Port #[must_use] to new attribute parsing infrastructure

Signed-off-by: Jonathan Brouwer <[email protected]>

Author: JonathanBrouwer

compiler/rustc_attr_data_structures/src/attributes.rs

@@ -233,8 +233,17 @@ pub enum AttributeKind {
 
     /// Represents `#[rustc_macro_transparency]`.
     MacroTransparency(Transparency),
+
+    /// Represents `#[must_use]`.
+    MustUse {
+        span: Span,
+        /// must_use can optionally have a reason: `#[must_use = "reason this must be used"]`
+        reason: Option<Symbol>,
+    },
+
     /// Represents `#[optimize(size|speed)]`
     Optimize(OptimizeAttr, Span),
+
     /// Represents [`#[repr]`](https://doc.rust-lang.org/stable/reference/type-layout.html#representations).
     Repr(ThinVec<(ReprAttr, Span)>),
 

compiler/rustc_attr_parsing/src/attributes/mod.rs

@@ -33,6 +33,7 @@ pub(crate) mod confusables;
 pub(crate) mod deprecation;
 pub(crate) mod inline;
 pub(crate) mod lint_helpers;
+pub(crate) mod must_use;
 pub(crate) mod repr;
 pub(crate) mod stability;
 pub(crate) mod transparency;

compiler/rustc_attr_parsing/src/attributes/must_use.rs

@@ -0,0 +1,40 @@
+use rustc_attr_data_structures::AttributeKind;
+use rustc_errors::DiagArgValue;
+use rustc_feature::{AttributeTemplate, template};
+use rustc_span::{Symbol, sym};
+
+use crate::attributes::{AttributeOrder, OnDuplicate, SingleAttributeParser};
+use crate::context::{AcceptContext, Stage};
+use crate::parser::ArgParser;
+use crate::session_diagnostics;
+
+pub(crate) struct MustUseParser;
+
+impl<S: Stage> SingleAttributeParser<S> for MustUseParser {
+    const PATH: &[Symbol] = &[sym::must_use];
+    const ATTRIBUTE_ORDER: AttributeOrder = AttributeOrder::KeepLast;
+    const ON_DUPLICATE: OnDuplicate<S> = OnDuplicate::WarnButFutureError;
+    const TEMPLATE: AttributeTemplate = template!(Word, NameValueStr: "reason");
+
+    fn convert(cx: &mut AcceptContext<'_, '_, S>, args: &ArgParser<'_>) -> Option<AttributeKind> {
+        Some(AttributeKind::MustUse {
+            span: cx.attr_span,
+            reason: match args {
+                ArgParser::NoArgs => None,
+                ArgParser::NameValue(name_value) => name_value.value_as_str(),
+                ArgParser::List(_) => {
+                    let suggestions =
+                        <Self as SingleAttributeParser<S>>::TEMPLATE.suggestions(false, "must_use");
+                    cx.emit_err(session_diagnostics::MustUseIllFormedAttributeInput {
+                        num_suggestions: suggestions.len(),
+                        suggestions: DiagArgValue::StrListSepByAnd(
+                            suggestions.into_iter().map(|s| format!("`{s}`").into()).collect(),
+                        ),
+                        span: cx.attr_span,
+                    });
+                    return None;
+                }
+            },
+        })
+    }
+}

compiler/rustc_attr_parsing/src/context.rs

@@ -20,6 +20,7 @@ use crate::attributes::confusables::ConfusablesParser;
 use crate::attributes::deprecation::DeprecationParser;
 use crate::attributes::inline::{InlineParser, RustcForceInlineParser};
 use crate::attributes::lint_helpers::AsPtrParser;
+use crate::attributes::must_use::MustUseParser;
 use crate::attributes::repr::{AlignParser, ReprParser};
 use crate::attributes::stability::{
     BodyStabilityParser, ConstStabilityIndirectParser, ConstStabilityParser, StabilityParser,
@@ -110,6 +111,7 @@ attribute_parsers!(
         Single<ConstStabilityIndirectParser>,
         Single<DeprecationParser>,
         Single<InlineParser>,
+        Single<MustUseParser>,
         Single<OptimizeParser>,
         Single<RustcForceInlineParser>,
         Single<TransparencyParser>,

compiler/rustc_attr_parsing/src/session_diagnostics.rs

@@ -436,6 +436,15 @@ pub(crate) struct IllFormedAttributeInput {
     pub suggestions: DiagArgValue,
 }
 
