serde/serde_codegen/src/de.rs

1067 lines
31 KiB
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use std::collections::HashSet;
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use aster;
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use syntax::ast::{
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self,
EnumDef,
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Ident,
Item,
MetaItem,
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};
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use syntax::codemap::Span;
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use syntax::ext::base::{Annotatable, ExtCtxt};
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use syntax::ext::build::AstBuilder;
use syntax::ptr::P;
use attr;
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use field;
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pub fn expand_derive_deserialize(
cx: &mut ExtCtxt,
span: Span,
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meta_item: &MetaItem,
annotatable: &Annotatable,
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push: &mut FnMut(Annotatable)
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) {
let item = match *annotatable {
Annotatable::Item(ref item) => item,
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_ => {
cx.span_err(
meta_item.span,
"`#[derive(Deserialize)]` may only be applied to structs and enums");
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return;
}
};
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let builder = aster::AstBuilder::new().span(span);
let generics = match item.node {
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ast::ItemKind::Struct(_, ref generics) => generics,
ast::ItemKind::Enum(_, ref generics) => generics,
_ => {
cx.span_err(
meta_item.span,
"`#[derive(Deserialize)]` may only be applied to structs and enums");
return;
}
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};
let impl_generics = builder.from_generics(generics.clone())
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.add_ty_param_bound(
builder.path().global().ids(&["serde", "de", "Deserialize"]).build()
)
.build();
let ty = builder.ty().path()
.segment(item.ident).with_generics(impl_generics.clone()).build()
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.build();
let body = match deserialize_body(cx, &builder, &item, &impl_generics, ty.clone()) {
Ok(body) => body,
Err(()) => {
// An error occured, but it should have been reported already.
return;
}
};
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let where_clause = &impl_generics.where_clause;
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let impl_item = quote_item!(cx,
impl $impl_generics ::serde::de::Deserialize for $ty $where_clause {
fn deserialize<__D>(deserializer: &mut __D) -> ::std::result::Result<$ty, __D::Error>
where __D: ::serde::de::Deserializer,
{
$body
}
}
).unwrap();
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push(Annotatable::Item(impl_item))
}
fn deserialize_body(
cx: &ExtCtxt,
builder: &aster::AstBuilder,
item: &Item,
impl_generics: &ast::Generics,
ty: P<ast::Ty>,
) -> Result<P<ast::Expr>, ()> {
// Note: While we don't have any container attributes, we still want to try to
// parse them so we can report a proper error if we get passed an unknown attribute.
let _ = try!(field::container_attrs(cx, item));
match item.node {
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ast::ItemKind::Struct(ref variant_data, _) => {
deserialize_item_struct(
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cx,
builder,
item,
impl_generics,
ty,
item.span,
variant_data,
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)
}
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ast::ItemKind::Enum(ref enum_def, _) => {
deserialize_item_enum(
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cx,
builder,
item.ident,
impl_generics,
ty,
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enum_def,
)
}
_ => {
cx.span_bug(item.span,
"expected ItemStruct or ItemEnum in #[derive(Deserialize)]")
}
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}
}
fn deserialize_item_struct(
cx: &ExtCtxt,
builder: &aster::AstBuilder,
item: &Item,
impl_generics: &ast::Generics,
ty: P<ast::Ty>,
span: Span,
variant_data: &ast::VariantData,
) -> Result<P<ast::Expr>, ()> {
match *variant_data {
ast::VariantData::Unit(_) => {
deserialize_unit_struct(
cx,
&builder,
item.ident,
)
}
