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use proc_macro::TokenStream;
use proc_macro2::Span;
use quote::{quote, quote_spanned, ToTokens};
pub(crate) fn test(args: TokenStream, item: TokenStream) -> TokenStream {
if !args.is_empty() {
return syn::Error::new_spanned(proc_macro2::TokenStream::from(args), "invalid argument")
.to_compile_error()
.into();
}
let mut input = syn::parse_macro_input!(item as syn::ItemFn);
if input.sig.asyncness.take().is_none() {
return syn::Error::new_spanned(input.sig.fn_token, "Only async functions are supported")
.to_compile_error()
.into();
}
// If type mismatch occurs, the current rustc points to the last statement.
let (last_stmt_start_span, last_stmt_end_span) = {
let mut last_stmt = input
.block
.stmts
.last()
.map(ToTokens::into_token_stream)
.unwrap_or_default()
.into_iter();
// `Span` on stable Rust has a limitation that only points to the first
// token, not the whole tokens. We can work around this limitation by
// using the first/last span of the tokens like
// `syn::Error::new_spanned` does.
let start = last_stmt.next().map_or_else(Span::call_site, |t| t.span());
let end = last_stmt.last().map_or(start, |t| t.span());
(start, end)
};
let path = quote_spanned! {last_stmt_start_span=>
::futures_test::__private
};
let body = &input.block;
input.block.stmts = vec![syn::Stmt::Expr(
syn::parse2(quote_spanned! {last_stmt_end_span=>
#path::block_on(async #body)
})
.unwrap(),
None,
)];
let gen = quote! {
#[::core::prelude::v1::test]
#input
};
gen.into()
}