port #[recursion_limit] to the new attribute parsing infrastructure

Author: jdonszelmann

compiler/rustc_attr_parsing/messages.ftl

@@ -195,3 +195,7 @@ attr_parsing_invalid_meta_item = expected a literal (`1u8`, `1.0f32`, `"string"`
 
 attr_parsing_suffixed_literal_in_attribute = suffixed literals are not allowed in attributes
     .help = instead of using a suffixed literal (`1u8`, `1.0f32`, etc.), use an unsuffixed version (`1`, `1.0`, etc.)
+
+attr_parsing_limit_invalid =
+    `limit` must be a non-negative integer
+    .label = {$error_str}

compiler/rustc_attr_parsing/src/attributes/crate_level.rs

@@ -1,7 +1,40 @@
-use rustc_feature::AttributeType;
+use std::num::IntErrorKind;
+
+use crate::session_diagnostics::LimitInvalid;
 
 use super::prelude::*;
 
+impl<S: Stage> AcceptContext<'_, '_, S> {
+    fn parse_limit_int(&self, nv: &NameValueParser) -> Option<usize> {
+        let Some(limit) = nv.value_as_str() else {
+            self.expected_string_literal(nv.value_span, Some(nv.value_as_lit()));
+            return None;
+        };
+
+        let error_str = match limit.as_str().parse() {
+            Ok(i) => return Some(i),
+            Err(e) => match e.kind() {
+                IntErrorKind::PosOverflow => "`limit` is too large",
+                IntErrorKind::Empty => "`limit` must be a non-negative integer",
+                IntErrorKind::InvalidDigit => "not a valid integer",
+                IntErrorKind::NegOverflow => {
+                    panic!(
+                        "`limit` should never negatively overflow since we're parsing into a usize and we'd get Empty instead"
+                    )
+                }
+                IntErrorKind::Zero => {
+                    panic!("zero is a valid `limit` so should have returned Ok() when parsing")
+                }
+                kind => panic!("unimplemented IntErrorKind variant: {:?}", kind),
+            },
+        };
+
+        self.emit_err(LimitInvalid { span: self.attr_span, value_span: nv.value_span, error_str });
+
+        None
+    }
+}
+
 pub(crate) struct CrateNameParser;
 
 impl<S: Stage> SingleAttributeParser<S> for CrateNameParser {
@@ -34,3 +67,30 @@ impl<S: Stage> SingleAttributeParser<S> for CrateNameParser {
         })
     }
 }
+
+pub(crate) struct RecursionLimitParser;
+
+impl<S: Stage> SingleAttributeParser<S> for RecursionLimitParser {
+    const PATH: &[Symbol] = &[sym::recursion_limit];
+    const ATTRIBUTE_ORDER: AttributeOrder = AttributeOrder::KeepOutermost;
+    const ON_DUPLICATE: OnDuplicate<S> = OnDuplicate::WarnButFutureError;
+    const TEMPLATE: AttributeTemplate = template!(NameValueStr: "N", "https://doc.rust-lang.org/reference/attributes/limits.html#the-recursion_limit-attribute");
+    const TYPE: AttributeType = AttributeType::CrateLevel;
+
+    // FIXME: recursion limit is allowed on all targets and ignored,
+    //        even though it should only be valid on crates of course
+    const ALLOWED_TARGETS: AllowedTargets = AllowedTargets::AllowList(ALL_TARGETS);
+
+    fn convert(cx: &mut AcceptContext<'_, '_, S>, args: &ArgParser<'_>) -> Option<AttributeKind> {
+        let ArgParser::NameValue(nv) = args else {
+            cx.expected_name_value(cx.attr_span, None);
+            return None;
+        };
+
+        Some(AttributeKind::RecursionLimit {
+            limit: cx.parse_limit_int(nv)?,
+            attr_span: cx.attr_span,
+            limit_span: nv.value_span,
+        })
+    }
+}