+#[derive(Diagnostic)]
+#[diag(attr_parsing_ill_formed_attribute_input)]
+pub(crate) struct MustUseIllFormedAttributeInput {
+    #[primary_span]
+    pub span: Span,
+    pub num_suggestions: usize,
+    pub suggestions: DiagArgValue,
+}
+
 #[derive(Diagnostic)]
 #[diag(attr_parsing_stability_outside_std, code = E0734)]
 pub(crate) struct StabilityOutsideStd {

compiler/rustc_lint/src/unused.rs

@@ -2,6 +2,7 @@ use std::iter;
 
 use rustc_ast::util::{classify, parser};
 use rustc_ast::{self as ast, ExprKind, HasAttrs as _, StmtKind};
+use rustc_attr_data_structures::{AttributeKind, find_attr};
 use rustc_errors::{MultiSpan, pluralize};
 use rustc_hir::def::{DefKind, Res};
 use rustc_hir::def_id::DefId;
@@ -368,10 +369,12 @@ impl<'tcx> LateLintPass<'tcx> for UnusedResults {
         }
 
         fn is_def_must_use(cx: &LateContext<'_>, def_id: DefId, span: Span) -> Option<MustUsePath> {
-            if let Some(attr) = cx.tcx.get_attr(def_id, sym::must_use) {
+            if let Some(reason) = find_attr!(
+                cx.tcx.get_all_attrs(def_id),
+                AttributeKind::MustUse { reason, .. } => reason
+            ) {
                 // check for #[must_use = "..."]
-                let reason = attr.value_str();
-                Some(MustUsePath::Def(span, def_id, reason))
+                Some(MustUsePath::Def(span, def_id, *reason))
             } else {
                 None
             }

compiler/rustc_parse/src/validate_attr.rs

@@ -293,6 +293,7 @@ fn emit_malformed_attribute(
             | sym::deprecated
             | sym::optimize
             | sym::cold
+            | sym::must_use
     ) {
         return;
     }

compiler/rustc_passes/src/check_attr.rs

@@ -163,6 +163,9 @@ impl<'tcx> CheckAttrVisitor<'tcx> {
                 Attribute::Parsed(AttributeKind::AsPtr(attr_span)) => {
                     self.check_applied_to_fn_or_method(hir_id, *attr_span, span, target)
                 }
+                Attribute::Parsed(AttributeKind::MustUse { span, .. }) => {
+                    self.check_must_use(hir_id, *span, target)
+                }
                 Attribute::Unparsed(_) => {
                     match attr.path().as_slice() {
                         [sym::diagnostic, sym::do_not_recommend, ..] => {
@@ -235,7 +238,6 @@ impl<'tcx> CheckAttrVisitor<'tcx> {
                         | [sym::const_trait, ..] => self.check_must_be_applied_to_trait(attr, span, target),
                         [sym::collapse_debuginfo, ..] => self.check_collapse_debuginfo(attr, span, target),
                         [sym::must_not_suspend, ..] => self.check_must_not_suspend(attr, span, target),
-                        [sym::must_use, ..] => self.check_must_use(hir_id, attr, target),
                         [sym::may_dangle, ..] => self.check_may_dangle(hir_id, attr),
                         [sym::rustc_pass_by_value, ..] => self.check_pass_by_value(attr, span, target),
                         [sym::rustc_allow_incoherent_impl, ..] => {
@@ -688,7 +690,8 @@ impl<'tcx> CheckAttrVisitor<'tcx> {
                             AttributeKind::Deprecation { .. }
                             | AttributeKind::Repr { .. }
                             | AttributeKind::Align { .. }
-                            | AttributeKind::Cold(..),
+                            | AttributeKind::Cold(..)
+                            | AttributeKind::MustUse { .. },
                         ) => {
                             continue;
                         }
@@ -1563,7 +1566,7 @@ impl<'tcx> CheckAttrVisitor<'tcx> {
     }
 