ast::VariantData::Tuple(ref fields, _) if fields.len() == 1 => {
deserialize_newtype_struct(
cx,
&builder,
item.ident,
impl_generics,
ty,
)
}
ast::VariantData::Tuple(ref fields, _) => {
if fields.iter().any(|field| !field.node.kind.is_unnamed()) {
cx.span_bug(span, "tuple struct has named fields")
}
deserialize_tuple_struct(
cx,
&builder,
item.ident,
impl_generics,
ty,
fields.len(),
)
}
ast::VariantData::Struct(ref fields, _) => {
if fields.iter().any(|field| field.node.kind.is_unnamed()) {
cx.span_bug(span, "struct has unnamed fields")
}
deserialize_struct(
cx,
&builder,
item.ident,
impl_generics,
ty,
fields,
)
}
}
}
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// Build `__Visitor<A, B, ...>(PhantomData<A>, PhantomData<B>, ...)`
fn deserialize_visitor(
builder: &aster::AstBuilder,
trait_generics: &ast::Generics,
forward_ty_params: Vec<ast::TyParam>,
forward_tys: Vec<P<ast::Ty>>
) -> Result<(P<ast::Item>, P<ast::Ty>, P<ast::Expr>, ast::Generics), ()> {
if trait_generics.ty_params.is_empty() && forward_tys.is_empty() {
Ok((
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builder.item().tuple_struct("__Visitor").build(),
builder.ty().id("__Visitor"),
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builder.expr().id("__Visitor"),
trait_generics.clone(),
))
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} else {
let placeholders : Vec<_> = trait_generics.ty_params.iter()
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.map(|t| builder.ty().id(t.ident))
.collect();
let mut trait_generics = trait_generics.clone();
let mut ty_params = forward_ty_params.clone();
ty_params.extend(trait_generics.ty_params.into_vec());
trait_generics.ty_params = P::from_vec(ty_params);
Ok((
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builder.item().tuple_struct("__Visitor")
.generics().with(trait_generics.clone()).build()
.with_tys({
let lifetimes = trait_generics.lifetimes.iter()
.map(|lifetime_def| {
builder.ty()
.phantom_data()
.ref_().lifetime(lifetime_def.lifetime.name)
.ty()
.unit()
});
let ty_params = trait_generics.ty_params.iter()
.map(|ty_param| {
builder.ty()
.phantom_data()
.id(ty_param.ident)
});
lifetimes.chain(ty_params)
})
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.build(),
builder.ty().path()
.segment("__Visitor").with_generics(trait_generics.clone()).build()
.build(),
builder.expr().call()
.path().segment("__Visitor")
.with_tys(forward_tys)
.with_tys(placeholders)
.build().build()
.with_args({
let len = trait_generics.lifetimes.len() + trait_generics.ty_params.len();
(0 .. len).map(|_| builder.expr().phantom_data())
})
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.build(),
trait_generics,
))
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}
}
fn deserializer_ty_param(builder: &aster::AstBuilder) -> ast::TyParam {
builder.ty_param("__D")
.trait_bound(builder.path()
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.global()
.segment("serde").build()
.segment("de").build()
.id("Deserializer")
.build())
.build()
.build()
}
fn deserializer_ty_arg(builder: &aster::AstBuilder) -> P<ast::Ty>{
builder.ty().id("__D")
}
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fn deserialize_unit_struct(
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cx: &ExtCtxt,
builder: &aster::AstBuilder,
type_ident: Ident,
) -> Result<P<ast::Expr>, ()> {
let type_name = builder.expr().str(type_ident);
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Ok(quote_expr!(cx, {
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struct __Visitor;
impl ::serde::de::Visitor for __Visitor {
type Value = $type_ident;
#[inline]
fn visit_unit<E>(&mut self) -> ::std::result::Result<$type_ident, E>
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where E: ::serde::de::Error,
{
Ok($type_ident)
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}
#[inline]
fn visit_seq<V>(&mut self, mut visitor: V) -> ::std::result::Result<$type_ident, V::Error>
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where V: ::serde::de::SeqVisitor,
{
try!(visitor.end());
self.visit_unit()
}
}
deserializer.visit_unit_struct($type_name, __Visitor)
}))
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}
fn deserialize_newtype_struct(
cx: &ExtCtxt,
builder: &aster::AstBuilder,
type_ident: Ident,
impl_generics: &ast::Generics,
ty: P<ast::Ty>,
) -> Result<P<ast::Expr>, ()> {
let where_clause = &impl_generics.where_clause;
let (visitor_item, visitor_ty, visitor_expr, visitor_generics) = try!(deserialize_visitor(
