Adding upstream version 1.64.0+dfsg1.upstream/1.64.0+dfsg1

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

5 files changed, 702 insertions, 0 deletions

diff --git a/vendor/futures-macro/src/executor.rs b/vendor/futures-macro/src/executor.rs
new file mode 100644
index 000000000..40a091f94
--- /dev/null
+++ b/vendor/futures-macro/src/executor.rs
@@ -0,0 +1,55 @@
+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(),
+    )];
+
+    let gen = quote! {
+        #[::core::prelude::v1::test]
+        #input
+    };
+
+    gen.into()
+}
diff --git a/vendor/futures-macro/src/join.rs b/vendor/futures-macro/src/join.rs
new file mode 100644
index 000000000..d427da27a
--- /dev/null
+++ b/vendor/futures-macro/src/join.rs
@@ -0,0 +1,143 @@
+//! The futures-rs `join! macro implementation.
+
+use proc_macro::TokenStream;
+use proc_macro2::{Span, TokenStream as TokenStream2};
+use quote::{format_ident, quote};
+use syn::parse::{Parse, ParseStream};
+use syn::{Expr, Ident, Token};
+
+#[derive(Default)]
+struct Join {
+    fut_exprs: Vec<Expr>,
+}
+
+impl Parse for Join {
+    fn parse(input: ParseStream<'_>) -> syn::Result<Self> {
+        let mut join = Self::default();
+
+        while !input.is_empty() {
+            join.fut_exprs.push(input.parse::<Expr>()?);
+
+            if !input.is_empty() {
+                input.parse::<Token![,]>()?;
+            }
+        }
+
+        Ok(join)
+    }
+}
+
+fn bind_futures(fut_exprs: Vec<Expr>, span: Span) -> (Vec<TokenStream2>, Vec<Ident>) {
+    let mut future_let_bindings = Vec::with_capacity(fut_exprs.len());
+    let future_names: Vec<_> = fut_exprs
+        .into_iter()
+        .enumerate()
+        .map(|(i, expr)| {
+            let name = format_ident!("_fut{}", i, span = span);
+            future_let_bindings.push(quote! {
+                // Move future into a local so that it is pinned in one place and
+                // is no longer accessible by the end user.
+                let mut #name = __futures_crate::future::maybe_done(#expr);
+            });
+            name
+        })
+        .collect();
+
+    (future_let_bindings, future_names)
+}
+
+/// The `join!` macro.
+pub(crate) fn join(input: TokenStream) -> TokenStream {
+    let parsed = syn::parse_macro_input!(input as Join);
+
+    // should be def_site, but that's unstable
+    let span = Span::call_site();
+
+    let (future_let_bindings, future_names) = bind_futures(parsed.fut_exprs, span);
+
+    let poll_futures = future_names.iter().map(|fut| {
+        quote! {
+            __all_done &= __futures_crate::future::Future::poll(
+                unsafe { __futures_crate::Pin::new_unchecked(&mut #fut) }, __cx).is_ready();
+        }
+    });
+    let take_outputs = future_names.iter().map(|fut| {
+        quote! {
+            unsafe { __futures_crate::Pin::new_unchecked(&mut #fut) }.take_output().unwrap(),
+        }
+    });
+
+    TokenStream::from(quote! { {
+        #( #future_let_bindings )*
+
+        __futures_crate::future::poll_fn(move |__cx: &mut __futures_crate::task::Context<'_>| {
+            let mut __all_done = true;
+            #( #poll_futures )*
+            if __all_done {
+                __futures_crate::task::Poll::Ready((
+                    #( #take_outputs )*
+                ))
+            } else {
+                __futures_crate::task::Poll::Pending
+            }
+        }).await
+    } })
+}
+
+/// The `try_join!` macro.
