The deleted branch was added in #45062, although it had not been tested.

I tried the following diff to find cases optimized by that, but I just
found the handling proved to be in vain in all cases I tried.
```diff
diff --git a/base/compiler/ssair/inlining.jl b/base/compiler/ssair/inlining.jl
index 318b21b09b..7e42a65aa4 100644
--- a/base/compiler/ssair/inlining.jl
+++ b/base/compiler/ssair/inlining.jl
@@ -1473,6 +1473,14 @@ function compute_inlining_cases(@nospecialize(info::CallInfo), flag::UInt32, sig
         handle_any_const_result!(cases,
             result, match, argtypes, info, flag, state; allow_abstract=true, allow_typevars=true)
         fully_covered = handled_all_cases = match.fully_covers
+        if length(cases) == 1 && fully_covered
+            println("first case: ", only_method)
+        elseif length(cases) == 1
+            atype = argtypes_to_type(sig.argtypes)
+            if atype isa DataType && cases[1].sig isa DataType
+                println("second case: ", only_method)
+            end
+        end
     elseif !handled_all_cases
         # if we've not seen all candidates, union split is valid only for dispatch tuples
         filter!(case::InliningCase->isdispatchtuple(case.sig), cases)
```