migrate rustc_macros to syn 2.0

10 files changed, 257 insertions, 338 deletions

diff --git a/compiler/rustc_macros/Cargo.toml b/compiler/rustc_macros/Cargo.toml
index 547c8debb50..745983e7e86 100644
--- a/compiler/rustc_macros/Cargo.toml
+++ b/compiler/rustc_macros/Cargo.toml
@@ -10,8 +10,8 @@ proc-macro = true
 annotate-snippets = "0.9"
 fluent-bundle = "0.15.2"
 fluent-syntax = "0.11"
-synstructure = "0.12.1"
-syn = { version = "1", features = ["full"] }
+synstructure = "0.13.0"
+syn = { version = "2", features = ["full"] }
 proc-macro2 = "1"
 quote = "1"
 unic-langid = { version = "0.9.0", features = ["macros"] }
diff --git a/compiler/rustc_macros/src/diagnostics/diagnostic_builder.rs b/compiler/rustc_macros/src/diagnostics/diagnostic_builder.rs
index 7fbe3bc2888..fb75d87f8d2 100644
--- a/compiler/rustc_macros/src/diagnostics/diagnostic_builder.rs
+++ b/compiler/rustc_macros/src/diagnostics/diagnostic_builder.rs
@@ -1,8 +1,7 @@
 #![deny(unused_must_use)]
 
 use crate::diagnostics::error::{
-    invalid_nested_attr, span_err, throw_invalid_attr, throw_invalid_nested_attr, throw_span_err,
-    DiagnosticDeriveError,
+    span_err, throw_invalid_attr, throw_span_err, DiagnosticDeriveError,
 };
 use crate::diagnostics::utils::{
     build_field_mapping, is_doc_comment, report_error_if_not_applied_to_span, report_type_error,
@@ -11,9 +10,8 @@ use crate::diagnostics::utils::{
 };
 use proc_macro2::{Ident, Span, TokenStream};
 use quote::{format_ident, quote};
-use syn::{
-    parse_quote, spanned::Spanned, Attribute, Meta, MetaList, MetaNameValue, NestedMeta, Path, Type,
-};
+use syn::Token;
+use syn::{parse_quote, spanned::Spanned, Attribute, Meta, Path, Type};
 use synstructure::{BindingInfo, Structure, VariantInfo};
 
 /// What kind of diagnostic is being derived - a fatal/error/warning or a lint?
@@ -77,7 +75,7 @@ impl DiagnosticDeriveBuilder {
         match ast.data {
             syn::Data::Struct(..) | syn::Data::Enum(..) => (),
             syn::Data::Union(..) => {
-                span_err(span, "diagnostic derives can only be used on structs and enums");
+                span_err(span, "diagnostic derives can only be used on structs and enums").emit();
             }
         }
 
@@ -160,8 +158,7 @@ impl<'a> DiagnosticDeriveVariantBuilder<'a> {
         };
 
         if let SubdiagnosticKind::MultipartSuggestion { .. } = subdiag {
-            let meta = attr.parse_meta()?;
-            throw_invalid_attr!(attr, &meta, |diag| diag
+            throw_invalid_attr!(attr, |diag| diag
                 .help("consider creating a `Subdiagnostic` instead"));
         }
 
@@ -191,71 +188,39 @@ impl<'a> DiagnosticDeriveVariantBuilder<'a> {
             return Ok(quote! {});
         }
 
-        let name = attr.path.segments.last().unwrap().ident.to_string();
+        let name = attr.path().segments.last().unwrap().ident.to_string();
         let name = name.as_str();
-        let meta = attr.parse_meta()?;
 
-        if name == "diag" {
-            let Meta::List(MetaList { ref nested, .. }) = meta else {
-                throw_invalid_attr!(
-                    attr,
-                    &meta
-                );
-            };
+        let mut first = true;
 
-            let mut nested_iter = nested.into_iter().peekable();
+        if name == "diag" {
+            let mut tokens = TokenStream::new();
+            attr.parse_nested_meta(|nested| {
+                let path = &nested.path;
 
-            match nested_iter.peek() {
-                Some(NestedMeta::Meta(Meta::Path(slug))) => {
-                    self.slug.set_once(slug.clone(), slug.span().unwrap());
-                    nested_iter.next();
+                if first && (nested.input.is_empty() || nested.input.peek(Token![,])) {
+                    self.slug.set_once(path.clone(), path.span().unwrap());
+                    first = false;
+                    return Ok(())
                 }
-                Some(NestedMeta::Meta(Meta::NameValue { .. })) => {}
-                Some(nested_attr) => throw_invalid_nested_attr!(attr, nested_attr, |diag| diag
-                    .help("a diagnostic slug is required as the first argument")),
-                None => throw_invalid_attr!(attr, &meta, |diag| diag
-                    .help("a diagnostic slug is required as the first argument")),
-            };
 
-            // Remaining attributes are optional, only `code = ".."` at the moment.
-            let mut tokens = TokenStream::new();
-            for nested_attr in nested_iter {
-                let (value, path) = match nested_attr {
-                    NestedMeta::Meta(Meta::NameValue(MetaNameValue {
-                        lit: syn::Lit::Str(value),
-                        path,
-                        ..
-                    })) => (value, path),
-                    NestedMeta::Meta(Meta::Path(_)) => {
-                        invalid_nested_attr(attr, nested_attr)
-                            .help("diagnostic slug must be the first argument")
-                            .emit();
-                        continue;
-                    }
-                    _ => {
-                        invalid_nested_attr(attr, nested_attr).emit();
-                        continue;
-                    }
+                first = false;
+
+                let Ok(nested) = nested.value() else {
+                    span_err(nested.input.span().unwrap(), "diagnostic slug must be the first argument").emit();
+                    return Ok(())
                 };
 
