple, ref fields) => {
-                if fields.iter().any(|field| field.ident.is_some()) {
-                    panic!("tuple struct has named fields");
-                }
                 serialize_tuple_struct(params, fields, &cont.attrs)
             }
             Data::Struct(Style::Newtype, ref fields) => {
@@ -191,8 +187,28 @@ fn serialize_body(cont: &Container, params: &Parameters) -> Fragment {
     }
 }
 
+fn serialize_transparent(cont: &Container, params: &Parameters) -> Fragment {
+    let fields = match cont.data {
+        Data::Struct(_, ref fields) => fields,
+        Data::Enum(_) => unreachable!(),
+    };
+
+    let self_var = &params.self_var;
+    let transparent_field = fields.iter().find(|f| f.attrs.transparent()).unwrap();
+    let member = &transparent_field.member;
+
+    let path = match transparent_field.attrs.serialize_with() {
+        Some(path) => quote!(#path),
+        None => quote!(_serde::Serialize::serialize),
+    };
+
+    quote_block! {
+        #path(&#self_var.#member, __serializer)
+    }
+}
+
 fn serialize_into(params: &Parameters, type_into: &syn::Type) -> Fragment {
-    let self_var = params.self_var;
+    let self_var = &params.self_var;
     quote_block! {
         _serde::Serialize::serialize(
             &_serde::export::Into::<#type_into>::into(_serde::export::Clone::clone(#self_var)),
@@ -304,8 +320,7 @@ fn serialize_struct_as_struct(
         .map(|field| match field.attrs.skip_serializing_if() {
             None => quote!(1),
             Some(path) => {
-                let ident = field.ident.expect("struct has unnamed fields");
-                let field_expr = get_member(params, field, &Member::Named(ident));
+                let field_expr = get_member(params, field, &field.member);
                 quote!(if #path(#field_expr) { 0 } else { 1 })
             }
         })
@@ -340,8 +355,7 @@ fn serialize_struct_as_map(
             .map(|field| match field.attrs.skip_serializing_if() {
                 None => quote!(1),
                 Some(path) => {
-                    let ident = field.ident.expect("struct has unnamed fields");
-                    let field_expr = get_member(params, field, &Member::Named(ident));
+                    let field_expr = get_member(params, field, &field.member);
                     quote!(if #path(#field_expr) { 0 } else { 1 })
                 }
             })
@@ -359,7 +373,7 @@ fn serialize_struct_as_map(
 fn serialize_enum(params: &Parameters, variants: &[Variant], cattrs: &attr::Container) -> Fragment {
     assert!(variants.len() as u64 <= u64::from(u32::max_value()));
 
-    let self_var = params.self_var;
+    let self_var = &params.self_var;
 
     let arms: Vec<_> = variants
         .iter()
@@ -381,9 +395,9 @@ fn serialize_variant(
     variant: &Variant,
     variant_index: u32,
     cattrs: &attr::Container,
-) -> Tokens {
+) -> TokenStream {
     let this = &params.this;
-    let variant_ident = variant.ident;
+    let variant_ident = &variant.ident;
 
     if variant.attrs.skip_serializing() {
         let skipped_msg = format!(
@@ -423,12 +437,9 @@ fn serialize_variant(
                 }
             }
             Style::Struct => {
-                let fields = variant
-                    .fields
-                    .iter()
-                    .map(|f| f.ident.expect("struct variant has unnamed fields"));
+                let members = variant.fields.iter().map(|f| &f.member);
                 quote! {
-                    #this::#variant_ident { #(ref #fields),* }
+                    #this::#variant_ident { #(ref #members),* }
                 }
             }
         };
@@ -534,7 +545,7 @@ fn serialize_internally_tagged_variant(
     let variant_name = variant.attrs.name().serialize_name();
 
     let enum_ident_str = params.type_name();
-    let variant_ident_str = variant.ident.as_ref();
+    let variant_ident_str = variant.ident.to_string();
 
