narrow-bare-rescue
Narrow Bare Rescue
Turn rescue _ -> fallback into rescue _ in [ExceptionType1, ExceptionType2] -> fallback
so programmer bugs propagate while known failure modes stay handled.
Why this matters
Bare rescues (rescue _ ->, rescue e -> — any form without an in clause) swallow
every exception, including UndefinedFunctionError from typos, KeyError from
misspelled map keys, and CompileError from bad HEEx templates. The symptom isn't a stack
trace — it's a silent {:error, :generic} or a nil fallback. Bugs that should surface
in tests or error reporters become quiet degradations.
The Erlang Secure Coding Guide makes
the same case at the BEAM level — rule LNG-002 ("Do Not Use catch") warns that the
legacy catch-all form conflates normal returns, throws, and errors. Bare rescue in Elixir
is the direct analogue.