Rollup of 5 pull requests

compiler/rustc_ast_lowering/src/path.rs

@@ -1,6 +1,7 @@
 use std::sync::Arc;
 
 use rustc_ast::{self as ast, *};
+use rustc_errors::StashKey;
 use rustc_hir::def::{DefKind, PartialRes, PerNS, Res};
 use rustc_hir::def_id::DefId;
 use rustc_hir::{self as hir, GenericArg};
@@ -298,7 +299,7 @@ impl<'hir, R: ResolverAstLoweringExt<'hir>> LoweringContext<'_, 'hir, R> {
                                 sym::return_type_notation,
                             );
                         }
-                        err.emit();
+                        err.stash(path_span, StashKey::ReturnTypeNotation);
                         (
                             GenericArgsCtor {
                                 args: Default::default(),

compiler/rustc_attr_parsing/src/attributes/cfg.rs

@@ -20,7 +20,9 @@ use rustc_span::{ErrorGuaranteed, Span, Symbol, sym};
 use thin_vec::ThinVec;
 
 use crate::context::{AcceptContext, ShouldEmit, Stage};
-use crate::parser::{ArgParser, MetaItemListParser, MetaItemOrLitParser, NameValueParser};
+use crate::parser::{
+    AllowExprMetavar, ArgParser, MetaItemListParser, MetaItemOrLitParser, NameValueParser,
+};
 use crate::session_diagnostics::{
     AttributeParseError, AttributeParseErrorReason, CfgAttrBadDelim, MetaBadDelimSugg,
     ParsedDescription,
@@ -363,6 +365,7 @@ fn parse_cfg_attr_internal<'a>(
     let meta = MetaItemOrLitParser::parse_single(
         parser,
         ShouldEmit::ErrorsAndLints { recovery: Recovery::Allowed },
+        AllowExprMetavar::Yes,
     )?;
     let pred_span = pred_start.with_hi(parser.token.span.hi());
 

compiler/rustc_attr_parsing/src/attributes/cfg_select.rs

@@ -12,7 +12,7 @@ use rustc_session::lint::BuiltinLintDiag;
 use rustc_session::lint::builtin::UNREACHABLE_CFG_SELECT_PREDICATES;
 use rustc_span::{ErrorGuaranteed, Span, Symbol, sym};
 
-use crate::parser::MetaItemOrLitParser;
+use crate::parser::{AllowExprMetavar, MetaItemOrLitParser};
 use crate::{AttributeParser, ParsedDescription, ShouldEmit, parse_cfg_entry};
 
 #[derive(Clone)]
@@ -94,6 +94,7 @@ pub fn parse_cfg_select(
             let meta = MetaItemOrLitParser::parse_single(
                 p,
                 ShouldEmit::ErrorsAndLints { recovery: Recovery::Allowed },
+                AllowExprMetavar::Yes,
             )
             .map_err(|diag| diag.emit())?;
             let cfg_span = meta.span();

compiler/rustc_attr_parsing/src/attributes/diagnostic/mod.rs

@@ -470,11 +470,12 @@ fn parse_filter(input: Symbol) -> FilterFormatString {
                 // if the integer type has been resolved, to allow targeting all integers.
                 // `"{integer}"` and `"{float}"` come from numerics that haven't been inferred yet,
                 // from the `Display` impl of `InferTy` to be precise.
+                // `"{union|enum|struct}"` is used as a special selector for ADTs.
                 //
                 // Don't try to format these later!
-                Position::ArgumentNamed(arg @ ("integer" | "integral" | "float")) => {
-                    LitOrArg::Lit(Symbol::intern(&format!("{{{arg}}}")))
-                }
+                Position::ArgumentNamed(
+                    arg @ ("integer" | "integral" | "float" | "union" | "enum" | "struct"),
+                ) => LitOrArg::Lit(Symbol::intern(&format!("{{{arg}}}"))),
 
                 Position::ArgumentNamed(arg) => LitOrArg::Arg(Symbol::intern(arg)),
                 Position::ArgumentImplicitlyIs(_) => LitOrArg::Lit(sym::empty_braces),

compiler/rustc_attr_parsing/src/interface.rs

@@ -14,7 +14,7 @@ use rustc_span::{DUMMY_SP, Span, Symbol, sym};
 
 use crate::context::{AcceptContext, FinalizeContext, FinalizeFn, SharedContext, Stage};
 use crate::early_parsed::{EARLY_PARSED_ATTRIBUTES, EarlyParsedState};
-use crate::parser::{ArgParser, PathParser, RefPathParser};
+use crate::parser::{AllowExprMetavar, ArgParser, PathParser, RefPathParser};
 use crate::session_diagnostics::ParsedDescription;
 use crate::{Early, Late, OmitDoc, ShouldEmit};
 
