From 43fa2a95c90d7ac4bb98d87e62630e9f549d00c2 Mon Sep 17 00:00:00 2001
From: cyrgani <ansgar.w.zielke@gmail.com>
Date: Thu, 11 Dec 2025 18:15:15 +0000
Subject: [PATCH] add regression test for `proc_macro` error subdiagnostics

---
 tests/ui/proc-macro/auxiliary/sub-error-diag.rs | 17 +++++++++++++++++
 tests/ui/proc-macro/sub-error-diag.rs           | 13 +++++++++++++
 tests/ui/proc-macro/sub-error-diag.stderr       | 11 +++++++++++
 3 files changed, 41 insertions(+)
 create mode 100644 tests/ui/proc-macro/auxiliary/sub-error-diag.rs
 create mode 100644 tests/ui/proc-macro/sub-error-diag.rs
 create mode 100644 tests/ui/proc-macro/sub-error-diag.stderr

diff --git a/tests/ui/proc-macro/auxiliary/sub-error-diag.rs b/tests/ui/proc-macro/auxiliary/sub-error-diag.rs
new file mode 100644
index 0000000000000..5ce8c5d90304a
--- /dev/null
+++ b/tests/ui/proc-macro/auxiliary/sub-error-diag.rs
@@ -0,0 +1,17 @@
+#![feature(proc_macro_diagnostic)]
+
+extern crate proc_macro;
+
+use proc_macro::{Diagnostic, Level, Span};
+
+#[proc_macro_attribute]
+pub fn proc_emit_err(
+    _: proc_macro::TokenStream,
+    input: proc_macro::TokenStream,
+) -> proc_macro::TokenStream {
+    Diagnostic::new(Level::Error, "Parent message")
+        .span_error(Span::call_site(), "Child message")
+        .emit();
+
+    input
+}
diff --git a/tests/ui/proc-macro/sub-error-diag.rs b/tests/ui/proc-macro/sub-error-diag.rs
new file mode 100644
index 0000000000000..11218fc66a371
--- /dev/null
+++ b/tests/ui/proc-macro/sub-error-diag.rs
@@ -0,0 +1,13 @@
+//@ proc-macro: sub-error-diag.rs
+
+// Regression test for issue https://github.com/rust-lang/rust/issues/145305, which used to cause an ICE
+// due to an assertion in the compiler that errors could not be subdiagnostics.
+
+extern crate sub_error_diag;
+
+//~? ERROR: Parent message
+#[sub_error_diag::proc_emit_err]
+//~^ ERROR: Child message
+fn foo() {}
+
+fn main() {}
diff --git a/tests/ui/proc-macro/sub-error-diag.stderr b/tests/ui/proc-macro/sub-error-diag.stderr
new file mode 100644
index 0000000000000..b5d83e4d52ae2
--- /dev/null
+++ b/tests/ui/proc-macro/sub-error-diag.stderr
@@ -0,0 +1,11 @@
+error: Parent message
+   |
+error: Child message
+  --> $DIR/sub-error-diag.rs:9:1
+   |
+LL | #[sub_error_diag::proc_emit_err]
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   = note: this error originates in the attribute macro `sub_error_diag::proc_emit_err` (in Nightly builds, run with -Z macro-backtrace for more info)
+
+error: aborting due to 1 previous error
+