builder,
impl_generics,
vec![deserializer_ty_param(builder)],
vec![deserializer_ty_arg(builder)],
));
let visit_seq_expr = deserialize_seq(
cx,
builder,
builder.path().id(type_ident).build(),
1,
);
let type_name = builder.expr().str(type_ident);
Ok(quote_expr!(cx, {
$visitor_item
impl $visitor_generics ::serde::de::Visitor for $visitor_ty $where_clause {
type Value = $ty;
#[inline]
fn visit_newtype_struct<D>(&mut self, deserializer: &mut D) -> ::std::result::Result<Self::Value, D::Error>
where D: ::serde::de::Deserializer,
{
let value = try!(::serde::de::Deserialize::deserialize(deserializer));
Ok($type_ident(value))
}
#[inline]
fn visit_seq<__V>(&mut self, mut visitor: __V) -> ::std::result::Result<$ty, __V::Error>
where __V: ::serde::de::SeqVisitor,
{
$visit_seq_expr
}
}
deserializer.visit_newtype_struct($type_name, $visitor_expr)
}))
}
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fn deserialize_tuple_struct(
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cx: &ExtCtxt,
builder: &aster::AstBuilder,
type_ident: Ident,
impl_generics: &ast::Generics,
ty: P<ast::Ty>,
fields: usize,
) -> Result<P<ast::Expr>, ()> {
let where_clause = &impl_generics.where_clause;
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let (visitor_item, visitor_ty, visitor_expr, visitor_generics) = try!(deserialize_visitor(
builder,
impl_generics,
vec![deserializer_ty_param(builder)],
vec![deserializer_ty_arg(builder)],
));
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let visit_seq_expr = deserialize_seq(
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cx,
builder,
builder.path().id(type_ident).build(),
fields,
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);
let type_name = builder.expr().str(type_ident);
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Ok(quote_expr!(cx, {
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$visitor_item
impl $visitor_generics ::serde::de::Visitor for $visitor_ty $where_clause {
type Value = $ty;
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#[inline]
fn visit_seq<__V>(&mut self, mut visitor: __V) -> ::std::result::Result<$ty, __V::Error>
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where __V: ::serde::de::SeqVisitor,
{
$visit_seq_expr
}
}
deserializer.visit_tuple_struct($type_name, $fields, $visitor_expr)
}))
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}
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fn deserialize_seq(
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cx: &ExtCtxt,
builder: &aster::AstBuilder,
struct_path: ast::Path,
fields: usize,
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) -> P<ast::Expr> {
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let let_values: Vec<P<ast::Stmt>> = (0 .. fields)
.map(|i| {
let name = builder.id(format!("__field{}", i));
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quote_stmt!(cx,
let $name = match try!(visitor.visit()) {
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Some(value) => { value },
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None => {
return Err(::serde::de::Error::end_of_stream());
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}
};
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).unwrap()
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})
.collect();
let result = builder.expr().call()
.build_path(struct_path)
.with_args((0 .. fields).map(|i| builder.expr().id(format!("__field{}", i))))
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.build();
quote_expr!(cx, {
$let_values
try!(visitor.end());
Ok($result)
})
}
fn deserialize_struct_as_seq(
cx: &ExtCtxt,
builder: &aster::AstBuilder,
struct_path: ast::Path,
fields: &[ast::StructField],
) -> Result<P<ast::Expr>, ()> {
let let_values: Vec<P<ast::Stmt>> = (0 .. fields.len())
.map(|i| {
let name = builder.id(format!("__field{}", i));
quote_stmt!(cx,
let $name = match try!(visitor.visit()) {
Some(value) => { value },
None => {
return Err(::serde::de::Error::end_of_stream());
}
};
).unwrap()
})
.collect();
let result = builder.expr().struct_path(struct_path)
.with_id_exprs(
fields.iter()
.enumerate()
.map(|(i, field)| {
(
match field.node.kind {
ast::NamedField(name, _) => name.clone(),
ast::UnnamedField(_) => {
cx.span_bug(field.span, "struct contains unnamed fields")
}
},
builder.expr().id(format!("__field{}", i)),
)
})
)
.build();
Ok(quote_expr!(cx, {
$let_values
try!(visitor.end());
Ok($result)
}))
}
fn deserialize_struct(