@@ -139,6 +139,7 @@ impl<'sess> AttributeParser<'sess, Early> {
         emit_errors: ShouldEmit,
         parse_fn: fn(cx: &mut AcceptContext<'_, '_, Early>, item: &ArgParser) -> Option<T>,
         template: &AttributeTemplate,
+        allow_expr_metavar: AllowExprMetavar,
     ) -> Option<T> {
         let ast::AttrKind::Normal(normal_attr) = &attr.kind else {
             panic!("parse_single called on a doc attr")
@@ -152,6 +153,7 @@ impl<'sess> AttributeParser<'sess, Early> {
             &parts,
             &sess.psess,
             emit_errors,
+            allow_expr_metavar,
         )?;
         Self::parse_single_args(
             sess,
@@ -333,6 +335,7 @@ impl<'sess, S: Stage> AttributeParser<'sess, S> {
                             &parts,
                             &self.sess.psess,
                             self.stage.should_emit(),
+                            AllowExprMetavar::No,
                         ) else {
                             continue;
                         };

compiler/rustc_attr_parsing/src/parser.rs

@@ -109,6 +109,7 @@ impl ArgParser {
         parts: &[Symbol],
         psess: &'sess ParseSess,
         should_emit: ShouldEmit,
+        allow_expr_metavar: AllowExprMetavar,
     ) -> Option<Self> {
         Some(match value {
             AttrArgs::Empty => Self::NoArgs,
@@ -122,6 +123,7 @@ impl ArgParser {
                         args.dspan.entire(),
                         psess,
                         ShouldEmit::ErrorsAndLints { recovery: Recovery::Forbidden },
+                        allow_expr_metavar,
                     ) {
                         Ok(p) => return Some(ArgParser::List(p)),
                         Err(e) => {
@@ -147,9 +149,15 @@ impl ArgParser {
                 }
 
                 Self::List(
-                    MetaItemListParser::new(&args.tokens, args.dspan.entire(), psess, should_emit)
-                        .map_err(|e| should_emit.emit_err(e))
-                        .ok()?,
+                    MetaItemListParser::new(
+                        &args.tokens,
+                        args.dspan.entire(),
+                        psess,
+                        should_emit,
+                        allow_expr_metavar,
+                    )
+                    .map_err(|e| should_emit.emit_err(e))
+                    .ok()?,
                 )
             }
             AttrArgs::Eq { eq_span, expr } => Self::NameValue(NameValueParser {
@@ -217,8 +225,9 @@ impl MetaItemOrLitParser {
     pub fn parse_single<'sess>(
         parser: &mut Parser<'sess>,
         should_emit: ShouldEmit,
+        allow_expr_metavar: AllowExprMetavar,
     ) -> PResult<'sess, MetaItemOrLitParser> {
-        let mut this = MetaItemListParserContext { parser, should_emit };
+        let mut this = MetaItemListParserContext { parser, should_emit, allow_expr_metavar };
         this.parse_meta_item_inner()
     }
 
@@ -404,9 +413,19 @@ fn expr_to_lit<'sess>(
     }
 }
 
+/// Whether expansions of `expr` metavariables from decrarative macros
+/// are permitted. Used when parsing meta items; currently, only `cfg` predicates
+/// enable this option
+#[derive(Clone, Copy, PartialEq, Eq)]
+pub enum AllowExprMetavar {
+    No,
+    Yes,
+}
+
 struct MetaItemListParserContext<'a, 'sess> {
     parser: &'a mut Parser<'sess>,
     should_emit: ShouldEmit,
+    allow_expr_metavar: AllowExprMetavar,
 }
 
 impl<'a, 'sess> MetaItemListParserContext<'a, 'sess> {
@@ -447,20 +466,44 @@ impl<'a, 'sess> MetaItemListParserContext<'a, 'sess> {
         Ok(lit)
     }
 
