feat(codegen): Inhibit generic bounds if skip_serializing
The generated code for a struct like:
struct Test<A, B, C> {
a: X<A>
#[serde(skip_serializing)]
b: B
#[serde(serialize_with="...")]
c: C
}
Used to be:
impl<A, B, C> Serialize for Test<A, B, C>
where A: Serialize,
B: Serialize,
C: Serialize,
{ ... }
Now it is:
impl<A, B, C> Serialize for Test<A, B, C>
where X<A>: Serialize,
{ ... }
Both `skip_serializing` and `serialize_with` mean the type does not need to
implement `Serialize`.
This commit is contained in:
David Tolnay
parent
708a310ab0
commit
19ec8bbdb9
@ -382,7 +382,7 @@ fn get_renames(cx: &ExtCtxt,
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Ok((ser_name, de_name))
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}
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fn get_serde_meta_items(attr: &ast::Attribute) -> Option<&[P<ast::MetaItem>]> {
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pub fn get_serde_meta_items(attr: &ast::Attribute) -> Option<&[P<ast::MetaItem>]> {
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match attr.node.value.node {
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ast::MetaItemKind::List(ref name, ref items) if name == &"serde" => {
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attr::mark_used(&attr);
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@ -60,11 +60,7 @@ fn serialize_item(
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}
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};
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let impl_generics = builder.from_generics(generics.clone())
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.add_ty_param_bound(
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builder.path().global().ids(&["serde", "ser", "Serialize"]).build()
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)
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.build();
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let impl_generics = build_impl_generics(cx, builder, item, generics);
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let ty = builder.ty().path()
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.segment(item.ident).with_generics(impl_generics.clone()).build()
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@ -89,6 +85,117 @@ fn serialize_item(
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).unwrap())
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}
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// All the generics in the input, plus a bound `T: Serialize` for each field
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// type that will be serialized by us.
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fn build_impl_generics(
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cx: &ExtCtxt,
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builder: &aster::AstBuilder,
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item: &Item,
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generics: &ast::Generics,
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) -> ast::Generics {
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let serialize_path = builder.path()
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.global()
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.ids(&["serde", "ser", "Serialize"])
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.build();
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builder.from_generics(generics.clone())
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.with_predicates(
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all_variants(cx, item).iter()
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.flat_map(|variant_data| all_struct_fields(variant_data))
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.filter(|field| serialized_by_us(field))
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.map(|field| &field.node.ty)
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.map(|ty| strip_reference(ty))
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.map(|ty| builder.where_predicate()
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// the type that is being bounded i.e. T
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.bound().build(ty.clone())
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// the bound i.e. Serialize
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.bound().trait_(serialize_path.clone()).build()
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.build()))
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.build()
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}
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fn all_variants<'a>(cx: &ExtCtxt, item: &'a Item) -> Vec<&'a ast::VariantData> {
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match item.node {
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ast::ItemKind::Struct(ref variant_data, _) => {
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vec![variant_data]
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}
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ast::ItemKind::Enum(ref enum_def, _) => {
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enum_def.variants.iter()
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.map(|variant| &variant.node.data)
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.collect()
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}
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_ => {
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cx.span_bug(item.span,
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"expected Item to be Struct or Enum in #[derive(Serialize)]");
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}
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}
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}
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fn all_struct_fields(variant_data: &ast::VariantData) -> &[ast::StructField] {
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match *variant_data {
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ast::VariantData::Struct(ref fields, _) |
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ast::VariantData::Tuple(ref fields, _) => {
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fields
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}
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ast::VariantData::Unit(_) => {
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&[]
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}
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}
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}
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// Fields with a `skip_serializing` or `serialize_with` attribute are not
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// serialized by us. All other fields will receive a `T: Serialize` bound where
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// T is the type of the field.
