Port #[ffi_const] to the new attribute system

compiler/rustc_attr_data_structures/src/attributes.rs

@@ -251,6 +251,9 @@ pub enum AttributeKind {
     /// Represents `#[export_stable]`.
     ExportStable,
 
+    /// Represents `#[ffi_const]`.
+    FfiConst(Span),
+
     /// Represents `#[ignore]`
     Ignore {
         span: Span,

compiler/rustc_attr_data_structures/src/encode_cross_crate.rs

@@ -27,6 +27,7 @@ impl AttributeKind {
             DocComment { .. } => Yes,
             ExportName { .. } => Yes,
             ExportStable => No,
+            FfiConst(..) => No,
             Ignore { .. } => No,
             Inline(..) => No,
             LinkName { .. } => Yes,

compiler/rustc_attr_parsing/src/attributes/link_attrs.rs

@@ -66,3 +66,10 @@ impl<S: Stage> NoArgsAttributeParser<S> for ExportStableParser {
     const ON_DUPLICATE: OnDuplicate<S> = OnDuplicate::Warn;
     const CREATE: fn(Span) -> AttributeKind = |_| AttributeKind::ExportStable;
 }
+
+pub(crate) struct FfiConstParser;
+impl<S: Stage> NoArgsAttributeParser<S> for FfiConstParser {
+    const PATH: &[Symbol] = &[sym::ffi_const];
+    const ON_DUPLICATE: OnDuplicate<S> = OnDuplicate::Warn;
+    const CREATE: fn(Span) -> AttributeKind = AttributeKind::FfiConst;
+}

compiler/rustc_attr_parsing/src/context.rs

@@ -22,7 +22,9 @@ use crate::attributes::codegen_attrs::{
 use crate::attributes::confusables::ConfusablesParser;
 use crate::attributes::deprecation::DeprecationParser;
 use crate::attributes::inline::{InlineParser, RustcForceInlineParser};
-use crate::attributes::link_attrs::{ExportStableParser, LinkNameParser, LinkSectionParser};
+use crate::attributes::link_attrs::{
+    ExportStableParser, FfiConstParser, LinkNameParser, LinkSectionParser,
+};
 use crate::attributes::lint_helpers::{AsPtrParser, PassByValueParser, PubTransparentParser};
 use crate::attributes::loop_match::{ConstContinueParser, LoopMatchParser};
 use crate::attributes::must_use::MustUseParser;
@@ -146,6 +148,7 @@ attribute_parsers!(
         Single<WithoutArgs<ConstContinueParser>>,
         Single<WithoutArgs<ConstStabilityIndirectParser>>,
         Single<WithoutArgs<ExportStableParser>>,
+        Single<WithoutArgs<FfiConstParser>>,
         Single<WithoutArgs<LoopMatchParser>>,
         Single<WithoutArgs<MayDangleParser>>,
         Single<WithoutArgs<NoImplicitPreludeParser>>,

compiler/rustc_codegen_ssa/src/codegen_attrs.rs

@@ -203,6 +203,9 @@ fn codegen_fn_attrs(tcx: TyCtxt<'_>, did: LocalDefId) -> CodegenFnAttrs {
                     UsedBy::Compiler => codegen_fn_attrs.flags |= CodegenFnAttrFlags::USED_COMPILER,
                     UsedBy::Linker => codegen_fn_attrs.flags |= CodegenFnAttrFlags::USED_LINKER,
                 },
+                AttributeKind::FfiConst(_) => {
+                    codegen_fn_attrs.flags |= CodegenFnAttrFlags::FFI_CONST
+                }
                 _ => {}
             }
         }
@@ -214,7 +217,6 @@ fn codegen_fn_attrs(tcx: TyCtxt<'_>, did: LocalDefId) -> CodegenFnAttrs {
         match name {
             sym::rustc_allocator => codegen_fn_attrs.flags |= CodegenFnAttrFlags::ALLOCATOR,
             sym::ffi_pure => codegen_fn_attrs.flags |= CodegenFnAttrFlags::FFI_PURE,
-            sym::ffi_const => codegen_fn_attrs.flags |= CodegenFnAttrFlags::FFI_CONST,
             sym::rustc_nounwind => codegen_fn_attrs.flags |= CodegenFnAttrFlags::NEVER_UNWIND,
             sym::rustc_reallocator => codegen_fn_attrs.flags |= CodegenFnAttrFlags::REALLOCATOR,
             sym::rustc_deallocator => codegen_fn_attrs.flags |= CodegenFnAttrFlags::DEALLOCATOR,