-    fn parse_attr_item(&mut self) -> PResult<'sess, MetaItemParser> {
-        if let Some(MetaVarKind::Meta { has_meta_form }) = self.parser.token.is_metavar_seq() {
-            return if has_meta_form {
-                let attr_item = self
-                    .parser
-                    .eat_metavar_seq(MetaVarKind::Meta { has_meta_form: true }, |this| {
-                        MetaItemListParserContext { parser: this, should_emit: self.should_emit }
-                            .parse_attr_item()
-                    })
-                    .unwrap();
-                Ok(attr_item)
-            } else {
-                self.parser.unexpected_any()
-            };
+    fn parse_meta_item(&mut self) -> PResult<'sess, MetaItemParser> {
+        if let Some(metavar) = self.parser.token.is_metavar_seq() {
+            match (metavar, self.allow_expr_metavar) {
+                (kind @ MetaVarKind::Expr { .. }, AllowExprMetavar::Yes) => {
+                    return self
+                        .parser
+                        .eat_metavar_seq(kind, |this| {
+                            MetaItemListParserContext {
+                                parser: this,
+                                should_emit: self.should_emit,
+                                allow_expr_metavar: AllowExprMetavar::Yes,
+                            }
+                            .parse_meta_item()
+                        })
+                        .ok_or_else(|| {
+                            self.parser.unexpected_any::<core::convert::Infallible>().unwrap_err()
+                        });
+                }
+                (MetaVarKind::Meta { has_meta_form }, _) => {
+                    return if has_meta_form {
+                        let attr_item = self
+                            .parser
+                            .eat_metavar_seq(MetaVarKind::Meta { has_meta_form: true }, |this| {
+                                MetaItemListParserContext {
+                                    parser: this,
+                                    should_emit: self.should_emit,
+                                    allow_expr_metavar: self.allow_expr_metavar,
+                                }
+                                .parse_meta_item()
+                            })
+                            .unwrap();
+                        Ok(attr_item)
+                    } else {
+                        self.parser.unexpected_any()
+                    };
+                }
+                _ => {}
+            }
         }
 
         let path = self.parser.parse_path(PathStyle::Mod)?;
@@ -469,8 +512,12 @@ impl<'a, 'sess> MetaItemListParserContext<'a, 'sess> {
         let args = if self.parser.check(exp!(OpenParen)) {
             let start = self.parser.token.span;
             let (sub_parsers, _) = self.parser.parse_paren_comma_seq(|parser| {
-                MetaItemListParserContext { parser, should_emit: self.should_emit }
-                    .parse_meta_item_inner()
+                MetaItemListParserContext {
+                    parser,
+                    should_emit: self.should_emit,
+                    allow_expr_metavar: self.allow_expr_metavar,
+                }
+                .parse_meta_item_inner()
             })?;
             let end = self.parser.prev_token.span;
             ArgParser::List(MetaItemListParser { sub_parsers, span: start.with_hi(end.hi()) })
@@ -492,7 +539,7 @@ impl<'a, 'sess> MetaItemListParserContext<'a, 'sess> {
             Ok(MetaItemOrLitParser::Lit(self.unsuffixed_meta_item_from_lit(token_lit)?))
         } else {
             let prev_pros = self.parser.approx_token_stream_pos();
-            match self.parse_attr_item() {
+            match self.parse_meta_item() {
                 Ok(item) => Ok(MetaItemOrLitParser::MetaItemParser(item)),
                 Err(err) => {
                     // If `parse_attr_item` made any progress, it likely has a more precise error we should prefer
@@ -580,13 +627,15 @@ impl<'a, 'sess> MetaItemListParserContext<'a, 'sess> {
         psess: &'sess ParseSess,
         span: Span,
         should_emit: ShouldEmit,
+        allow_expr_metavar: AllowExprMetavar,
     ) -> PResult<'sess, MetaItemListParser> {
         let mut parser = Parser::new(psess, tokens, None);
         if let ShouldEmit::ErrorsAndLints { recovery } = should_emit {
             parser = parser.recovery(recovery);
         }
 
-        let mut this = MetaItemListParserContext { parser: &mut parser, should_emit };
+        let mut this =
+            MetaItemListParserContext { parser: &mut parser, should_emit, allow_expr_metavar };
 
         // Presumably, the majority of the time there will only be one attr.
         let mut sub_parsers = ThinVec::with_capacity(1);
@@ -618,8 +667,15 @@ impl MetaItemListParser {
         span: Span,
         psess: &'sess ParseSess,
         should_emit: ShouldEmit,
+        allow_expr_metavar: AllowExprMetavar,
     ) -> Result<Self, Diag<'sess>> {
-        MetaItemListParserContext::parse(tokens.clone(), psess, span, should_emit)
+        MetaItemListParserContext::parse(
+            tokens.clone(),
+            psess,
+            span,
+            should_emit,
+            allow_expr_metavar,
+        )
     }
 
