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//! Extensions for [`syn`] types.
use proc_macro2::Span;
use sealed::sealed;
use syn::{punctuated::Punctuated, token};
/// Extension of a [`syn::Data`].
#[sealed]
pub trait Data {
/// Parses [`syn::Fields::Named`] from this consumed [`syn::Data::Struct`]
/// and returns owning iterator over them.
///
/// # Errors
///
/// - If this [`syn::Data`] is not a [`syn::Data::Struct`].
/// - If this [`syn::Data::Struct`] doesn't consist of
/// [`syn::Fields::Named`].
fn named_fields(self) -> syn::Result<Punctuated<syn::Field, token::Comma>>;
/// Parses [`syn::Fields::Named`] from this borrowed [`syn::Data::Struct`]
/// and returns referencing iterator over them.
///
/// # Errors
///
/// - If this [`syn::Data`] is not a [`syn::Data::Struct`].
/// - If this [`syn::Data::Struct`] doesn't consist of
/// [`syn::Fields::Named`].
fn named_fields_ref(
&self,
) -> syn::Result<&Punctuated<syn::Field, token::Comma>>;
/// Parses [`syn::Fields::Unnamed`] from this consumed [`syn::Data::Struct`]
/// and returns owning iterator over them.
///
/// # Errors
///
/// - If this [`syn::Data`] is not a [`syn::Data::Struct`].
/// - If this [`syn::Data::Struct`] doesn't consist of
/// [`syn::Fields::Unnamed`].
fn unnamed_fields(
self,
) -> syn::Result<Punctuated<syn::Field, token::Comma>>;
/// Parses [`syn::Fields::Unnamed`] from this borrowed [`syn::Data::Struct`]
/// and returns referencing iterator over them.
///
/// # Errors
///
/// - If this [`syn::Data`] is not a [`syn::Data::Struct`].
/// - If this [`syn::Data::Struct`] doesn't consist of
/// [`syn::Fields::Unnamed`].
fn unnamed_fields_ref(
&self,
) -> syn::Result<&Punctuated<syn::Field, token::Comma>>;
}
#[sealed]
impl Data for syn::Data {
fn named_fields(self) -> syn::Result<Punctuated<syn::Field, token::Comma>> {
match self {
syn::Data::Struct(data) => match data.fields {
syn::Fields::Named(f) => Ok(f.named),
fields @ (syn::Fields::Unnamed(_) | syn::Fields::Unit) => {
Err(syn::Error::new_spanned(
fields,
"expected named struct fields only",
))
}
},
syn::Data::Enum(data) => Err(syn::Error::new_spanned(
data.enum_token,
"expected struct only",
)),
syn::Data::Union(data) => Err(syn::Error::new_spanned(
data.union_token,
"expected struct only",
)),
}
}
fn named_fields_ref(
&self,
) -> syn::Result<&Punctuated<syn::Field, token::Comma>> {
match self {
syn::Data::Struct(data) => match &data.fields {
syn::Fields::Named(f) => Ok(&f.named),
fields @ (syn::Fields::Unnamed(_) | syn::Fields::Unit) => {
Err(syn::Error::new_spanned(
fields,
"expected named struct fields only",
))
}
},
syn::Data::Enum(data) => Err(syn::Error::new_spanned(
data.enum_token,
"expected struct only",
)),
syn::Data::Union(data) => Err(syn::Error::new_spanned(
data.union_token,
"expected struct only",
)),
}
}
fn unnamed_fields(
self,
) -> syn::Result<Punctuated<syn::Field, token::Comma>> {
match self {
syn::Data::Struct(data) => match data.fields {
syn::Fields::Unnamed(f) => Ok(f.unnamed),
fields @ (syn::Fields::Named(_) | syn::Fields::Unit) => {
Err(syn::Error::new_spanned(
fields,
"expected unnamed struct fields only",
))
}
},
syn::Data::Enum(data) => Err(syn::Error::new_spanned(
data.enum_token,
"expected struct only",
)),
syn::Data::Union(data) => Err(syn::Error::new_spanned(
data.union_token,
"expected struct only",
)),
}
}
fn unnamed_fields_ref(
&self,
) -> syn::Result<&Punctuated<syn::Field, token::Comma>> {
match self {
syn::Data::Struct(data) => match &data.fields {
syn::Fields::Unnamed(f) => Ok(&f.unnamed),
fields @ (syn::Fields::Named(_) | syn::Fields::Unit) => {
Err(syn::Error::new_spanned(
fields,
"expected unnamed struct fields only",
))
}
},
syn::Data::Enum(data) => Err(syn::Error::new_spanned(
data.enum_token,
"expected struct only",
)),
syn::Data::Union(data) => Err(syn::Error::new_spanned(
data.union_token,
"expected struct only",
)),
}
}
}
/// Extension of a [`syn::Ident`](struct@syn::Ident).
#[sealed]
pub trait Ident {
/// Creates a new [`syn::Ident`] out of the given string value with a
/// [`Span::call_site`].
///
/// [`syn::Ident`]: struct@syn::Ident
#[must_use]
fn new_on_call_site(ident: &str) -> syn::Ident;
}
#[sealed]
impl Ident for syn::Ident {
#[inline]
fn new_on_call_site(string: &str) -> Self {
Self::new(string, Span::call_site())
}
}