-                let nested_name = path.segments.last().unwrap().ident.to_string();
-                // Struct attributes are only allowed to be applied once, and the diagnostic
-                // changes will be set in the initialisation code.
-                let span = value.span().unwrap();
-                match nested_name.as_str() {
-                    "code" => {
-                        self.code.set_once((), span);
-
-                        let code = value.value();
-                        tokens.extend(quote! {
-                            #diag.code(rustc_errors::DiagnosticId::Error(#code.to_string()));
-                        });
-                    }
-                    _ => invalid_nested_attr(attr, nested_attr)
-                        .help("only `code` is a valid nested attributes following the slug")
-                        .emit(),
+                if path.is_ident("code") {
+                    self.code.set_once((), path.span().unwrap());
+
+                    let code = nested.parse::<TokenStream>()?;
+                    tokens.extend(quote! {
+                        #diag.code(rustc_errors::DiagnosticId::Error(#code.to_string()));
+                    });
                 }
-            }
+                Ok(())
+            })?;
             return Ok(tokens);
         }
 
@@ -270,7 +235,7 @@ impl<'a> DiagnosticDeriveVariantBuilder<'a> {
                 Ok(self.add_subdiagnostic(&fn_ident, slug))
             }
             SubdiagnosticKind::Label | SubdiagnosticKind::Suggestion { .. } => {
-                throw_invalid_attr!(attr, &meta, |diag| diag
+                throw_invalid_attr!(attr, |diag| diag
                     .help("`#[label]` and `#[suggestion]` can only be applied to fields"));
             }
             SubdiagnosticKind::MultipartSuggestion { .. } => unreachable!(),
@@ -309,7 +274,7 @@ impl<'a> DiagnosticDeriveVariantBuilder<'a> {
                     return quote! {};
                 }
 
-                let name = attr.path.segments.last().unwrap().ident.to_string();
+                let name = attr.path().segments.last().unwrap().ident.to_string();
                 let needs_clone =
                     name == "primary_span" && matches!(inner_ty, FieldInnerTy::Vec(_));
                 let (binding, needs_destructure) = if needs_clone {
@@ -343,11 +308,10 @@ impl<'a> DiagnosticDeriveVariantBuilder<'a> {
         binding: TokenStream,
     ) -> Result<TokenStream, DiagnosticDeriveError> {
         let diag = &self.parent.diag;
-        let meta = attr.parse_meta()?;
 
-        let ident = &attr.path.segments.last().unwrap().ident;
+        let ident = &attr.path().segments.last().unwrap().ident;
         let name = ident.to_string();
-        match (&meta, name.as_str()) {
+        match (&attr.meta, name.as_str()) {
             // Don't need to do anything - by virtue of the attribute existing, the
             // `set_arg` call will not be generated.
             (Meta::Path(_), "skip_arg") => return Ok(quote! {}),
@@ -361,7 +325,7 @@ impl<'a> DiagnosticDeriveVariantBuilder<'a> {
                         });
                     }
                     DiagnosticDeriveKind::LintDiagnostic => {
-                        throw_invalid_attr!(attr, &meta, |diag| {
+                        throw_invalid_attr!(attr, |diag| {
                             diag.help("the `primary_span` field attribute is not valid for lint diagnostics")
                         })
                     }
@@ -378,26 +342,34 @@ impl<'a> DiagnosticDeriveVariantBuilder<'a> {
                     return Ok(quote! { #diag.subdiagnostic(#binding); });
                 }
             }
-            (Meta::List(MetaList { ref nested, .. }), "subdiagnostic") => {
-                if nested.len() == 1
-                    && let Some(NestedMeta::Meta(Meta::Path(path))) = nested.first()
-                    && path.is_ident("eager") {
-                        let handler = match &self.parent.kind {
-                            DiagnosticDeriveKind::Diagnostic { handler } => handler,
-                            DiagnosticDeriveKind::LintDiagnostic => {
-                                throw_invalid_attr!(attr, &meta, |diag| {
-                                    diag.help("eager subdiagnostics are not supported on lints")
-                                })
-                            }
-                        };
-                        return Ok(quote! { #diag.eager_subdiagnostic(#handler, #binding); });
-                } else {
-                    throw_invalid_attr!(attr, &meta, |diag| {
-                        diag.help(
-                            "`eager` is the only supported nested attribute for `subdiagnostic`",
-                        )
-                    })
+            (Meta::List(meta_list), "subdiagnostic") => {
+                let err = || {
+                    span_err(
+                        meta_list.span().unwrap(),
+                        "`eager` is the only supported nested attribute for `subdiagnostic`",
+                    )
+                    .emit();
+                };
+
+                let Ok(p): Result<Path, _> = meta_list.parse_args() else {
+                    err();
+                    return Ok(quote! {});
+                };
+
+                if !p.is_ident("eager") {
+                    err();
+                    return Ok(quote! {});
                 }
+
+                let handler = match &self.parent.kind {
+                    DiagnosticDeriveKind::Diagnostic { handler } => handler,
+                    DiagnosticDeriveKind::LintDiagnostic => {
+                        throw_invalid_attr!(attr, |diag| {
+                            diag.help("eager subdiagnostics are not supported on lints")
+                        })
+                    }
+                };
+                return Ok(quote! { #diag.eager_subdiagnostic(#handler, #binding); });
             }
             _ => (),
         }
@@ -432,7 +404,7 @@ impl<'a> DiagnosticDeriveVariantBuilder<'a> {
                 code_init,
             } => {
                 if let FieldInnerTy::Vec(_) = info.ty {
-                    throw_invalid_attr!(attr, &meta, |diag| {
+                    throw_invalid_attr!(attr, |diag| {
                         diag
                         .note("`#[suggestion(...)]` applied to `Vec` field is ambiguous")
                         .help("to show a suggestion consisting of multiple parts, use a `Subdiagnostic` annotated with `#[multipart_suggestion(...)]`")
diff --git a/compiler/rustc_macros/src/diagnostics/error.rs b/compiler/rustc_macros/src/diagnostics/error.rs
index 2d62d593163..b37dc826d28 100644
--- a/compiler/rustc_macros/src/diagnostics/error.rs
+++ b/compiler/rustc_macros/src/diagnostics/error.rs
@@ -1,7 +1,7 @@
 use proc_macro::{Diagnostic, Level, MultiSpan};
 use proc_macro2::TokenStream;
 use quote::quote;
-use syn::{spanned::Spanned, Attribute, Error as SynError, Meta, NestedMeta};
+use syn::{spanned::Spanned, Attribute, Error as SynError, Meta};
 