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cx: &ExtCtxt,
builder: &aster::AstBuilder,
type_ident: Ident,
impl_generics: &ast::Generics,
ty: P<ast::Ty>,
fields: &[ast::StructField],
) -> Result<P<ast::Expr>, ()> {
let where_clause = &impl_generics.where_clause;
let (visitor_item, visitor_ty, visitor_expr, visitor_generics) = try!(deserialize_visitor(
builder,
&impl_generics,
vec![deserializer_ty_param(builder)],
vec![deserializer_ty_arg(builder)],
));
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let type_path = builder.path().id(type_ident).build();
let visit_seq_expr = try!(deserialize_struct_as_seq(
cx,
builder,
type_path.clone(),
fields,
));
let (field_visitor, fields_stmt, visit_map_expr) = try!(deserialize_struct_visitor(
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cx,
builder,
type_path.clone(),
fields,
));
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let type_name = builder.expr().str(type_ident);
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Ok(quote_expr!(cx, {
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$field_visitor
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$visitor_item
impl $visitor_generics ::serde::de::Visitor for $visitor_ty $where_clause {
type Value = $ty;
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#[inline]
fn visit_seq<__V>(&mut self, mut visitor: __V) -> ::std::result::Result<$ty, __V::Error>
where __V: ::serde::de::SeqVisitor,
{
$visit_seq_expr
}
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#[inline]
fn visit_map<__V>(&mut self, mut visitor: __V) -> ::std::result::Result<$ty, __V::Error>
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where __V: ::serde::de::MapVisitor,
{
$visit_map_expr
}
}
$fields_stmt
deserializer.visit_struct($type_name, FIELDS, $visitor_expr)
}))
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}
fn deserialize_item_enum(
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cx: &ExtCtxt,
builder: &aster::AstBuilder,
type_ident: Ident,
impl_generics: &ast::Generics,
ty: P<ast::Ty>,
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enum_def: &EnumDef,
) -> Result<P<ast::Expr>, ()> {
let where_clause = &impl_generics.where_clause;
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let type_name = builder.expr().str(type_ident);
let variant_visitor = deserialize_field_visitor(
cx,
builder,
enum_def.variants.iter()
.map(|variant| {
let expr = builder.expr().str(variant.node.name);
attr::FieldAttrsBuilder::new(cx, builder)
.name(expr)
.default()
.build()
})
.collect()
);
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let variants_expr = builder.expr().ref_().slice()
.with_exprs(
enum_def.variants.iter()
.map(|variant| {
builder.expr().str(variant.node.name)
})
)
.build();
let variants_stmt = quote_stmt!(cx,
const VARIANTS: &'static [&'static str] = $variants_expr;
).unwrap();
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// Match arms to extract a variant from a string
let mut variant_arms = vec![];
for (i, variant) in enum_def.variants.iter().enumerate() {
let variant_name = builder.pat().enum_()
.id("__Field").id(format!("__field{}", i)).build()
.build();
let expr = try!(deserialize_variant(
cx,
builder,
type_ident,
impl_generics,
ty.clone(),
variant,
));
let arm = quote_arm!(cx, $variant_name => { $expr });
variant_arms.push(arm);
}
let (visitor_item, visitor_ty, visitor_expr, visitor_generics) = try!(deserialize_visitor(
builder,
impl_generics,
vec![deserializer_ty_param(builder)],
vec![deserializer_ty_arg(builder)],
));
Ok(quote_expr!(cx, {
$variant_visitor
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$visitor_item
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impl $visitor_generics ::serde::de::EnumVisitor for $visitor_ty $where_clause {
type Value = $ty;
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fn visit<__V>(&mut self, mut visitor: __V) -> ::std::result::Result<$ty, __V::Error>
where __V: ::serde::de::VariantVisitor,
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{
match try!(visitor.visit_variant()) {
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$variant_arms
}
}
}
$variants_stmt
deserializer.visit_enum($type_name, VARIANTS, $visitor_expr)
}))
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}
fn deserialize_variant(
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cx: &ExtCtxt,
builder: &aster::AstBuilder,
type_ident: Ident,
generics: &ast::Generics,
ty: P<ast::Ty>,
variant: &ast::Variant,
