Credence.Rule.DescriptiveNames (credence v0.3.0)

Maintainability rule: Detects single-letter variable names in function signatures.

Using single-letter names like a, x, or n forces the reader to keep track of the variable's purpose in their short-term memory. Replacing these with descriptive names reduces cognitive load and makes the code self-documenting.

While common in mathematical contexts, in software development, explicit names like index, accumulator, or user_id make the logic much easier to reason about at a glance.

Bad

# Named functions
def handle_event(e, s), do: {:ok, s}

# Anonymous functions
Enum.reduce(list, 0, fn x, acc -> x + acc end)

Good

# Named functions
def handle_event(event, state), do: {:ok, state}

# Anonymous functions
Enum.reduce(list, 0, fn price, total_sum -> price + total_sum end)

# Single underscores (ignored by this rule)
def handle_call(_msg, _from, state), do: {:reply, :ok, state}