Enforce correct number of arguments for "x86-interrupt" functions

compiler/rustc_ast_passes/src/ast_validation.rs

@@ -405,6 +405,17 @@ 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.
+                            let inputs = &sig.decl.inputs;
+                            let param_count = inputs.len();
+                            if !matches!(param_count, 1 | 2) {
+                                let mut spans: Vec<Span> =
+                                    inputs.iter().map(|arg| arg.span).collect();
+                                if spans.is_empty() {
+                                    spans = vec![sig.span];
+                                }
+                                self.dcx().emit_err(errors::AbiX86Interrupt { spans, param_count });
+                            }
+
                             if let FnRetTy::Ty(ref ret_ty) = sig.decl.output
                                 && match &ret_ty.kind {
                                     TyKind::Never => false,