) -> Result<P<ast::Expr>, ()> {
let variant_ident = variant.node.name;
match variant.node.data {
ast::VariantData::Unit(_) => {
Ok(quote_expr!(cx, {
try!(visitor.visit_unit());
Ok($type_ident::$variant_ident)
}))
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}
ast::VariantData::Tuple(ref args, _) if args.len() == 1 => {
Ok(quote_expr!(cx, {
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let val = try!(visitor.visit_newtype());
Ok($type_ident::$variant_ident(val))
}))
}
ast::VariantData::Tuple(ref fields, _) => {
deserialize_tuple_variant(
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cx,
builder,
type_ident,
variant_ident,
generics,
ty,
fields.len(),
)
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}
ast::VariantData::Struct(ref fields, _) => {
deserialize_struct_variant(
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cx,
builder,
type_ident,
variant_ident,
generics,
ty,
fields,
)
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}
}
}
fn deserialize_tuple_variant(
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cx: &ExtCtxt,
builder: &aster::AstBuilder,
type_ident: ast::Ident,
variant_ident: ast::Ident,
generics: &ast::Generics,
ty: P<ast::Ty>,
fields: usize,
) -> Result<P<ast::Expr>, ()> {
let where_clause = &generics.where_clause;
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let (visitor_item, visitor_ty, visitor_expr, visitor_generics) = try!(deserialize_visitor(
builder,
generics,
vec![deserializer_ty_param(builder)],
vec![deserializer_ty_arg(builder)],
));
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let visit_seq_expr = deserialize_seq(
cx,
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builder,
builder.path().id(type_ident).id(variant_ident).build(),
fields,
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);
Ok(quote_expr!(cx, {
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$visitor_item
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impl $visitor_generics ::serde::de::Visitor for $visitor_ty $where_clause {
type Value = $ty;
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fn visit_seq<__V>(&mut self, mut visitor: __V) -> ::std::result::Result<$ty, __V::Error>
where __V: ::serde::de::SeqVisitor,
{
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$visit_seq_expr
}
}
visitor.visit_tuple($fields, $visitor_expr)
}))
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}
fn deserialize_struct_variant(
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cx: &ExtCtxt,
builder: &aster::AstBuilder,
type_ident: ast::Ident,
variant_ident: ast::Ident,
generics: &ast::Generics,
ty: P<ast::Ty>,
fields: &[ast::StructField],
) -> Result<P<ast::Expr>, ()> {
let where_clause = &generics.where_clause;
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let type_path = builder.path()
.id(type_ident)
.id(variant_ident)
.build();
let visit_seq_expr = try!(deserialize_struct_as_seq(
cx,
builder,
type_path.clone(),
fields,
));
let (field_visitor, fields_stmt, field_expr) = try!(deserialize_struct_visitor(
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cx,
builder,
type_path,
fields,
));
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let (visitor_item, visitor_ty, visitor_expr, visitor_generics) = try!(deserialize_visitor(
builder,
generics,
vec![deserializer_ty_param(builder)],
vec![deserializer_ty_arg(builder)],
));
Ok(quote_expr!(cx, {
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$field_visitor
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$visitor_item
impl $visitor_generics ::serde::de::Visitor for $visitor_ty $where_clause {
type Value = $ty;
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#[inline]
fn visit_seq<__V>(&mut self, mut visitor: __V) -> ::std::result::Result<$ty, __V::Error>
where __V: ::serde::de::SeqVisitor,
{
$visit_seq_expr
}
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#[inline]
fn visit_map<__V>(&mut self, mut visitor: __V) -> ::std::result::Result<$ty, __V::Error>
where __V: ::serde::de::MapVisitor,
{
$field_expr
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}
}
$fields_stmt
visitor.visit_struct(FIELDS, $visitor_expr)
}))
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}
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fn deserialize_field_visitor(
cx: &ExtCtxt,
builder: &aster::AstBuilder,
field_attrs: Vec<attr::FieldAttrs>,
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) -> Vec<P<ast::Item>> {
// Create the field names for the fields.
