Update proc-macro2, syn, and quote to 1.0

futures-async-stream-macro/Cargo.toml

@@ -19,6 +19,6 @@ proc-macro = true
 [features]
 
 [dependencies]
-proc-macro2 = "0.4.13"
-quote = "0.6.8"
-syn = { version = "0.15.41", features = ["full", "visit-mut"] }
+proc-macro2-next = "1.0.0-rc1"
+quote-next = "1.0.0-rc1" # https://github.com/dtolnay/quote/issues/124
+syn-next = { version = "1.0.0-rc2", features = ["full", "visit-mut"] } # https://github.com/dtolnay/syn/issues/687

futures-async-stream-macro/src/elision.rs

@@ -3,7 +3,7 @@ use syn::{
     punctuated::Punctuated,
     token::Comma,
     visit_mut::{self, VisitMut},
-    ArgSelfRef, FnArg, GenericArgument, GenericParam, Lifetime, LifetimeDef, TypeReference,
+    FnArg, GenericArgument, GenericParam, Lifetime, LifetimeDef, Receiver, TypeReference,
 };
 
 pub(super) fn unelide_lifetimes(
@@ -54,8 +54,10 @@ impl<'a> UnelideLifetimes<'a> {
 }
 
 impl VisitMut for UnelideLifetimes<'_> {
-    fn visit_arg_self_ref_mut(&mut self, arg: &mut ArgSelfRef) {
-        self.visit_opt_lifetime(&mut arg.lifetime);
+    fn visit_receiver_mut(&mut self, receiver: &mut Receiver) {
+        if let Some((_, lifetime)) = &mut receiver.reference {
+            self.visit_opt_lifetime(lifetime);
+        }
     }
 
     fn visit_type_reference_mut(&mut self, ty: &mut TypeReference) {

futures-async-stream-macro/src/lib.rs

@@ -10,7 +10,7 @@ extern crate proc_macro;
 
 use proc_macro::{Delimiter, Group, TokenStream, TokenTree};
 use quote::ToTokens;
-use syn::{Expr, ExprForLoop};
+use syn::{parse::Nothing, Expr, ExprForLoop};
 
 #[macro_use]
 mod utils;
@@ -19,8 +19,6 @@ mod elision;
 mod stream;
 mod visitor;
 
-use crate::utils::Nothing;
-
 /// Processes streams using a for loop.
 #[proc_macro_attribute]
 pub fn for_await(args: TokenStream, input: TokenStream) -> TokenStream {

futures-async-stream-macro/src/stream.rs

@@ -4,8 +4,8 @@ use syn::{
     parse::{Parse, ParseStream},
     token,
     visit_mut::VisitMut,
-    ArgCaptured, Attribute, Block, Expr, FnArg, FnDecl, Ident, ItemFn, MethodSig, Pat, PatIdent,
-    Result, ReturnType, Token, TraitItemMethod, Type, TypeTuple, Visibility,
+    Attribute, Block, Expr, FnArg, Ident, ItemFn, Pat, PatIdent, PatType, Result, ReturnType,
+    Signature, Token, TraitItemMethod, Type, TypeTuple, Visibility,
 };
 
 use crate::{
@@ -107,27 +107,14 @@ impl Parse for Args {
 struct FnSig {
     attrs: Vec<Attribute>,
     vis: Visibility,
-    sig: MethodSig,
+    sig: Signature,
     block: Block,
     semi: Option<Token![;]>,
 }
 
 impl From<ItemFn> for FnSig {
     fn from(item: ItemFn) -> Self {
-        Self {
-            attrs: item.attrs,
-            vis: item.vis,
-            sig: MethodSig {
-                constness: item.constness,
-                asyncness: item.asyncness,
-                unsafety: item.unsafety,
-                abi: item.abi,
-                ident: item.ident,
-                decl: *item.decl,
-            },
-            block: *item.block,
-            semi: None,
-        }
+        Self { attrs: item.attrs, vis: item.vis, sig: item.sig, block: *item.block, semi: None }
     }
 }
 
