Update to syn 2 (#354)

Effectively bumps MSRV to 1.56.0, due to syn 2 minimum requirements.

Co-authored-by: Matthew Maurer <mmaurer@google.com>

.github/workflows/ci.yml

@@ -54,7 +54,7 @@ jobs:
       fail-fast: false
       matrix:
         rust:
-          - '1.37'
+          - '1.56'
           - stable
           - beta
           - nightly
@@ -87,7 +87,7 @@ jobs:
       - run: cargo build --manifest-path tests/no-std/Cargo.toml --target thumbv6m-none-eabi
       - run: cargo build --manifest-path tests/rust-2015/Cargo.toml --target thumbv6m-none-eabi
       - run: cargo minimal-versions build --workspace --all-features --ignore-private
-        if: matrix.rust != '1.37'
+        if: matrix.rust != '1.56'
 
   miri:
     runs-on: ubuntu-latest

Cargo.toml

@@ -2,7 +2,7 @@
 name = "pin-project"
 version = "1.0.12"
 edition = "2018"
-rust-version = "1.37"
+rust-version = "1.56"
 license = "Apache-2.0 OR MIT"
 repository = "https://github.com/taiki-e/pin-project"
 keywords = ["pin", "macros", "attribute"]
@@ -39,7 +39,7 @@ trybuild = "=1.0.67"
 
 # For test on MSRV.
 once_cell = "=1.14"
-serde = "=1.0.156"
+serde = "1.0.159"
 toml = "=0.5.9"
 
 [patch.crates-io]

README.md

@@ -3,7 +3,7 @@
 [![crates.io](https://img.shields.io/crates/v/pin-project?style=flat-square&logo=rust)](https://crates.io/crates/pin-project)
 [![docs.rs](https://img.shields.io/badge/docs.rs-pin--project-blue?style=flat-square&logo=docs.rs)](https://docs.rs/pin-project)
 [![license](https://img.shields.io/badge/license-Apache--2.0_OR_MIT-blue?style=flat-square)](#license)
-[![rustc](https://img.shields.io/badge/rustc-1.37+-blue?style=flat-square&logo=rust)](https://www.rust-lang.org)
+[![rustc](https://img.shields.io/badge/rustc-1.56+-blue?style=flat-square&logo=rust)](https://www.rust-lang.org)
 [![build status](https://img.shields.io/github/actions/workflow/status/taiki-e/pin-project/ci.yml?branch=main&style=flat-square&logo=github)](https://github.com/taiki-e/pin-project/actions)
 