 #[derive(Debug)]
 pub(crate) enum DiagnosticDeriveError {
@@ -53,6 +53,7 @@ fn path_to_string(path: &syn::Path) -> String {
 }
 
 /// Returns an error diagnostic on span `span` with msg `msg`.
+#[must_use]
 pub(crate) fn span_err(span: impl MultiSpan, msg: &str) -> Diagnostic {
     Diagnostic::spanned(span, Level::Error, msg)
 }
@@ -72,10 +73,10 @@ macro_rules! throw_span_err {
 pub(crate) use throw_span_err;
 
 /// Returns an error diagnostic for an invalid attribute.
-pub(crate) fn invalid_attr(attr: &Attribute, meta: &Meta) -> Diagnostic {
+pub(crate) fn invalid_attr(attr: &Attribute) -> Diagnostic {
     let span = attr.span().unwrap();
-    let path = path_to_string(&attr.path);
-    match meta {
+    let path = path_to_string(attr.path());
+    match attr.meta {
         Meta::Path(_) => span_err(span, &format!("`#[{path}]` is not a valid attribute")),
         Meta::NameValue(_) => {
             span_err(span, &format!("`#[{path} = ...]` is not a valid attribute"))
@@ -89,51 +90,11 @@ pub(crate) fn invalid_attr(attr: &Attribute, meta: &Meta) -> Diagnostic {
 ///
 /// For methods that return a `Result<_, DiagnosticDeriveError>`:
 macro_rules! throw_invalid_attr {
-    ($attr:expr, $meta:expr) => {{ throw_invalid_attr!($attr, $meta, |diag| diag) }};
-    ($attr:expr, $meta:expr, $f:expr) => {{
-        let diag = crate::diagnostics::error::invalid_attr($attr, $meta);
+    ($attr:expr) => {{ throw_invalid_attr!($attr, |diag| diag) }};
+    ($attr:expr, $f:expr) => {{
+        let diag = crate::diagnostics::error::invalid_attr($attr);
         return Err(crate::diagnostics::error::_throw_err(diag, $f));
     }};
 }
 
 pub(crate) use throw_invalid_attr;
-
-/// Returns an error diagnostic for an invalid nested attribute.
-pub(crate) fn invalid_nested_attr(attr: &Attribute, nested: &NestedMeta) -> Diagnostic {
-    let name = attr.path.segments.last().unwrap().ident.to_string();
-    let name = name.as_str();
-
-    let span = nested.span().unwrap();
-    let meta = match nested {
-        syn::NestedMeta::Meta(meta) => meta,
-        syn::NestedMeta::Lit(_) => {
-            return span_err(span, &format!("`#[{name}(\"...\")]` is not a valid attribute"));
-        }
-    };
-
-    let span = meta.span().unwrap();
-    let path = path_to_string(meta.path());
-    match meta {
-        Meta::NameValue(..) => {
-            span_err(span, &format!("`#[{name}({path} = ...)]` is not a valid attribute"))
-        }
-        Meta::Path(..) => span_err(span, &format!("`#[{name}({path})]` is not a valid attribute")),
-        Meta::List(..) => {
-            span_err(span, &format!("`#[{name}({path}(...))]` is not a valid attribute"))
-        }
-    }
-}
-
-/// Emit an error diagnostic for an invalid nested attribute (optionally performing additional
-/// decoration using the `FnOnce` passed in `diag`) and return `Err(ErrorHandled)`.
-///
-/// For methods that return a `Result<_, DiagnosticDeriveError>`:
-macro_rules! throw_invalid_nested_attr {
-    ($attr:expr, $nested_attr:expr) => {{ throw_invalid_nested_attr!($attr, $nested_attr, |diag| diag) }};
-    ($attr:expr, $nested_attr:expr, $f:expr) => {{
-        let diag = crate::diagnostics::error::invalid_nested_attr($attr, $nested_attr);
-        return Err(crate::diagnostics::error::_throw_err(diag, $f));
-    }};
-}
-
-pub(crate) use throw_invalid_nested_attr;
diff --git a/compiler/rustc_macros/src/diagnostics/subdiagnostic.rs b/compiler/rustc_macros/src/diagnostics/subdiagnostic.rs
index 90660fc1f93..2f42a3b0bd4 100644
--- a/compiler/rustc_macros/src/diagnostics/subdiagnostic.rs
+++ b/compiler/rustc_macros/src/diagnostics/subdiagnostic.rs
@@ -1,8 +1,7 @@
 #![deny(unused_must_use)]
 
 use crate::diagnostics::error::{
-    invalid_attr, span_err, throw_invalid_attr, throw_invalid_nested_attr, throw_span_err,
-    DiagnosticDeriveError,
+    invalid_attr, span_err, throw_invalid_attr, throw_span_err, DiagnosticDeriveError,
 };
 use crate::diagnostics::utils::{
     build_field_mapping, is_doc_comment, new_code_ident,
@@ -11,7 +10,7 @@ use crate::diagnostics::utils::{
 };
 use proc_macro2::TokenStream;
 use quote::{format_ident, quote};
-use syn::{spanned::Spanned, Attribute, Meta, MetaList, NestedMeta, Path};
+use syn::{spanned::Spanned, Attribute, Meta, MetaList, Path};
 use synstructure::{BindingInfo, Structure, VariantInfo};
 
 use super::utils::{build_suggestion_code, AllowMultipleAlternatives};
@@ -39,7 +38,8 @@ impl SubdiagnosticDeriveBuilder {
                     span_err(
                         span,
                         "`#[derive(Subdiagnostic)]` can only be used on structs and enums",
-                    );
+                    )
+                    .emit();
                 }
             }
 