@@ -164,15 +151,15 @@ fn parse_async_stream_fn(args: TokenStream, input: TokenStream) -> Result<TokenS
     if let Some(constness) = item.sig.constness {
         return Err(error!(constness, "async stream may not be const"));
     }
-    if let Some(variadic) = item.sig.decl.variadic {
+    if let Some(variadic) = item.sig.variadic {
         return Err(error!(variadic, "async stream may not be variadic"));
     }
 
     if item.sig.asyncness.is_none() {
-        return Err(error!(item.sig.decl.fn_token, "async stream must be declared as async"));
+        return Err(error!(item.sig.fn_token, "async stream must be declared as async"));
     }
 
-    if let ReturnType::Type(_, ty) = &item.sig.decl.output {
+    if let ReturnType::Type(_, ty) = &item.sig.output {
         match &**ty {
             Type::Tuple(TypeTuple { elems, .. }) if elems.is_empty() => {}
             _ => return Err(error!(ty, "async stream must return the unit type")),
@@ -184,8 +171,7 @@ fn parse_async_stream_fn(args: TokenStream, input: TokenStream) -> Result<TokenS
 
 fn expand_async_stream_fn(item: FnSig, args: &Args) -> TokenStream {
     let FnSig { attrs, vis, sig, mut block, semi } = item;
-    let MethodSig { unsafety, abi, ident, decl, .. } = sig;
-    let FnDecl { inputs, mut generics, fn_token, .. } = decl;
+    let Signature { unsafety, abi, fn_token, ident, mut generics, inputs, .. } = sig;
     let where_clause = &generics.where_clause;
 
     // Desugar `async fn`
@@ -212,29 +198,33 @@ fn expand_async_stream_fn(item: FnSig, args: &Args) -> TokenStream {
     let mut patterns = Vec::new();
     let mut temp_bindings = Vec::new();
     for (i, input) in inputs.into_iter().enumerate() {
-        match input {
-            FnArg::Captured(ArgCaptured { pat: Pat::Ident(ref pat), .. })
-                if pat.ident == "self" =>
-            {
+        if let FnArg::Typed(PatType { attrs, pat, ty, colon_token }) = input {
+            let captured_naturally = match &*pat {
                 // `self: Box<Self>` will get captured naturally
-                inputs_no_patterns.push(input);
-            }
-            FnArg::Captured(ArgCaptured {
-                pat: pat @ Pat::Ident(PatIdent { by_ref: Some(_), .. }),
-                ty,
-                colon_token,
-            }) => {
+                Pat::Ident(pat) if pat.ident == "self" => true,
+                Pat::Ident(PatIdent { by_ref: Some(_), .. }) => false,
+                // Other arguments get captured naturally
+                _ => true,
+            };
+            if captured_naturally {
+                inputs_no_patterns.push(FnArg::Typed(PatType { attrs, pat, ty, colon_token }));
+                continue;
+            } else {
                 // `ref a: B` (or some similar pattern)
                 patterns.push(pat);
                 let ident = Ident::new(&format!("__arg_{}", i), Span::call_site());
                 temp_bindings.push(ident.clone());
-                let pat = PatIdent { by_ref: None, mutability: None, ident, subpat: None }.into();
-                inputs_no_patterns.push(ArgCaptured { pat, ty, colon_token }.into());
-            }
-            _ => {
-                // Other arguments get captured naturally
-                inputs_no_patterns.push(input);
+                let pat = Box::new(Pat::Ident(PatIdent {
+                    attrs: Vec::new(),
+                    by_ref: None,
+                    mutability: None,
+                    ident,
+                    subpat: None,
+                }));
+                inputs_no_patterns.push(PatType { attrs, pat, ty, colon_token }.into());
             }
+        } else {
+            inputs_no_patterns.push(input);
         }
     }
 

futures-async-stream-macro/src/utils.rs

@@ -2,11 +2,7 @@ use std::mem;
 
 use proc_macro2::{Span, TokenStream, TokenTree};
 use quote::ToTokens;
-use syn::{
-    parse::{Parse, ParseStream},
-    punctuated::Punctuated,
-    token, Expr, ExprTuple, ExprVerbatim, Result,
-};
+use syn::{punctuated::Punctuated, token, Expr, ExprTuple};
 
 pub(crate) fn first_last<T: ToTokens>(tokens: &T) -> (Span, Span) {
     let mut spans = TokenStream::new();
@@ -44,7 +40,7 @@ pub(crate) fn replace_expr<F>(this: &mut Expr, f: F)
 where
     F: FnOnce(Expr) -> Expr,
 {
-    *this = f(mem::replace(this, Expr::Verbatim(ExprVerbatim { tts: TokenStream::new() })));
+    *this = f(mem::replace(this, Expr::Verbatim(TokenStream::new())));
 }
 
 pub(super) fn replace_boxed_expr<F>(expr: &mut Option<Box<Expr>>, f: F)
@@ -60,16 +56,6 @@ where
     }
 }
 
