Port #[rustc_must_implement_one_of] to attribute parser

compiler/rustc_attr_parsing/src/attributes/rustc_internal.rs

@@ -1,4 +1,5 @@
 use rustc_ast::{LitIntType, LitKind, MetaItemLit};
+use rustc_session::errors;
 
 use super::prelude::*;
 use super::util::parse_single_integer;
@@ -13,6 +14,52 @@ impl<S: Stage> NoArgsAttributeParser<S> for RustcMainParser {
     const CREATE: fn(Span) -> AttributeKind = |_| AttributeKind::RustcMain;
 }
 
+pub(crate) struct RustcMustImplementOneOfParser;
+
+impl<S: Stage> SingleAttributeParser<S> for RustcMustImplementOneOfParser {
+    const PATH: &[Symbol] = &[sym::rustc_must_implement_one_of];
+    const ON_DUPLICATE: OnDuplicate<S> = OnDuplicate::Error;
+    const ALLOWED_TARGETS: AllowedTargets = AllowedTargets::AllowList(&[Allow(Target::Trait)]);
+    const ATTRIBUTE_ORDER: AttributeOrder = AttributeOrder::KeepInnermost;
+    const TEMPLATE: AttributeTemplate = template!(List: &["function1, function2, ..."]);
+    fn convert(cx: &mut AcceptContext<'_, '_, S>, args: &ArgParser) -> Option<AttributeKind> {
+        let Some(list) = args.list() else {
+            cx.expected_list(cx.attr_span, args);
+            return None;
+        };
+
+        let mut fn_names = ThinVec::new();
+
+        let inputs: Vec<_> = list.mixed().collect();
+
+        if inputs.len() < 2 {
+            cx.expected_list_with_num_args_or_more(2, list.span);
+            return None;
+        }
+
+        let mut errored = false;
+        for argument in inputs {
+            let Some(meta) = argument.meta_item() else {
+                cx.expected_identifier(argument.span());
+                return None;
+            };
+
+            let Some(ident) = meta.ident() else {
+                cx.dcx().emit_err(errors::MustBeNameOfAssociatedFunction { span: meta.span() });
+                errored = true;
+                continue;
+            };
+
+            fn_names.push(ident);
+        }
+        if errored {
+            return None;
+        }
+
+        Some(AttributeKind::RustcMustImplementOneOf { attr_span: cx.attr_span, fn_names })
+    }
+}
+
 pub(crate) struct RustcNeverReturnsNullPointerParser;
 
 impl<S: Stage> NoArgsAttributeParser<S> for RustcNeverReturnsNullPointerParser {

compiler/rustc_attr_parsing/src/context.rs

@@ -63,8 +63,9 @@ use crate::attributes::rustc_internal::{
     RustcLayoutScalarValidRangeEndParser, RustcLayoutScalarValidRangeStartParser,
     RustcLegacyConstGenericsParser, RustcLintDiagnosticsParser, RustcLintOptDenyFieldAccessParser,
     RustcLintOptTyParser, RustcLintQueryInstabilityParser,
-    RustcLintUntrackedQueryInformationParser, RustcMainParser, RustcNeverReturnsNullPointerParser,
-    RustcNoImplicitAutorefsParser, RustcObjectLifetimeDefaultParser, RustcScalableVectorParser,
+    RustcLintUntrackedQueryInformationParser, RustcMainParser, RustcMustImplementOneOfParser,
+    RustcNeverReturnsNullPointerParser, RustcNoImplicitAutorefsParser,
+    RustcObjectLifetimeDefaultParser, RustcScalableVectorParser,
     RustcSimdMonomorphizeLaneLimitParser,
 };
 use crate::attributes::semantics::MayDangleParser;
@@ -215,6 +216,7 @@ attribute_parsers!(
         Single<RustcLayoutScalarValidRangeStartParser>,
         Single<RustcLegacyConstGenericsParser>,
         Single<RustcLintOptDenyFieldAccessParser>,
+        Single<RustcMustImplementOneOfParser>,
         Single<RustcObjectLifetimeDefaultParser>,
         Single<RustcScalableVectorParser>,
         Single<RustcSimdMonomorphizeLaneLimitParser>,
@@ -490,6 +492,17 @@ impl<'f, 'sess: 'f, S: Stage> AcceptContext<'f, 'sess, S> {
         self.emit_parse_error(span, AttributeParseErrorReason::ExpectedList)
     }
 