@@ -192,7 +192,7 @@ impl<'parent, 'a> SubdiagnosticDeriveVariantBuilder<'parent, 'a> {
             };
 
             let Some(slug) = slug else {
-                let name = attr.path.segments.last().unwrap().ident.to_string();
+                let name = attr.path().segments.last().unwrap().ident.to_string();
                 let name = name.as_str();
 
                 throw_span_err!(
@@ -265,17 +265,18 @@ impl<'parent, 'a> SubdiagnosticDeriveVariantBuilder<'parent, 'a> {
         info: FieldInfo<'_>,
         clone_suggestion_code: bool,
     ) -> Result<TokenStream, DiagnosticDeriveError> {
-        let meta = attr.parse_meta()?;
-        match meta {
-            Meta::Path(path) => self.generate_field_code_inner_path(kind_stats, attr, info, path),
-            Meta::List(list @ MetaList { .. }) => self.generate_field_code_inner_list(
+        match &attr.meta {
+            Meta::Path(path) => {
+                self.generate_field_code_inner_path(kind_stats, attr, info, path.clone())
+            }
+            Meta::List(list) => self.generate_field_code_inner_list(
                 kind_stats,
                 attr,
                 info,
                 list,
                 clone_suggestion_code,
             ),
-            _ => throw_invalid_attr!(attr, &meta),
+            _ => throw_invalid_attr!(attr),
         }
     }
 
@@ -296,7 +297,7 @@ impl<'parent, 'a> SubdiagnosticDeriveVariantBuilder<'parent, 'a> {
             "skip_arg" => Ok(quote! {}),
             "primary_span" => {
                 if kind_stats.has_multipart_suggestion {
-                    invalid_attr(attr, &Meta::Path(path))
+                    invalid_attr(attr)
                         .help(
                             "multipart suggestions use one or more `#[suggestion_part]`s rather \
                             than one `#[primary_span]`",
@@ -309,7 +310,7 @@ impl<'parent, 'a> SubdiagnosticDeriveVariantBuilder<'parent, 'a> {
                     // FIXME(#100717): support `Option<Span>` on `primary_span` like in the
                     // diagnostic derive
                     if !matches!(info.ty, FieldInnerTy::Plain(_)) {
-                        throw_invalid_attr!(attr, &Meta::Path(path), |diag| {
+                        throw_invalid_attr!(attr, |diag| {
                             let diag = diag.note("there must be exactly one primary span");
 
                             if kind_stats.has_normal_suggestion {
@@ -335,7 +336,7 @@ impl<'parent, 'a> SubdiagnosticDeriveVariantBuilder<'parent, 'a> {
                     span_err(span, "`#[suggestion_part(...)]` attribute without `code = \"...\"`")
                         .emit();
                 } else {
-                    invalid_attr(attr, &Meta::Path(path))
+                    invalid_attr(attr)
                         .help(
                             "`#[suggestion_part(...)]` is only valid in multipart suggestions, \
                              use `#[primary_span]` instead",
@@ -375,7 +376,7 @@ impl<'parent, 'a> SubdiagnosticDeriveVariantBuilder<'parent, 'a> {
                     span_attrs.push("primary_span")
                 }
 
-                invalid_attr(attr, &Meta::Path(path))
+                invalid_attr(attr)
                     .help(format!(
                         "only `{}`, `applicability` and `skip_arg` are valid field attributes",
                         span_attrs.join(", ")
@@ -394,7 +395,7 @@ impl<'parent, 'a> SubdiagnosticDeriveVariantBuilder<'parent, 'a> {
         kind_stats: KindsStatistics,
         attr: &Attribute,
         info: FieldInfo<'_>,
-        list: MetaList,
+        list: &MetaList,
         clone_suggestion_code: bool,
     ) -> Result<TokenStream, DiagnosticDeriveError> {
         let span = attr.span().unwrap();
@@ -405,7 +406,7 @@ impl<'parent, 'a> SubdiagnosticDeriveVariantBuilder<'parent, 'a> {
         match name {
             "suggestion_part" => {
                 if !kind_stats.has_multipart_suggestion {
-                    throw_invalid_attr!(attr, &Meta::List(list), |diag| {
+                    throw_invalid_attr!(attr, |diag| {
                         diag.help(
                             "`#[suggestion_part(...)]` is only valid in multipart suggestions",
                         )
@@ -417,31 +418,26 @@ impl<'parent, 'a> SubdiagnosticDeriveVariantBuilder<'parent, 'a> {
                 report_error_if_not_applied_to_span(attr, &info)?;
 