     if let Some(path) = variant.attrs.serialize_with() {
         let ser = wrap_serialize_variant_with(params, path, variant);
@@ -656,15 +667,11 @@ fn serialize_adjacently_tagged_variant(
                 unreachable!()
             }
         }
-        Style::Newtype => vec![Ident::new("__field0", Span::call_site())],
+        Style::Newtype => vec![Member::Named(Ident::new("__field0", Span::call_site()))],
         Style::Tuple => (0..variant.fields.len())
-            .map(|i| Ident::new(&format!("__field{}", i), Span::call_site()))
-            .collect(),
-        Style::Struct => variant
-            .fields
-            .iter()
-            .map(|f| f.ident.expect("struct variant has unnamed fields"))
+            .map(|i| Member::Named(Ident::new(&format!("__field{}", i), Span::call_site())))
             .collect(),
+        Style::Struct => variant.fields.iter().map(|f| f.member.clone()).collect(),
     };
 
     let (_, ty_generics, where_clause) = params.generics.split_for_impl();
@@ -850,10 +857,10 @@ fn serialize_struct_variant<'a>(
 
     let len = serialized_fields
         .map(|field| {
-            let ident = field.ident.expect("struct has unnamed fields");
+            let member = &field.member;
 
             match field.attrs.skip_serializing_if() {
-                Some(path) => quote!(if #path(#ident) { 0 } else { 1 }),
+                Some(path) => quote!(if #path(#member) { 0 } else { 1 }),
                 None => quote!(1),
             }
         })
@@ -929,7 +936,7 @@ fn serialize_struct_variant_with_flatten<'a>(
         } => {
             let this = &params.this;
             let fields_ty = fields.iter().map(|f| &f.ty);
-            let fields_ident = &fields.iter().map(|f| f.ident).collect::<Vec<_>>();
+            let members = &fields.iter().map(|f| &f.member).collect::<Vec<_>>();
 
             let (_, ty_generics, where_clause) = params.generics.split_for_impl();
             let wrapper_generics = bound::with_lifetime_bound(&params.generics, "'__a");
@@ -946,7 +953,7 @@ fn serialize_struct_variant_with_flatten<'a>(
                     where
                         __S: _serde::Serializer,
                     {
-                        let (#(#fields_ident,)*) = self.data;
+                        let (#(#members,)*) = self.data;
                         let #let_mut __serde_state = try!(_serde::Serializer::serialize_map(
                             __serializer,
                             _serde::export::None));
@@ -961,7 +968,7 @@ fn serialize_struct_variant_with_flatten<'a>(
                     #variant_index,
                     #variant_name,
                     &__EnumFlatten {
-                        data: (#(#fields_ident,)*),
+                        data: (#(#members,)*),
                         phantom: _serde::export::PhantomData::<#this #ty_generics>,
                     })
             }
@@ -997,7 +1004,7 @@ fn serialize_tuple_struct_visitor(
     params: &Parameters,
     is_enum: bool,
     tuple_trait: &TupleTrait,
-) -> Vec<Tokens> {
+) -> Vec<TokenStream> {
     fields
         .iter()
         .enumerate()
@@ -1045,17 +1052,17 @@ fn serialize_struct_visitor(
     params: &Parameters,
     is_enum: bool,
     struct_trait: &StructTrait,
-) -> Vec<Tokens> {
+) -> Vec<TokenStream> {
     fields
         .iter()
         .filter(|&field| !field.attrs.skip_serializing())
         .map(|field| {
-            let field_ident = field.ident.expect("struct has unnamed field");
+            let member = &field.member;
 
             let mut field_expr = if is_enum {
-                quote!(#field_ident)
+                quote!(#member)
             } else {
-                get_member(params, field, &Member::Named(field_ident))
+                get_member(params, field, &member)
             };
 
             let key_expr = field.attrs.name().serialize_name();
@@ -1109,8 +1116,8 @@ fn wrap_serialize_field_with(
     params: &Parameters,
     field_ty: &syn::Type,
     serialize_with: &syn::ExprPath,
-    field_expr: &Tokens,
-) -> Tokens {
+    field_expr: &TokenStream,
+) -> TokenStream {
     wrap_serialize_with(params, serialize_with, &[field_ty], &[quote!(#field_expr)])
 }
 