+pub(crate) fn try_join(input: TokenStream) -> TokenStream {
+    let parsed = syn::parse_macro_input!(input as Join);
+
+    // should be def_site, but that's unstable
+    let span = Span::call_site();
+
+    let (future_let_bindings, future_names) = bind_futures(parsed.fut_exprs, span);
+
+    let poll_futures = future_names.iter().map(|fut| {
+        quote! {
+            if __futures_crate::future::Future::poll(
+                unsafe { __futures_crate::Pin::new_unchecked(&mut #fut) }, __cx).is_pending()
+            {
+                __all_done = false;
+            } else if unsafe { __futures_crate::Pin::new_unchecked(&mut #fut) }.output_mut().unwrap().is_err() {
+                // `.err().unwrap()` rather than `.unwrap_err()` so that we don't introduce
+                // a `T: Debug` bound.
+                // Also, for an error type of ! any code after `err().unwrap()` is unreachable.
+                #[allow(unreachable_code)]
+                return __futures_crate::task::Poll::Ready(
+                    __futures_crate::Err(
+                        unsafe { __futures_crate::Pin::new_unchecked(&mut #fut) }.take_output().unwrap().err().unwrap()
+                    )
+                );
+            }
+        }
+    });
+    let take_outputs = future_names.iter().map(|fut| {
+        quote! {
+            // `.ok().unwrap()` rather than `.unwrap()` so that we don't introduce
+            // an `E: Debug` bound.
+            // Also, for an ok type of ! any code after `ok().unwrap()` is unreachable.
+            #[allow(unreachable_code)]
+            unsafe { __futures_crate::Pin::new_unchecked(&mut #fut) }.take_output().unwrap().ok().unwrap(),
+        }
+    });
+
+    TokenStream::from(quote! { {
+        #( #future_let_bindings )*
+
+        #[allow(clippy::diverging_sub_expression)]
+        __futures_crate::future::poll_fn(move |__cx: &mut __futures_crate::task::Context<'_>| {
+            let mut __all_done = true;
+            #( #poll_futures )*
+            if __all_done {
+                __futures_crate::task::Poll::Ready(
+                    __futures_crate::Ok((
+                        #( #take_outputs )*
+                    ))
+                )
+            } else {
+                __futures_crate::task::Poll::Pending
+            }
+        }).await
+    } })
+}
diff --git a/vendor/futures-macro/src/lib.rs b/vendor/futures-macro/src/lib.rs
new file mode 100644
index 000000000..0afe34b83
--- /dev/null
+++ b/vendor/futures-macro/src/lib.rs
@@ -0,0 +1,61 @@
+//! The futures-rs procedural macro implementations.
+
+#![warn(rust_2018_idioms, single_use_lifetimes, unreachable_pub)]
+#![doc(test(
+    no_crate_inject,
+    attr(
+        deny(warnings, rust_2018_idioms, single_use_lifetimes),
+        allow(dead_code, unused_assignments, unused_variables)
+    )
+))]
+
+// Since https://github.com/rust-lang/cargo/pull/7700 `proc_macro` is part of the prelude for
+// proc-macro crates, but to support older compilers we still need this explicit `extern crate`.
+#[allow(unused_extern_crates)]
+extern crate proc_macro;
+
+use proc_macro::TokenStream;
+
+mod executor;
+mod join;
+mod select;
+mod stream_select;
+
+/// The `join!` macro.
+#[proc_macro]
+pub fn join_internal(input: TokenStream) -> TokenStream {
+    crate::join::join(input)
+}
+
+/// The `try_join!` macro.
+#[proc_macro]
+pub fn try_join_internal(input: TokenStream) -> TokenStream {
+    crate::join::try_join(input)
+}
+
+/// The `select!` macro.
+#[proc_macro]
+pub fn select_internal(input: TokenStream) -> TokenStream {
+    crate::select::select(input)
+}
+
+/// The `select_biased!` macro.
+#[proc_macro]
+pub fn select_biased_internal(input: TokenStream) -> TokenStream {
+    crate::select::select_biased(input)
+}
+
+// TODO: Change this to doc comment once rustdoc bug fixed: https://github.com/rust-lang/futures-rs/pull/2435
+// The `test` attribute.
+#[proc_macro_attribute]
+pub fn test_internal(input: TokenStream, item: TokenStream) -> TokenStream {
+    crate::executor::test(input, item)
+}
+
+/// The `stream_select!` macro.
