port #[type_length_limit] to the new attribute parsing infrastructure

compiler/rustc_attr_parsing/src/attributes/crate_level.rs

@@ -120,3 +120,30 @@ impl<S: Stage> SingleAttributeParser<S> for MoveSizeLimitParser {
         })
     }
 }
+
+pub(crate) struct TypeLengthLimitParser;
+
+impl<S: Stage> SingleAttributeParser<S> for TypeLengthLimitParser {
+    const PATH: &[Symbol] = &[sym::type_length_limit];
+    const ATTRIBUTE_ORDER: AttributeOrder = AttributeOrder::KeepOutermost;
+    const ON_DUPLICATE: OnDuplicate<S> = OnDuplicate::WarnButFutureError;
+    const TEMPLATE: AttributeTemplate = template!(NameValueStr: "N");
+    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::AllowListWarnRest(&[Target::Crate]);
+
+    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::TypeLengthLimit {
+            limit: cx.parse_limit_int(nv)?,
+            attr_span: cx.attr_span,
+            limit_span: nv.value_span,
+        })
+    }
+}

compiler/rustc_attr_parsing/src/context.rs

@@ -24,7 +24,9 @@ use crate::attributes::codegen_attrs::{
     UsedParser,
 };
 use crate::attributes::confusables::ConfusablesParser;
-use crate::attributes::crate_level::{CrateNameParser, MoveSizeLimitParser, RecursionLimitParser};
+use crate::attributes::crate_level::{
+    CrateNameParser, MoveSizeLimitParser, RecursionLimitParser, TypeLengthLimitParser,
+};
 use crate::attributes::deprecation::DeprecationParser;
 use crate::attributes::dummy::DummyParser;
 use crate::attributes::inline::{InlineParser, RustcForceInlineParser};
@@ -196,6 +198,7 @@ attribute_parsers!(
         Single<ShouldPanicParser>,
         Single<SkipDuringMethodDispatchParser>,
         Single<TransparencyParser>,
+        Single<TypeLengthLimitParser>,
         Single<WithoutArgs<AllowIncoherentImplParser>>,
         Single<WithoutArgs<AllowInternalUnsafeParser>>,
         Single<WithoutArgs<AsPtrParser>>,

compiler/rustc_hir/src/attrs/data_structures.rs

@@ -667,6 +667,9 @@ pub enum AttributeKind {
     /// Represents `#[type_const]`.
     TypeConst(Span),
 
+    /// Represents `#[type_length_limit]`
+    TypeLengthLimit { attr_span: Span, limit_span: Span, limit: usize },
+
     /// Represents `#[rustc_unsafe_specialization_marker]`.
     UnsafeSpecializationMarker(Span),
 

compiler/rustc_hir/src/attrs/encode_cross_crate.rs

@@ -91,6 +91,7 @@ impl AttributeKind {
             TargetFeature { .. } => No,
             TrackCaller(..) => Yes,
             TypeConst(..) => Yes,
+            TypeLengthLimit { .. } => Yes,
             UnsafeSpecializationMarker(..) => No,
             UnstableFeatureBound(..) => No,
             Used { .. } => No,

compiler/rustc_passes/src/check_attr.rs

@@ -272,6 +272,7 @@ impl<'tcx> CheckAttrVisitor<'tcx> {
                     | AttributeKind::CrateName { .. }
                     | AttributeKind::RecursionLimit { .. }
                     | AttributeKind::MoveSizeLimit { .. }
+                    | AttributeKind::TypeLengthLimit { .. }
                 ) => { /* do nothing  */ }
                 Attribute::Unparsed(attr_item) => {
                     style = Some(attr_item.style);