+    pub(crate) fn expected_list_with_num_args_or_more(
+        &self,
+        args: usize,
+        span: Span,
+    ) -> ErrorGuaranteed {
+        self.emit_parse_error(
+            span,
+            AttributeParseErrorReason::ExpectedListWithNumArgsOrMore { args },
+        )
+    }
+
     pub(crate) fn expected_list_or_no_args(&self, span: Span) -> ErrorGuaranteed {
         self.emit_parse_error(span, AttributeParseErrorReason::ExpectedListOrNoArgs)
     }

compiler/rustc_attr_parsing/src/parser.rs

@@ -8,7 +8,9 @@ use std::fmt::{Debug, Display};
 
 use rustc_ast::token::{self, Delimiter, MetaVarKind};
 use rustc_ast::tokenstream::TokenStream;
-use rustc_ast::{AttrArgs, Expr, ExprKind, LitKind, MetaItemLit, Path, StmtKind, UnOp};
+use rustc_ast::{
+    AttrArgs, Expr, ExprKind, LitKind, MetaItemLit, Path, PathSegment, StmtKind, UnOp,
+};
 use rustc_ast_pretty::pprust;
 use rustc_errors::{Diag, PResult};
 use rustc_hir::{self as hir, AttrPath};
@@ -256,6 +258,11 @@ impl Debug for MetaItemParser {
 }
 
 impl MetaItemParser {
+    /// For a single-segment meta item, returns its name; otherwise, returns `None`.
+    pub fn ident(&self) -> Option<Ident> {
+        if let [PathSegment { ident, .. }] = self.path.0.segments[..] { Some(ident) } else { None }
+    }
+
     pub fn span(&self) -> Span {
         if let Some(other) = self.args.span() {
             self.path.borrow().span().with_hi(other.hi())

compiler/rustc_attr_parsing/src/session_diagnostics.rs

@@ -520,6 +520,9 @@ pub(crate) enum AttributeParseErrorReason<'a> {
     ExpectedSingleArgument,
     ExpectedList,
     ExpectedListOrNoArgs,
+    ExpectedListWithNumArgsOrMore {
+        args: usize,
+    },
     ExpectedNameValueOrNoArgs,
     UnexpectedLiteral,
     ExpectedNameValue(Option<Symbol>),
@@ -596,6 +599,9 @@ impl<'a, G: EmissionGuarantee> Diagnostic<'a, G> for AttributeParseError<'_> {
             AttributeParseErrorReason::ExpectedListOrNoArgs => {
                 diag.span_label(self.span, "expected a list or no arguments here");
             }
+            AttributeParseErrorReason::ExpectedListWithNumArgsOrMore { args } => {
+                diag.span_label(self.span, format!("expected {args} or more items"));
+            }
             AttributeParseErrorReason::ExpectedNameValueOrNoArgs => {
                 diag.span_label(self.span, "didn't expect a list here");
             }

compiler/rustc_hir/src/attrs/data_structures.rs

@@ -949,6 +949,9 @@ pub enum AttributeKind {
     /// Represents `#[rustc_main]`.
     RustcMain,
 
+    /// Represents `#[rustc_must_implement_one_of]`
+    RustcMustImplementOneOf { attr_span: Span, fn_names: ThinVec<Ident> },
+
     /// Represents `#[rustc_never_returns_null_ptr]`
     RustcNeverReturnsNullPointer,
 

compiler/rustc_hir/src/attrs/encode_cross_crate.rs

@@ -100,6 +100,7 @@ impl AttributeKind {
             RustcLintQueryInstability => Yes,
             RustcLintUntrackedQueryInformation => Yes,
             RustcMain => No,
+            RustcMustImplementOneOf { .. } => No,
             RustcNeverReturnsNullPointer => Yes,
             RustcNoImplicitAutorefs => Yes,
             RustcObjectLifetimeDefault => No,

compiler/rustc_hir_analysis/messages.ftl

@@ -208,14 +208,6 @@ hir_analysis_field_already_declared_previous_nested =
     .previous_decl_label = `{$field_name}` first declared here in this unnamed field
     .previous_nested_field_decl_note = field `{$field_name}` first declared here
 