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fn serialized_by_us(field: &ast::StructField) -> bool {
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for meta_items in field.node.attrs.iter().filter_map(attr::get_serde_meta_items) {
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for meta_item in meta_items {
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match meta_item.node {
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ast::MetaItemKind::Word(ref name) if name == &"skip_serializing" => {
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return false
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}
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ast::MetaItemKind::NameValue(ref name, _) if name == &"serialize_with" => {
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return false
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}
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_ => {}
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}
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}
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}
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true
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}
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// This is required to handle types that use both a reference and a value of
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// the same type, as in:
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//
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// enum Test<'a, T> where T: 'a {
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// Lifetime(&'a T),
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// NoLifetime(T),
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// }
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//
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// Preserving references, we would generate an impl like:
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//
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// impl<'a, T> Serialize for Test<'a, T>
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// where &'a T: Serialize,
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// T: Serialize { ... }
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//
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// And taking a reference to one of the elements would fail with:
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//
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// error: cannot infer an appropriate lifetime for pattern due
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// to conflicting requirements [E0495]
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// Test::NoLifetime(ref v) => { ... }
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// ^~~~~
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//
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// Instead, we strip references before adding `T: Serialize` bounds in order to
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// generate:
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//
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// impl<'a, T> Serialize for Test<'a, T>
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// where T: Serialize { ... }
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fn strip_reference(ty: &P<ast::Ty>) -> &P<ast::Ty> {
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match ty.node {
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ast::TyKind::Rptr(_, ref mut_ty) => &mut_ty.ty,
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_ => ty
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}
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}
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fn serialize_body(
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cx: &ExtCtxt,
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builder: &aster::AstBuilder,
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@ -10,23 +10,33 @@ use token::{
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assert_de_tokens_error
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};
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trait Trait: Sized {
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trait MyDefault: Sized {
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fn my_default() -> Self;
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}
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trait ShouldSkip: Sized {
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fn should_skip(&self) -> bool;
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}
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trait SerializeWith: Sized {
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fn serialize_with<S>(&self, ser: &mut S) -> Result<(), S::Error>
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where S: Serializer;
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}
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trait DeserializeWith: Sized {
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fn deserialize_with<D>(de: &mut D) -> Result<Self, D::Error>
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where D: Deserializer;
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}
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impl Trait for i32 {
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impl MyDefault for i32 {
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fn my_default() -> Self { 123 }
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}
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impl ShouldSkip for i32 {
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fn should_skip(&self) -> bool { *self == 123 }
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}
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impl SerializeWith for i32 {
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fn serialize_with<S>(&self, ser: &mut S) -> Result<(), S::Error>
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where S: Serializer
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{
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@ -36,7 +46,9 @@ impl Trait for i32 {
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false.serialize(ser)
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}
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}
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}
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impl DeserializeWith for i32 {
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fn deserialize_with<D>(de: &mut D) -> Result<Self, D::Error>
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where D: Deserializer
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{
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@ -49,11 +61,11 @@ impl Trait for i32 {
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}
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#[derive(Debug, PartialEq, Serialize, Deserialize)]
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struct DefaultStruct<A, B: Default, C> where C: Trait {
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struct DefaultStruct<A, B: Default, C> where C: MyDefault {
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a1: A,
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#[serde(default)]
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a2: B,
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#[serde(default="Trait::my_default")]
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#[serde(default="MyDefault::my_default")]
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a3: C,
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}
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@ -95,12 +107,12 @@ fn test_default_struct() {
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}
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#[derive(Debug, PartialEq, Serialize, Deserialize)]
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enum DefaultEnum<A, B: Default, C> where C: Trait {
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enum DefaultEnum<A, B: Default, C> where C: MyDefault {
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Struct {
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a1: A,
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#[serde(default)]
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a2: B,
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#[serde(default="Trait::my_default")]
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#[serde(default="MyDefault::my_default")]
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a3: C,
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}
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}
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@ -389,11 +401,11 @@ fn test_rename_enum() {