+#[proc_macro]
+pub fn stream_select_internal(input: TokenStream) -> TokenStream {
+    crate::stream_select::stream_select(input.into())
+        .unwrap_or_else(syn::Error::into_compile_error)
+        .into()
+}
diff --git a/vendor/futures-macro/src/select.rs b/vendor/futures-macro/src/select.rs
new file mode 100644
index 000000000..0c8e5f1ca
--- /dev/null
+++ b/vendor/futures-macro/src/select.rs
@@ -0,0 +1,330 @@
+//! The futures-rs `select! macro implementation.
+
+use proc_macro::TokenStream;
+use proc_macro2::Span;
+use quote::{format_ident, quote};
+use syn::parse::{Parse, ParseStream};
+use syn::{parse_quote, Expr, Ident, Pat, Token};
+
+mod kw {
+    syn::custom_keyword!(complete);
+}
+
+struct Select {
+    // span of `complete`, then expression after `=> ...`
+    complete: Option<Expr>,
+    default: Option<Expr>,
+    normal_fut_exprs: Vec<Expr>,
+    normal_fut_handlers: Vec<(Pat, Expr)>,
+}
+
+#[allow(clippy::large_enum_variant)]
+enum CaseKind {
+    Complete,
+    Default,
+    Normal(Pat, Expr),
+}
+
+impl Parse for Select {
+    fn parse(input: ParseStream<'_>) -> syn::Result<Self> {
+        let mut select = Self {
+            complete: None,
+            default: None,
+            normal_fut_exprs: vec![],
+            normal_fut_handlers: vec![],
+        };
+
+        while !input.is_empty() {
+            let case_kind = if input.peek(kw::complete) {
+                // `complete`
+                if select.complete.is_some() {
+                    return Err(input.error("multiple `complete` cases found, only one allowed"));
+                }
+                input.parse::<kw::complete>()?;
+                CaseKind::Complete
+            } else if input.peek(Token![default]) {
+                // `default`
+                if select.default.is_some() {
+                    return Err(input.error("multiple `default` cases found, only one allowed"));
+                }
+                input.parse::<Ident>()?;
+                CaseKind::Default
+            } else {
+                // `<pat> = <expr>`
+                let pat = input.parse()?;
+                input.parse::<Token![=]>()?;
+                let expr = input.parse()?;
+                CaseKind::Normal(pat, expr)
+            };
+
+            // `=> <expr>`
+            input.parse::<Token![=>]>()?;
+            let expr = input.parse::<Expr>()?;
+
+            // Commas after the expression are only optional if it's a `Block`
+            // or it is the last branch in the `match`.
+            let is_block = match expr {
+                Expr::Block(_) => true,
+                _ => false,
+            };
+            if is_block || input.is_empty() {
+                input.parse::<Option<Token![,]>>()?;
+            } else {
+                input.parse::<Token![,]>()?;
+            }
+
+            match case_kind {
+                CaseKind::Complete => select.complete = Some(expr),
+                CaseKind::Default => select.default = Some(expr),
+                CaseKind::Normal(pat, fut_expr) => {
+                    select.normal_fut_exprs.push(fut_expr);
+                    select.normal_fut_handlers.push((pat, expr));
+                }
+            }
+        }
+
+        Ok(select)
+    }
+}
+
+// Enum over all the cases in which the `select!` waiting has completed and the result
+// can be processed.
+//
+// `enum __PrivResult<_1, _2, ...> { _1(_1), _2(_2), ..., Complete }`
+fn declare_result_enum(
+    result_ident: Ident,
+    variants: usize,
+    complete: bool,
+    span: Span,
+) -> (Vec<Ident>, syn::ItemEnum) {
+    // "_0", "_1", "_2"
+    let variant_names: Vec<Ident> =
+        (0..variants).map(|num| format_ident!("_{}", num, span = span)).collect();
+
+    let type_parameters = &variant_names;
+    let variants = &variant_names;
+
+    let complete_variant = if complete { Some(quote!(Complete)) } else { None };
+
+    let enum_item = parse_quote! {
+        enum #result_ident<#(#type_parameters,)*> {
+            #(
+                #variants(#type_parameters),
+            )*
+            #complete_variant
+        }
+    };
+
+    (variant_names, enum_item)
+}
+
+/// The `select!` macro.