@@ -1118,16 +1125,18 @@ fn wrap_serialize_variant_with(
     params: &Parameters,
     serialize_with: &syn::ExprPath,
     variant: &Variant,
-) -> Tokens {
+) -> TokenStream {
     let field_tys: Vec<_> = variant.fields.iter().map(|field| field.ty).collect();
     let field_exprs: Vec<_> = variant
         .fields
         .iter()
-        .enumerate()
-        .map(|(i, field)| {
-            let id = field
-                .ident
-                .unwrap_or_else(|| Ident::new(&format!("__field{}", i), Span::call_site()));
+        .map(|field| {
+            let id = match field.member {
+                Member::Named(ref ident) => ident.clone(),
+                Member::Unnamed(ref member) => {
+                    Ident::new(&format!("__field{}", member.index), Span::call_site())
+                }
+            };
             quote!(#id)
         })
         .collect();
@@ -1143,8 +1152,8 @@ fn wrap_serialize_with(
     params: &Parameters,
     serialize_with: &syn::ExprPath,
     field_tys: &[&syn::Type],
-    field_exprs: &[Tokens],
-) -> Tokens {
+    field_exprs: &[TokenStream],
+) -> TokenStream {
     let this = &params.this;
     let (_, ty_generics, where_clause) = params.generics.split_for_impl();
 
@@ -1190,7 +1199,7 @@ fn wrap_serialize_with(
 //     _serde::ser::SerializeStruct::end(__serde_state)
 //
 // where we want to omit the `mut` to avoid a warning.
-fn mut_if(is_mut: bool) -> Option<Tokens> {
+fn mut_if(is_mut: bool) -> Option<TokenStream> {
     if is_mut {
         Some(quote!(mut))
     } else {
@@ -1198,8 +1207,8 @@ fn mut_if(is_mut: bool) -> Option<Tokens> {
     }
 }
 
-fn get_member(params: &Parameters, field: &Field, member: &Member) -> Tokens {
-    let self_var = params.self_var;
+fn get_member(params: &Parameters, field: &Field, member: &Member) -> TokenStream {
+    let self_var = &params.self_var;
     match (params.is_remote, field.attrs.getter()) {
         (false, None) => quote!(&#self_var.#member),
         (true, None) => {
@@ -1224,7 +1233,7 @@ enum StructTrait {
 }
 
 impl StructTrait {
-    fn serialize_field(&self, span: Span) -> Tokens {
+    fn serialize_field(&self, span: Span) -> TokenStream {
         match *self {
             StructTrait::SerializeMap => {
                 quote_spanned!(span=> _serde::ser::SerializeMap::serialize_entry)
@@ -1238,7 +1247,7 @@ impl StructTrait {
         }
     }
 
-    fn skip_field(&self, span: Span) -> Option<Tokens> {
+    fn skip_field(&self, span: Span) -> Option<TokenStream> {
         match *self {
             StructTrait::SerializeMap => None,
             StructTrait::SerializeStruct => {
@@ -1258,7 +1267,7 @@ enum TupleTrait {
 }
 
 impl TupleTrait {
-    fn serialize_element(&self, span: Span) -> Tokens {
+    fn serialize_element(&self, span: Span) -> TokenStream {
         match *self {
             TupleTrait::SerializeTuple => {
                 quote_spanned!(span=> _serde::ser::SerializeTuple::serialize_element)

serde_derive/src/try.rs

@@ -1,13 +1,12 @@
-use proc_macro2::{Op, Spacing};
-use quote::Tokens;
+use proc_macro2::{Punct, Spacing, TokenStream};
 
