Port #[export_name] to the new attribute parsing infrastructure

Signed-off-by: Jonathan Brouwer <jonathantbrouwer@gmail.com>

compiler/rustc_attr_parsing/src/attributes/codegen_attrs.rs

@@ -6,7 +6,7 @@ use rustc_span::{Span, Symbol, sym};
 use super::{AcceptMapping, AttributeOrder, AttributeParser, OnDuplicate, SingleAttributeParser};
 use crate::context::{AcceptContext, FinalizeContext, Stage};
 use crate::parser::ArgParser;
-use crate::session_diagnostics::NakedFunctionIncompatibleAttribute;
+use crate::session_diagnostics::{NakedFunctionIncompatibleAttribute, NullOnExport};
 
 pub(crate) struct OptimizeParser;
 
@@ -59,6 +59,33 @@ impl<S: Stage> SingleAttributeParser<S> for ColdParser {
     }
 }
 
+pub(crate) struct ExportNameParser;
+
+impl<S: Stage> SingleAttributeParser<S> for ExportNameParser {
+    const PATH: &[rustc_span::Symbol] = &[sym::export_name];
+    const ATTRIBUTE_ORDER: AttributeOrder = AttributeOrder::KeepFirst;
+    const ON_DUPLICATE: OnDuplicate<S> = OnDuplicate::WarnButFutureError;
+    const TEMPLATE: AttributeTemplate = template!(NameValueStr: "name");
+
+    fn convert(cx: &mut AcceptContext<'_, '_, S>, args: &ArgParser<'_>) -> Option<AttributeKind> {
+        let Some(nv) = args.name_value() else {
+            cx.expected_name_value(cx.attr_span, None);
+            return None;
+        };
+        let Some(name) = nv.value_as_str() else {
+            cx.expected_string_literal(nv.value_span, Some(nv.value_as_lit()));
+            return None;
+        };
+        if name.as_str().contains('\0') {
+            // `#[export_name = ...]` will be converted to a null-terminated string,
+            // so it may not contain any null characters.
+            cx.emit_err(NullOnExport { span: cx.attr_span });
+            return None;
+        }
+        Some(AttributeKind::ExportName { name, span: cx.attr_span })
+    }
+}
+
 #[derive(Default)]
 pub(crate) struct NakedParser {
     span: Option<Span>,

compiler/rustc_attr_parsing/src/context.rs

@@ -16,7 +16,7 @@ use rustc_span::{DUMMY_SP, ErrorGuaranteed, Span, Symbol, sym};
 
 use crate::attributes::allow_unstable::{AllowConstFnUnstableParser, AllowInternalUnstableParser};
 use crate::attributes::codegen_attrs::{
-    ColdParser, NakedParser, NoMangleParser, OptimizeParser, TrackCallerParser,
+    ColdParser, ExportNameParser, NakedParser, NoMangleParser, OptimizeParser, TrackCallerParser,
 };
 use crate::attributes::confusables::ConfusablesParser;
 use crate::attributes::deprecation::DeprecationParser;
@@ -117,6 +117,7 @@ attribute_parsers!(
         Single<ConstContinueParser>,
         Single<ConstStabilityIndirectParser>,
         Single<DeprecationParser>,
+        Single<ExportNameParser>,
         Single<InlineParser>,
         Single<LoopMatchParser>,
         Single<MayDangleParser>,

compiler/rustc_attr_parsing/src/session_diagnostics.rs

@@ -445,6 +445,13 @@ pub(crate) struct MustUseIllFormedAttributeInput {
     pub suggestions: DiagArgValue,
 }
 
+#[derive(Diagnostic)]
+#[diag(attr_parsing_null_on_export, code = E0648)]
+pub(crate) struct NullOnExport {
+    #[primary_span]
+    pub span: Span,
+}
+
 #[derive(Diagnostic)]
 #[diag(attr_parsing_stability_outside_std, code = E0734)]
 pub(crate) struct StabilityOutsideStd {