+pub(crate) fn select(input: TokenStream) -> TokenStream {
+    select_inner(input, true)
+}
+
+/// The `select_biased!` macro.
+pub(crate) fn select_biased(input: TokenStream) -> TokenStream {
+    select_inner(input, false)
+}
+
+fn select_inner(input: TokenStream, random: bool) -> TokenStream {
+    let parsed = syn::parse_macro_input!(input as Select);
+
+    // should be def_site, but that's unstable
+    let span = Span::call_site();
+
+    let enum_ident = Ident::new("__PrivResult", span);
+
+    let (variant_names, enum_item) = declare_result_enum(
+        enum_ident.clone(),
+        parsed.normal_fut_exprs.len(),
+        parsed.complete.is_some(),
+        span,
+    );
+
+    // bind non-`Ident` future exprs w/ `let`
+    let mut future_let_bindings = Vec::with_capacity(parsed.normal_fut_exprs.len());
+    let bound_future_names: Vec<_> = parsed
+        .normal_fut_exprs
+        .into_iter()
+        .zip(variant_names.iter())
+        .map(|(expr, variant_name)| {
+            match expr {
+                syn::Expr::Path(path) => {
+                    // Don't bind futures that are already a path.
+                    // This prevents creating redundant stack space
+                    // for them.
+                    // Passing Futures by path requires those Futures to implement Unpin.
+                    // We check for this condition here in order to be able to
+                    // safely use Pin::new_unchecked(&mut #path) later on.
+                    future_let_bindings.push(quote! {
+                        __futures_crate::async_await::assert_fused_future(&#path);
+                        __futures_crate::async_await::assert_unpin(&#path);
+                    });
+                    path
+                }
+                _ => {
+                    // Bind and pin the resulting Future on the stack. This is
+                    // necessary to support direct select! calls on !Unpin
+                    // Futures. The Future is not explicitly pinned here with
+                    // a Pin call, but assumed as pinned. The actual Pin is
+                    // created inside the poll() function below to defer the
+                    // creation of the temporary pointer, which would otherwise
+                    // increase the size of the generated Future.
+                    // Safety: This is safe since the lifetime of the Future
+                    // is totally constraint to the lifetime of the select!
+                    // expression, and the Future can't get moved inside it
+                    // (it is shadowed).
+                    future_let_bindings.push(quote! {
+                        let mut #variant_name = #expr;
+                    });
+                    parse_quote! { #variant_name }
+                }
+            }
+        })
+        .collect();
+
+    // For each future, make an `&mut dyn FnMut(&mut Context<'_>) -> Option<Poll<__PrivResult<...>>`
+    // to use for polling that individual future. These will then be put in an array.
+    let poll_functions = bound_future_names.iter().zip(variant_names.iter()).map(
+        |(bound_future_name, variant_name)| {
+            // Below we lazily create the Pin on the Future below.
+            // This is done in order to avoid allocating memory in the generator
+            // for the Pin variable.
+            // Safety: This is safe because one of the following condition applies:
+            // 1. The Future is passed by the caller by name, and we assert that
+            //    it implements Unpin.
