Rollup merge of #143075 - workingjubilee:interrupts-may-return-nevermore, r=davidtwco

compiler: Allow `extern "interrupt" fn() -> !`

While reviewing rust-lang/rust#142633 I overlooked a few details because I was kind of excited.

- Fixes rust-lang/rust#143072

2 files changed, 15 insertions, 3 deletions

diff --git a/compiler/rustc_ast_passes/messages.ftl b/compiler/rustc_ast_passes/messages.ftl
index 340a1a239c5..28d7c6613c8 100644
--- a/compiler/rustc_ast_passes/messages.ftl
+++ b/compiler/rustc_ast_passes/messages.ftl
@@ -17,7 +17,7 @@ ast_passes_abi_must_not_have_parameters_or_return_type=
 
 ast_passes_abi_must_not_have_return_type=
     invalid signature for `extern {$abi}` function
-    .note = functions with the "custom" ABI cannot have a return type
+    .note = functions with the {$abi} ABI cannot have a return type
     .help = remove the return type
 
 ast_passes_assoc_const_without_body =
diff --git a/compiler/rustc_ast_passes/src/ast_validation.rs b/compiler/rustc_ast_passes/src/ast_validation.rs
index f62b8d1d576..f0b67755761 100644
--- a/compiler/rustc_ast_passes/src/ast_validation.rs
+++ b/compiler/rustc_ast_passes/src/ast_validation.rs
@@ -390,7 +390,13 @@ impl<'a> AstValidator<'a> {
                         if let InterruptKind::X86 = interrupt_kind {
                             // "x86-interrupt" is special because it does have arguments.
                             // FIXME(workingjubilee): properly lint on acceptable input types.
-                            if let FnRetTy::Ty(ref ret_ty) = sig.decl.output {
+                            if let FnRetTy::Ty(ref ret_ty) = sig.decl.output
+                                && match &ret_ty.kind {
+                                    TyKind::Never => false,
+                                    TyKind::Tup(tup) if tup.is_empty() => false,
+                                    _ => true,
+                                }
+                            {
                                 self.dcx().emit_err(errors::AbiMustNotHaveReturnType {
                                     span: ret_ty.span,
                                     abi,
@@ -449,7 +455,13 @@ impl<'a> AstValidator<'a> {
 
     fn reject_params_or_return(&self, abi: ExternAbi, ident: &Ident, sig: &FnSig) {
         let mut spans: Vec<_> = sig.decl.inputs.iter().map(|p| p.span).collect();
-        if let FnRetTy::Ty(ref ret_ty) = sig.decl.output {
+        if let FnRetTy::Ty(ref ret_ty) = sig.decl.output
+            && match &ret_ty.kind {
+                TyKind::Never => false,
+                TyKind::Tup(tup) if tup.is_empty() => false,
+                _ => true,
+            }
+        {
             spans.push(ret_ty.span);
         }