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|
use syn::parse::{Parse, ParseStream};
use syn::punctuated::Punctuated;
use syn::Token;
use super::*;
/// Expand the `castable!` macro.
pub fn castable(stream: TokenStream) -> Result<TokenStream> {
let castable: Castable = syn::parse2(stream)?;
let ty = &castable.ty;
if castable.casts.is_empty() && castable.name.is_none() {
bail!(castable.ty, "expected at least one pattern");
}
let is_func = create_is_func(&castable);
let cast_func = create_cast_func(&castable);
let describe_func = create_describe_func(&castable);
let dynamic_impls = castable.name.as_ref().map(|name| {
quote! {
impl ::typst::model::Type for #ty {
const TYPE_NAME: &'static str = #name;
}
impl From<#ty> for ::typst::model::Value {
fn from(v: #ty) -> Self {
::typst::model::Value::Dyn(::typst::model::Dynamic::new(v))
}
}
}
});
Ok(quote! {
impl ::typst::model::Cast for #ty {
#is_func
#cast_func
#describe_func
}
#dynamic_impls
})
}
/// Create the castable's `is` function.
fn create_is_func(castable: &Castable) -> TokenStream {
let mut string_arms = vec![];
let mut cast_checks = vec![];
for cast in &castable.casts {
match &cast.pattern {
Pattern::Str(lit) => {
string_arms.push(quote! { #lit => return true });
}
Pattern::Ty(_, ty) => {
cast_checks.push(quote! {
if <#ty as ::typst::model::Cast>::is(value) {
return true;
}
});
}
}
}
let dynamic_check = castable.name.is_some().then(|| {
quote! {
if let ::typst::model::Value::Dyn(dynamic) = &value {
if dynamic.is::<Self>() {
return true;
}
}
}
});
let str_check = (!string_arms.is_empty()).then(|| {
quote! {
if let ::typst::model::Value::Str(string) = &value {
match string.as_str() {
#(#string_arms,)*
_ => {}
}
}
}
});
quote! {
fn is(value: &typst::model::Value) -> bool {
#dynamic_check
#str_check
#(#cast_checks)*
false
}
}
}
/// Create the castable's `cast` function.
fn create_cast_func(castable: &Castable) -> TokenStream {
let mut string_arms = vec![];
let mut cast_checks = vec![];
for cast in &castable.casts {
let expr = &cast.expr;
match &cast.pattern {
Pattern::Str(lit) => {
string_arms.push(quote! { #lit => return Ok(#expr) });
}
Pattern::Ty(binding, ty) => {
cast_checks.push(quote! {
if <#ty as ::typst::model::Cast>::is(&value) {
let #binding = <#ty as ::typst::model::Cast>::cast(value)?;
return Ok(#expr);
}
});
}
}
}
let dynamic_check = castable.name.is_some().then(|| {
quote! {
if let ::typst::model::Value::Dyn(dynamic) = &value {
if let Some(concrete) = dynamic.downcast::<Self>() {
return Ok(concrete.clone());
}
}
}
});
let str_check = (!string_arms.is_empty()).then(|| {
quote! {
if let ::typst::model::Value::Str(string) = &value {
match string.as_str() {
#(#string_arms,)*
_ => {}
}
}
}
});
quote! {
fn cast(value: ::typst::model::Value) -> ::typst::diag::StrResult<Self> {
#dynamic_check
#str_check
#(#cast_checks)*
<Self as ::typst::model::Cast>::error(value)
}
}
}
/// Create the castable's `describe` function.
fn create_describe_func(castable: &Castable) -> TokenStream {
let mut infos = vec![];
for cast in &castable.casts {
let docs = documentation(&cast.attrs);
infos.push(match &cast.pattern {
Pattern::Str(lit) => {
quote! { ::typst::model::CastInfo::Value(#lit.into(), #docs) }
}
Pattern::Ty(_, ty) => {
quote! { <#ty as ::typst::model::Cast>::describe() }
}
});
}
if let Some(name) = &castable.name {
infos.push(quote! {
CastInfo::Type(#name)
});
}
quote! {
fn describe() -> ::typst::model::CastInfo {
#(#infos)+*
}
}
}
struct Castable {
ty: syn::Type,
name: Option<syn::LitStr>,
casts: Punctuated<Cast, Token![,]>,
}
impl Parse for Castable {
fn parse(input: ParseStream) -> Result<Self> {
let ty = input.parse()?;
let mut name = None;
if input.peek(Token![:]) {
let _: syn::Token![:] = input.parse()?;
name = Some(input.parse()?);
}
let _: syn::Token![,] = input.parse()?;
let casts = Punctuated::parse_terminated(input)?;
Ok(Self { ty, name, casts })
}
}
struct Cast {
attrs: Vec<syn::Attribute>,
pattern: Pattern,
expr: syn::Expr,
}
impl Parse for Cast {
fn parse(input: ParseStream) -> Result<Self> {
let attrs = input.call(syn::Attribute::parse_outer)?;
let pattern = input.parse()?;
let _: syn::Token![=>] = input.parse()?;
let expr = input.parse()?;
Ok(Self { attrs, pattern, expr })
}
}
enum Pattern {
Str(syn::LitStr),
Ty(syn::Pat, syn::Type),
}
impl Parse for Pattern {
fn parse(input: ParseStream) -> Result<Self> {
if input.peek(syn::LitStr) {
Ok(Pattern::Str(input.parse()?))
} else {
let pat = input.parse()?;
let _: syn::Token![:] = input.parse()?;
let ty = input.parse()?;
Ok(Pattern::Ty(pat, ty))
}
}
}
|
