[mmtk-macro] Update syn dependency to 2.0

Author: wks

macros/Cargo.toml

@@ -13,6 +13,6 @@ proc-macro = true
 
 [dependencies]
 proc-macro2 = "1.0.37"
-syn = { version = "1.0.91", features = ["extra-traits"] }
+syn = { version = "2.0.29", features = ["extra-traits"] }
 quote = "1.0.18"
 proc-macro-error = "1.0.4"

macros/src/lib.rs

@@ -34,35 +34,35 @@ pub fn derive_plan_trace_object(input: TokenStream) -> TokenStream {
     let ident = input.ident;
     let (impl_generics, ty_generics, where_clause) = input.generics.split_for_impl();
 
-    let output = if let syn::Data::Struct(syn::DataStruct {
+    let syn::Data::Struct(syn::DataStruct {
         fields: syn::Fields::Named(ref fields),
         ..
-    }) = input.data
-    {
-        let spaces = util::get_fields_with_attribute(fields, "trace");
-        let post_scan_spaces = util::get_fields_with_attribute(fields, "post_scan");
-        let fallback = util::get_unique_field_with_attribute(fields, "fallback_trace");
+    }) = input.data else {
+        abort_call_site!("`#[derive(PlanTraceObject)]` only supports structs with named fields.");
+    };
+
+    let spaces = util::get_fields_with_attribute(fields, "trace");
+    let post_scan_spaces = util::get_fields_with_attribute(fields, "post_scan");
+    let fallback = util::get_unique_field_with_attribute(fields, "fallback_trace");
+
+    let trace_object_function =
+        plan_trace_object_impl::generate_trace_object(&spaces, &fallback, &ty_generics);
+    let post_scan_object_function = plan_trace_object_impl::generate_post_scan_object(
+        &post_scan_spaces,
+        &fallback,
+        &ty_generics,
+    );
+    let may_move_objects_function =
+        plan_trace_object_impl::generate_may_move_objects(&spaces, &fallback, &ty_generics);
 
-        let trace_object_function =
-            plan_trace_object_impl::generate_trace_object(&spaces, &fallback, &ty_generics);
-        let post_scan_object_function = plan_trace_object_impl::generate_post_scan_object(
-            &post_scan_spaces,
-            &fallback,
-            &ty_generics,
-        );
-        let may_move_objects_function =
-            plan_trace_object_impl::generate_may_move_objects(&spaces, &fallback, &ty_generics);
-        quote! {
-            impl #impl_generics crate::plan::PlanTraceObject #ty_generics for #ident #ty_generics #where_clause {
-                #trace_object_function
+    let output = quote! {
+        impl #impl_generics crate::plan::PlanTraceObject #ty_generics for #ident #ty_generics #where_clause {
+            #trace_object_function
 
-                #post_scan_object_function
+            #post_scan_object_function
 
-                #may_move_objects_function
-            }
+            #may_move_objects_function
         }
-    } else {
-        abort_call_site!("`#[derive(PlanTraceObject)]` only supports structs with named fields.")
     };
 
     // Debug the output - use the following code to debug the generated code (when cargo exapand is not working)

macros/src/plan_trace_object_impl.rs

@@ -1,6 +1,7 @@
 use proc_macro2::TokenStream as TokenStream2;
+use proc_macro_error::abort_call_site;
 use quote::quote;
-use syn::{Field, TypeGenerics};
+use syn::{Expr, Field, TypeGenerics};
 
 use crate::util;
 
@@ -16,20 +17,23 @@ pub(crate) fn generate_trace_object<'a>(
 
         // Figure out copy
         let trace_attr = util::get_field_attribute(f, "trace").unwrap();
-        let copy = if !trace_attr.tokens.is_empty() {
-            use syn::Token;
-            use syn::NestedMeta;
-            use syn::punctuated::Punctuated;
-
-            let args = trace_attr.parse_args_with(Punctuated::<NestedMeta, Token![,]>::parse_terminated).unwrap();
-            // CopySemantics::X is a path.
-            if let Some(NestedMeta::Meta(syn::Meta::Path(p))) = args.first() {
-                quote!{ Some(#p) }
-            } else {
+        let copy = match &trace_attr.meta {
+            syn::Meta::Path(_) => {
+                // #[trace]
                 quote!{ None }
-            }
-        } else {
-            quote!{ None }
+            },
+            syn::Meta::List(list) => {
+                // #[trace(CopySemantics::BlahBlah)]
+                let copy_semantics = list.parse_args::<Expr>().unwrap_or_else(|_| {
+                    abort_call_site!("In `#[trace(copy_semantics)]`, copy_semantics must be an expression.");
+                });
+
+                quote!{ Some(#copy_semantics) }
+            },
+            syn::Meta::NameValue(_) => {
+                // #[trace = BlahBlah]
+                abort_call_site!("The #[trace] macro does not support name-value form.");
+            },
         };
 
         quote! {

macros/src/util.rs

@@ -5,11 +5,11 @@ pub fn get_field_attribute<'f>(field: &'f Field, attr_name: &str) -> Option<&'f
     let attrs = field
         .attrs
         .iter()
-        .filter(|a| a.path.is_ident(attr_name))
+        .filter(|a| a.path().is_ident(attr_name))
         .collect::<Vec<_>>();
     if attrs.len() > 1 {
         let second_attr = attrs.get(1).unwrap();
-        abort! { second_attr.path.span(), "Duplicated attribute: #[{}]", attr_name }
+        abort! { second_attr.path().span(), "Duplicated attribute: #[{}]", attr_name }
     };
 
     attrs.get(0).cloned()
@@ -35,7 +35,7 @@ pub fn get_unique_field_with_attribute<'f>(
                 result = Some(field);
                 continue;
             } else {
-                let span = attr.path.span();
+                let span = attr.path().span();
                 abort! { span, "At most one field in a struct can have the #[{}] attribute.", attr_name };
             }
         }