compiler/rustc_parse/src/validate_attr.rs

@@ -272,6 +272,7 @@ pub fn check_builtin_meta_item(
             name,
             sym::inline
                 | sym::export_stable
+                | sym::ffi_const
                 | sym::may_dangle
                 | sym::rustc_as_ptr
                 | sym::rustc_pub_transparent

compiler/rustc_passes/src/check_attr.rs

@@ -207,6 +207,9 @@ impl<'tcx> CheckAttrVisitor<'tcx> {
                 Attribute::Parsed(AttributeKind::ExportStable) => {
                     // handled in `check_export`
                 }
+                &Attribute::Parsed(AttributeKind::FfiConst(attr_span)) => {
+                    self.check_ffi_const(attr_span, target)
+                }
                 Attribute::Parsed(
                     AttributeKind::BodyStability { .. }
                     | AttributeKind::ConstStabilityIndirect
@@ -304,7 +307,6 @@ impl<'tcx> CheckAttrVisitor<'tcx> {
                             self.check_has_incoherent_inherent_impls(attr, span, target)
                         }
                         [sym::ffi_pure, ..] => self.check_ffi_pure(attr.span(), attrs, target),
-                        [sym::ffi_const, ..] => self.check_ffi_const(attr.span(), target),
                         [sym::link_ordinal, ..] => self.check_link_ordinal(attr, span, target),
                         [sym::link, ..] => self.check_link(hir_id, attr, span, target),
                         [sym::macro_use, ..] | [sym::macro_escape, ..] => {
@@ -1509,7 +1511,7 @@ impl<'tcx> CheckAttrVisitor<'tcx> {
             self.dcx().emit_err(errors::FfiPureInvalidTarget { attr_span });
             return;
         }
-        if attrs.iter().any(|a| a.has_name(sym::ffi_const)) {
+        if find_attr!(attrs, AttributeKind::FfiConst(_)) {
             // `#[ffi_const]` functions cannot be `#[ffi_pure]`
             self.dcx().emit_err(errors::BothFfiConstAndPure { attr_span });
         }

tests/ui/attributes/malformed-attrs.stderr

@@ -146,12 +146,6 @@ error: malformed `link_ordinal` attribute input
 LL |     #[link_ordinal]
    |     ^^^^^^^^^^^^^^^ help: must be of the form: `#[link_ordinal(ordinal)]`
 
-error: malformed `ffi_const` attribute input
-  --> $DIR/malformed-attrs.rs:171:5
-   |
-LL |     #[unsafe(ffi_const = 1)]
-   |     ^^^^^^^^^^^^^^^^^^^^^^^^ help: must be of the form: `#[ffi_const]`
-
 error: malformed `linkage` attribute input
   --> $DIR/malformed-attrs.rs:173:5
    |
@@ -540,6 +534,15 @@ LL | #[rustc_layout_scalar_valid_range_end]
    | expected this to be a list
    | help: must be of the form: `#[rustc_layout_scalar_valid_range_end(end)]`
 
+error[E0565]: malformed `ffi_const` attribute input
+  --> $DIR/malformed-attrs.rs:171:5
+   |
+LL |     #[unsafe(ffi_const = 1)]
+   |     ^^^^^^^^^^^^^^^^^^^---^^
+   |     |                  |
+   |     |                  didn't expect any arguments here
+   |     help: must be of the form: `#[ffi_const]`
+
 error[E0565]: malformed `non_exhaustive` attribute input
   --> $DIR/malformed-attrs.rs:197:1
    |