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Reduce dependence on type inference

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This commit is contained in:
David Tolnay
2016-05-07 12:33:59 -07:00
parent 8378267b9b
commit f4414bfc14
5 changed files with 178 additions and 61 deletions
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serde_codegen/src/de.rs
+114 -13
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@@ -509,12 +509,14 @@ fn deserialize_seq(
fn deserialize_struct_as_seq(
cx: &ExtCtxt,
builder: &aster::AstBuilder,
type_ident: Ident,
struct_path: ast::Path,
impl_generics: &ast::Generics,
fields: &[(&ast::StructField, attr::FieldAttrs)],
) -> Result<P<ast::Expr>, Error> {
let let_values: Vec<_> = fields.iter()
.enumerate()
.map(|(i, &(_, ref attrs))| {
.map(|(i, &(field, ref attrs))| {
let name = builder.id(format!("__field{}", i));
if attrs.skip_deserializing_field() {
let default = attrs.expr_is_missing();
@@ -522,10 +524,24 @@ fn deserialize_struct_as_seq(
let $name = $default;
).unwrap()
} else {
let deserialize_with = attrs.deserialize_with();
let visit = match attrs.deserialize_with() {
None => {
let field_ty = &field.ty;
quote_expr!(cx, try!(visitor.visit::<$field_ty>()))
}
Some(path) => {
let (wrapper, wrapper_impl, wrapper_ty) = wrap_deserialize_with(
cx, builder, type_ident, impl_generics, &field.ty, path);
quote_expr!(cx, {
$wrapper
$wrapper_impl
try!(visitor.visit::<$wrapper_ty>()).map(|wrap| wrap.value)
})
}
};
quote_stmt!(cx,
let $name = match try!(visitor.visit()) {
Some(value) => { $deserialize_with(value) },
let $name = match $visit {
Some(value) => { value },
None => {
return Err(_serde::de::Error::end_of_stream());
}
@@ -587,14 +603,18 @@ fn deserialize_struct(
let visit_seq_expr = try!(deserialize_struct_as_seq(
cx,
builder,
type_ident,
type_path.clone(),
impl_generics,
&fields_with_attrs,
));
let (field_visitor, fields_stmt, visit_map_expr) = try!(deserialize_struct_visitor(
cx,
builder,
type_ident,
type_path.clone(),
impl_generics,
&fields_with_attrs,
container_attrs,
));
@@ -843,14 +863,18 @@ fn deserialize_struct_variant(
let visit_seq_expr = try!(deserialize_struct_as_seq(
cx,
builder,
type_ident,
type_path.clone(),
generics,
&fields_with_attrs,
));
let (field_visitor, fields_stmt, field_expr) = try!(deserialize_struct_visitor(
cx,
builder,
type_ident,
type_path,
generics,
&fields_with_attrs,
container_attrs,
));
@@ -1011,10 +1035,8 @@ fn deserialize_field_visitor(
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>
phantom: ::std::marker::PhantomData<D>
}
impl<__D> _serde::de::Visitor for __FieldVisitor<__D>
@@ -1041,7 +1063,11 @@ fn deserialize_field_visitor(
}
}
deserializer.deserialize_struct_field(__FieldVisitor::<D>{ phantom: PhantomData })
deserializer.deserialize_struct_field(
__FieldVisitor::<D>{
phantom: ::std::marker::PhantomData
}
)
}
}
).unwrap();
@@ -1052,7 +1078,9 @@ fn deserialize_field_visitor(
fn deserialize_struct_visitor(
cx: &ExtCtxt,
builder: &aster::AstBuilder,
type_ident: Ident,
struct_path: ast::Path,
impl_generics: &ast::Generics,
fields: &[(&ast::StructField, attr::FieldAttrs)],
container_attrs: &attr::ContainerAttrs,
) -> Result<(Vec<P<ast::Item>>, ast::Stmt, P<ast::Expr>), Error> {
@@ -1071,7 +1099,9 @@ fn deserialize_struct_visitor(
let visit_map_expr = try!(deserialize_map(
cx,
builder,
type_ident,
struct_path,
impl_generics,
fields,
container_attrs,
));
@@ -1100,7 +1130,9 @@ fn deserialize_struct_visitor(
fn deserialize_map(
cx: &ExtCtxt,
builder: &aster::AstBuilder,
type_ident: Ident,
struct_path: ast::Path,
impl_generics: &ast::Generics,
fields: &[(&ast::StructField, attr::FieldAttrs)],
container_attrs: &attr::ContainerAttrs,
) -> Result<P<ast::Expr>, Error> {
@@ -1114,17 +1146,34 @@ fn deserialize_map(
// Declare each field that will be deserialized.
