Add regression test for issue 99173

AprilNEA · AprilNEA · commit b3c3604f624e · 2025-12-30T17:59:40.000+08:00
Adds a test for nested proc-macro calls where the inner macro returns an
empty TokenStream.
This previously caused an ICE in rustc_resolve.
diff --git a/tests/ui/proc-macro/auxiliary/nested-empty-proc-macro.rs b/tests/ui/proc-macro/auxiliary/nested-empty-proc-macro.rs
@@ -0,0 +1,18 @@
+// Auxiliary proc-macro for issue #99173
+// Tests that nested proc-macro calls with empty output don't cause ICE
+
+extern crate proc_macro;
+
+use proc_macro::TokenStream;
+
+// This macro returns an empty TokenStream
+#[proc_macro]
+pub fn ignore(_input: TokenStream) -> TokenStream {
+    TokenStream::new()
+}
+
+// This macro generates code that calls the `ignore` macro
+#[proc_macro]
+pub fn outer_macro(_input: TokenStream) -> TokenStream {
+    "nested_empty_proc_macro::ignore!(42)".parse().unwrap()
+}
diff --git a/tests/ui/proc-macro/nested-empty-proc-macro.rs b/tests/ui/proc-macro/nested-empty-proc-macro.rs
@@ -0,0 +1,12 @@
+//@ check-pass
+//@ proc-macro: nested-empty-proc-macro.rs
+
+// Regression test for issue #99173
+// Tests that nested proc-macro calls where the inner macro returns
+// an empty TokenStream don't cause an ICE.
+
+extern crate nested_empty_proc_macro;
+
+fn main() {
+    nested_empty_proc_macro::outer_macro!(1 * 2 * 3 * 7);
+}