 // None of our generated code requires the `From::from` error conversion
 // performed by the standard library's `try!` macro. With this simplified macro
 // we see a significant improvement in type checking and borrow checking time of
 // the generated code and a slight improvement in binary size.
-pub fn replacement() -> Tokens {
+pub fn replacement() -> TokenStream {
     // Cannot pass `$expr` to `quote!` prior to Rust 1.17.0 so interpolate it.
-    let dollar = Op::new('$', Spacing::Alone);
+    let dollar = Punct::new('$', Spacing::Alone);
 
     quote! {
         #[allow(unused_macros)]

serde_derive_internals/Cargo.toml

@@ -15,8 +15,8 @@ include = ["Cargo.toml", "lib.rs", "src/**/*.rs", "README.md", "LICENSE-APACHE",
 path = "lib.rs"
 
 [dependencies]
-proc-macro2 = "0.3"
-syn = { version = "0.13", default-features = false, features = ["derive", "parsing", "clone-impls"] }
+proc-macro2 = "0.4"
+syn = { version = "0.14", default-features = false, features = ["derive", "parsing", "clone-impls"] }
 
 [badges]
 travis-ci = { repository = "serde-rs/serde" }

serde_test/Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "serde_test"
-version = "1.0.56" # remember to update html_root_url
+version = "1.0.59" # remember to update html_root_url
 authors = ["Erick Tryzelaar <erick.tryzelaar@gmail.com>", "David Tolnay <dtolnay@gmail.com>"]
 license = "MIT/Apache-2.0"
 description = "Token De/Serializer for testing De/Serialize implementations"

serde_test/src/de.rs

@@ -599,7 +599,8 @@ impl<'de, 'a> MapAccess<'de> for EnumMapVisitor<'a, 'de> {
     {
         match self.variant.take() {
             Some(Token::Str(variant)) => seed.deserialize(variant.into_deserializer()).map(Some),
-            Some(Token::Bytes(variant)) => seed.deserialize(BytesDeserializer { value: variant })
+            Some(Token::Bytes(variant)) => seed
+                .deserialize(BytesDeserializer { value: variant })
                 .map(Some),
             Some(Token::U32(variant)) => seed.deserialize(variant.into_deserializer()).map(Some),
             Some(other) => unexpected!(other),

serde_test/src/lib.rs

@@ -161,7 +161,7 @@
 //! # }
 //! ```
 
-#![doc(html_root_url = "https://docs.rs/serde_test/1.0.56")]
+#![doc(html_root_url = "https://docs.rs/serde_test/1.0.59")]
 #![cfg_attr(feature = "cargo-clippy", deny(clippy, clippy_pedantic))]
 // Whitelisted clippy lints
 #![cfg_attr(feature = "cargo-clippy", allow(float_cmp))]

test_suite/tests/compile-fail/transparent/at_most_one.rs

@@ -0,0 +1,20 @@
+// Copyright 2018 Serde Developers
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+#[macro_use]
+extern crate serde_derive;
+
+#[derive(Serialize)] //~ ERROR: proc-macro derive panicked
+#[serde(transparent)]
+struct S {
+    //~^^^ HELP: #[serde(transparent)] requires struct to have at most one transparent field
+    a: u8,
+    b: u8,
+}
+
+fn main() {}

test_suite/tests/compile-fail/transparent/de_at_least_one.rs

@@ -0,0 +1,22 @@
+// Copyright 2018 Serde Developers
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+#[macro_use]
+extern crate serde_derive;
+
+#[derive(Deserialize)] //~ ERROR: proc-macro derive panicked
+#[serde(transparent)]
+struct S {
+    //~^^^ HELP: #[serde(transparent)] requires at least one field that is neither skipped nor has a default
+    #[serde(skip)]
+    a: u8,
+    #[serde(default)]
+    b: u8,
+}
+
+fn main() {}

test_suite/tests/compile-fail/transparent/ser_at_least_one.rs

@@ -0,0 +1,20 @@
+// Copyright 2018 Serde Developers
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+#[macro_use]
+extern crate serde_derive;
+
+#[derive(Serialize)] //~ ERROR: proc-macro derive panicked
+#[serde(transparent)]
+struct S {
+    //~^^^ HELP: #[serde(transparent)] requires at least one field that is not skipped
+    #[serde(skip)]
+    a: u8,
+}
+
+fn main() {}