-// See https://github.com/dtolnay/syn/commit/82a3aed7ecfd07fc2f7f322b01d2413ffea6c5e7
-/// An empty syntax tree node that consumes no tokens when parsed.
-pub(crate) struct Nothing;
-
-impl Parse for Nothing {
-    fn parse(_input: ParseStream<'_>) -> Result<Self> {
-        Ok(Nothing)
-    }
-}
-
 macro_rules! error {
     ($span:expr, $msg:expr) => {
         syn::Error::new_spanned($span, $msg)

futures-async-stream-macro/src/visitor.rs

@@ -1,13 +1,14 @@
 use quote::{quote, quote_spanned};
 use syn::{
+    parse::Nothing,
     spanned::Spanned,
     visit_mut::{self, VisitMut},
-    Expr, ExprCall, ExprField, ExprForLoop, ExprYield, Item, Member,
+    Expr, ExprAwait, ExprCall, ExprForLoop, ExprYield, Item,
 };
 
 use crate::{
     async_stream_block,
-    utils::{expr_compile_error, replace_boxed_expr, replace_expr, Nothing},
+    utils::{expr_compile_error, replace_boxed_expr, replace_expr},
 };
 
 pub(crate) use Scope::{Closure, Future, Stream};
@@ -56,7 +57,7 @@ impl Visitor {
                 return;
             }
             let attr = attrs.pop().unwrap();
-            if let Err(e) = syn::parse2::<Nothing>(attr.tts) {
+            if let Err(e) = syn::parse2::<Nothing>(attr.tokens) {
                 *expr = expr_compile_error(&e);
                 return;
             }
@@ -135,7 +136,7 @@ impl Visitor {
             if let Expr::Macro(mut expr) = expr {
                 if expr.mac.path.is_ident("async_stream_block") {
                     let mut e: ExprCall =
-                        syn::parse(async_stream_block(expr.mac.tts.into())).unwrap();
+                        syn::parse(async_stream_block(expr.mac.tokens.into())).unwrap();
                     e.attrs.append(&mut expr.attrs);
                     Expr::Call(e)
                 } else {
@@ -157,13 +158,8 @@ impl Visitor {
             return;
         }
 
-        if let Expr::Field(ExprField { base, member, .. }) = expr {
-            match &member {
-                Member::Named(x) if x == "await" => {}
-                _ => return,
-            }
-
-            *expr = syn::parse2(quote_spanned! { member.span() => {
+        if let Expr::Await(ExprAwait { base, await_token, .. }) = expr {
+            *expr = syn::parse2(quote_spanned! { await_token.span() => {
                 let mut __pinned = #base;
                 loop {
                     if let ::futures_async_stream::core_reexport::task::Poll::Ready(x) =
@@ -200,7 +196,7 @@ impl VisitMut for Visitor {
         visit_mut::visit_expr_mut(self, expr);
         match expr {
             Expr::Yield(expr) => self.visit_yield(expr),
-            Expr::Field(_) => self.visit_await(expr),
+            Expr::Await(_) => self.visit_await(expr),
             Expr::ForLoop(_) => self.visit_for_loop(expr),
             Expr::Macro(_) => self.visit_macro(expr),
             _ => {}

tests/ui/invalid-function.stderr

@@ -10,7 +10,11 @@ error: async stream may not be const
 9 | const fn constness() {} //~ ERROR async stream may not be const
   | ^^^^^
 
-error: async stream must be declared as async
+error: expected `:`
+  --> $DIR/invalid-function.rs:11:1
+   |
+11 | #[async_stream(item = ())]
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error: async stream must be declared as async
   --> $DIR/invalid-function.rs:15:1