 <!-- tidy:crate-doc:start -->
@@ -18,7 +18,7 @@ Add this to your `Cargo.toml`:
 pin-project = "1"
 ```
 
-*Compiler support: requires rustc 1.37+*
+*Compiler support: requires rustc 1.56+*
 
 ## Examples
 

pin-project-internal/Cargo.toml

@@ -2,7 +2,7 @@
 name = "pin-project-internal"
 version = "1.0.12"
 edition = "2018"
-rust-version = "1.37"
+rust-version = "1.56"
 license = "Apache-2.0 OR MIT"
 repository = "https://github.com/taiki-e/pin-project"
 keywords = ["pin", "macros", "attribute"]
@@ -20,7 +20,7 @@ proc-macro = true
 [dependencies]
 proc-macro2 = "1"
 quote = "1"
-syn = { version = "1.0.56", features = ["full", "visit-mut"] }
+syn = { version = "2.0.1", features = ["full", "visit-mut"] }
 
 [dev-dependencies]
 pin-project = { path = ".." }

pin-project-internal/src/pin_project/args.rs

@@ -16,10 +16,9 @@ pub(super) fn parse_args(attrs: &[Attribute]) -> Result<Args> {
     impl Parse for Input {
         fn parse(input: ParseStream<'_>) -> Result<Self> {
             Ok(Self((|| {
-                let content = input.parenthesized().ok()?;
-                let private = content.parse::<Ident>().ok()?;
+                let private = input.parse::<Ident>().ok()?;
                 if private == "__private" {
-                    content.parenthesized().ok()?.parse::<TokenStream>().ok()
+                    input.parenthesized().ok()?.parse::<TokenStream>().ok()
                 } else {
                     None
                 }
@@ -31,10 +30,10 @@ pub(super) fn parse_args(attrs: &[Attribute]) -> Result<Args> {
         bail!(attr, "duplicate #[pin_project] attribute");
     }
 
-    let mut attrs = attrs.iter().filter(|attr| attr.path.is_ident(PIN));
+    let mut attrs = attrs.iter().filter(|attr| attr.path().is_ident(PIN));
 
     let prev = if let Some(attr) = attrs.next() {
-        (attr, syn::parse2::<Input>(attr.tokens.clone()).unwrap().0)
+        (attr, syn::parse2::<Input>(attr.meta.require_list()?.tokens.clone())?.0)
     } else {
         // This only fails if another macro removes `#[pin]`.
         bail!(TokenStream::new(), "#[pin_project] attribute has been removed");
@@ -46,7 +45,7 @@ pub(super) fn parse_args(attrs: &[Attribute]) -> Result<Args> {
         // has the same span as `#[pin_project]`, it is possible
         // that a useless error message will be generated.
         // So, use the span of `prev_attr` if it is not a valid attribute.
-        let res = syn::parse2::<Input>(attr.tokens.clone()).unwrap().0;
+        let res = syn::parse2::<Input>(attr.meta.require_list()?.tokens.clone())?.0;
         let span = match (prev_res, res) {
             (Some(_), _) => attr,
             (None, _) => prev_attr,

pin-project-internal/src/pin_project/derive.rs

@@ -1,9 +1,9 @@
 use proc_macro2::{Delimiter, Group, Span, TokenStream};
 use quote::{format_ident, quote, quote_spanned, ToTokens};
 use syn::{
-    parse_quote, token, visit_mut::VisitMut, Attribute, Data, DataEnum, DeriveInput, Error, Field,
-    Fields, FieldsNamed, FieldsUnnamed, Generics, Ident, Index, Lifetime, LifetimeDef, Meta,
-    MetaList, MetaNameValue, NestedMeta, Result, Token, Type, Variant, Visibility, WhereClause,
+    parse_quote, punctuated::Punctuated, token, visit_mut::VisitMut, Attribute, Data, DataEnum,
+    DeriveInput, Error, Field, Fields, FieldsNamed, FieldsUnnamed, Generics, Ident, Index,
+    Lifetime, LifetimeParam, Meta, Result, Token, Type, Variant, Visibility, WhereClause,
 };
 
 use super::{
@@ -305,7 +305,7 @@ fn validate_struct(ident: &Ident, fields: &Fields) -> Result<()> {
 fn validate_enum(brace_token: token::Brace, variants: &Variants) -> Result<()> {
     if variants.is_empty() {
         return Err(Error::new(
-            brace_token.span,
+            brace_token.span.join(),
             "#[pin_project] attribute may not be used on enums without variants",
         ));
     }
@@ -569,7 +569,9 @@ fn visit_fields<'a>(
     let mut proj_move = TokenStream::new();
     let mut pinned_bindings = Vec::with_capacity(fields.len());
 
-    for (i, Field { attrs, vis, ident, colon_token, ty }) in fields.iter().enumerate() {
+    for (i, Field { attrs, vis, ident, colon_token, ty, mutability: _ }) in
+        fields.iter().enumerate()
+    {
         let binding = ident.clone().unwrap_or_else(|| format_ident!("_{}", i));
         proj_pat.extend(quote!(#binding,));
         let lifetime = &cx.proj.lifetime;
@@ -768,7 +770,7 @@ fn make_unpin_impl(cx: &Context<'_>) -> TokenStream {
             // This ensures that any unused type parameters
             // don't end up with `Unpin` bounds.
             let lifetime_fields = cx.orig.generics.lifetimes().enumerate().map(