-hir_analysis_function_not_found_in_trait = function not found in this trait
-
-hir_analysis_function_not_have_default_implementation = function doesn't have a default implementation
-    .note = required by this annotation
-
-hir_analysis_functions_names_duplicated = functions names are duplicated
-    .note = all `#[rustc_must_implement_one_of]` arguments must be unique
-
 hir_analysis_generic_args_on_overridden_impl = could not resolve generic parameters on overridden impl
 
 hir_analysis_impl_not_marked_default = `{$ident}` specializes an item from a parent `impl`, but that item is not marked `default`
@@ -381,16 +373,6 @@ hir_analysis_missing_type_params =
         *[other] parameters
     } must be specified on the object type
 
-hir_analysis_must_be_name_of_associated_function = must be a name of an associated function
-
-hir_analysis_must_implement_not_function = not a function
-
-hir_analysis_must_implement_not_function_note = all `#[rustc_must_implement_one_of]` arguments must be associated function names
-
-hir_analysis_must_implement_not_function_span_note = required by this annotation
-
-hir_analysis_must_implement_one_of_attribute = the `#[rustc_must_implement_one_of]` attribute must be used with at least 2 args
-
 hir_analysis_no_variant_named = no variant named `{$ident}` found for enum `{$ty}`
 
 hir_analysis_not_supported_delegation = {$descr}

compiler/rustc_hir_analysis/src/check/check.rs

@@ -1340,9 +1340,7 @@ fn check_impl_items_against_trait<'tcx>(
         }
 
         if let Some(missing_items) = must_implement_one_of {
-            let attr_span = tcx
-                .get_attr(trait_ref.def_id, sym::rustc_must_implement_one_of)
-                .map(|attr| attr.span());
+            let attr_span = find_attr!(tcx.get_all_attrs(trait_ref.def_id), AttributeKind::RustcMustImplementOneOf {attr_span, ..} => *attr_span);
 
             missing_items_must_implement_one_of_err(
                 tcx,

compiler/rustc_hir_analysis/src/collect.rs

@@ -22,7 +22,6 @@ use std::ops::Bound;
 use rustc_abi::{ExternAbi, Size};
 use rustc_ast::Recovered;
 use rustc_data_structures::fx::{FxHashSet, FxIndexMap};
-use rustc_data_structures::unord::UnordMap;
 use rustc_errors::{
     Applicability, Diag, DiagCtxtHandle, E0228, ErrorGuaranteed, StashKey, struct_span_code_err,
 };
@@ -916,84 +915,15 @@ fn trait_def(tcx: TyCtxt<'_>, def_id: LocalDefId) -> ty::TraitDef {
     } else {
         ty::trait_def::TraitSpecializationKind::None
     };
-    let must_implement_one_of = attrs
-        .iter()
-        .find(|attr| attr.has_name(sym::rustc_must_implement_one_of))
-        // Check that there are at least 2 arguments of `#[rustc_must_implement_one_of]`
-        // and that they are all identifiers
-        .and_then(|attr| match attr.meta_item_list() {
-            Some(items) if items.len() < 2 => {
-                tcx.dcx().emit_err(errors::MustImplementOneOfAttribute { span: attr.span() });
-
-                None
-            }
-            Some(items) => items
-                .into_iter()
-                .map(|item| item.ident().ok_or(item.span()))
-                .collect::<Result<Box<[_]>, _>>()
-                .map_err(|span| {
-                    tcx.dcx().emit_err(errors::MustBeNameOfAssociatedFunction { span });
-                })
-                .ok()
-                .zip(Some(attr.span())),
-            // Error is reported by `rustc_attr!`
-            None => None,
-        })
-        // Check that all arguments of `#[rustc_must_implement_one_of]` reference
-        // functions in the trait with default implementations
-        .and_then(|(list, attr_span)| {
-            let errors = list.iter().filter_map(|ident| {
-                let item = tcx
-                    .associated_items(def_id)
-                    .filter_by_name_unhygienic(ident.name)
-                    .find(|item| item.ident(tcx) == *ident);
-
-                match item {
-                    Some(item) if matches!(item.kind, ty::AssocKind::Fn { .. }) => {
-                        if !item.defaultness(tcx).has_value() {
-                            tcx.dcx().emit_err(errors::FunctionNotHaveDefaultImplementation {
-                                span: tcx.def_span(item.def_id),
-                                note_span: attr_span,
-                            });
 