test_suite/tests/test_annotations.rs

@@ -15,6 +15,7 @@ extern crate serde;
 use self::serde::de::{self, Unexpected};
 use self::serde::{Deserialize, Deserializer, Serialize, Serializer};
 use std::collections::HashMap;
+use std::marker::PhantomData;
 
 extern crate serde_test;
 use self::serde_test::{
@@ -2074,15 +2075,11 @@ fn test_flatten_untagged_enum() {
     #[derive(Serialize, Deserialize, PartialEq, Debug)]
     #[serde(untagged)]
     enum Inner {
-        Variant {
-            a: i32,
-        },
+        Variant { a: i32 },
     }
 
     let data = Outer {
-        inner: Inner::Variant {
-            a: 0,
-        }
+        inner: Inner::Variant { a: 0 },
     };
 
     assert_tokens(
@@ -2118,12 +2115,8 @@ fn test_flatten_option() {
 
     assert_tokens(
         &Outer {
-            inner1: Some(Inner1 {
-                inner1: 1,
-            }),
-            inner2: Some(Inner2 {
-                inner2: 2,
-            }),
+            inner1: Some(Inner1 { inner1: 1 }),
+            inner2: Some(Inner2 { inner2: 2 }),
         },
         &[
             Token::Map { len: None },
@@ -2137,9 +2130,7 @@ fn test_flatten_option() {
 
     assert_tokens(
         &Outer {
-            inner1: Some(Inner1 {
-                inner1: 1,
-            }),
+            inner1: Some(Inner1 { inner1: 1 }),
             inner2: None,
         },
         &[
@@ -2153,9 +2144,7 @@ fn test_flatten_option() {
     assert_tokens(
         &Outer {
             inner1: None,
-            inner2: Some(Inner2 {
-                inner2: 2,
-            }),
+            inner2: Some(Inner2 { inner2: 2 }),
         },
         &[
             Token::Map { len: None },
@@ -2170,9 +2159,44 @@ fn test_flatten_option() {
             inner1: None,
             inner2: None,
         },
-        &[
-            Token::Map { len: None },
-            Token::MapEnd,
-        ],
+        &[Token::Map { len: None }, Token::MapEnd],
     );
 }
+
+#[test]
+fn test_transparent_struct() {
+    #[derive(Serialize, Deserialize, PartialEq, Debug)]
+    #[serde(transparent)]
+    struct Transparent {
+        #[serde(skip)]
+        a: bool,
+        b: u32,
+        #[serde(skip)]
+        c: bool,
+        d: PhantomData<()>,
+    }
+
+    assert_tokens(
+        &Transparent {
+            a: false,
+            b: 1,
+            c: false,
+            d: PhantomData,
+        },
+        &[Token::U32(1)],
+    );
+}
+
+#[test]
+fn test_transparent_tuple_struct() {
+    #[derive(Serialize, Deserialize, PartialEq, Debug)]
+    #[serde(transparent)]
+    struct Transparent(
+        #[serde(skip)] bool,
+        u32,
+        #[serde(skip)] bool,
+        PhantomData<()>,
+    );
+
+    assert_tokens(&Transparent(false, 1, false, PhantomData), &[Token::U32(1)]);
+}

test_suite/tests/test_gen.rs

@@ -643,6 +643,24 @@ fn test_gen() {
     struct ImpliciltyBorrowedOption<'a> {
         option: std::option::Option<&'a str>,
     }
+
+    #[derive(Serialize, Deserialize)]
+    #[serde(untagged)]
+    enum UntaggedNewtypeVariantWith {
+        Newtype(
+            #[serde(serialize_with = "ser_x")]
+            #[serde(deserialize_with = "de_x")]
+            X,
+        ),
+    }
+
+    #[derive(Serialize, Deserialize)]
+    #[serde(transparent)]
+    struct TransparentWith {
+        #[serde(serialize_with = "ser_x")]
+        #[serde(deserialize_with = "de_x")]
+        x: X,
+    }
 }
 
 //////////////////////////////////////////////////////////////////////////