TestLastModifiedPass asserted that a dense lattice state is always
present after running the data flow solver. However, in interprocedural
analysis mode (the default), private functions that are never called
from any callee in the module are not analyzed, so no lattice state is
computed for their program points.
Replace the assertion with a null check that prints "<not computed>"
when the lattice state is absent. This matches the expected behavior:
unreachable code in interprocedural mode simply has no computed analysis
result.
Add a regression test for the case where a tagged op is inside an
unreachable private function.
Fixes#128333
Assisted-by: Claude Code
e6e0e2b57e