1 files changed, 41 insertions, 0 deletions
diff --git a/src/test/ui/associated-types/issue-54108.rs b/src/test/ui/associated-types/issue-54108.rs
new file mode 100644
index 000000000..87f67ce4b
--- /dev/null
+++ b/src/test/ui/associated-types/issue-54108.rs
@@ -0,0 +1,41 @@
+use std::ops::Add;
+
+pub trait Encoder {
+    type Size: Add<Output = Self::Size>;
+
+    fn foo(&self) -> Self::Size;
+}
+
+pub trait SubEncoder: Encoder {
+    type ActualSize;
+
+    fn bar(&self) -> Self::Size;
+}
+
+impl<T> Encoder for T
+where
+    T: SubEncoder,
+{
+    type Size = <Self as SubEncoder>::ActualSize;
+    //~^ ERROR: cannot add `<T as SubEncoder>::ActualSize` to `<T as SubEncoder>::ActualSize`
+
+    fn foo(&self) -> Self::Size {
+        self.bar() + self.bar()
+    }
+}
+
+pub struct UnitEncoder;
+
+impl SubEncoder for UnitEncoder {
+    type ActualSize = ();
+
+    fn bar(&self) {}
+}
+
+pub fn fun<R: Encoder>(encoder: &R) {
+    encoder.foo();
+}
+
+fn main() {
+    fun(&UnitEncoder {});
+}