                 let mut code = None;
-                for nested_attr in list.nested.iter() {
-                    let NestedMeta::Meta(ref meta) = nested_attr else {
-                        throw_invalid_nested_attr!(attr, nested_attr);
-                    };
-
-                    let span = meta.span().unwrap();
-                    let nested_name = meta.path().segments.last().unwrap().ident.to_string();
-                    let nested_name = nested_name.as_str();
-
-                    match nested_name {
-                        "code" => {
-                            let code_field = new_code_ident();
-                            let formatting_init = build_suggestion_code(
-                                &code_field,
-                                meta,
-                                self,
-                                AllowMultipleAlternatives::No,
-                            );
-                            code.set_once((code_field, formatting_init), span);
-                        }
-                        _ => throw_invalid_nested_attr!(attr, nested_attr, |diag| {
-                            diag.help("`code` is the only valid nested attribute")
-                        }),
+
+                list.parse_nested_meta(|nested| {
+                    if nested.path.is_ident("code") {
+                        let code_field = new_code_ident();
+                        let formatting_init = build_suggestion_code(
+                            &code_field,
+                            nested,
+                            self,
+                            AllowMultipleAlternatives::No,
+                        );
+                        code.set_once((code_field, formatting_init), span);
+                    } else {
+                        span_err(
+                            nested.path.span().unwrap(),
+                            "`code` is the only valid nested attribute",
+                        )
+                        .emit();
                     }
-                }
+                    Ok(())
+                })?;
 
                 let Some((code_field, formatting_init)) = code.value() else {
                     span_err(span, "`#[suggestion_part(...)]` attribute without `code = \"...\"`")
@@ -458,7 +454,7 @@ impl<'parent, 'a> SubdiagnosticDeriveVariantBuilder<'parent, 'a> {
                 };
                 Ok(quote! { suggestions.push((#binding, #code_field)); })
             }
-            _ => throw_invalid_attr!(attr, &Meta::List(list), |diag| {
+            _ => throw_invalid_attr!(attr, |diag| {
                 let mut span_attrs = vec![];
                 if kind_stats.has_multipart_suggestion {
                     span_attrs.push("suggestion_part");
diff --git a/compiler/rustc_macros/src/diagnostics/utils.rs b/compiler/rustc_macros/src/diagnostics/utils.rs
index 65bb154d7f3..38292df6d85 100644
--- a/compiler/rustc_macros/src/diagnostics/utils.rs
+++ b/compiler/rustc_macros/src/diagnostics/utils.rs
@@ -1,5 +1,5 @@
 use crate::diagnostics::error::{
-    span_err, throw_invalid_attr, throw_invalid_nested_attr, throw_span_err, DiagnosticDeriveError,
+    span_err, throw_invalid_attr, throw_span_err, DiagnosticDeriveError,
 };
 use proc_macro::Span;
 use proc_macro2::{Ident, TokenStream};
@@ -8,11 +8,13 @@ use std::cell::RefCell;
 use std::collections::{BTreeSet, HashMap};
 use std::fmt;
 use std::str::FromStr;
+use syn::meta::ParseNestedMeta;
+use syn::punctuated::Punctuated;
+use syn::{parenthesized, LitStr, Path, Token};
 use syn::{spanned::Spanned, Attribute, Field, Meta, Type, TypeTuple};
-use syn::{MetaList, MetaNameValue, NestedMeta, Path};
 use synstructure::{BindingInfo, VariantInfo};
 
-use super::error::{invalid_attr, invalid_nested_attr};
+use super::error::invalid_attr;
 
 thread_local! {
     pub static CODE_IDENT_COUNT: RefCell<u32> = RefCell::new(0);
@@ -60,8 +62,8 @@ pub(crate) fn report_type_error(
     attr: &Attribute,
     ty_name: &str,
 ) -> Result<!, DiagnosticDeriveError> {
-    let name = attr.path.segments.last().unwrap().ident.to_string();
-    let meta = attr.parse_meta()?;
+    let name = attr.path().segments.last().unwrap().ident.to_string();
+    let meta = &attr.meta;
 
     throw_span_err!(
         attr.span().unwrap(),
@@ -422,55 +424,53 @@ pub(super) enum AllowMultipleAlternatives {
 /// `#[suggestion*(code("foo", "bar"))]` attribute field
 pub(super) fn build_suggestion_code(
     code_field: &Ident,
-    meta: &Meta,
+    nested: ParseNestedMeta<'_>,
     fields: &impl HasFieldMap,
     allow_multiple: AllowMultipleAlternatives,
 ) -> TokenStream {
-    let values = match meta {
-        // `code = "foo"`
-        Meta::NameValue(MetaNameValue { lit: syn::Lit::Str(s), .. }) => vec![s],
-        // `code("foo", "bar")`
-        Meta::List(MetaList { nested, .. }) => {
+    let values = match (|| {
+        let values: Vec<LitStr> = if let Ok(val) = nested.value() {
+            vec![val.parse()?]
+        } else {
+            let content;
+            parenthesized!(content in nested.input);
+
             if let AllowMultipleAlternatives::No = allow_multiple {
                 span_err(
-                    meta.span().unwrap(),
+                    nested.input.span().unwrap(),
                     "expected exactly one string literal for `code = ...`",
                 )
                 .emit();
                 vec![]
-            } else if nested.is_empty() {
-                span_err(
-                    meta.span().unwrap(),
-                    "expected at least one string literal for `code(...)`",
-                )
-                .emit();
-                vec![]
             } else {
-                nested
-                    .into_iter()
-                    .filter_map(|item| {
-                        if let NestedMeta::Lit(syn::Lit::Str(s)) = item {
-                            Some(s)
-                        } else {
-                            span_err(
-                                item.span().unwrap(),
-                                "`code(...)` must contain only string literals",
-                            )
-                            .emit();
-                            None
-                        }
-                    })
-                    .collect()
+                let literals = Punctuated::<LitStr, Token![,]>::parse_terminated(&content);
+
+                match literals {
+                    Ok(p) if p.is_empty() => {
+                        span_err(
+                            content.span().unwrap(),
+                            "expected at least one string literal for `code(...)`",
+                        )
+                        .emit();
+                        vec![]
+                    }
+                    Ok(p) => p.into_iter().collect(),
+                    Err(_) => {
+                        span_err(
+                            content.span().unwrap(),
+                            "`code(...)` must contain only string literals",
+                        )
+                        .emit();
+                        vec![]
+                    }
+                }
             }
-        }
-        _ => {
-            span_err(
-                meta.span().unwrap(),
-                r#"`code = "..."`/`code(...)` must contain only string literals"#,
-            )
-            .emit();
-            vec![]
-        }
+        };
+
+        Ok(values)
+    })() {
+        Ok(x) => x,
+        Err(e) => return e.into_compile_error(),
     };
 
     if let AllowMultipleAlternatives::Yes = allow_multiple {
@@ -601,11 +601,9 @@ impl SubdiagnosticKind {
 
         let span = attr.span().unwrap();
 