let field_idents: Vec<ast::Ident> = (0 .. field_attrs.len())
.map(|i| builder.id(format!("__field{}", i)))
.collect();
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let field_enum = builder.item()
.attr().allow(&["non_camel_case_types"])
.enum_("__Field")
.with_variants(
field_idents.iter().map(|field_ident| {
builder.variant(field_ident).unit()
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})
)
.build();
let index_field_arms: Vec<_> = field_idents.iter()
.enumerate()
.map(|(field_index, field_ident)| {
quote_arm!(cx, $field_index => { Ok(__Field::$field_ident) })
})
.collect();
let index_body = quote_expr!(cx,
match value {
$index_field_arms
_ => { Err(::serde::de::Error::syntax("expected a field")) }
}
);
// A set of all the formats that have specialized field attributes
let formats = field_attrs.iter()
.fold(HashSet::new(), |mut set, field_expr| {
set.extend(field_expr.formats());
set
});
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// Match arms to extract a field from a string
let default_field_arms: Vec<_> = field_idents.iter()
.zip(field_attrs.iter())
.map(|(field_ident, field_expr)| {
let expr = field_expr.default_key_expr();
quote_arm!(cx, $expr => { Ok(__Field::$field_ident) })
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})
.collect();
let str_body = if formats.is_empty() {
// No formats specific attributes, so no match on format required
quote_expr!(cx,
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match value {
$default_field_arms
_ => { Err(::serde::de::Error::unknown_field(value)) }
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})
} else {
let field_arms: Vec<_> = formats.iter()
.map(|fmt| {
field_idents.iter()
.zip(field_attrs.iter())
.map(|(field_ident, field_expr)| {
let expr = field_expr.key_expr(fmt);
quote_arm!(cx, $expr => { Ok(__Field::$field_ident) })
})
.collect::<Vec<_>>()
})
.collect();
let fmt_matches: Vec<_> = formats.iter()
.zip(field_arms.iter())
.map(|(ref fmt, ref arms)| {
quote_arm!(cx, $fmt => {
match value {
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$arms
_ => {
Err(::serde::de::Error::unknown_field(value))
}
}})
})
.collect();
quote_expr!(cx,
match __D::format() {
$fmt_matches
_ => match value {
$default_field_arms
_ => { Err(::serde::de::Error::unknown_field(value)) }
}
}
)
};
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let impl_item = quote_item!(cx,
impl ::serde::de::Deserialize for __Field {
#[inline]
fn deserialize<D>(deserializer: &mut D) -> ::std::result::Result<__Field, D::Error>
where D: ::serde::de::Deserializer,
{
use std::marker::PhantomData;
struct __FieldVisitor<D> {
phantom: PhantomData<D>
}
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impl<__D> ::serde::de::Visitor for __FieldVisitor<__D>
where __D: ::serde::de::Deserializer
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{
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type Value = __Field;
fn visit_usize<E>(&mut self, value: usize) -> ::std::result::Result<__Field, E>
where E: ::serde::de::Error,
{
$index_body
}
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fn visit_str<E>(&mut self, value: &str) -> ::std::result::Result<__Field, E>
where E: ::serde::de::Error,
{
$str_body
}
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fn visit_bytes<E>(&mut self, value: &[u8]) -> ::std::result::Result<__Field, E>
where E: ::serde::de::Error,
{
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// TODO: would be better to generate a byte string literal match
match ::std::str::from_utf8(value) {
Ok(s) => self.visit_str(s),
_ => {
Err(
::serde::de::Error::syntax(
"could not convert a byte string to a String"
)
)
}
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}
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}
}
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deserializer.visit_struct_key(__FieldVisitor::<D>{ phantom: PhantomData })
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}
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}
).unwrap();
vec![field_enum, impl_item]
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}
