swc_macros_common/binder.rs
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//! # Example
//!
//! `_binded_a`, `_binded_b` and `_binded_0` in below example are
//! `BindedField`.
//!
//! ```rust
//! struct S {
//! a: u8,
//! b: u16,
//! }
//! let s = S { a: 0, b: 0 };
//! match s {
//! S {
//! a: _binded_a,
//! b: _binded_b,
//! } => {}
//! }
//! enum E {
//! V1 { a: u8 },
//! V2(u16),
//! V3,
//! }
//! let e = E::V1 { a: 0 };
//! match e {
//! E::V1 { a: _binded_a } => {}
//! E::V2(_binded_0) => {}
//! E::V3 => {}
//! }
//! ```
//!
//!
//! -----
//!
//! Adopted from `synstructure`.
use proc_macro2::TokenStream;
use quote::ToTokens;
use syn::{
punctuated::Pair,
token::{Mut, Ref},
*,
};
use crate::{def_site, is_attr_name, syn_ext::PairExt};
/// Used to bind whole struct or enum.
#[derive(Debug, Clone)]
pub struct Binder<'a> {
ident: &'a Ident,
body: &'a Data,
attrs: &'a [Attribute],
}
impl<'a> Binder<'a> {
///
/// - `attrs`: Attributes of the type.
pub const fn new(ident: &'a Ident, body: &'a Data, attrs: &'a [Attribute]) -> Self {
Binder { ident, body, attrs }
}
pub fn new_from(input: &'a DeriveInput) -> Self {
Self::new(&input.ident, &input.data, &input.attrs)
}
pub fn variants(&self) -> Vec<VariantBinder<'a>> {
match *self.body {
Data::Enum(DataEnum { ref variants, .. }) => {
let enum_name = &self.ident;
variants
.iter()
.map(|v| VariantBinder::new(Some(enum_name), &v.ident, &v.fields, &v.attrs))
.collect()
}
Data::Struct(DataStruct { ref fields, .. }) => {
vec![VariantBinder::new(None, self.ident, fields, self.attrs)]
}
Data::Union(_) => unimplemented!("Binder for union type"),
}
}
}
/// Variant.
#[derive(Debug, Clone)]
pub struct VariantBinder<'a> {
/// None for struct.
enum_name: Option<&'a Ident>,
/// Name of variant.
name: &'a Ident,
data: &'a Fields,
attrs: &'a [Attribute],
}
impl<'a> VariantBinder<'a> {
pub const fn new(
enum_name: Option<&'a Ident>,
name: &'a Ident,
data: &'a Fields,
attrs: &'a [Attribute],
) -> Self {
VariantBinder {
enum_name,
name,
data,
attrs,
}
}
pub const fn variant_name(&self) -> &Ident {
self.name
}
pub const fn data(&self) -> &Fields {
self.data
}
pub const fn attrs(&self) -> &[Attribute] {
self.attrs
}
/// `EnumName::VariantName` for enum, and `StructName` for struct.
pub fn qual_path(&self) -> Path {
match self.enum_name {
Some(enum_name) => {
let vn = &self.name;
parse_quote!(#enum_name::#vn)
}
None => self.name.clone().into(),
}
}
///
/// - `prefix`: prefix of field binding.
pub fn bind(
&self,
prefix: &str,
by_ref: Option<Ref>,
mutability: Option<Mut>,
) -> (Pat, Vec<BindedField<'a>>) {
let path = self.qual_path();
let (pat, bindings) = match *self.data {
Fields::Unit => {
// EnumName::VariantName
let pat = Pat::Path(PatPath {
qself: None,
path,
attrs: Default::default(),
});
// Unit struct does not have any field to bind
(pat, Vec::new())
}
Fields::Named(FieldsNamed {
named: ref fields,
brace_token,
}) => {
let mut bindings = Vec::new();
let fields = fields
.pairs()
.map(|e| {
let (t, p) = e.into_tuple();
Pair::new(t, p.cloned())
})
.enumerate()
.map(|(idx, f)| {
f.map_item(|f| {
let ident = f
.ident
.clone()
.expect("field of struct-like variants should have name");
let binded_ident =
Ident::new(&format!("{}{}", prefix, ident), ident.span());
bindings.push(BindedField {
idx,
binded_ident: binded_ident.clone(),
field: f,
});
FieldPat {
attrs: f
.attrs
.iter()
.filter(|attr| is_attr_name(attr, "cfg"))
.cloned()
.collect(),
colon_token: f.colon_token,
member: Member::Named(ident),
pat: Box::new(Pat::Ident(PatIdent {
by_ref,
mutability,
ident: binded_ident,
subpat: None,
attrs: Default::default(),
})),
}
})
})
.collect();
// EnumName::VariantName { fields }
let pat = Pat::Struct(PatStruct {
attrs: Default::default(),
qself: None,
path,
brace_token,
fields,
rest: None,
});
(pat, bindings)
}
Fields::Unnamed(FieldsUnnamed {
unnamed: ref fields,
paren_token,
}) => {
// TODO
let mut bindings = Vec::new();
let pats = fields
.pairs()
.map(|e| {
let (t, p) = e.into_tuple();
Pair::new(t, p.cloned())
})
.enumerate()
.map(|(idx, f)| {
f.map_item(|f| {
let binded_ident =
Ident::new(&format!("{}{}", prefix, idx), def_site());
bindings.push(BindedField {
idx,
binded_ident: binded_ident.clone(),
field: f,
});
Pat::Ident(PatIdent {
by_ref,
mutability,
ident: binded_ident,
subpat: None,
attrs: Default::default(),
})
})
})
.collect();
// EnumName::VariantName ( fields )
let pat = Pat::TupleStruct(PatTupleStruct {
attrs: Default::default(),
qself: None,
path,
paren_token,
elems: pats,
});
(pat, bindings)
}
};
// if we don't need to move fields, we should match on reference to make tuple
// work.
// let pat = match by_ref {
// Some(ref_token) => Pat::Ref(PatRef {
// pat: box pat,
// and_token: ref_token.0.as_token(),
// mutability,
// }),
// None => pat,
// };
(pat, bindings)
}
}
/// Binded field. Note that this struct acts like a binded variable for
/// `quote!`.
#[derive(Debug, Clone)]
pub struct BindedField<'a> {
binded_ident: Ident,
idx: usize,
field: &'a Field,
}
impl BindedField<'_> {
pub const fn idx(&self) -> usize {
self.idx
}
/// Name of field binding.
pub const fn name(&self) -> &Ident {
&self.binded_ident
}
pub const fn field(&self) -> &Field {
self.field
}
}
impl ToTokens for BindedField<'_> {
fn to_tokens(&self, t: &mut TokenStream) {
self.binded_ident.to_tokens(t)
}
}