jni-toolbox/macro/src/ret.rs

80 lines
2.8 KiB
Rust

use proc_macro2::{Span, TokenStream};
use quote::ToTokens;
use syn::{ReturnType, Type};
use crate::ext::bare_type;
#[derive(Clone)]
pub(crate) struct ReturnOptions {
pub(crate) ty: Option<Box<Type>>,
pub(crate) result: bool,
pub(crate) pointer: bool,
pub(crate) void: bool,
}
const PRIMITIVE_TYPES: [&str; 7] = ["i8", "i16", "i32", "i64", "f32", "f64", "bool"];
impl ReturnOptions {
pub(crate) fn parse_signature(ret: &ReturnType) -> Result<Self, syn::Error> {
match ret {
syn::ReturnType::Default => Ok(Self { ty: None, result: false, void: true, pointer: false }),
syn::ReturnType::Type(_tok, ty) => match bare_type(ty.clone()) {
Some(path) => {
let Some(last) = path.path.segments.last() else {
return Err(syn::Error::new(Span::call_site(), "empty Result type is not valid"));
};
if last.ident == "Result" {
match &last.arguments {
syn::PathArguments::None => return Err(syn::Error::new(Span::call_site(), "Result without generics is not valid")),
syn::PathArguments::Parenthesized(_) => return Err(syn::Error::new(Span::call_site(), "Parenthesized Result is not valid")),
syn::PathArguments::AngleBracketed(ref generics) => for generic in generics.args.iter() {
match generic {
syn::GenericArgument::Lifetime(_) => continue,
syn::GenericArgument::Type(ty) => {
// TODO checking by making ty a token stream and then string equals is not exactly great!
let pointer = !PRIMITIVE_TYPES.iter().any(|t| ty.to_token_stream().to_string() == *t);
return Ok(Self { ty: Some(Box::new(ty.clone())), result: true, void: is_void(ty), pointer });
},
_ => return Err(syn::Error::new(Span::call_site(), "unexpected type in Result"))
}
}
}
}
let pointer = !PRIMITIVE_TYPES.iter().any(|t| last.ident == t);
Ok(Self { ty: Some(Box::new(Type::Path(path.clone()))), result: false, void: false, pointer })
},
None => Err(syn::Error::new(Span::call_site(), "unsupported return type")),
},
}
}
pub(crate) fn tokens(&self) -> TokenStream {
match &self.ty { // TODO why do we need to invoke syn::Token! macro ???
None => ReturnType::Default.to_token_stream(),
Some(t) => quote::quote!( -> <#t as jni_toolbox::IntoJava<'local>>::Ret )
}
}
}
fn is_void(ty: &syn::Type) -> bool {
match ty {
Type::Array(_) => false,
Type::BareFn(_) => false,
Type::Group(g) => is_void(&g.elem),
Type::ImplTrait(_) => false,
Type::Infer(_) => false,
Type::Macro(_) => false,
Type::Never(_) => true,
Type::Paren(p) => is_void(&p.elem),
Type::Path(p) => p.path.segments.is_empty(),
Type::Ptr(_) => false,
Type::Reference(_) => false,
Type::Slice(_) => false,
Type::TraitObject(_) => false,
Type::Tuple(x) => x.elems.is_empty(),
Type::Verbatim(_) => false,
_ => todo!(),
}
}