+            // 2. The Future is created in scope of the select! function and will
+            //    not be moved for the duration of it. It is thereby stack-pinned
+            quote! {
+                let mut #variant_name = |__cx: &mut __futures_crate::task::Context<'_>| {
+                    let mut #bound_future_name = unsafe {
+                        __futures_crate::Pin::new_unchecked(&mut #bound_future_name)
+                    };
+                    if __futures_crate::future::FusedFuture::is_terminated(&#bound_future_name) {
+                        __futures_crate::None
+                    } else {
+                        __futures_crate::Some(__futures_crate::future::FutureExt::poll_unpin(
+                            &mut #bound_future_name,
+                            __cx,
+                        ).map(#enum_ident::#variant_name))
+                    }
+                };
+                let #variant_name: &mut dyn FnMut(
+                    &mut __futures_crate::task::Context<'_>
+                ) -> __futures_crate::Option<__futures_crate::task::Poll<_>> = &mut #variant_name;
+            }
+        },
+    );
+
+    let none_polled = if parsed.complete.is_some() {
+        quote! {
+            __futures_crate::task::Poll::Ready(#enum_ident::Complete)
+        }
+    } else {
+        quote! {
+            panic!("all futures in select! were completed,\
+                    but no `complete =>` handler was provided")
+        }
+    };
+
+    let branches = parsed.normal_fut_handlers.into_iter().zip(variant_names.iter()).map(
+        |((pat, expr), variant_name)| {
+            quote! {
+                #enum_ident::#variant_name(#pat) => { #expr },
+            }
+        },
+    );
+    let branches = quote! { #( #branches )* };
+
+    let complete_branch = parsed.complete.map(|complete_expr| {
+        quote! {
+            #enum_ident::Complete => { #complete_expr },
+        }
+    });
+
+    let branches = quote! {
+        #branches
+        #complete_branch
+    };
+
+    let await_select_fut = if parsed.default.is_some() {
+        // For select! with default this returns the Poll result
+        quote! {
+            __poll_fn(&mut __futures_crate::task::Context::from_waker(
+                __futures_crate::task::noop_waker_ref()
+            ))
+        }
+    } else {
+        quote! {
+            __futures_crate::future::poll_fn(__poll_fn).await
+        }
+    };
+
+    let execute_result_expr = if let Some(default_expr) = &parsed.default {
+        // For select! with default __select_result is a Poll, otherwise not
+        quote! {
+            match __select_result {
+                __futures_crate::task::Poll::Ready(result) => match result {
+                    #branches
+                },
+                _ => #default_expr
+            }
+        }
+    } else {
+        quote! {
+            match __select_result {
+                #branches
+            }
+        }
+    };
+
+    let shuffle = if random {
+        quote! {
+            __futures_crate::async_await::shuffle(&mut __select_arr);
+        }
+    } else {
+        quote!()
+    };
+
+    TokenStream::from(quote! { {
+        #enum_item
+
+        let __select_result = {
+            #( #future_let_bindings )*
+
+            let mut __poll_fn = |__cx: &mut __futures_crate::task::Context<'_>| {
+                let mut __any_polled = false;
+
+                #( #poll_functions )*
+
+                let mut __select_arr = [#( #variant_names ),*];
+                #shuffle
+                for poller in &mut __select_arr {
+                    let poller: &mut &mut dyn FnMut(
+                        &mut __futures_crate::task::Context<'_>
+                    ) -> __futures_crate::Option<__futures_crate::task::Poll<_>> = poller;
+                    match poller(__cx) {
+                        __futures_crate::Some(x @ __futures_crate::task::Poll::Ready(_)) =>
+                            return x,
+                        __futures_crate::Some(__futures_crate::task::Poll::Pending) => {
+                            __any_polled = true;
+                        }
+                        __futures_crate::None => {}
+                    }
+                }
+
+                if !__any_polled {
+                    #none_polled
+                } else {
+                    __futures_crate::task::Poll::Pending
+                }
+            };
+
+            #await_select_fut
+        };
+
+        #execute_result_expr
+    } })
+}
diff --git a/vendor/futures-macro/src/stream_select.rs b/vendor/futures-macro/src/stream_select.rs
new file mode 100644
index 000000000..9927b5307
--- /dev/null
+++ b/vendor/futures-macro/src/stream_select.rs
@@ -0,0 +1,113 @@
+use proc_macro2::TokenStream;
+use quote::{format_ident, quote, ToTokens};
+use syn::{parse::Parser, punctuated::Punctuated, Expr, Index, Token};
+
+/// The `stream_select!` macro.
+pub(crate) fn stream_select(input: TokenStream) -> Result<TokenStream, syn::Error> {
+    let args = Punctuated::<Expr, Token![,]>::parse_terminated.parse2(input)?;
+    if args.len() < 2 {
+        return Ok(quote! {
+           compile_error!("stream select macro needs at least two arguments.")
