Fix ICE from #105101

2 files changed, 38 insertions, 0 deletions

diff --git a/src/test/ui/deriving/issue-105101.rs b/src/test/ui/deriving/issue-105101.rs
new file mode 100644
index 00000000000..1a377feb919
--- /dev/null
+++ b/src/test/ui/deriving/issue-105101.rs
@@ -0,0 +1,9 @@
+// compile-flags: --crate-type=lib
+
+#[derive(Default)] //~ ERROR multiple declared defaults
+enum E {
+    #[default]
+    A,
+    #[default]
+    A, //~ ERROR defined multiple times
+}
diff --git a/src/test/ui/deriving/issue-105101.stderr b/src/test/ui/deriving/issue-105101.stderr
new file mode 100644
index 00000000000..0f6f67043f3
--- /dev/null
+++ b/src/test/ui/deriving/issue-105101.stderr
@@ -0,0 +1,29 @@
+error: multiple declared defaults
+  --> $DIR/issue-105101.rs:3:10
+   |
+LL | #[derive(Default)]
+   |          ^^^^^^^
+...
+LL |     A,
+   |     - first default
+LL |     #[default]
+LL |     A,
+   |     - additional default
+   |
+   = note: only one variant can be default
+   = note: this error originates in the derive macro `Default` (in Nightly builds, run with -Z macro-backtrace for more info)
+
+error[E0428]: the name `A` is defined multiple times
+  --> $DIR/issue-105101.rs:8:5
+   |
+LL |     A,
+   |     - previous definition of the type `A` here
+LL |     #[default]
+LL |     A,
+   |     ^ `A` redefined here
+   |
+   = note: `A` must be defined only once in the type namespace of this enum
+
+error: aborting due to 2 previous errors
+
+For more information about this error, try `rustc --explain E0428`.