add regression test for #79148

Author: TaKO8Ki

src/test/ui/proc-macro/auxiliary/re-export.rs

@@ -0,0 +1,19 @@
+// force-host
+// no-prefer-dynamic
+
+#![crate_type = "proc-macro"]
+
+extern crate proc_macro;
+
+use proc_macro::TokenStream;
+
+#[proc_macro]
+pub fn cause_ice(_: TokenStream) -> TokenStream {
+    "
+        enum IceCause {
+            Variant,
+        }
+
+        pub use IceCause::Variant;
+    ".parse().unwrap()
+}

src/test/ui/proc-macro/issue-79148.rs

@@ -0,0 +1,10 @@
+// aux-build:re-export.rs
+// edition:2018
+
+extern crate re_export;
+
+use re_export::cause_ice;
+
+cause_ice!(); //~ ERROR `Variant` is only public within the crate, and cannot be re-exported outside
+
+fn main() {}

src/test/ui/proc-macro/issue-79148.stderr

@@ -0,0 +1,16 @@
+error[E0364]: `Variant` is only public within the crate, and cannot be re-exported outside
+  --> $DIR/issue-79148.rs:8:1
+   |
+LL | cause_ice!();
+   | ^^^^^^^^^^^^
+   |
+note: consider marking `Variant` as `pub` in the imported module
+  --> $DIR/issue-79148.rs:8:1
+   |
+LL | cause_ice!();
+   | ^^^^^^^^^^^^
+   = note: this error originates in the macro `cause_ice` (in Nightly builds, run with -Z macro-backtrace for more info)
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0364`.