     /// Warns against some misuses of `#[must_use]`
-    fn check_must_use(&self, hir_id: HirId, attr: &Attribute, target: Target) {
+    fn check_must_use(&self, hir_id: HirId, attr_span: Span, target: Target) {
         if matches!(
             target,
             Target::Fn
@@ -1603,7 +1606,7 @@ impl<'tcx> CheckAttrVisitor<'tcx> {
         self.tcx.emit_node_span_lint(
             UNUSED_ATTRIBUTES,
             hir_id,
-            attr.span(),
+            attr_span,
             errors::MustUseNoEffect { article, target },
         );
     }

src/rustdoc-json-types/lib.rs

@@ -37,8 +37,8 @@ pub type FxHashMap<K, V> = HashMap<K, V>; // re-export for use in src/librustdoc
 // will instead cause conflicts. See #94591 for more. (This paragraph and the "Latest feature" line
 // are deliberately not in a doc comment, because they need not be in public docs.)
 //
-// Latest feature: improve handling of generic args
-pub const FORMAT_VERSION: u32 = 51;
+// Latest feature: Pretty printing of must_use attributes changed
+pub const FORMAT_VERSION: u32 = 52;
 
 /// The root of the emitted JSON blob.
 ///
@@ -277,8 +277,8 @@ pub struct PolyTrait {
 /// A set of generic arguments provided to a path segment, e.g.
 ///
 /// ```text
-/// std::option::Option<u32>
-///                    ^^^^^
+/// std::option::Option::<u32>::None
+///                      ^^^^^
 /// ```
 #[derive(Clone, Debug, PartialEq, Eq, Hash, Serialize, Deserialize)]
 #[serde(rename_all = "snake_case")]
@@ -331,7 +331,7 @@ pub enum GenericArg {
     Const(Constant),
     /// A generic argument that's explicitly set to be inferred.
     /// ```text
-    /// std::vec::Vec::<_>
+    /// std::vec::Vec::<_>::new()
     ///                 ^
     /// ```
     Infer,
@@ -362,7 +362,7 @@ pub struct AssocItemConstraint {
     /// The name of the associated type/constant.
     pub name: String,
     /// Arguments provided to the associated type/constant.
-    pub args: Option<Box<GenericArgs>>,
+    pub args: GenericArgs,
     /// The kind of bound applied to the associated type/constant.
     pub binding: AssocItemConstraintKind,
 }
@@ -1118,7 +1118,7 @@ pub enum Type {
         /// <core::slice::IterMut<'static, u32> as BetterIterator>::Item<'static>
         /// //                                                          ^^^^^^^^^
         /// ```
-        args: Option<Box<GenericArgs>>,
+        args: Box<GenericArgs>,
         /// The type with which this type is associated.
         ///
         /// ```ignore (incomplete expression)

src/tools/clippy/clippy_lints/src/functions/must_use.rs

@@ -15,14 +15,17 @@ use clippy_utils::ty::is_must_use_ty;
 use clippy_utils::visitors::for_each_expr_without_closures;
 use clippy_utils::{return_ty, trait_ref_of_method};
 use rustc_trait_selection::error_reporting::InferCtxtErrorExt;
+use rustc_attr_data_structures::AttributeKind;
+use rustc_span::Symbol;
+use rustc_attr_data_structures::find_attr;
 
 use core::ops::ControlFlow;
 
 use super::{DOUBLE_MUST_USE, MUST_USE_CANDIDATE, MUST_USE_UNIT};
 
