In span mode (hs-parse-ast), parse-cmd is used to extract source info from
arbitrary expressions like literals and property access — not just callables.
Guard the "expected function call" error with hs-span-mode so span mode
passes all expression types through, while execution mode still rejects
non-callable expressions.
Also handle span mode's hs-ast dict nodes (kind="call") in the callable?
check, since method calls are wrapped in span mode.
giles
c26cd500b4