move_ref_pattern: don't ICE on unreachable 2xby-move conflicts

src/test/ui/pattern/move-ref-patterns/by-move-sub-pat-unreachable.rs

@@ -0,0 +1,15 @@
+// When conflicts between by-move bindings in `by_move_1 @ has_by_move` patterns
+// happen and that code is unreachable according to borrowck, we accept this code.
+// In particular, we want to ensure here that an ICE does not happen, which it did originally.
+
+// check-pass
+
+#![feature(move_ref_pattern)]
+#![feature(bindings_after_at)]
+
+fn main() {
+    return;
+
+    struct S;
+    let a @ (b, c) = (S, S);
+}