This is now passing, actually.

For some reason that was not visible before the change to the prompt diag suppression.

interpreter/cling/test/Prompt/ClashingDeclsKnownFail.C

@@ -7,7 +7,6 @@
 //------------------------------------------------------------------------------
 
 // RUN: cat %s | %cling -Xclang -verify
-// XFAIL: *
 
 // The test exposes a weakness in the declaration extraction of types. As
 // reported in issue ROOT-5248.