fn deserialize_struct_visitor(
cx: &ExtCtxt,
builder: &aster::AstBuilder,
struct_path: ast::Path,
fields: &[ast::StructField],
) -> Result<(Vec<P<ast::Item>>, P<ast::Stmt>, P<ast::Expr>), ()> {
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let field_visitor = deserialize_field_visitor(
cx,
builder,
try!(field::struct_field_attrs(cx, builder, fields)),
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);
let visit_map_expr = try!(deserialize_map(
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cx,
builder,
struct_path,
fields,
));
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let fields_expr = builder.expr().ref_().slice()
.with_exprs(
fields.iter()
.map(|field| {
match field.node.kind {
ast::NamedField(name, _) => builder.expr().str(name),
ast::UnnamedField(_) => {
cx.span_bug(field.span, "struct contains unnamed fields")
}
}
})
)
.build();
let fields_stmt = quote_stmt!(cx,
const FIELDS: &'static [&'static str] = $fields_expr;
).unwrap();
Ok((field_visitor, fields_stmt, visit_map_expr))
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}
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fn deserialize_map(
cx: &ExtCtxt,
builder: &aster::AstBuilder,
struct_path: ast::Path,
fields: &[ast::StructField],
) -> Result<P<ast::Expr>, ()> {
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// Create the field names for the fields.
let field_names: Vec<ast::Ident> = (0 .. fields.len())
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.map(|i| builder.id(format!("__field{}", i)))
.collect();
// Declare each field.
let let_values: Vec<P<ast::Stmt>> = field_names.iter()
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.map(|field_name| quote_stmt!(cx, let mut $field_name = None;).unwrap())
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.collect();
// Match arms to extract a value for a field.
let value_arms: Vec<ast::Arm> = field_names.iter()
.map(|field_name| {
quote_arm!(cx,
__Field::$field_name => {
$field_name = Some(try!(visitor.visit_value()));
}
)
})
.collect();
let field_attrs = try!(field::struct_field_attrs(cx, builder, fields));
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let extract_values: Vec<P<ast::Stmt>> = field_names.iter()
.zip(field_attrs.iter())
.map(|(field_name, field_attr)| {
let missing_expr = if field_attr.use_default() {
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quote_expr!(cx, ::std::default::Default::default())
} else {
let formats = field_attr.formats();
let arms : Vec<_> = formats.iter()
.map(|format| {
let key_expr = field_attr.key_expr(format);
quote_arm!(cx, $format => { $key_expr })
})
.collect();
let default = field_attr.default_key_expr();
if arms.is_empty() {
quote_expr!(cx, try!(visitor.missing_field($default)))
} else {
quote_expr!(
cx,
try!(visitor.missing_field(
match __D::format() {
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$arms
_ => { $default }
})))
}
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};
quote_stmt!(cx,
let $field_name = match $field_name {
Some($field_name) => $field_name,
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None => $missing_expr
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};
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).unwrap()
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})
.collect();
let result = builder.expr().struct_path(struct_path)
.with_id_exprs(
fields.iter()
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.zip(field_names.iter())
.map(|(field, field_name)| {
(
match field.node.kind {
ast::NamedField(name, _) => name.clone(),
ast::UnnamedField(_) => {
cx.span_bug(field.span, "struct contains unnamed fields")
}
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},
builder.expr().id(field_name),
)
})
)
.build();
Ok(quote_expr!(cx, {
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$let_values
while let Some(key) = try!(visitor.visit_key()) {
match key {
$value_arms
}
}
$extract_values
try!(visitor.end());
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Ok($result)
}))
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}