-        let name = attr.path.segments.last().unwrap().ident.to_string();
+        let name = attr.path().segments.last().unwrap().ident.to_string();
         let name = name.as_str();
 
-        let meta = attr.parse_meta()?;
-
         let mut kind = match name {
             "label" => SubdiagnosticKind::Label,
             "note" => SubdiagnosticKind::Note,
@@ -618,7 +616,7 @@ impl SubdiagnosticKind {
                     name.strip_prefix("suggestion").and_then(SuggestionKind::from_suffix)
                 {
                     if suggestion_kind != SuggestionKind::Normal {
-                        invalid_attr(attr, &meta)
+                        invalid_attr(attr)
                             .help(format!(
                                 r#"Use `#[suggestion(..., style = "{suggestion_kind}")]` instead"#
                             ))
@@ -635,7 +633,7 @@ impl SubdiagnosticKind {
                     name.strip_prefix("multipart_suggestion").and_then(SuggestionKind::from_suffix)
                 {
                     if suggestion_kind != SuggestionKind::Normal {
-                        invalid_attr(attr, &meta)
+                        invalid_attr(attr)
                             .help(format!(
                                 r#"Use `#[multipart_suggestion(..., style = "{suggestion_kind}")]` instead"#
                             ))
@@ -647,16 +645,16 @@ impl SubdiagnosticKind {
                         applicability: None,
                     }
                 } else {
-                    throw_invalid_attr!(attr, &meta);
+                    throw_invalid_attr!(attr);
                 }
             }
         };
 
-        let nested = match meta {
-            Meta::List(MetaList { ref nested, .. }) => {
+        let list = match &attr.meta {
+            Meta::List(list) => {
                 // An attribute with properties, such as `#[suggestion(code = "...")]` or
                 // `#[error(some::slug)]`
-                nested
+                list
             }
             Meta::Path(_) => {
                 // An attribute without a slug or other properties, such as `#[note]` - return
@@ -678,52 +676,51 @@ impl SubdiagnosticKind {
                 }
             }
             _ => {
-                throw_invalid_attr!(attr, &meta)
+                throw_invalid_attr!(attr)
             }
         };
 
         let mut code = None;
         let mut suggestion_kind = None;
 
-        let mut nested_iter = nested.into_iter().peekable();
+        let mut first = true;
+        let mut slug = None;
 
-        // Peek at the first nested attribute: if it's a slug path, consume it.
-        let slug = if let Some(NestedMeta::Meta(Meta::Path(path))) = nested_iter.peek() {
-            let path = path.clone();
-            // Advance the iterator.
-            nested_iter.next();
-            Some(path)
-        } else {
-            None
-        };
-
-        for nested_attr in nested_iter {
-            let meta = match nested_attr {
-                NestedMeta::Meta(ref meta) => meta,
-                NestedMeta::Lit(_) => {
-                    invalid_nested_attr(attr, nested_attr).emit();
-                    continue;
+        list.parse_nested_meta(|nested| {
+            if nested.input.is_empty() || nested.input.peek(Token![,]) {
+                if first {
+                    slug = Some(nested.path);
+                } else {
+                    span_err(nested.input.span().unwrap(), "a diagnostic slug must be the first argument to the attribute").emit();
                 }
-            };
 
-            let span = meta.span().unwrap();
-            let nested_name = meta.path().segments.last().unwrap().ident.to_string();
+                first = false;
+                return Ok(());
+            }
+
+            first = false;
+
+            let nested_name = nested.path.segments.last().unwrap().ident.to_string();
             let nested_name = nested_name.as_str();
 
-            let string_value = match meta {
-                Meta::NameValue(MetaNameValue { lit: syn::Lit::Str(value), .. }) => Some(value),
+            let path_span = nested.path.span().unwrap();
+            let val_span = nested.input.span().unwrap();
 
-                Meta::Path(_) => throw_invalid_nested_attr!(attr, nested_attr, |diag| {
-                    diag.help("a diagnostic slug must be the first argument to the attribute")
-                }),
-                _ => None,
-            };
+            macro get_string() {
+                {
+                    let Ok(value) = nested.value().and_then(|x| x.parse::<LitStr>()) else {
+                        span_err(val_span, "expected `= \"xxx\"`").emit();
+                        return Ok(());
+                    };
+                    value
+                }
+            }
 
             match (nested_name, &mut kind) {
                 ("code", SubdiagnosticKind::Suggestion { code_field, .. }) => {
                     let code_init = build_suggestion_code(
                         code_field,
-                        meta,
+                        nested,
                         fields,
                         AllowMultipleAlternatives::Yes,
                     );
@@ -734,13 +731,9 @@ impl SubdiagnosticKind {
                     SubdiagnosticKind::Suggestion { ref mut applicability, .. }
                     | SubdiagnosticKind::MultipartSuggestion { ref mut applicability, .. },
                 ) => {
-                    let Some(value) = string_value else {
-                        invalid_nested_attr(attr, nested_attr).emit();
-                        continue;
-                    };
-
+                    let value = get_string!();
                     let value = Applicability::from_str(&value.value()).unwrap_or_else(|()| {
-                        span_err(span, "invalid applicability").emit();
+                        span_err(value.span().unwrap(), "invalid applicability").emit();
                         Applicability::Unspecified
                     });
                     applicability.set_once(value, span);
@@ -750,10 +743,7 @@ impl SubdiagnosticKind {
                     SubdiagnosticKind::Suggestion { .. }
                     | SubdiagnosticKind::MultipartSuggestion { .. },
                 ) => {
-                    let Some(value) = string_value else {
-                        invalid_nested_attr(attr, nested_attr).emit();
-                        continue;
-                    };
+                    let value = get_string!();
 
                     let value = value.value().parse().unwrap_or_else(|()| {
                         span_err(value.span().unwrap(), "invalid suggestion style")
@@ -767,22 +757,24 @@ impl SubdiagnosticKind {
 