-                            return Some(());
-                        }
-
-                        return None;
-                    }
-                    Some(item) => {
-                        tcx.dcx().emit_err(errors::MustImplementNotFunction {
-                            span: tcx.def_span(item.def_id),
-                            span_note: errors::MustImplementNotFunctionSpanNote { span: attr_span },
-                            note: errors::MustImplementNotFunctionNote {},
-                        });
-                    }
-                    None => {
-                        tcx.dcx().emit_err(errors::FunctionNotFoundInTrait { span: ident.span });
-                    }
-                }
-
-                Some(())
-            });
-
-            (errors.count() == 0).then_some(list)
-        })
-        // Check for duplicates
-        .and_then(|list| {
-            let mut set: UnordMap<Symbol, Span> = Default::default();
-            let mut no_dups = true;
-
-            for ident in &*list {
-                if let Some(dup) = set.insert(ident.name, ident.span) {
-                    tcx.dcx()
-                        .emit_err(errors::FunctionNamesDuplicated { spans: vec![dup, ident.span] });
-
-                    no_dups = false;
-                }
-            }
-
-            no_dups.then_some(list)
-        });
+    let must_implement_one_of = find_attr!(
+        attrs,
+        AttributeKind::RustcMustImplementOneOf { fn_names, .. } =>
+            fn_names
+                .iter()
+                .cloned()
+                .collect::<Box<[_]>>()
+    );
 
     let deny_explicit_impl = find_attr!(attrs, AttributeKind::DenyExplicitImpl(_));
     let implement_via_object = !find_attr!(attrs, AttributeKind::DoNotImplementViaObject(_));

compiler/rustc_hir_analysis/src/errors.rs

@@ -741,66 +741,6 @@ pub(crate) struct ParenSugarAttribute {
     pub span: Span,
 }
 
-#[derive(Diagnostic)]
-#[diag(hir_analysis_must_implement_one_of_attribute)]
-pub(crate) struct MustImplementOneOfAttribute {
-    #[primary_span]
-    pub span: Span,
-}
-
-#[derive(Diagnostic)]
-#[diag(hir_analysis_must_be_name_of_associated_function)]
-pub(crate) struct MustBeNameOfAssociatedFunction {
-    #[primary_span]
-    pub span: Span,
-}
-
-#[derive(Diagnostic)]
-#[diag(hir_analysis_function_not_have_default_implementation)]
-pub(crate) struct FunctionNotHaveDefaultImplementation {
-    #[primary_span]
-    pub span: Span,
-    #[note]
-    pub note_span: Span,
-}
-
-#[derive(Diagnostic)]
-#[diag(hir_analysis_must_implement_not_function)]
-pub(crate) struct MustImplementNotFunction {
-    #[primary_span]
-    pub span: Span,
-    #[subdiagnostic]
-    pub span_note: MustImplementNotFunctionSpanNote,
-    #[subdiagnostic]
-    pub note: MustImplementNotFunctionNote,
-}
-
-#[derive(Subdiagnostic)]
-#[note(hir_analysis_must_implement_not_function_span_note)]
-pub(crate) struct MustImplementNotFunctionSpanNote {
-    #[primary_span]
-    pub span: Span,
-}
-
-#[derive(Subdiagnostic)]
-#[note(hir_analysis_must_implement_not_function_note)]
-pub(crate) struct MustImplementNotFunctionNote {}
-
-#[derive(Diagnostic)]
-#[diag(hir_analysis_function_not_found_in_trait)]
-pub(crate) struct FunctionNotFoundInTrait {
-    #[primary_span]
-    pub span: Span,
-}
-
-#[derive(Diagnostic)]
-#[diag(hir_analysis_functions_names_duplicated)]
-#[note]
-pub(crate) struct FunctionNamesDuplicated {
-    #[primary_span]
-    pub spans: Vec<Span>,
-}
-
 #[derive(Diagnostic)]
 #[diag(hir_analysis_simd_ffi_highly_experimental)]
 #[help]