let let_values: Vec<ast::Stmt> = fields_attrs_names.iter()
.filter(|&&(_, ref attrs, _)| !attrs.skip_deserializing_field())
.map(|&(_, _, name)| quote_stmt!(cx, let mut $name = None;).unwrap())
.map(|&(field, _, name)| {
let field_ty = &field.ty;
quote_stmt!(cx, let mut $name: Option<$field_ty> = None;).unwrap()
})
.collect();
// Match arms to extract a value for a field.
let value_arms = fields_attrs_names.iter()
.filter(|&&(_, ref attrs, _)| !attrs.skip_deserializing_field())
.map(|&(_, ref attrs, name)| {
let deserialize_with = attrs.deserialize_with();
.map(|&(field, ref attrs, name)| {
let visit = match attrs.deserialize_with() {
None => {
let field_ty = &field.ty;
quote_expr!(cx, try!(visitor.visit_value::<$field_ty>()))
}
Some(path) => {
let (wrapper, wrapper_impl, wrapper_ty) = wrap_deserialize_with(
cx, builder, type_ident, impl_generics, &field.ty, path);
quote_expr!(cx, ({
$wrapper
$wrapper_impl
try!(visitor.visit_value::<$wrapper_ty>()).value
}))
}
};
quote_arm!(cx,
__Field::$name => {
$name = Some($deserialize_with(try!(visitor.visit_value())));
$name = Some($visit);
}
)
})
@@ -1192,7 +1241,7 @@ fn deserialize_map(
Ok(quote_expr!(cx, {
$let_values
while let Some(key) = try!(visitor.visit_key()) {
while let Some(key) = try!(visitor.visit_key::<__Field>()) {
match key {
$value_arms
$skipped_arms
@@ -1222,3 +1271,55 @@ fn fields_with_attrs<'a>(
})
.collect()
}
/// This function wraps the expression in `#[serde(deserialize_with="...")]` in
/// a trait to prevent it from accessing the internal `Deserialize` state.
fn wrap_deserialize_with(
cx: &ExtCtxt,
builder: &aster::AstBuilder,
type_ident: Ident,
impl_generics: &ast::Generics,
field_ty: &P<ast::Ty>,
deserialize_with: &ast::Path,
) -> (ast::Stmt, ast::Stmt, ast::Path) {
// Quasi-quoting doesn't do a great job of expanding generics into paths,
// so manually build it.
let wrapper_ty = builder.path()
.segment("__SerdeDeserializeWithStruct")
.with_generics(impl_generics.clone())
.build()
.build();
let where_clause = &impl_generics.where_clause;
let phantom_ty = builder.path()
.segment(type_ident)
.with_generics(builder.from_generics(impl_generics.clone())
.strip_ty_params()
.build())
.build()
.build();
(
quote_stmt!(cx,
struct __SerdeDeserializeWithStruct $impl_generics $where_clause {
value: $field_ty,
phantom: ::std::marker::PhantomData<$phantom_ty>,
}
).unwrap(),
quote_stmt!(cx,
impl $impl_generics _serde::de::Deserialize for $wrapper_ty $where_clause {
fn deserialize<D>(__d: &mut D) -> ::std::result::Result<Self, D::Error>
where D: _serde::de::Deserializer
{
let value = try!($deserialize_with(__d));
Ok(__SerdeDeserializeWithStruct {
value: value,
phantom: ::std::marker::PhantomData,
})
}
}
).unwrap(),
wrapper_ty,
)
}