-                |(i, LifetimeDef { lifetime, .. })| {
+                |(i, LifetimeParam { lifetime, .. })| {
                     let field_ident = format_ident!("__lifetime{}", i);
                     quote!(#field_ident: &#lifetime ())
                 },
@@ -1016,33 +1018,26 @@ fn make_proj_impl(
 /// - Generates a function that borrows fields without an unsafe block and
 ///   forbidding `unaligned_references` lint.
 fn ensure_not_packed(orig: &OriginalType<'_>, fields: Option<&Fields>) -> Result<TokenStream> {
-    for meta in orig.attrs.iter().filter_map(|attr| attr.parse_meta().ok()) {
-        if let Meta::List(list) = meta {
+    for attr in orig.attrs {
+        if let Meta::List(ref list) = attr.meta {
             if list.path.is_ident("repr") {
-                for repr in list.nested.iter() {
-                    match repr {
-                        NestedMeta::Meta(Meta::Path(path))
-                        | NestedMeta::Meta(Meta::List(MetaList { path, .. }))
-                        | NestedMeta::Meta(Meta::NameValue(MetaNameValue { path, .. })) => {
-                            if path.is_ident("packed") {
-                                let msg = if fields.is_none() {
-                                    // #[repr(packed)] cannot be apply on enums and will be rejected by rustc.
-                                    // However, we should not rely on the behavior of rustc that rejects this.
-                                    // https://github.com/taiki-e/pin-project/pull/324#discussion_r612388001
-                                    "#[repr(packed)] attribute should be applied to a struct or union"
-                                } else if let NestedMeta::Meta(Meta::NameValue(..)) = repr {
-                                    // #[repr(packed = "")] is not valid format of #[repr(packed)] and will be
-                                    // rejected by rustc.
-                                    // However, we should not rely on the behavior of rustc that rejects this.
-                                    // https://github.com/taiki-e/pin-project/pull/324#discussion_r612388001
-                                    "#[repr(packed)] attribute should not be name-value pair"
-                                } else {
-                                    "#[pin_project] attribute may not be used on #[repr(packed)] types"
-                                };
-                                bail!(repr, msg);
-                            }
-                        }
-                        NestedMeta::Lit(..) => {}
+                for repr in list.parse_args_with(Punctuated::<Meta, Token![,]>::parse_terminated)? {
+                    if repr.path().is_ident("packed") {
+                        let msg = if fields.is_none() {
+                            // #[repr(packed)] cannot be apply on enums and will be rejected by rustc.
+                            // However, we should not rely on the behavior of rustc that rejects this.
+                            // https://github.com/taiki-e/pin-project/pull/324#discussion_r612388001
+                            "#[repr(packed)] attribute should be applied to a struct or union"
+                        } else if repr.require_name_value().is_ok() {
+                            // #[repr(packed = "")] is not valid format of #[repr(packed)] and will be
+                            // rejected by rustc.
+                            // However, we should not rely on the behavior of rustc that rejects this.
+                            // https://github.com/taiki-e/pin-project/pull/324#discussion_r612388001
+                            "#[repr(packed)] attribute should not be name-value pair"
+                        } else {
+                            "#[pin_project] attribute may not be used on #[repr(packed)] types"
+                        };
+                        bail!(repr, msg);
                     }
                 }
             }

pin-project-internal/src/pinned_drop.rs

@@ -1,16 +1,18 @@
 use proc_macro2::TokenStream;
 use quote::{format_ident, quote, ToTokens};
 use syn::{
-    parse_quote, spanned::Spanned, visit_mut::VisitMut, Error, FnArg, GenericArgument, ImplItem,
-    ItemImpl, Pat, PatIdent, Path, PathArguments, Result, ReturnType, Signature, Token, Type,
-    TypePath, TypeReference,
+    parse_quote, spanned::Spanned, token::Colon, visit_mut::VisitMut, Error, FnArg,
+    GenericArgument, Ident, ImplItem, ItemImpl, Pat, PatIdent, PatType, Path, PathArguments,
+    Result, ReturnType, Signature, Token, Type, TypePath, TypeReference,
 };
 