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}
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#[derive(Debug, PartialEq, Serialize)]
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struct SkipSerializingStruct<'a, B, C> where C: Trait {
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struct SkipSerializingStruct<'a, B, C> where C: ShouldSkip {
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a: &'a i8,
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#[serde(skip_serializing)]
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b: B,
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#[serde(skip_serializing_if="Trait::should_skip")]
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#[serde(skip_serializing_if="ShouldSkip::should_skip")]
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c: C,
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}
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@ -440,12 +452,12 @@ fn test_skip_serializing_struct() {
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}
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#[derive(Debug, PartialEq, Serialize)]
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enum SkipSerializingEnum<'a, B, C> where C: Trait {
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enum SkipSerializingEnum<'a, B, C> where C: ShouldSkip {
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Struct {
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a: &'a i8,
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#[serde(skip_serializing)]
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_b: B,
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#[serde(skip_serializing_if="Trait::should_skip")]
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#[serde(skip_serializing_if="ShouldSkip::should_skip")]
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c: C,
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}
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}
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@ -492,10 +504,62 @@ fn test_skip_serializing_enum() {
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);
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}
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#[derive(Debug, PartialEq)]
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struct NotSerializeStruct(i8);
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#[derive(Debug, PartialEq)]
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enum NotSerializeEnum { Trouble }
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impl SerializeWith for NotSerializeEnum {
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fn serialize_with<S>(&self, ser: &mut S) -> Result<(), S::Error>
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where S: Serializer
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{
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"trouble".serialize(ser)
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}
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}
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#[derive(Debug, PartialEq, Serialize)]
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struct SerializeWithStruct<'a, B> where B: Trait {
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struct ContainsNotSerialize<'a, B, C, D> where B: 'a, D: SerializeWith {
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a: &'a Option<i8>,
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#[serde(skip_serializing)]
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b: &'a B,
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#[serde(skip_serializing)]
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c: Option<C>,
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#[serde(serialize_with="SerializeWith::serialize_with")]
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d: D,
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}
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#[test]
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fn test_elt_not_serialize() {
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let a = 1;
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assert_ser_tokens(
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&ContainsNotSerialize {
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a: &Some(a),
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b: &NotSerializeStruct(2),
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c: Some(NotSerializeEnum::Trouble),
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d: NotSerializeEnum::Trouble,
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},
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&[
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Token::StructStart("ContainsNotSerialize", Some(2)),
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Token::StructSep,
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Token::Str("a"),
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Token::Option(true),
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Token::I8(1),
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Token::StructSep,
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Token::Str("d"),
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Token::Str("trouble"),
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Token::StructEnd,
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]
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);
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}
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#[derive(Debug, PartialEq, Serialize)]
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struct SerializeWithStruct<'a, B> where B: SerializeWith {
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a: &'a i8,
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#[serde(serialize_with="Trait::serialize_with")]
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#[serde(serialize_with="SerializeWith::serialize_with")]
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b: B,
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}
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@ -544,10 +608,10 @@ fn test_serialize_with_struct() {
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}
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#[derive(Debug, PartialEq, Serialize)]
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enum SerializeWithEnum<'a, B> where B: Trait {
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enum SerializeWithEnum<'a, B> where B: SerializeWith {
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Struct {
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a: &'a i8,
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#[serde(serialize_with="Trait::serialize_with")]
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#[serde(serialize_with="SerializeWith::serialize_with")]
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b: B,
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}
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}
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@ -597,9 +661,9 @@ fn test_serialize_with_enum() {
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}
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#[derive(Debug, PartialEq, Deserialize)]
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struct DeserializeWithStruct<B> where B: Trait {
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struct DeserializeWithStruct<B> where B: DeserializeWith {
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a: i8,
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#[serde(deserialize_with="Trait::deserialize_with")]
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#[serde(deserialize_with="DeserializeWith::deserialize_with")]
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b: B,
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}
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@ -647,10 +711,10 @@ fn test_deserialize_with_struct() {
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}
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#[derive(Debug, PartialEq, Deserialize)]
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enum DeserializeWithEnum<B> where B: Trait {
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enum DeserializeWithEnum<B> where B: DeserializeWith {
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Struct {
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a: i8,
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#[serde(deserialize_with="Trait::deserialize_with")]
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#[serde(deserialize_with="DeserializeWith::deserialize_with")]
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b: B,
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}
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}
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