+        });
+    }
+    let generic_idents = (0..args.len()).map(|i| format_ident!("_{}", i)).collect::<Vec<_>>();
+    let field_idents = (0..args.len()).map(|i| format_ident!("__{}", i)).collect::<Vec<_>>();
+    let field_idents_2 = (0..args.len()).map(|i| format_ident!("___{}", i)).collect::<Vec<_>>();
+    let field_indices = (0..args.len()).map(Index::from).collect::<Vec<_>>();
+    let args = args.iter().map(|e| e.to_token_stream());
+
+    Ok(quote! {
+        {
+            #[derive(Debug)]
+            struct StreamSelect<#(#generic_idents),*> (#(Option<#generic_idents>),*);
+
+            enum StreamEnum<#(#generic_idents),*> {
+                #(
+                    #generic_idents(#generic_idents)
+                ),*,
+                None,
+            }
+
+            impl<ITEM, #(#generic_idents),*> __futures_crate::stream::Stream for StreamEnum<#(#generic_idents),*>
+            where #(#generic_idents: __futures_crate::stream::Stream<Item=ITEM> + ::std::marker::Unpin,)*
+            {
+                type Item = ITEM;
+
+                fn poll_next(mut self: ::std::pin::Pin<&mut Self>, cx: &mut __futures_crate::task::Context<'_>) -> __futures_crate::task::Poll<Option<Self::Item>> {
+                    match self.get_mut() {
+                        #(
+                            Self::#generic_idents(#generic_idents) => ::std::pin::Pin::new(#generic_idents).poll_next(cx)
+                        ),*,
+                        Self::None => panic!("StreamEnum::None should never be polled!"),
+                    }
+                }
+            }
+
+            impl<ITEM, #(#generic_idents),*> __futures_crate::stream::Stream for StreamSelect<#(#generic_idents),*>
+            where #(#generic_idents: __futures_crate::stream::Stream<Item=ITEM> + ::std::marker::Unpin,)*
+            {
+                type Item = ITEM;
+
+                fn poll_next(mut self: ::std::pin::Pin<&mut Self>, cx: &mut __futures_crate::task::Context<'_>) -> __futures_crate::task::Poll<Option<Self::Item>> {
+                    let Self(#(ref mut #field_idents),*) = self.get_mut();
+                    #(
+                        let mut #field_idents_2 = false;
+                    )*
+                    let mut any_pending = false;
+                    {
+                        let mut stream_array = [#(#field_idents.as_mut().map(|f| StreamEnum::#generic_idents(f)).unwrap_or(StreamEnum::None)),*];
+                        __futures_crate::async_await::shuffle(&mut stream_array);
+
+                        for mut s in stream_array {
+                            if let StreamEnum::None = s {
+                                continue;
+                            } else {
+                                match __futures_crate::stream::Stream::poll_next(::std::pin::Pin::new(&mut s), cx) {
+                                    r @ __futures_crate::task::Poll::Ready(Some(_)) => {
+                                        return r;
+                                    },
+                                    __futures_crate::task::Poll::Pending => {
+                                        any_pending = true;
+                                    },
+                                    __futures_crate::task::Poll::Ready(None) => {
+                                        match s {
+                                            #(
+                                                StreamEnum::#generic_idents(_) => { #field_idents_2 = true; }
+                                            ),*,
+                                            StreamEnum::None => panic!("StreamEnum::None should never be polled!"),
+                                        }
+                                    },
+                                }
+                            }
+                        }
+                    }
+                    #(
+                        if #field_idents_2 {
+                            *#field_idents = None;
+                        }
+                    )*
+                    if any_pending {
+                        __futures_crate::task::Poll::Pending
+                    } else {
+                        __futures_crate::task::Poll::Ready(None)
+                    }
+                }
+
+                fn size_hint(&self) -> (usize, Option<usize>) {
+                    let mut s = (0, Some(0));
+                    #(
+                        if let Some(new_hint) = self.#field_indices.as_ref().map(|s| s.size_hint()) {
+                            s.0 += new_hint.0;
+                            // We can change this out for `.zip` when the MSRV is 1.46.0 or higher.
+                            s.1 = s.1.and_then(|a| new_hint.1.map(|b| a + b));
+                        }
+                    )*
+                    s
+                }
+            }
+
+            StreamSelect(#(Some(#args)),*)
+
+        }
+    })
+}