-use crate::utils::{parse_as_empty, prepend_underscore_to_self, ReplaceReceiver, SliceExt};
+use crate::utils::{ReplaceReceiver, SliceExt};
 
 pub(crate) fn attribute(args: &TokenStream, mut input: ItemImpl) -> TokenStream {
     let res = (|| -> Result<()> {
-        parse_as_empty(args)?;
+        if !args.is_empty() {
+            bail!(args, "unexpected argument: `{}`", args)
+        }
         validate_impl(&input)?;
         expand_impl(&mut input);
         Ok(())
@@ -85,7 +87,7 @@ fn validate_impl(item: &ItemImpl) -> Result<()> {
         ImplItem::Type(item) => {
             bail!(item, "type `{}` is not a member of trait `PinnedDrop`", item.ident)
         }
-        ImplItem::Method(method) => {
+        ImplItem::Fn(method) => {
             validate_sig(&method.sig)?;
             if i == 0 {
                 Ok(())
@@ -124,14 +126,15 @@ fn validate_sig(sig: &Signature) -> Result<()> {
 
     match sig.inputs.len() {
         1 => {}
-        0 => return Err(Error::new(sig.paren_token.span, INVALID_ARGUMENT)),
+        0 => return Err(Error::new(sig.paren_token.span.join(), INVALID_ARGUMENT)),
         _ => bail!(sig.inputs, INVALID_ARGUMENT),
     }
 
-    if let Some(FnArg::Typed(arg)) = sig.receiver() {
+    if let Some(arg) = sig.receiver() {
         // (mut) self: <path>
         if let Some(path) = get_ty_path(&arg.ty) {
-            let ty = path.segments.last().unwrap();
+            let ty =
+                path.segments.last().expect("Type paths should always have at least one segment");
             if let PathArguments::AngleBracketed(args) = &ty.arguments {
                 // (mut) self: (<path>::)<ty><&mut <elem>..>
                 if let Some(GenericArgument::Type(Type::Reference(TypeReference {
@@ -175,25 +178,16 @@ fn validate_sig(sig: &Signature) -> Result<()> {
 // }
 //
 fn expand_impl(item: &mut ItemImpl) {
-    fn get_arg_pat(arg: &mut FnArg) -> Option<&mut PatIdent> {
-        if let FnArg::Typed(arg) = arg {
-            if let Pat::Ident(ident) = &mut *arg.pat {
-                return Some(ident);
-            }
-        }
-        None
-    }
-
     // `PinnedDrop` is a private trait and should not appear in docs.
     item.attrs.push(parse_quote!(#[doc(hidden)]));
 
-    let path = &mut item.trait_.as_mut().unwrap().1;
+    let path = &mut item.trait_.as_mut().expect("unexpected inherent impl").1;
     *path = parse_quote_spanned! { path.span() =>
         ::pin_project::__private::PinnedDrop
     };
 
     let method =
-        if let ImplItem::Method(method) = &mut item.items[0] { method } else { unreachable!() };
+        if let ImplItem::Fn(method) = &mut item.items[0] { method } else { unreachable!() };
 
     // `fn drop(mut self: Pin<&mut Self>)` -> `fn __drop_inner<T>(mut __self: Pin<&mut Receiver>)`
     let drop_inner = {
@@ -203,8 +197,20 @@ fn expand_impl(item: &mut ItemImpl) {
         drop_inner.block.stmts.insert(0, parse_quote!(fn #ident() {}));
         drop_inner.sig.ident = ident;
         drop_inner.sig.generics = item.generics.clone();
-        let self_pat = get_arg_pat(&mut drop_inner.sig.inputs[0]).unwrap();
-        prepend_underscore_to_self(&mut self_pat.ident);
+        let receiver = drop_inner.sig.receiver().expect("drop() should have a receiver").clone();
+        let pat = Box::new(Pat::Ident(PatIdent {
+            attrs: Vec::new(),
+            by_ref: None,
+            mutability: receiver.mutability,
+            ident: Ident::new("__self", receiver.self_token.span()),
+            subpat: None,
+        }));
+        drop_inner.sig.inputs[0] = FnArg::Typed(PatType {
+            attrs: receiver.attrs,
+            pat,
+            colon_token: Colon::default(),
+            ty: receiver.ty,
+        });
         let self_ty = if let Type::Path(ty) = &*item.self_ty { ty } else { unreachable!() };
         let mut visitor = ReplaceReceiver(self_ty);
         visitor.visit_signature_mut(&mut drop_inner.sig);
@@ -214,9 +220,12 @@ fn expand_impl(item: &mut ItemImpl) {
 
     // `fn drop(mut self: Pin<&mut Self>)` -> `unsafe fn drop(self: Pin<&mut Self>)`
     method.sig.unsafety = Some(<Token![unsafe]>::default());
-    let self_pat = get_arg_pat(&mut method.sig.inputs[0]).unwrap();
-    self_pat.mutability = None;
-    let self_token = &self_pat.ident;
+    let self_token = if let FnArg::Receiver(ref mut rec) = method.sig.inputs[0] {
+        rec.mutability = None;
+        &rec.self_token
+    } else {
+        panic!("drop() should have a receiver")
+    };
 
     method.block.stmts = parse_quote! {
         #[allow(clippy::needless_pass_by_value)] // This lint does not warn the receiver.