                 // Invalid nested attribute
                 (_, SubdiagnosticKind::Suggestion { .. }) => {
-                    invalid_nested_attr(attr, nested_attr)
+                    span_err(path_span, "invalid nested attribute")
                         .help(
                             "only `style`, `code` and `applicability` are valid nested attributes",
                         )
                         .emit();
                 }
                 (_, SubdiagnosticKind::MultipartSuggestion { .. }) => {
-                    invalid_nested_attr(attr, nested_attr)
+                    span_err(path_span, "invalid nested attribute")
                         .help("only `style` and `applicability` are valid nested attributes")
-                        .emit()
+                        .emit();
                 }
                 _ => {
-                    invalid_nested_attr(attr, nested_attr).emit();
+                    span_err(path_span, "invalid nested attribute").emit();
                 }
             }
-        }
+
+            Ok(())
+        })?;
 
         match kind {
             SubdiagnosticKind::Suggestion {
@@ -845,5 +837,5 @@ pub(super) fn should_generate_set_arg(field: &Field) -> bool {
 }
 
 pub(super) fn is_doc_comment(attr: &Attribute) -> bool {
-    attr.path.segments.last().unwrap().ident == "doc"
+    attr.path().segments.last().unwrap().ident == "doc"
 }
diff --git a/compiler/rustc_macros/src/hash_stable.rs b/compiler/rustc_macros/src/hash_stable.rs
index 63bdcea87f8..75a2f7009c2 100644
--- a/compiler/rustc_macros/src/hash_stable.rs
+++ b/compiler/rustc_macros/src/hash_stable.rs
@@ -1,6 +1,6 @@
 use proc_macro2::{self, Ident};
 use quote::quote;
-use syn::{self, parse_quote, Meta, NestedMeta};
+use syn::{self, parse_quote};
 
 struct Attributes {
     ignore: bool,
@@ -10,32 +10,29 @@ struct Attributes {
 fn parse_attributes(field: &syn::Field) -> Attributes {
     let mut attrs = Attributes { ignore: false, project: None };
     for attr in &field.attrs {
-        if let Ok(meta) = attr.parse_meta() {
-            if !meta.path().is_ident("stable_hasher") {
-                continue;
+        let meta = &attr.meta;
+        if !meta.path().is_ident("stable_hasher") {
+            continue;
+        }
+        let mut any_attr = false;
+        let _ = attr.parse_nested_meta(|nested| {
+            if nested.path.is_ident("ignore") {
+                attrs.ignore = true;
+                any_attr = true;
             }
-            let mut any_attr = false;
-            if let Meta::List(list) = meta {
-                for nested in list.nested.iter() {
-                    if let NestedMeta::Meta(meta) = nested {
-                        if meta.path().is_ident("ignore") {
-                            attrs.ignore = true;
-                            any_attr = true;
-                        }
-                        if meta.path().is_ident("project") {
-                            if let Meta::List(list) = meta {
-                                if let Some(NestedMeta::Meta(meta)) = list.nested.iter().next() {
-                                    attrs.project = meta.path().get_ident().cloned();
-                                    any_attr = true;
-                                }
-                            }
-                        }
+            if nested.path.is_ident("project") {
+                let _ = nested.parse_nested_meta(|meta| {
+                    if attrs.project.is_none() {
+                        attrs.project = meta.path.get_ident().cloned();
                     }
-                }
-            }
-            if !any_attr {
-                panic!("error parsing stable_hasher");
+                    any_attr = true;
+                    Ok(())
+                });
             }
+            Ok(())
+        });
+        if !any_attr {
+            panic!("error parsing stable_hasher");
         }
     }
     attrs
diff --git a/compiler/rustc_macros/src/newtype.rs b/compiler/rustc_macros/src/newtype.rs
index 89ea89cf502..04e762e91de 100644
--- a/compiler/rustc_macros/src/newtype.rs
+++ b/compiler/rustc_macros/src/newtype.rs
@@ -25,7 +25,7 @@ impl Parse for Newtype {
         let mut encodable = true;
         let mut ord = true;
 
-        attrs.retain(|attr| match attr.path.get_ident() {
+        attrs.retain(|attr| match attr.path().get_ident() {
             Some(ident) => match &*ident.to_string() {
                 "custom_encodable" => {
                     encodable = false;
@@ -36,22 +36,22 @@ impl Parse for Newtype {
                     false
                 }
                 "max" => {
-                    let Ok(Meta::NameValue(literal) )= attr.parse_meta() else {
+                    let Meta::NameValue(MetaNameValue { value: Expr::Lit(lit), .. }) = &attr.meta else {
                         panic!("#[max = NUMBER] attribute requires max value");
                     };
 
-                    if let Some(old) = max.replace(literal.lit) {
+                    if let Some(old) = max.replace(lit.lit.clone()) {
                         panic!("Specified multiple max: {old:?}");
                     }
 
                     false
                 }
                 "debug_format" => {
-                    let Ok(Meta::NameValue(literal) )= attr.parse_meta() else {
+                    let Meta::NameValue(MetaNameValue { value: Expr::Lit(lit), .. } ) = &attr.meta else {
                         panic!("#[debug_format = FMT] attribute requires a format");
                     };
 