compiler/rustc_attr_parsing/src/attributes/prelude.rs

@@ -2,6 +2,7 @@
 // templates
 pub(super) use rustc_feature::{AttributeTemplate, template};
 // data structures
+pub(super) use rustc_feature::AttributeType;
 pub(super) use rustc_hir::attrs::AttributeKind;
 pub(super) use rustc_hir::lints::AttributeLintKind;
 pub(super) use rustc_hir::{MethodKind, Target};

compiler/rustc_attr_parsing/src/context.rs

@@ -24,7 +24,7 @@ use crate::attributes::codegen_attrs::{
     UsedParser,
 };
 use crate::attributes::confusables::ConfusablesParser;
-use crate::attributes::crate_level::CrateNameParser;
+use crate::attributes::crate_level::{CrateNameParser, RecursionLimitParser};
 use crate::attributes::deprecation::DeprecationParser;
 use crate::attributes::dummy::DummyParser;
 use crate::attributes::inline::{InlineParser, RustcForceInlineParser};
@@ -184,6 +184,7 @@ attribute_parsers!(
         Single<OptimizeParser>,
         Single<PathAttributeParser>,
         Single<ProcMacroDeriveParser>,
+        Single<RecursionLimitParser>,
         Single<RustcBuiltinMacroParser>,
         Single<RustcForceInlineParser>,
         Single<RustcLayoutScalarValidRangeEnd>,

compiler/rustc_attr_parsing/src/session_diagnostics.rs

@@ -836,3 +836,13 @@ pub(crate) struct InvalidAttrStyle {
     pub target_span: Option<Span>,
     pub target: Target,
 }
+
+#[derive(Diagnostic)]
+#[diag(attr_parsing_limit_invalid)]
+pub(crate) struct LimitInvalid<'a> {
+    #[primary_span]
+    pub span: Span,
+    #[label]
+    pub value_span: Span,
+    pub error_str: &'a str,
+}

compiler/rustc_hir/src/attrs/data_structures.rs

@@ -494,6 +494,9 @@ pub enum AttributeKind {
     /// Represents `#[rustc_pub_transparent]` (used by the `repr_transparent_external_private_fields` lint).
     PubTransparent(Span),
 
+    /// Represents [`#[recursion_limit]`](https://doc.rust-lang.org/reference/attributes/limits.html#the-recursion_limit-attribute)
+    RecursionLimit { attr_span: Span, limit_span: Span, limit: usize },
+
     /// Represents [`#[repr]`](https://doc.rust-lang.org/stable/reference/type-layout.html#representations).
     Repr { reprs: ThinVec<(ReprAttr, Span)>, first_span: Span },
 

compiler/rustc_hir/src/attrs/encode_cross_crate.rs

@@ -74,6 +74,7 @@ impl AttributeKind {
             ProcMacroAttribute(..) => No,
             ProcMacroDerive { .. } => No,
             PubTransparent(..) => Yes,
+            RecursionLimit { .. } => No,
             Repr { .. } => No,
             RustcBuiltinMacro { .. } => Yes,
             RustcLayoutScalarValidRangeEnd(..) => Yes,

compiler/rustc_hir/src/attrs/pretty_printing.rs

@@ -146,7 +146,7 @@ macro_rules! print_tup {
 
 print_tup!(A B C D E F G H);
 print_skip!(Span, (), ErrorGuaranteed);
-print_disp!(u16, bool, NonZero<u32>);
+print_disp!(u16, bool, NonZero<u32>, usize);
 print_debug!(
     Symbol,
     Ident,

compiler/rustc_passes/src/check_attr.rs

@@ -252,6 +252,7 @@ impl<'tcx> CheckAttrVisitor<'tcx> {
                     | AttributeKind::Linkage(..)
                     | AttributeKind::MustUse { .. }
                     | AttributeKind::CrateName { .. }
+                    | AttributeKind::RecursionLimit { .. }
                 ) => { /* do nothing  */ }
                 Attribute::Unparsed(attr_item) => {
                     style = Some(attr_item.style);