1 files changed, 22 insertions, 0 deletions
diff --git a/tests/ui/trait-bounds/duplicate-relaxed-bounds.rs b/tests/ui/trait-bounds/duplicate-relaxed-bounds.rs
new file mode 100644
index 00000000000..a1681ddec77
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+++ b/tests/ui/trait-bounds/duplicate-relaxed-bounds.rs
@@ -0,0 +1,22 @@
+fn dupes<T: ?Sized + ?Sized + ?Iterator + ?Iterator>() {}
+//~^ ERROR duplicate relaxed `Sized` bounds
+//~| ERROR duplicate relaxed `Iterator` bounds
+//~| ERROR bound modifier `?` can only be applied to `Sized`
+//~| ERROR bound modifier `?` can only be applied to `Sized`
+
+trait Trait {
+    // We used to say "type parameter has more than one relaxed default bound"
+    // even on *associated types* like here. Test that we no longer do that.
+    type Type: ?Sized + ?Sized;
+    //~^ ERROR duplicate relaxed `Sized` bounds
+    //~| ERROR duplicate relaxed `Sized` bounds
+}
+
+// We used to emit an additional error about "multiple relaxed default bounds".
+// However, multiple relaxed bounds are actually *fine* if they're distinct.
+// Ultimately, we still reject this because `Sized` is
+// the only (stable) default trait, so we're fine.
+fn not_dupes<T: ?Sized + ?Iterator>() {}
+//~^ ERROR bound modifier `?` can only be applied to `Sized`
+
+fn main() {}