 pub(super) fn check_item<'tcx>(cx: &LateContext<'tcx>, item: &'tcx hir::Item<'_>) {
     let attrs = cx.tcx.hir_attrs(item.hir_id());
-    let attr = cx.tcx.get_attr(item.owner_id, sym::must_use);
+    let attr = find_attr!(cx.tcx.hir_attrs(item.hir_id()), AttributeKind::MustUse { span, reason } => (span, reason));
     if let hir::ItemKind::Fn {
         ref sig,
         body: ref body_id,
@@ -31,8 +34,8 @@ pub(super) fn check_item<'tcx>(cx: &LateContext<'tcx>, item: &'tcx hir::Item<'_>
     {
         let is_public = cx.effective_visibilities.is_exported(item.owner_id.def_id);
         let fn_header_span = item.span.with_hi(sig.decl.output.span().hi());
-        if let Some(attr) = attr {
-            check_needless_must_use(cx, sig.decl, item.owner_id, item.span, fn_header_span, attr, attrs, sig);
+        if let Some((attr_span, reason)) = attr {
+            check_needless_must_use(cx, sig.decl, item.owner_id, item.span, fn_header_span, *attr_span, *reason, attrs, sig);
         } else if is_public && !is_proc_macro(attrs) && !attrs.iter().any(|a| a.has_name(sym::no_mangle)) {
             check_must_use_candidate(
                 cx,
@@ -52,9 +55,9 @@ pub(super) fn check_impl_item<'tcx>(cx: &LateContext<'tcx>, item: &'tcx hir::Imp
         let is_public = cx.effective_visibilities.is_exported(item.owner_id.def_id);
         let fn_header_span = item.span.with_hi(sig.decl.output.span().hi());
         let attrs = cx.tcx.hir_attrs(item.hir_id());
-        let attr = cx.tcx.get_attr(item.owner_id, sym::must_use);
-        if let Some(attr) = attr {
-            check_needless_must_use(cx, sig.decl, item.owner_id, item.span, fn_header_span, attr, attrs, sig);
+        let attr = find_attr!(cx.tcx.hir_attrs(item.hir_id()), AttributeKind::MustUse { span, reason } => (span, reason));
+        if let Some((attr_span, reason)) = attr {
+            check_needless_must_use(cx, sig.decl, item.owner_id, item.span, fn_header_span, *attr_span, *reason, attrs, sig);
         } else if is_public && !is_proc_macro(attrs) && trait_ref_of_method(cx, item.owner_id).is_none() {
             check_must_use_candidate(
                 cx,
@@ -75,9 +78,9 @@ pub(super) fn check_trait_item<'tcx>(cx: &LateContext<'tcx>, item: &'tcx hir::Tr
         let fn_header_span = item.span.with_hi(sig.decl.output.span().hi());
 
         let attrs = cx.tcx.hir_attrs(item.hir_id());
-        let attr = cx.tcx.get_attr(item.owner_id, sym::must_use);
-        if let Some(attr) = attr {
-            check_needless_must_use(cx, sig.decl, item.owner_id, item.span, fn_header_span, attr, attrs, sig);
+        let attr = find_attr!(cx.tcx.hir_attrs(item.hir_id()), AttributeKind::MustUse { span, reason } => (span, reason));
+        if let Some((attr_span, reason)) = attr {
+            check_needless_must_use(cx, sig.decl, item.owner_id, item.span, fn_header_span, *attr_span, *reason, attrs, sig);
         } else if let hir::TraitFn::Provided(eid) = *eid {
             let body = cx.tcx.hir_body(eid);
             if attr.is_none() && is_public && !is_proc_macro(attrs) {
@@ -103,7 +106,8 @@ fn check_needless_must_use(
     item_id: hir::OwnerId,
     item_span: Span,
     fn_header_span: Span,
-    attr: &Attribute,
+    attr_span: Span,
+    reason: Option<Symbol>,
     attrs: &[Attribute],
     sig: &FnSig<'_>,
 ) {
@@ -119,7 +123,7 @@ fn check_needless_must_use(
                 "this unit-returning function has a `#[must_use]` attribute",
                 |diag| {
                     diag.span_suggestion(
-                        attr.span(),
+                        attr_span,
                         "remove the attribute",
                         "",
                         Applicability::MachineApplicable,
@@ -137,11 +141,11 @@ fn check_needless_must_use(
                 MUST_USE_UNIT,
                 fn_header_span,
                 "this unit-returning function has a `#[must_use]` attribute",
-                Some(attr.span()),
+                Some(attr_span),
                 "remove `must_use`",
             );
         }
-    } else if attr.value_str().is_none() && is_must_use_ty(cx, return_ty(cx, item_id)) {
+    } else if reason.is_none() && is_must_use_ty(cx, return_ty(cx, item_id)) {
         // Ignore async functions unless Future::Output type is a must_use type
         if sig.header.is_async() {
             let infcx = cx.tcx.infer_ctxt().build(cx.typing_mode());