     /// Lets you pick and choose as what you want to parse each element in the list

compiler/rustc_builtin_macros/src/cfg.rs

@@ -4,10 +4,9 @@
 
 use rustc_ast::tokenstream::TokenStream;
 use rustc_ast::{AttrStyle, token};
-use rustc_attr_parsing as attr;
-use rustc_attr_parsing::parser::MetaItemOrLitParser;
+use rustc_attr_parsing::parser::{AllowExprMetavar, MetaItemOrLitParser};
 use rustc_attr_parsing::{
-    AttributeParser, CFG_TEMPLATE, ParsedDescription, ShouldEmit, parse_cfg_entry,
+    self as attr, AttributeParser, CFG_TEMPLATE, ParsedDescription, ShouldEmit, parse_cfg_entry,
 };
 use rustc_expand::base::{DummyResult, ExpandResult, ExtCtxt, MacEager, MacroExpanderResult};
 use rustc_hir::attrs::CfgEntry;
@@ -44,6 +43,7 @@ fn parse_cfg(cx: &ExtCtxt<'_>, span: Span, tts: TokenStream) -> Result<CfgEntry,
     let meta = MetaItemOrLitParser::parse_single(
         &mut parser,
         ShouldEmit::ErrorsAndLints { recovery: Recovery::Allowed },
+        AllowExprMetavar::Yes,
     )
     .map_err(|diag| diag.emit())?;
     let cfg = AttributeParser::parse_single_args(

compiler/rustc_errors/src/lib.rs

@@ -386,6 +386,7 @@ pub enum StashKey {
     /// it's a method call without parens. If later on in `hir_typeck` we find out that this is
     /// the case we suppress this message and we give a better suggestion.
     GenericInFieldExpr,
+    ReturnTypeNotation,
 }
 
 fn default_track_diagnostic<R>(diag: DiagInner, f: &mut dyn FnMut(DiagInner) -> R) -> R {

compiler/rustc_expand/src/config.rs

@@ -10,9 +10,10 @@ use rustc_ast::{
     self as ast, AttrItemKind, AttrKind, AttrStyle, Attribute, DUMMY_NODE_ID, EarlyParsedAttribute,
     HasAttrs, HasTokens, MetaItem, MetaItemInner, NodeId, NormalAttr,
 };
-use rustc_attr_parsing as attr;
+use rustc_attr_parsing::parser::AllowExprMetavar;
 use rustc_attr_parsing::{
-    AttributeParser, CFG_TEMPLATE, EvalConfigResult, ShouldEmit, eval_config_entry, parse_cfg,
+    self as attr, AttributeParser, CFG_TEMPLATE, EvalConfigResult, ShouldEmit, eval_config_entry,
+    parse_cfg,
 };
 use rustc_data_structures::flat_map_in_place::FlatMapInPlace;
 use rustc_errors::msg;
@@ -402,6 +403,7 @@ impl<'a> StripUnconfigured<'a> {
             emit_errors,
             parse_cfg,
             &CFG_TEMPLATE,
+            AllowExprMetavar::Yes,
         ) else {
             // Cfg attribute was not parsable, give up
             return EvalConfigResult::True;

compiler/rustc_expand/src/expand.rs

@@ -13,6 +13,7 @@ use rustc_ast::{
     TyKind, token,
 };
 use rustc_ast_pretty::pprust;
+use rustc_attr_parsing::parser::AllowExprMetavar;
 use rustc_attr_parsing::{
     AttributeParser, CFG_TEMPLATE, Early, EvalConfigResult, ShouldEmit, eval_config_entry,
     parse_cfg, validate_attr,
@@ -2224,6 +2225,7 @@ impl<'a, 'b> InvocationCollector<'a, 'b> {
             ShouldEmit::ErrorsAndLints { recovery: Recovery::Allowed },
             parse_cfg,
             &CFG_TEMPLATE,
+            AllowExprMetavar::Yes,
         ) else {
             // Cfg attribute was not parsable, give up
             return EvalConfigResult::True;

compiler/rustc_hir_analysis/src/errors.rs

@@ -1807,6 +1807,13 @@ pub(crate) struct CmseImplTrait {
 pub(crate) struct BadReturnTypeNotation {
     #[primary_span]
     pub span: Span,
+    #[suggestion(
+        "furthermore, argument types not allowed with return type notation",
+        applicability = "maybe-incorrect",
+        code = "(..)",
+        style = "verbose"
+    )]
+    pub suggestion: Option<Span>,
 }
 
 #[derive(Diagnostic)]