-                    if let Some(old) = debug_format.replace(literal.lit) {
+                    if let Some(old) = debug_format.replace(lit.lit.clone()) {
                         panic!("Specified multiple debug format options: {old:?}");
                     }
 
diff --git a/compiler/rustc_macros/src/query.rs b/compiler/rustc_macros/src/query.rs
index 08e42a8a08f..f85ba38003c 100644
--- a/compiler/rustc_macros/src/query.rs
+++ b/compiler/rustc_macros/src/query.rs
@@ -15,7 +15,7 @@ mod kw {
 /// Ensures only doc comment attributes are used
 fn check_attributes(attrs: Vec<Attribute>) -> Result<Vec<Attribute>> {
     let inner = |attr: Attribute| {
-        if !attr.path.is_ident("doc") {
+        if !attr.path().is_ident("doc") {
             Err(Error::new(attr.span(), "attributes not supported on queries"))
         } else if attr.style != AttrStyle::Outer {
             Err(Error::new(
@@ -48,7 +48,7 @@ impl Parse for Query {
         let name: Ident = input.parse()?;
         let arg_content;
         parenthesized!(arg_content in input);
-        let key = arg_content.parse()?;
+        let key = Pat::parse_single(&arg_content)?;
         arg_content.parse::<Token![:]>()?;
         let arg = arg_content.parse()?;
         let result = input.parse()?;
@@ -158,7 +158,7 @@ fn parse_query_modifiers(input: ParseStream<'_>) -> Result<QueryModifiers> {
             } else {
                 None
             };
-            let list = attr_content.parse_terminated(Expr::parse)?;
+            let list = attr_content.parse_terminated(Expr::parse, Token![,])?;
             try_insert!(desc = (tcx, list));
         } else if modifier == "cache_on_disk_if" {
             // Parse a cache modifier like:
@@ -166,7 +166,7 @@ fn parse_query_modifiers(input: ParseStream<'_>) -> Result<QueryModifiers> {
             let args = if input.peek(token::Paren) {
                 let args;
                 parenthesized!(args in input);
-                let tcx = args.parse()?;
+                let tcx = Pat::parse_single(&args)?;
                 Some(tcx)
             } else {
                 None
diff --git a/compiler/rustc_macros/src/type_foldable.rs b/compiler/rustc_macros/src/type_foldable.rs
index 388e254cd64..5ee4d879313 100644
--- a/compiler/rustc_macros/src/type_foldable.rs
+++ b/compiler/rustc_macros/src/type_foldable.rs
@@ -1,5 +1,5 @@
 use quote::{quote, ToTokens};
-use syn::{parse_quote, Attribute, Meta, NestedMeta};
+use syn::parse_quote;
 
 pub fn type_foldable_derive(mut s: synstructure::Structure<'_>) -> proc_macro2::TokenStream {
     if let syn::Data::Union(_) = s.ast().data {
@@ -17,21 +17,20 @@ pub fn type_foldable_derive(mut s: synstructure::Structure<'_>) -> proc_macro2::
         vi.construct(|_, index| {
             let bind = &bindings[index];
 
+            let mut fixed = false;
+
             // retain value of fields with #[type_foldable(identity)]
-            let fixed = bind
-                .ast()
-                .attrs
-                .iter()
-                .map(Attribute::parse_meta)
-                .filter_map(Result::ok)
-                .flat_map(|attr| match attr {
-                    Meta::List(list) if list.path.is_ident("type_foldable") => list.nested,
-                    _ => Default::default(),
-                })
-                .any(|nested| match nested {
-                    NestedMeta::Meta(Meta::Path(path)) => path.is_ident("identity"),
-                    _ => false,
+            bind.ast().attrs.iter().for_each(|x| {
+                if !x.path().is_ident("type_foldable") {
+                    return;
+                }
+                let _ = x.parse_nested_meta(|nested| {
+                    if nested.path.is_ident("identity") {
+                        fixed = true;
+                    }
+                    Ok(())
                 });
+            });
 
             if fixed {
                 bind.to_token_stream()
diff --git a/compiler/rustc_macros/src/type_visitable.rs b/compiler/rustc_macros/src/type_visitable.rs
index f6f4c4779c3..dcd505a105e 100644
--- a/compiler/rustc_macros/src/type_visitable.rs
+++ b/compiler/rustc_macros/src/type_visitable.rs
@@ -1,5 +1,5 @@
 use quote::quote;
-use syn::{parse_quote, Attribute, Meta, NestedMeta};
+use syn::parse_quote;
 
 pub fn type_visitable_derive(mut s: synstructure::Structure<'_>) -> proc_macro2::TokenStream {
     if let syn::Data::Union(_) = s.ast().data {
@@ -8,19 +8,21 @@ pub fn type_visitable_derive(mut s: synstructure::Structure<'_>) -> proc_macro2:
 
     // ignore fields with #[type_visitable(ignore)]
     s.filter(|bi| {
-        !bi.ast()
-            .attrs
-            .iter()
-            .map(Attribute::parse_meta)
-            .filter_map(Result::ok)
-            .flat_map(|attr| match attr {
-                Meta::List(list) if list.path.is_ident("type_visitable") => list.nested,
-                _ => Default::default(),
-            })
-            .any(|nested| match nested {
-                NestedMeta::Meta(Meta::Path(path)) => path.is_ident("ignore"),
-                _ => false,
-            })
+        let mut ignored = false;
+
+        bi.ast().attrs.iter().for_each(|attr| {
+            if !attr.path().is_ident("type_visitable") {
+                return;
+            }
+            let _ = attr.parse_nested_meta(|nested| {
+                if nested.path.is_ident("ignore") {
+                    ignored = true;
+                }
+                Ok(())
+            });
+        });
+
+        !ignored
     });
 
     if !s.ast().generics.lifetimes().any(|lt| lt.lifetime.ident == "tcx") {