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use attr;
use proc_macro2;
use syn;
use syn::spanned::Spanned as SynSpanned;
#[derive(Debug)]
pub struct Input<'a> {
pub attrs: attr::Input,
pub body: Body<'a>,
pub generics: &'a syn::Generics,
pub ident: syn::Ident,
pub span: proc_macro2::Span,
}
#[derive(Debug)]
pub enum Body<'a> {
Enum(Vec<Variant<'a>>),
Struct(Style, Vec<Field<'a>>),
}
#[derive(Debug)]
pub struct Variant<'a> {
pub attrs: attr::Input,
pub fields: Vec<Field<'a>>,
pub ident: syn::Ident,
pub style: Style,
}
#[derive(Debug)]
pub struct Field<'a> {
pub attrs: attr::Field,
pub ident: Option<syn::Ident>,
pub ty: &'a syn::Type,
pub span: proc_macro2::Span,
}
#[derive(Clone, Copy, Debug)]
pub enum Style {
Struct,
Tuple,
Unit,
}
impl<'a> Input<'a> {
pub fn from_ast(
item: &'a syn::DeriveInput,
errors: &mut proc_macro2::TokenStream,
) -> Result<Input<'a>, ()> {
let attrs = attr::Input::from_ast(&item.attrs, errors)?;
let body = match item.data {
syn::Data::Enum(syn::DataEnum { ref variants, .. }) => {
Body::Enum(enum_from_ast(variants, errors)?)
}
syn::Data::Struct(syn::DataStruct { ref fields, .. }) => {
let (style, fields) = struct_from_ast(fields, errors)?;
Body::Struct(style, fields)
}
syn::Data::Union(..) => {
errors.extend(
syn::Error::new_spanned(item, "derivative does not support unions")
.to_compile_error(),
);
return Err(());
}
};
Ok(Input {
attrs,
body,
generics: &item.generics,
ident: item.ident.clone(),
span: item.span(),
})
}
pub fn is_trivial_enum(&self) -> bool {
match &self.body {
Body::Enum(e) => e.iter().all(|v| v.is_unit()),
Body::Struct(..) => false,
}
}
}
impl<'a> Body<'a> {
pub fn all_fields(&self) -> Vec<&Field> {
match *self {
Body::Enum(ref variants) => variants
.iter()
.flat_map(|variant| variant.fields.iter())
.collect(),
Body::Struct(_, ref fields) => fields.iter().collect(),
}
}
pub fn is_empty(&self) -> bool {
match *self {
Body::Enum(ref variants) => variants.is_empty(),
Body::Struct(_, ref fields) => fields.is_empty(),
}
}
}
impl<'a> Variant<'a> {
pub fn is_unit(&self) -> bool {
self.fields.is_empty()
}
}
fn enum_from_ast<'a>(
variants: &'a syn::punctuated::Punctuated<syn::Variant, syn::token::Comma>,
errors: &mut proc_macro2::TokenStream,
) -> Result<Vec<Variant<'a>>, ()> {
variants
.iter()
.map(|variant| {
let (style, fields) = struct_from_ast(&variant.fields, errors)?;
Ok(Variant {
attrs: attr::Input::from_ast(&variant.attrs, errors)?,
fields,
ident: variant.ident.clone(),
style,
})
})
.collect()
}
fn struct_from_ast<'a>(
fields: &'a syn::Fields,
errors: &mut proc_macro2::TokenStream,
) -> Result<(Style, Vec<Field<'a>>), ()> {
match *fields {
syn::Fields::Named(ref fields) => {
Ok((Style::Struct, fields_from_ast(&fields.named, errors)?))
}
syn::Fields::Unnamed(ref fields) => {
Ok((Style::Tuple, fields_from_ast(&fields.unnamed, errors)?))
}
syn::Fields::Unit => Ok((Style::Unit, Vec::new())),
}
}
fn fields_from_ast<'a>(
fields: &'a syn::punctuated::Punctuated<syn::Field, syn::token::Comma>,
errors: &mut proc_macro2::TokenStream,
) -> Result<Vec<Field<'a>>, ()> {
fields
.iter()
.map(|field| {
Ok(Field {
attrs: attr::Field::from_ast(field, errors)?,
ident: field.ident.clone(),
ty: &field.ty,
span: field.span(),
})
})
.collect()
}